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Old 11-05-2007, 03:05 PM   #1
mulishaflesh969
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Default the M20 stroker FAQ's

Alright. I have researched all that my eyes could take for the past week. and i see alot of wish-wash back and forth statements. One person says this can be done, another says no, this has to be done. As a somewhat new member, and only being in the e30 scene for almost a year, i have gotten my hands dirty, and i am well rounded with majority of the work. But as well as a majority of the others out there in the e30 world, we all want straight out answers to our questions about a m20 stroker. This includes anything from a basic stroker job, to a all out, $10K job (if its ever been completed, another rumor).

Like my questions:

1. Pistons - What pistons does one need? some say i could use 'I' pistons, others say use SETA pistons, and most of the people say use custom pistons... but some of us don't have pockets to pay 800 bucks minimum for some pistons that are just 1mm overbore.

2. crank - eta? s50? 524td? which one is it and what performance gains does it supply?

3. Bore - Another riff raff statement. i read that you could just slap a head on, and it does the job. others say ore the cylinders out to 86mm +/-. But this goes back to the pistons statement. what advantage does a bigger bore actually give someone? better compression? more hp? more top end power?

4. rockers - Some say at high rpm's stock m20 rockers will snap and break... is this fact or opinion? Some say if you use a stiffer valve spring, which wont cause lift as much, which in turn saves a rocker.

5. Port & polish - Good to be done, or have to be done? i know the advantages help better airflow in and out, but can a stroker survive without it?

6. Head gasket - Which one could we use? I, e, or would it have to be custom to fit an overbore?

7. AFM - 325i, 535i, or 533i?

8. fuel injectors - 325i's, 535's, or 323's? are all of these same flow rates? same amount of flow to keep up with typical stroker HP?

9. Throttle body - Which one is best to use for this motor setup? a 325i (which i thought is the same a 325e's), or a bigger throttle body?

10. camshaft - I heard you could use a 325i's camshaft... but what are the advantages of using a camshaft with a higher number? would it benefit the motor any if someone was to spend the extra cash up front for a better cam?

11. Head bolt's - "If your car has the older style hex head bolts, replace them with the torx because the hex bolts do not expand at high temperatures" if im correct, doesn't metal, in any was shape or form, expand at higher temperatures?

12. Throttle position switch - I was told you could use a 325i's TPS, but what other options are there? from a e36?

13. Oxygen sensor - If we already have one installed, whats the point on getting another? we would be running the same fuel (if not a higher octane an example: 91)... why would we need another?

14. Ignition wire set - Should this be a upgraded over stock item? or could the wire set off a 325i do the trick?

15. Brake booster - I thought we were building a motor here, not a brake system... why should we get another brake booster?

16. 3.73 limited slip - what actual, proven, graphed advantages does a 3.73 give? i have a 2.92, and a 3.XX from my eta that i might weld... would a 2.92 do the job as well, or was i fucked by the big green weenie?

17. Exhaust manifold - Shouldn't someone put actual headers on this motor? i mean, i would think the stock manifolds hold back some pressure, and therefor lack some power gains, correct? a nice cheap set of IE's should free up some power, if im correct. . . correct?

18. Stand alone - Mega squirt, or is there another type that does more/ as much as MS and with the same outcome?

19. Turbo - Is this setup turbo friendly? if i was to wake up one morning and throw on a setup, will this motor shit out, or keep up?

20. Fuel pressure regulator - Does one need one? what should it be? AFPR?

21. Fuel pump - Can a stock fuel pump keep up with the motor? i wouldn't want to starve the motor of fuel, therefor lacking power. would a upgraded fuel pump be necessary? and what should it be?

22. IE Oil Pan windage tray/baffle - Someone suggested this, but no evidence that it performs as thought... is it another personal preference? what advantages would it give?

23. Clutch/flywheel - Should one upgrade their clutch/flywheel while they are at it? would a oem stand up to the challenge? i know i like to do a burnout or two already, and clutch slip will be a bitch, so upgrade, or not upgrade?

Overall, how much power would someone really get from a build like this? if its a full rebuild, or if its just slapping parts together, what numbers should we expect?

I'm simply taking all the information im finding all over the www and putting it all together, and it still doesn't come out clear. like the eta crank, people say is strong enough to be shot, but people say its only good up to 6000 rpms. if my rev limiter will be 7500 +/-, i want something that can withstand the extra 1500 +/-. as well as the limited slip. is it fact, or personal opinion? please don't post a link that leads someone to another page or forum that has no information on what were looking for.

