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Old 10-27-2004, 11:40 AM   #1
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Lightbulb - - - - Turbo E30 FAQ: - - - -

This thread is meant to be ongoing and growing.. if you have any questions pertaining to the turbo FAQ, please start a new topic.

__________________________________________________ __________

Not up for "rolling your own" ?

TCD makes a "kit"

__________________________________________________ __________

Best advice given in a while:

Originally Posted by Rolla1990 View Post
Very good advice. Just research, research, research! There is TONS of information on this website about every facet of turbo setup and fuel management. Make yourself a list of what parts you'll need as you do your research. Come up with a "game plan" before you begin buying things and it will save you time, money, and frustration in the long run. Make yourself a budget as you price out the parts, and then add some for mistakes/problems/fixes along the way. It also helps if you car is not your daily driver. I've had my car torn apart all winter just so I can "do it right" and finally had it running on Megasquirt last week.

This stuff takes time, money, and brain power. You don't necessarily have to be smart to build a good setup, but you need the ability to learn from other people's mistakes, and reason your way through tough problems.

__________________________________________________ __________

Having trouble getting started?
We suggest you start with a book.
"Forced Induction Performance Tuning" by A. Graham Bell is more in depth.
"Maximum Boost" by Corky Bell is a good overview/introduction book.

A few quotes from Maximum Boost:

How much power can I expect from a turbocharged engine?
With currently available fuels, 7 to 12 psi boost is a practical upper limit for stock engines (at sea-level elevation). Intercooling permits this when elaborately and properly done. Certainly not all turbo kits or systems will perform the same, due to widely varying engineering efforts on the above items. Special preparation of engines specifically for turbo applications can frequently permit boost pressures of 15 to 20 psi. To claim, calculate, or estimate a specific figure for power from a turbo engine can be precarious indeed.
Of known dyno runs on piston engines with a variety of turbo systems, the lowest output we have achieved is .052 bhp/cid psi and the highest is .077 bhp/cid psi. The variance is due to the engines' basic designs. To guess at the output of your own engine, choose a logical boost level and multiply each of the two values by both displacement in cubic inches and boost pressure plus 14.7.
Example: A 350 cid engine with 10 psi boost
Lower value = 0.052 x 350 x (10 + 14.7) = 449 bhp
Higher value = 0.077 x 350 x (10 + 14.7) = 666 bhp

Does the rated boost of a kit have any merit?
It does if, and only if, the conditions required to achieve that boost are defined and accurate. For example:
. Was the gasoline used commercially available pump gas?
. Were octane boosters used?
. Was detonation present?
. What was intake air temperature?
. Is this the same boost-pressure setting the buyer will receive?

Considering the large power increases offered by the turbocharger, what keeps the entire structure of the engine from going south?
A proper answer to this question is a complete analysis of the inertial, power, and thermal loads before and after turbo installation. If this is performed, ' the conclusion will be two interesting bits of information:
. The inertial loads in a modern internal combustion street engine are so large at maximum power that the power component of the total load is of little significance. For example, to induce as much power load into a conrod bearing as the bearing already sees from inertial loads, the actual power of the engine would need to increase approximately 50%.
. The thermal load in an engine not originally designed for a turbocharger will cause an increase in component and cooling-system temperatures when operating under boost. The components and cooling system can handle the temperature increase for a limited period. This is true for Buicks, Porsches, Saabs, Volvos, Nissans, etc. It is also true for all aftermarket turbo kits. The time limit is subject to many conditions. Experience has led me to believe that the time limit at full boost is on the order of 20 to 25 seconds. This is an operational restriction but not one of any consequence. Consider, for example: How fast will you be traveling if you hold full throttle in a 325 bhp Toyota Supra for twenty seconds? The answer is obviously an impractically high rate of speed.

When should the turbo start producing boost?
In most cases, there are trade-offs between a low boost threshold and maximum power. To bias the turbo size toward low-speed boost capability generally means operating the turbo in a very inefficient flow range at the engine's top end. Conversely, if maximum power is to be achieved, the turbo will usually be so large that no boost will be available until the last half of the rev range. Compromise is obviously necessary. A reasonable balance between low speed response and top-end power is to size the turbo such that it begins producing boost at about 30% of the redline rpm, this varies with the cam profile.

How will the turbocharger affect driveability?
Driveability of fuel-injected engines will remain the same. Driveability of blow-through carbureted engines will remain virtually the same. The starting of carbureted engines will be degraded slightly. Please note that draw-through units will virtually always degrade drive ability and starting somewhat, with cold weather proving the Achilles' heel of a draw-through system.

Will the turbocharger hurt my mileage?
Yes. The turbo, when installed as an aftermarket item on a spark-ignition engine, is not an economizer and cannot be construed as such. There is no engineering basis for making such claims. If you are led into purchasing a turbo under the premise of improving your fuel mileage, be sure to get a written guarantee. When not operating under boost, a turbocharger is a small system restriction. This restriction causes a small loss in volumetric efficiency. Volumetric efficiency and fuel economy are definitely tied together. If your driving habits are about the same as most, your mileage will drop about 10% city and 5% highway. No miracles here.

Will the turbocharger affect engine wear and maintenance?
Certainly the turbo will affect engine wear. Do you really expect to add power and not increase wear? No miracles here either. If you drive vigorously but with some respect for the equipment, you can expect about 90% of normal engine life.

Will the transmission and drivetrain be adversely affected?
Very unlikely. Consider that the drivetrain endures more torque in first gear from the stock engine than almost any turbo can produce in second gear. Occasionally a clutch comes along that won't do the extra duty. Most clutch problems are going to crop up when shifting habits are less than acceptable. Not to worry.

What does it feel like to drive a properly set up turbo car?
A turbo can justifiably be called a torque multiplier: the more boost, the more torque. This situation is analogous to gear ratios. For example, a third gear with a tranny ratio of 1.4 will develop 40% more torque at the rear wheels than a fourth-gear ratio of 1.0. A boost pressure of6 psi will increase torque by about 40% (using an intercooler). Thus you can see that 6 psi boost will produce fourth-gear acceleration virtually equal to a stock automobile's thirdgear capability. Imagine what the proper turbo car will do in second gear! Another reasonable comparison is that a proper turbo car operating at 10 psi boost will do 0-60 in two-thirds the original time; i.e., 6 seconds versus 9 seconds.

__________________________________________________ __________

Q: What plugs should I use? what should I gap them to?
A: NGK BPR7ES plugs are a good standard 'turbo' plug for modest boost and up. They are 2 degrees colder than stock, for 1.5+ bar even colder plugs are recommended. Gap them to 0.6 mm or even less if you still experience a misfire, closing the plug gap can affect combustion efficiency on low/cruise loads, a too small gap is no good either and a stronger ignition system is the remedy.
Always read your plugs to determine if you are in the correct heat range, and a look at the ceramic is always interesting - to check for specks of aluminum from detonation tendencies.

I found some more information about NGK spark plugs, and their related part numbers for heat ranges.


Apparently, the lower the number, the hotter the plug. So that would make a BPR7ES Hotter (not colder) than a BPR8ES. Stock would be BPR5ES, or for the v-power series, ZGR5A. Unfortunately they do not make a ZGR7A or something of the sort.

General thumb of rule, every 75-100 hp added, you take 1 step colder.

Oh and if you also want to know, the BPR-ES plugs are JIS height (53mm), where as our m20's want ISO height (50.5mm), Not that it really matters, but heres some pictures.

We can also use other plugs like iridium plugs (BPR-EIX). I hearsay that you are able to gap the iridium plugs contrary to what some may say, you just have to be extremely careful not to break the fragile center electrode.

Many say its better off to just stick with coppers.

EDIT: Heres the guide for Bosch


Bosch plug heat ranges go backwards compared to NGK.

- blueapplesoda

Q: What head bolts or studs should i use?
A: Studs are highly recommended.

Get ARP head studs from Carr Inustries or VAC Motorsports.

VAC Motorsports only have their internal part number, not the ARP part number. ARP does not list headstuds for the BMW M20 engine at all.

Apparently they make studs for some other engine that are slightly longer than what's required for M20 and VAC just gets them, repackages them and then shortens them. I don't know what engine that is. Some Suzuki Swift GTI uses m10x1.5, but it's not listed in ARP catalogue. I suspect some Honda engines (from ARP catalogue) might be M10x1.5, but i dont know, would be best to confirm with Honda guru.
- mops

Raceware studs is an alternative. http://www.raceware-fasteners.com/

This is to be considered your last alternative:
Metric blue head bolts can be found at http://www.mcmaster.com/
part number 91303a306 (same as 91303a900) $11.86 per pack of 5, (as of 6-18-08) need 3 packs.
class 12.9, 8mm hex socket, blue coated steel m10x1.5mmx150mm, partially threaded, grade 12.9, 176,900 psi tensile strength.

Here is a good thread on what people do for torquing the head down. Many people have had success torquing the head bolts/studs to 80ft-lbs.

Q: Where can I find a turbo manifold for my car?
A: there are multiple options for this, typically, people will either use an adapter, modify a 324td manifold to work, or make their own manifold or manifold adapter.

666 Fabrication makes a stock exhaust manifold adapter and full tubular exhaust (and intake!) manifolds: http://www.666fabrication.com/
Available with different flanges and wastegate options.

The Pro Turbo manifold adapter: http://www.proturbo.fi/
roughly 300-400 dollars depending on the exchange rate..
This is an adapter to the original manifold: (click for pic)
contact Jason Bover (swartz) to order.

Examples of tubular DIY manifolds: (click for pic)

Q: Where can I get an exhaust system from the turbo to the back of the car?
A: No company makes a "turbo" exhaust for the e30, so it must be custom. There are some high flow catalytic converters, resonators and mufflers though, made by companies like Magnaflow. A common size for more than 300 hp is ** diameter. A lot of people like Stainless Steel, but its debatable if it is worth the extra cost. Mandrel bent pipes are essential for the best, smooth system with no bottlenecks, thats where it gets expensive. Luckly the e30 exhaust is fairly straight
- atmh

Q: Is the stock headgasket and head bolts enough?
A: The M20 headgasket goes bad for two reasons when you go FI on it, not including the obvious which is poor tuning:

1. Bad head design.
2. Heat.

BMW decided to have water jacket grooves around the cylinders in the M20 head and this is exactly where the headgasket gives in. The head flexes, especially if the engine is tuned to run hot, as the aluminum gets softer. To help the headgasket stay in place, the head can be reinforced by welding the water jackets, leaving the actual holesa alone (where the water flows). This is a problem with M10 and M30 heads, but was fixed by BMW on the late M30 heads. Pictures of the problem and the solution can be seen here:

Welding the head also solves another issue: Cracks in the head. It is very common that the head cracks when the headgasket gets pushed out as hot gases enter the water and the thermal expansion sky rockets locally.

Head studs or non-stretch heavy duty bolts help a lot and solves the problem for all but the most extreme engines (1+ bar of boost, 400-450 + crank hp). Many of us use the factory headgasket and have had relatively good luck with it as long as the head is bolted down snug with studs or good non-stretching bolts. You can use Permatex copper "spray a gasket" - that can be found at most any local atuo parts store. It makes the gasket surface sticky, helping it adhere to the surface, increases surface tension and helps to prevent gasket "pushing".