Im not planning on making a macho kick everyones ass motor in my garage. im going to do what i have to do to get it done by the end of the year/winter to go out and eat some people in the spring (i have my eyes set on a select few e36's, 240's, and some other built e30's, not to forget v6 domestics with v8 exhaust setups muahaha). I understand that this will cost money and time, but im not looking to spend more than the car is worth (sentimental value included, of course).

Everyones ideas are suggested to be commented. this includes the .02's to the $5.98's. I hope this will help alot of people out, and i hope it will get enough views and information, to make another sticky for a simple DIY.

*** If someone has a dyno sheet, or something along the lines of proof of what a stroker setup your running has done and can do, please post. give as much info about what setup your running as well (ie: cams, crank, head, bore, pistons, ect.)
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Old 11-05-2007, 05:23 PM   #2
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what is your budget? If you can't spend $$$ on pistons I'd suggest buying an m20 Seta motor and calling it quits.

The reason why there are so many opinions out there is because there are about 30 different combinations of "stroker motors" and for every combination there are 30-50 people (educated or not) who want to weigh in their opinion.

They say on the internet that 86mm is the largest bore you can go, they say on the internet that rockers break over 7krpm, they say lots of things on the internet...

post up your budget and choose a crank then let the rest fall into place.

Stroker threads should be started (I'm a culprit of this too) by saying 'eta stroker', m5x stroker, s5x stroker, etc. not by saying 2.7L stroker because I can get to 2.7L with a stock I motor by boring it out...

how much can u spend and what crank do you want to run? start there.
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Old 11-05-2007, 05:32 PM   #3
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that's right. how much $$$ you are prepared to spend and what are your power/reliability/drivability goals ?
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Old 11-05-2007, 07:04 PM   #4
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I have both a eta, and a i motor. i just dont know what the advantages of everything are. thats what im trying to get to. people have used different parts, why? thats the question.

Why use a s50 crank over a eta crank? why bore it out to 2 over, than one over?

Power wise, i want some low end torque, and top end power. more rpm's to work with, and better numbers. not to drag race, but if i felt like punching it to kick a honda's ass, it could.

Realibility wise, i want it to start when i start it. i want it to operate as a functional motor. not get 500 miles here, replace parts, 200 here, replace more parts. a constant functional engine. treated the same as any other motor.

Drivablity goal wise, like i said, can eat a honda for lunch, but has enough power to respect. i dont want it to kill tires all week long, but i do want it to have enough power to throw around when i go out and slide (this 4k rpm band is killin me).

I have read the strictly eta site a few times, and it seems like he paid too much for not enough. i dont want to spend 2 grand for something a chipped 325i can beat. I want my money to actually go towards real power.

I know its possible, im just wondering the best configuration to go with. and id like to see proof. its the he said she said i saw he saw bullshit that doesnt to justice.
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Old 11-05-2007, 07:08 PM   #5
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I dont want to use anything that would require large amount of money or time to do. like if a s50 crank doesnt drop n play, its outta the picture.
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Old 11-05-2007, 07:08 PM   #6
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We could make this a really good FAQ to end the discussions.. How about it?
The questions asked above could simply be answered as is, in detail.
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Old 11-05-2007, 07:36 PM   #7
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please do. its what im wanting.
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Old 11-05-2007, 08:25 PM   #8
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Speed costs money - how fast do you want to go?

+1234 - would be an excellent FAQ.

Eta crank is cheap and easy to get... back in the day it was the only crank (before the m/s5x cranks were built). They used those because it was all they had. Most guys go the least common denominator route - ie. they take the cheapest (least expensive) parts that are known to produce the largest displacement motor and build a motor. Differences in bore are this - do you want a 2.7, 2.8 or 2.9L? Or 2.9, 3.0, 3.1, or 3.2L? The stock bore is 84mm... if you add stroke AND bore you get more displacement.

Why is a question you need to answer yourself. Very few guys (or girls) spend the cash to fully build a motor because it is not needed. If you are going to build eveything, crank, rods, pistons, valves, rockers, cam, machine work, etc. you are building a race motor. This is the age old problem that no one wants to realize. It can be done and it has been done - just by professionals who have built full race motors but people start chasing power and talk talk talk...

I would put forth that a Stroker FAQ would be created based on experiences and budgets... sort of a compilation of builds since no single build is the same.