Some alternatives to using only the stock head gasket are :
1. MLS headgasket
2. O-rings around the cylinder
3. Copper headgasket (not easy to find)

TCD sells MLS headgaskets for the M20:

Here's a nice article on O-ringing head/block here:

Remember that there is an upside to using the stock headgasket with a welded head - if you have tuning problems or have detonation for some other reason, be glad that you only have to replace the headgasket and not pistons and piston rings, or worse, as the pressure has to go somewhere.

Q: What parts do i use for the turbo oil lines and fittings?
A: you need a male 12mmx 1.5pitch thread and preferrably a 1/8" npt thread on the other side of the fitting for the feed, [it then can be easly adapted to AN or other NPT fittings] if you plan to use the oil pressure switch location. You can run a length of copper gauge tubing if you want to reduce the oil pressure, [1/8th coper pipe] and then run your line off of that restrictor, or you can just run a 1/4 line up to the turbo using barbed fittings and have 60psi at idle and 15psi at warm idle. Lots of drain options. get the biggest drain hose you can make fit properly, and drill and tap a fitting in the oil pan's front passenger side corner. [make shure the oil return is abolve the level of oil in your oil pan.] I used a bulhead fitting with a 90deg elbow pointing up.
- screaming_bmwe30

my fittings : engine block ; female. 12x1.5mm male to 1/8 female adapter, 1/8th npt male female female 3 way t fitting, one side goes to a 1/8th NPT male to 12 X 1.5 female adapter conected to the factory oil pressure sensor. the other side of the T fitting goes to a 1/8 NPT female to AN4 SS line to a an4 to 1/4 pipe adapter to a 1/4 npt 3 way t fitting to the elec. oil pressure sending unit. then 1/8 npt to an 4 to another an4 line to the turbo. an4 to adaper to 1/4 npt to the turbo. oil return is an an8 to a bulkhead an8 fitting drilled into the pan.

since my first go at the oil return, i have revised it. im certan that oil burning issues are related to imporper oil return. on my first setup the return line was sourced into the top front passenger side corner of the oil pan, it was a -8 return line and 90 degree fitting.
this is how my oil return was: http://www.bimmerjim.com/images/MyBM...ttings_008.jpg ....my thoughts... OEM turbo cars dont use oil restrictors to the turbo oil feed.... so this is why i revised my oil return.. moved the return higher on the oil pan. i made it a -10 return instead of an -8. click the links below for pictures. you can see by the slant of the engine that the old location of the oil return was actualy somewhat below the oil level. also, because of the slant of the engine, the oil was forced to go uphill to return to the pan. but because of room constraints, that was the only place i thought that it could go, but with more resources, i was able to put the return well above the oil level.

heres the fittings i used after a fair amount of tial and error:
(1) 6176191 BULKHEAD ADAPTOR NUT, AN10 ea $3.95

(1) 6179064 AN10 Stat-O-Seals pr $4.95

(2) 617310-CUT #10, 9/16" ID, LOW PRESSURE HOSE, CUT-TO-LENGTH EACH FOOT $7.45

(1) 6171011 45┬░ FULL FLOW HOSE END, #10 ea $20.25

(1) 6171004 STRAIGHT FULL FLOW HOSE END, #10 ea $8.95

(1) 6177026 90┬░ AN10 O-RING FITTING ea $29.95
TOTAL = $75.50

with this oil return, i shouldnt need to restrict the oil pressure to the turbo.
- bimmerjim®

The oil feed line is taken from the stock oil press switch located in the right side of the block, near the oil filter, you can attach a "T" fitting in there so you can keep your oil switch and the line to feed the turbo with oil.

In my case is a custom made. Try to keep the oil at 5-9 PSI @ idle in WARM condition and max oil press in the turbo mouth at 25-30 PSI, also in warm. So you can save your seals of the turbo and won't kill it. I added an adjustable key to regulate the press and flow of the oil in the low section. (click for pic)

- diego

Ok there seems to be a lot of inquiry on the oil-line and oil-return setup and where to get the items. So I came up an extensive explanation...if it seems familiar to one particular person's PM reply...then well yeah I'm lazy Mr. Green

The original forum thread to follow along is http://www.e30tech.com/forum/showthread.php?t=22270

The big thing was to get the adapter for socket where the OEM oil-pressure sensor would go. You need a M12x1.5 to 1/8 npt adapter, you can get that from here http://store.yahoo.com/fittingsandad...mettofemp.html

As far as the brass fittings you can get those cheaper and easier from any hardware store.

The 4 AN to 1/8 npt adapter I got from www.atpturbo.com but I'm sure there's plenty of places to get them from.

The steel-braided oil-inlet hoses and the oil-return hoses I got from www.atpturbo.com . For the oil-inlet I got the 36 inch hose, for the oil-return I got it custom length of 22 inch.
Also just as a precaution you should get the oil line restrictor adapter, it's a 1/8 npt adapter with a .06 hole in it. I had to learn the hard way. But just in case you like to learn the same way as me, then you can get a T3 turbo oil-seal kit from http://www.turbochargers.com/store/p...6470a89b3b526c

On the bottom of the turbo is the oil-return adapter which is just a 10 AN adapter for a T3 turbo. You can get those anywhere, I got mine on evilbay.

On the oil pan there's a 10 AN bulkhead adapter that I got from http://www.amstreetrod.com/985008ASR.php4 and the corresponding bulkhead nuts for it http://www.amstreetrod.com/992408ASR.php4
Also don't forget to pick up some aluminum crush washers http://www.amstreetrod.com/177003ASR.php4

Now if you've a equal length manifold and your oil-filter is a little to close to your manifold you can relocate your filter with this http://store.summitracing.com/partde...5&autoview=sku
I also ended up running that through to an oil cooler, recommended if you're boosting http://store.summitracing.com/partde...0&autoview=sku

Anyways, as always...I'll help out any way I can

Q: Can I supply the turbo too much oil pressure?
Here is fact directly from the Holset service manual for the HX35 and HX40 model:
Holset permits oil return pipes to decline at an overall angle of not less than 30 degrees below horizontal. All turbocharger applications require a pipe of internal diameter greater than 19 mm which has integrated connectors. To ensure oil returns into the engine under all operating conditions, the return connection into the engine sump must not be submerged and the outlet flange of the turbocharger must be 50 mm above the maximum oil level of the engine sump pan. Crankcase pressure should be limited ideally to 0.8 kPa (0.12 lbf/in2) but 1.4 kPa (0.20 lbf/in2) can be accepted by reference to Holset.

Oil pressure of 150 kPa (20 lbf/in2) must show at the oil inlet within 3 - 4 seconds of engine firing to prevent damage to turbocharger bearing system. A flexible supply pipe is recommended.

The minimum oil pressure when the engine is on load must be 210 kPa (30 lbf/in2). Maximum permissible operating pressure is 500 kPa (72 lbf/in2) although 600 kPa (88 lbf/in2) is permitted during cold start up. Under idling conditions pressure should not fall below 70 kPa (10 lbf/in2).

Recommended oil flows for the turbochargers are 2 litre/min at idle and 3 litre/min above maximumtorque speed.
Too much oil pressure is never good and may damage and leak past the seals. Keeping the oil pressure low enough will also promote a faster spool, this goes for all hydrodynamic bearing turbos. Many have not a clue about this!

A good general rule is to have a small restriction at the turbo oil inlet of 2-3 mm ID. The feed should always be larger than this, to allow a buffer of oil pressure if you will.
Some turbos have a built-in restriction, most ball-bearing turbos do, but regular oil bearing turbos must be checked!

Q: Does the oil return HAVE to be tapped into the oil pan?
A: Technically... no, it dosent have to be tapped back to the pan. The oil return could be sent to the valve cover, cylinder head, block or pan. The rule is: the oil as to be returned to the engine in a location that is not subject to positive oil pressure. A return to a place that is under oil pressure will want to feed oil back up the return line. Typically, its easiest to gravity feed the oil to the pan because it is usually below the turbo. The valve cover, head, or engine block is usually above the turbo. So if you wanted to return the oil to anywhere above the turbo you would need to have an independant oil sump for the turbo and a pump to pump that oil to any alternate return source. One drawback to warn of returning oil to the side of the block is the oil could run against the rods and crank and cause power loss from windage.

It is important that a gravity return oil line not be obstructed, bent so that oil has to go uphill, or below the level of oil in the pan.

Q: My car is blowing blue smoke now after the turbo install, WHY?
A: It's because of one of four reasons. Bad turbo, too much oil pressure, incorrect oil return to engine from the turbo, or the crank case is not properly ventilated.

Check for excess shaft play in your turbo, if it's normal, make sure your oil return from the turbo is unobstructed and above the level of oil in your pan while the car is resting. Also make sure nothing from the charge pipes is still conected to your valve cover and your valve cover is properly ventilated with a good filter breather.

Often, a proper oil return will allow anyone to run full oil pressure to the turbo unrestricted. Most turbos are originaly designed to be fed with full oil pressure. But it also says in the book "maximum boost" by Corky Bell (the turbo FAQ bible) that turbos only need to be bathed in oil. No actual oil pressure should be excerted on the bearings and bushings of the turbo. A simple gravity feed and gravity return is adequate.

When a turbo cannot remove the oil it is fed, the oil follows the path of least resistance, witch usually is out through the compressor housing and into your intake or out your turbine housing and into your exhaust.

Q: What IS excess shaft play?
A: Holset specifies 0.3-0.5 mm of radial movement as acceptable (measured at the tip of the exhaust/intake wheel) on the HX40. Axial movement should be even less. Any more than those numbers and you're in for a rebuild. If you put one finger on the tip of the intake wheel and move the exhaust tip side to side and back and forth, you should not feel much of that on the intake wheel. On ball bearing turbos the axial play must be even less to be acceptable.

Q: What kind of turbo is suitable for my car ?
A: Really depends on how you want your set-up, the key is finding a turbo that will yield the highest efficency for the boost you plan on running. Generally small turbos spool fast and early, but die up top and are only efficient in low boost range and can be potentially dangerous to push hard due to excessive back pressure forcing exhaust gases back into the cylinders during valve overlap.
The larger the turbine, the greater importance must be put on a well designed manifold as the exhaust pulses must be used efficiently to get as low rpm boost threshold as possible. Divided entry turbines, split pulse manifolds and good boost control are key factors to get the best response out of the system. Once on boost, a large turbine has very quick transient response.

If you intend on making a mean street machine or auto crosser that makes about 215-220 wheel horse, you can use small turbo like a large T3 turbo. A T3 super 60 for example. It will spool early and can provide full boost to redline if your boosting a moderate 0.5 bar. If you would like more of a street strip car that makes about 300 hp, you'll want a medium size turbo like a Garrett GT30, Holset HX35 or Schwitzer S2xx and run about 1 bar of boost. Generally drag only cars have very large turbos and run alot of boost (20-30psi) with anti-lag features through more advanced engine management, (maybe even some nitrous) to make the turbo spool faster.