If not go to the MM website and read up! I'm about $1,800 into my build and all I've done is get a crank, prepped rods and an intake manifold. It'll be an 80mm crank x 87mm bore with ~10.5:1 compression... Should be fun about $2,500 later...
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Old 11-05-2007, 11:09 PM   #9
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i am willing to help with a stroker faq just not on a forum where i have to read alot at a time. like now i am tried and about to go to sleep. tomorrow i may review what the questions are and answer the ones i can.
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Old 11-06-2007, 04:57 AM   #10
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Here are my opinions on a NA m20 stroker

Quote:
Originally Posted by mulishaflesh969 View Post
1. Pistons - What pistons does one need? some say i could use 'I' pistons, others say use SETA pistons, and most of the people say use custom pistons... but some of us don't have pockets to pay 800 bucks minimum for some pistons that are just 1mm overbore.
I Pistons: - with ETA 81mm crank, ETA 130mm rods, and I “885” (885=325i head) head gives low CR (~8:1) ideal for FI, not so for NA. One of the so called “budget strokers”

I Pistons: - with M52 (e36 328i) 84mm crank, ETA 130mm rods, 885 head skimmed ~0.5mm = CR ~9.5 quite reasonable CR.

E Pistons: with ETA 81mm crank ETA 130mm rods and I “731” head no change in CR, (731 323i heads are rare in US and not as good as 325i 885 head).

Custom pistons: almost whatever rods, whatever crank you like, whatever CR you like and allow oversized bores.

Quote:
Originally Posted by mulishaflesh969 View Post
2. crank - eta? s50? 524td? which one is it and what performance gains does it supply?
ETA = cast 81mm TD = forged 81mm drop straight in.
M52 = forged 84mm, requires simple sleeve for oil seal, perhaps a machined intermediate shaft.
S50 = forged 86mm, requires custom pistons, sleeve for oil seal, a machined intermediate shaft some rods may not clear block.
S52/M54 = forged 89.6mm, requires custom pistons, sleeve for oil seal, a machined intermediate shaft, some rods may not clear block.

ETA crank will be fine on a budget or medium build upto 7k rpm any more than this and you should have gone with a bigger crank to begin with as you need lots of $$$ to make power after 7k rpm and a bigger crank has no real downsides when $$$ aren’t much of an issue.

The bigger the better on these cars however the 86 and 89.6mm will require custom pistons $$$ and the 84, 86 and 89.6mm a little more effort to make things work with clearances etc.

Quote:
Originally Posted by mulishaflesh969 View Post
3. Bore - Another riff raff statement. i read that you could just slap a head on, and it does the job. others say ore the cylinders out to 86mm +/-. But this goes back to the pistons statement. what advantage does a bigger bore actually give someone? better compression? more hp? more top end power?
Bigger bore = more swept capacity or displacement = more power and torque. This needs custom pistons so 86mm (+2) works well with STD gasket. Bigger bore could also allow unshrouding of oversize intake valves.

Quote:
Originally Posted by mulishaflesh969 View Post
4. rockers - Some say at high rpm's stock m20 rockers will snap and break... is this fact or opinion? Some say if you use a stiffer valve spring, which wont cause lift as much, which in turn saves a rocker.
Safe enough for upto 7k especially if new, the worst thing is sustained high rpms and old age……..for improved life you can have them inspected, peened and polished then next level is billet rockers. Stiffer springs prevent float which is bad (the float is bad preventing it is good) but going too stiff puts more load on them as do high lift cams.

Quote:
Originally Posted by mulishaflesh969 View Post
5. Port & polish - Good to be done, or have to be done? i know the advantages help better airflow in and out, but can a stroker survive without it?
Good to have done especially with a stroker but not essential if $$$ are tight.

Quote:
Originally Posted by mulishaflesh969 View Post
6. Head gasket - Which one could we use? I, e, or would it have to be custom to fit an overbore?
I and E are the same but std is good for 86mm, this may depend on which pistons you use. eg MM 86mm Wiseco pistons use std Goetze head gasket. The bore size is not equal to the piston diameter at the crown because clearance is measure using the diameter of the piston the pin boss height which is more than at the piston crown plus ther are chamfers.

Quote:
Originally Posted by mulishaflesh969 View Post
7. AFM - 325i, 535i, or 533i?
If your going to remap the chip with emulator or have the means to adjust the AFR use 535i AFM otherwise on a budget stroker with generic 2.7 chip use m20 AFM. You can also try M30 AFM with bugger injectors but it does not always produce good results.
For better results use a piggyback and MAF or MS/standalone which use MAP sensor or Alpha N

Quote:
Originally Posted by mulishaflesh969 View Post
8. fuel injectors - 325i's, 535's, or 323's? are all of these same flow rates? same amount of flow to keep up with typical stroker HP?
e36 325i injectors (17lb?) should do a 2.7, 535i injectors (19lb?) should do most others but a good stroker 3L may need a bit more so 21-24lb will do the job with ease.

Quote:
Originally Posted by mulishaflesh969 View Post
9. Throttle body - Which one is best to use for this motor setup? a 325i (which i thought is the same a 325e's), or a bigger throttle body?
the 325i is the best of the std ones, BBTB are available aswell for the slight bit extra performance.