Looking at the compressor wheel inducer (the smallest diameter inside the intake) is a good indicator of the maximum air flow possible with that turbo. It will usually be most efficient between 1.5-2.0 bar of boost, there are few exceptions to this rule. That means that at lower boost it will not flow as much.

General recommendations on compressor wheel inducer vs max recommended hp:
40-45 mm : 300 hp
45-50 mm : 400 hp
50-55 mm : 475 hp
55-60 mm : 550 hp

Q:I was just looking at different Holsets and I noticed that most of them have split exhaust housings, why?

The diesel truck turbos are all about efficiency, a divided entry will use the pulse energy better than a turbo with a single entry. The theory behind this is that there is a steady train of pulses arriving at the turbine. There are specific cylinders which should be combined to enter in each inlet so that the time delay between any two consecutive pulses is the same. On a 6 cyl inline BMW engine you should route 1+2+3 to one inlet and 4+5+6 to the other. On 4 cyl engines it's 1+4 and 2+3. The same reasoning can be applied to explain why twin turbo setups spool fast, and not only because of their potentially lighter/smaller axles and wheels providing less inertia.

At full load the need for pulse energy is lower, it's more about flow and a lot of the exhaust gas is bypassed through the wastegate anyway. Many "race turbos" are only found with a single entry as they are constantly under load in typical use.

An engine with less cylinders will benefit more from the pulse separation! So it's more important on a 4 cyl than a 6 cyl.

Pretty much 99% of large frame turbos use a divided entry for performance reasons. One can use a larger housing to get less pumping losses from the engine, while retaining the response you'd get from a smaller single entry housing.
A turbine housing designed to take advantage of a split pulse manifold will appear large and spool later with a single entry log type manifold. Money is better spent on stock manifold adapter designed for divided entry turbines.

- iXer

Basically both entries are on a different angle with respect to the turbine. One entry is directed more towards of the outside turbine blades (for quick spool) and the other is directed more towards the inside of the turbine wheel (this works better once turbine is spinning at some rpm). Basically one entry provides more leverage on the turbine blade that other and each is better in some cases, so you essentially get 'best of both worlds'.

Ideally you would want adjustable turbine blades (just like a propeller in an aircraft), because, large angle of attack is better for generating trust when gas speeds are high, while when the gas speeds are low, you want rather shallow angle of attack (lol, thats analysis compared to aircraft prop, but hey.. it's the same principle after all)....

- mops

Q: What type of engine management will suit my application?
A: Theres a bunch of engine management units out there like:

Perfect Power's SMT-6 along with other products.
Apexi AFC

Standalone fuel only management
MegaSquirt (can control spark with mods)

Full standalone engine management
VEMS Genboard

Just to name a few and the most popular ones. to suit you the best its recommended that you research all the available options and choose for yourself which one will work best for you. Most of the time the best option is the ECU with which you can get personal help with from friends who know how to work with the particular ECU, or nearby installers if you have a higher budget.

Q: What size of injectors I need, and should I upgrade my fuel pump?
A: This also depends on how much boost your planning to use and what fuel managament you choose. For 9 - 12psi with a stand-alone fuel management unit i would say injector sizing of around 34lbs or more to be safe. 24lb/hr injectors in conjunction with an FMU are typically the maximum size the factory ECU can deal with. some people have had sucess using 30 lb/hr injectors with some modification to the AFM when using the factory ECU and an FMU.

Some formulas:

500cc per minute is approximately equal to 49lbs per hour which is equal to approximately 100hp.
lbs/hour = cc per minute / 10.2
lbs per hour = HP / 2.04
cc per minute = lbs per hour x 10.2
cc per minute = HP x 5
HP = cc per minute / 5
HP = lbs per hour x 2.04

Here is a realy great link to a very large database of avalable fuel injectors:
-> http://users.erols.com/srweiss/tableifc.htm

Most of the guys upgrade their fuel pumps with Walbro 255 (high pressure - 140 psi max. works good for cars with an FMU) or Walbro 307 (low pressure (50-60 psi, good for standalone managements with large injectors) these fuel pumps can be found pretty easily on ebay or other online retailers.

The best alround alternative if you're on gasoline and looking for up to 500 turbocharged hp is the Bosch 044 in-line or the 040 in-tank pumps. These handle 5 bar fuel pressure very well.

Q: Will my stock clutch hold boost ?
A: Stock clutch should handle quite a beating but it wont last much and it'll start slipping in higher rpms. members have used a Spec III clutch, Centerforce dual friction, or the Clutchnet 6 Puck metalic with good results. a warning: Pucked clutches can be unforgiving. often pucked clutches have a brutal ON or OFF personality. they also chatter while geing engauged slowly, but bite VERY hard and hold alot of power. The stock clutch is good up to 220 whp.
- bimmerjim

This is a dyno graph of what happens when the stock clutch slips.
- matt

I'm using an unsprung 4-puck...and i wanted to make a note at how good the drivability is. It chatters just a bit pulling out of first gear, sometimes....but i drive in traffic everyday...and i've had no problems with it. It's a 110$ (shipped) way to hold a lot more power than stock. So far..under some overboost situations...I'm guessing the disk has held up to about 280whp in short bursts. I think it should hold 300whp pretty easily. Pedal pressure is identical to stock.

- screaming_bmwe30

The clutch disc of choice for many Swedish turbo E30s is the one sold by a company called Dalhems, but these are really US based Kennedy Engineering discs. You can find a 228 mm 4-puck sintered disc for a very decent price shipped to anywhere in the world.

- iXer

Q: What camshaft will work best for my turbocharged E30?
A: There is no universal M20 turbo cam shaft. What cam shafts that work in the engine is determined basically by three things:
- Manifold design
- Turbo charger size
- Pressure (boost and back pressure from the turbo+manifold)

This affects the duration of intake/exhaust valve opening and how much overlap is possible without affecting cylinder scavenging and filling.
Ultimately, the factory cam shaft works very well on a turbocharged car as long as all parameters seem normal, like increasing boost results in the expected power increase. If that is not the case, many things could be wrong:
- Too small turbine (excessive back pressure)
- Intake or exhaust leaks
- Malfunctioning wastegate or boost control

If you're looking for insane power increases, up to 500 crank hp out of what was originally a 170 hp N/A engine, then you better do some research and talk to a cam grinder. You should not expect low-end grunt with a turbo that flows enough for 500 crank hp on a 170 hp N/A engine.

Q:How much should I expect to spend on my turbo setup?
A: that is completely relevant to how much you WANT to spend. a typical MINIMUM cost install can range between 800 to 1400 dollars depending on the builders resources, and mostly all used parts. You can save a ton of money by doing it yourself and fabricating your own parts. On average people spend about 3000 on a turbo setup. At a maximum, the sky is the limit. You could build the motor, the head, gat a big scary ball bearing turbo, a 4000 dollar Motec engine management, etc.... etc.... It's easy to spend alot, and you get what you pay for. If you buy quality new parts, they will last, and you may even save money in the long run.

Q: What parts do i need to make my own turbo kit?
A: These are the bare minimum parts needed to make a turbo system functional. With the bare minimums it would be safe to boost about 5-8 psi.
Turbo Manifold / manifold adapter
Turbo - with internal wastegate
Charge pipes
Rubber conectors
Oil inlet and oultet fittings
Exhaust downpipe

This is the list of the adtional parts that are not needed, but.. highly recommended.
Intercooler (air to air or water to air)
Silicone couplers,
T bolt clamps
Standalone engine management
Large injectors (36 lb/hr +)
Bigger better fuel pump
Monitoring devices and datalogging, the more you know the safer you are.

Q: What needs to be done to the "e" valve springs to handle boost?
A: How well the valves seal have little do to with the boost and more to do with the weight of the valves/retainer, the rpm, valve lift and the steepness of the cam lobes. If you use the stock cam and rev limiter you will be alright, but raise the rev limiter and you may experience valve float. This is why upgraded springs are common with most cam shaft upgrades due to more lift, higher valve accelerations and simply higher rotating speed.

- iXer

Q: What gauges should i use and what are some possible placements for the gauges?
A: The more you know, the better off you are. Gauges I consider mandatory additions for any vehicle that is boosted are:
- Oil pressure gauge (and big warning light!)
- EGT gauge
- Boost/vacuum gauge

If you have any sort of fuel controller or management a wideband O2 (WBO2) sensor is highly recomended, recently a lot of standalone ECUs come with built-in controllers for wideband sensors. It is the most valuable tuning tool!
If your turbo car uses an FMU, I would highly recomend getting a fuel pressure gauge.

The boost/vac, oil pressure and fuel pressure are all pretty much self explanatory, except maybe an explanation of where to place the sensors.

In summary, there should be a short write up (paragraph) on where/what to buy, and where to place them. I would do it, but I don't know enough, I will add what I can, feel free to correct any errors.

Boost/vac sensor should be placed as close to the compressor outlet as possible for precise boost control. Placing it at the inake manifold will allow for more accurate boost pressure readings going into the engine, but makes the boost control a bit more laggy and harder to control.

Oil pressure sensor should be placed immediately before the oil goes into the turbo, it is important to measure this so that the oil seals do not get blown from too much pressure, and to get better response from the turbo (too much pressure is not good).

With exhaust temperature sensors you can expect very different readings between different sensors (speed of temperature change) and their placement. I recommend putting the sensor at most an inch away from the head on the exhaust manifold, at cylinder 6.

Here is a part list from Summit Racing for different oil pressure lines. These use adapters and fittings for -4AN lines and 1/4" NPT fitting for the turbo. This is almost identical to what I am using, though I have my T fitting closer to the turbo, instead of on the block. If you see any problems with this setup, let me know and I will change it. -> means that it converts. ^ means that it is a part of the T mentioned above. You may be able to find better prices elsewhere, but summitracing was easy to find parts from, and they were all in stock. The hose I chose for the prices is 3 feet long, which is plenty, you can order however much you need, just make sure its -4AN female/female.
M = Male F = Female

There are no restrictors in these lines, I have been running turbocharged for 2 years now with no problems.

Part | Part Number | Price

Stock Oil Pressure Sender and Oil Pressure Gauge

12x1.5mm M -> -4AN M | EAR-9919BFGERL | 9.69
-4AN F -> -4AN F Coupler | AER-FBM2914 | 10.25
-4AN M TEE | EAR-982604ERL | 7.50
Outlet 1. 1/8" NPT M ----- Oil Pressure Gauge ^
Outlet 2. -4AN M ^
-4AN F TEE | EAR-982604ERL | 7.50
Outlet 1. -4AN M ^
1a. 1/8" NPT F -> 1/8NPT F | EAR-991001ERL | 2.95
1b. 1/8" NPT F -> 12x1.5mm M | ATM-2277 | 8.95
Outlet 2. -4AN M ^
-4AN F Hose -> -4AN F Hose | NOS-15240NOS | 26.69
-4AN M -> -4AN F 90' Fitting | NOS-17535NOS | 8.99
-4AN M -> 1/4" NPT Fitting | AER-FBM2002 | 2.95
Total: 85.47

Stock Oil Pressure Sender

12x1.5mm M -> -4AN M | EAR-9919BFGERL | 9.69
-4AN F -> -4AN F Coupler | AER-FBM2914 | 10.25
-4AN M TEE | EAR-982604ERL | 7.50
Outlet 1. 1/8" ^
1a. 1/8" NPT F -> 1/8NPT F | EAR-991001ERL | 2.95
1b. 1/8" NPT F -> 12x1.5mm F | ATM-2277 | 8.95
Outlet 2. -4AN M ^
-4AN F Hose -> -4AN F Hose | NOS-15240NOS | 26.69
-4AN M -> -4AN F 90' Fitting | NOS-17535NOS | 8.99
-4AN M -> 1/4" NPT Fitting | AER-FBM2002 | 2.95
Total: 77.97

Oil Pressure Gauge

12x1.5mm M -> -4AN M | EAR-9919BFGERL | 9.69
-4AN F -> -4AN F Coupler | AER-FBM2914 | 10.25
-4AN M TEE | EAR-982604ERL | 7.50
Outlet 1. 1/8" NPT M ----- Oil Pressure Gauge ^
Outlet 2. -4AN M ^
-4AN F Hose -> -4AN F Hose | NOS-15240NOS | 26.69
-4AN M -> -4AN F 90' Fitting | NOS-17535NOS | 8.99
-4AN M -> 1/4" NPT Fitting | AER-FBM2002 | 2.95
Total: 66.07
- matt325is

Here's a pic of diego's EGT source location from the factory cast manifolds. http://www.we-todd-did-racing.com/we...MXk1NDE%3D.jpg

What clutch should i use now that im overpowering my stock clutch?
A: Very common in Sweden is to use the Sachs 'racing' pressure plate for 228 mm flywheels. It's called '618' due to the production number ending in those numbers. It can hold 500 Nm with the stock organic disc and 700+ Nm with a sintered 4-puck disc. Sintered pucks grab hard, so generally use as strong a pressure plate as you need to avoid straining the driveline.

- iXer

Ireland engeneering sell a 6-puck clutch-disc, sprung or unsprung for a very decent price. Check out there prices: www.bmw2002.com
You may need to call to get a price for the sprung clutch disk because i dont think its listed on there site, but i had one for quite some time. I used an OEM pressure plate, and OEM lightened flywheel. I used it for a summer and the pressure plate let a spring go near the end of the season. That caused the clutch to glaze on a couple of disks. This is a great clutch for the money. Grabs very very hard. But, makes drivability difficult. The clutch is very much ON or OFF and is difficult to slip smoothly at a light. Mine chattered at idle and was unpredictible as to when it would activate. Nevertheless, it grabbed hard and never slipped. But - not a very good clutch for a daily. IMO. http://www.bimmerjim.com/images/MyBM...etrain_006.jpg this is how the 6 puck looked right after removing it. notice the spring on the top of the OEM pressure plate sticking out.
Closeups: http://www.bimmerjim.com/images/MyBM...etrain_021.jpg

So, i went to a centerforce dual friction. this clutch is much more expensive, but worth it IMO. this clutch behaves just like a stock clutch except it has a slightly heavier pedal but not nearly as heavy as the 6-puck (go figure). It grabs just as hard between shifts as the 6-puck and driveability is awesome. It made the car fun to drive on the street again.


- Bimmerjim®

I run a spec stage 3 clutch and have honestly had nothing but good luck with it. It is not bad at all on the street and it hooks up like you wouldn't believe.

- iflytii

Q: Where do I put my EGT sensor ?
Depending on the sensor you can use varying insertion depth. I prefer the thin 1.5 mm sensors with about 3-4 mm insertion depth, these are very fast and will react as well and faster than a 3 mm K-type probe in the middle of the exhaust port.

EGT sensor should be placed as close the the exhaust port on the head as possible, placing multiple sensors on various locations on the manifold and exhaust system can allow for very accurate and precise tuning to get the most out of a turbo setup, but that goes beyond the scope of this write up.

A complete stock 325i has 780 ░C @ 6000 rpm...measured directly in the header.

Do not trust an EGT meter alone to tell you what's going on. Always check the ignition plugs for equal coloration and wear! This is hard to attain, some will always run hotter than others due to intake manifold air flow and cooling system design.

- iXer

Q: What effect does exhaust back pressure have?

Any intake boost leaks will directly affect the exhaust back pressure as the turbine has to work a lot harder for even a small boost leak. It is a very good tuning tool to watch EBP, you could say it's a direct indication on how hard the turbine is working. Preferrably this pressure is datalogged and not just monitored on a gauge, depends on your requirements.
Combine this with boost pressure readings and you'll be able to spot when things go wrong. Once the exhaust back pressure starts to rise unexpectedly above the intake boost pressure it's time to be careful, you're at the limit of the compressor or turbine. Check for intake boost leaks, if you have any you will most likely gain a lot of response as well as lowering the exhaust back pressure.

Where you measure is important, preferrably at the turbine inlet, you can use brake line copper tube to carry the pressure signal and use rubber hose when you get away from the hot zone and then connect to a pressure gauge (0 to 5 bar operating range is good).

A healthy pressure ratio is hard to define, with a "stock" cam you can accept a lot of back pressure if you need a fast spool-up and just run rich and safe at the top to have some margin (and loose a lot of power) which is something many seem to prefer, at least in the US.

Up top there are a lot of power to be had by lowering exhaust back pressure to avoid fouling the charge air (less volumetric efficiency and ultimately leading to detonation). Here is why a large turbo both makes more power at the same boost and is a lot safer for the engine. It's not necessarily the power that kills.. It is said that big turbos "eat knock for breakfast", this is why.

I guess even as high as 1:2 pressure ratio is doable on most BMW N/A engines, and even more than that on modern 4 (and 5) valves/cyl engines which don't need as aggressive cams as our favourite M20 engine.

Personally I think that on an 'i' it's a good idea to keep a 1:1 ratio or even better to simplify a lot of things and make the most power. With an efficient setup you can run larger turbines than you think, simply because you can still have a low boost threshold and great response. Consider tubular exhaust manifolds, modern diesel turbochargers, 'power slit' compressor housings, divided entry turbine housings, pulse split (pulse preservation), ..

- iXer

Q: How do I test for intake leaks ?
Put the car in the highest gear to prevent the pressurized air from pushing any pistons down. Try to make sure that the engine is not at TDC to avoid cam overlap on any cylinder, this will be difficult to do the more cylinders you have, with 6 or more you're bound to have some overlap so don't bother with stopping overlap. If you don't mind removing the cam, this will surely prevent any air leaking past the head!
Even if you can't avoid cam overlap, the air will leak through to the exhaust and you won't hear much of that. If you have leaks in the pressure pipes, you can usually hear this clearly. Feel with your hands around hose connections and other places.
If you want to pressure test the exhaust too, unbolt the downpipe and plug the exhaust port on the turbo, that way you're testing everything and don't have to worry about keeping all valves in the engine closed - in fact make sure it's at TDC where you're guarantueed to have overlap.

Use a pressure regulator, only allow 1 bar / 14.5 psi unless you like risking your life (pipes and hoses attacking your head, breaking your arms, etc..).
If you survive the test - all the boost you've gained might take you down instead.

- 89' 325i - gt3582rle, 8 point cage, copper o-ringed stock block, ported and welded head, metric blue's, megasquirt II v3, Coil ign, 52lb inj, mod fuel rail, walbro 255, 1:1 rrfpr, 3" turbo back, 11 lb flywheel, centerforce pressure plate, sprung 6 puck, z3 shifter, line lock.

Last edited by atmh : 09-16-2009 at 12:24 PM. Reason: added info about torquing the head down
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Old 06-15-2008, 06:30 AM   #2
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E30: 89 325i M50 Turbo
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Is there a typo in this part?

Stock Oil Pressure Sender and Oil Pressure Gauge

12x1.5mm M -> -4AN M | EAR-9919BFGERL | 9.69
-4AN F -> -4AN F Coupler | AER-FBM2914 | 10.25
-4AN M TEE | EAR-982604ERL | 7.50
Outlet 1. 1/8" NPT M ----- Oil Pressure Gauge ^
Outlet 2. -4AN M ^
-4AN F TEE | EAR-982604ERL | 7.50
Outlet 1. -4AN M ^
1a. 1/8" NPT F -> 1/8NPT F | EAR-991001ERL | 2.95
1b. 1/8" NPT F -> 12x1.5mm M | ATM-2277 | 8.95
Outlet 2. -4AN M ^
-4AN F Hose -> -4AN F Hose | NOS-15240NOS | 26.69
-4AN M -> -4AN F 90' Fitting | NOS-17535NOS | 8.99
-4AN M -> 1/4" NPT Fitting | AER-FBM2002 | 2.95
Total: 85.47

One is supposed to be male, and the other female, but they both have the same part numbers?
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Old 08-21-2008, 12:30 PM   #3
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Originally Posted by bimmerjim« View Post
How much power can I expect from a turbocharged engine?
Of known dyno runs on piston engines with a variety of turbo systems, the lowest output we have achieved is .052 bhp/cid psi and the highest is .077 bhp/cid psi. The variance is due to the engines' basic designs. To guess at the output of your own engine, choose a logical boost level and multiply each of the two values by both displacement in cubic inches and boost pressure plus 14.7.
Example: A 350 cid engine with 10 psi boost
Lower value = 0.052 x 350 x (10 + 14.7) = 449 bhp
Higher value = 0.077 x 350 x (10 + 14.7) = 666 bhp
based on this,

2.5L = 152.56cid
10psi = 196~290HP (split = 240)
15psi = 235~348HP (split = 289)

twin turbo project

Originally Posted by u3b3rg33k View Post
If you ever sell that car, tell me first. I want to be the first to not be able to afford it.
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Old 10-12-2008, 01:16 AM   #4
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Originally Posted by wiglaf View Post
based on this,

2.5L = 152.56cid
10psi = 196~290HP (split = 240)
15psi = 235~348HP (split = 289)
Isn't that a little underrated or is that right?

I want about 300, and I thought I saw some people getting 300 with lower boost than 15psi.
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Old 10-12-2008, 01:23 AM   #5
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and thank you for the read, I printed it out for good measure.
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Old 10-12-2008, 11:42 AM   #6
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Originally Posted by Aptyp View Post
Isn't that a little underrated or is that right?

I want about 300, and I thought I saw some people getting 300 with lower boost than 15psi.
I think those numbers are very conservative. They follow the old "no replacement for displacement" philosophy. There are many other variables besides displacement and boost. An M50 w/ 15 psi of boost should be able to make nearly 400 rwhp with the right combination of parts and tune.

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Old 11-06-2009, 06:09 PM   #7
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Oil Cooler and Filter Relocation
If you have no stud sticking out of the block for the filter to spin onto and are left with a female thread into the block - it is M20x1.5

If you have a hollow stud sticking out of the block with a male thread - it is 3/4-16

Hope that helps anyone searching to fit a oil cooler and/or filter relocation kit.
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Old 07-12-2010, 04:35 AM   #8
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too much info, thanks for posting this thread
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Old 08-20-2010, 03:14 PM   #9
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This Is awsome info...
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Old 10-07-2010, 02:31 AM   #10
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This thread has been my "night-life" in it's entirety for the past 3 nights. lol.
Love it.

Thank you.
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