Quote:
Originally Posted by mulishaflesh969 View Post
10. camshaft - I heard you could use a 325i's camshaft... but what are the advantages of using a camshaft with a higher number? would it benefit the motor any if someone was to spend the extra cash up front for a better cam?
Cams are very important and deserve a separate thread.

The 325i cam will make a lot of low end and midrange torque but fade at top end and probably requires <10:1 CR to run without ignition retard. On a hotter cam you can use more CR and get more top end but may lose some low end depending on how wild you go. Usually a 270-280degree is reasonable…anymore than this requires some thought as to the type of power band you want (track car or streetcar). The cam you use also has to match the CR. The last thing you want to do is over cam your m20.

Quote:
Originally Posted by mulishaflesh969 View Post
11. Head bolt's - "If your car has the older style hex head bolts, replace them with the torx because the hex bolts do not expand at high temperatures" if im correct, doesn't metal, in any was shape or form, expand at higher temperatures?
Replace hex ones with torx which are torque to yield so you can use once only. Other options are studs from ARP or racetep, MM head bolts (special for m20) or metric blue’s which seem to be nothing more than a Grade12.9 socket head bolt which are cheap as chips.

Quote:
Originally Posted by mulishaflesh969 View Post
12. Throttle position switch - I was told you could use a 325i's TPS, but what other options are there? from a e36?
depends on the ECU, but use the std throttle switch if using motronic its perfectly fine. With standalone there are others you could adapt to the TB.

Quote:
Originally Posted by mulishaflesh969 View Post
13. Oxygen sensor - If we already have one installed what’s the point on getting another? we would be running the same fuel (if not a higher octane an example: 91)... why would we need another?
std one is fine unless you want to do some live tuning (need a fuel controller, piggyback or standalone like MS) which requires a faster reacting and more accurate wideband O2 to do the job.

Quote:
Originally Posted by mulishaflesh969 View Post
14. Ignition wire set - Should this be a upgraded over stock item? or could the wire set off a 325i do the trick?
any set in good condition designed for the engine are fine.

Quote:
Originally Posted by mulishaflesh969 View Post
15. Brake booster - I thought we were building a motor here, not a brake system... why should we get another brake booster?
applicable when doing a motor swap or custom intake manifold.

Quote:
Originally Posted by mulishaflesh969 View Post
16. 3.73 limited slip - what actual, proven, graphed advantages does a 3.73 give? i have a 2.92, and a 3.XX from my eta that i might weld... would a 2.92 do the job as well, or was i fucked by the big green weenie?
LSD is a must unless you like doing burn outs.
A 3.73 will have the engine spinning faster at any speed over a 2.x or higher than 3.73 which gives more torque to the wheels = more acceleration.
Disadvantages are extra revs = extra friction = more fuel and more noise and more shifting.

Quote:
Originally Posted by mulishaflesh969 View Post
17. Exhaust manifold - Shouldn't someone put actual headers on this motor? i mean, i would think the stock manifolds hold back some pressure, and therefor lack some power gains, correct? a nice cheap set of IE's should free up some power, if im correct. . . correct?
a good long tube set is worth the money for midrange and top end gains. BTB, RD, Alpina, Hartge and Bavauto are some that are proven. These are tuned not simply long pretty pipes welded together.

Quote:
Originally Posted by mulishaflesh969 View Post
18. Stand alone - Mega squirt, or is there another type that does more/ as much as MS and with the same outcome?
could use Motec, Haltech, Autronic, Wolf, Microtech…….the list goes and all will do enough to run a m20 but are more $$$ than MS. If you aren’t DIY goto a tuner and see what he recommends and perahps use that. There are also piggybacks such as unichip, SMT etc

Quote:
Originally Posted by mulishaflesh969 View Post
19. Turbo - Is this setup turbo friendly? if i was to wake up one morning and throw on a setup, will this motor shit out, or keep up?
ETA crank, ETA rods and 325i head are turbo friendly only in that it has a low CR and the cam is suitable for turbo.

Quote:
Originally Posted by mulishaflesh969 View Post
20. Fuel pressure regulator - Does one need one? what should it be? AFPR?
use standard 3b reg

Quote:
Originally Posted by mulishaflesh969 View Post
21. Fuel pump - Can a stock fuel pump keep up with the motor? i wouldn't want to starve the motor of fuel, therefor lacking power. would a upgraded fuel pump be necessary? and what should it be?
Fine for NA. low boost

Quote:
Originally Posted by mulishaflesh969 View Post
22. IE Oil Pan windage tray/baffle - Someone suggested this, but no evidence that it performs as thought... is it another personal preference? what advantages would it give?
only thing here is if you track the car to prevent oil starvation a baffle can be added. Crank scrapers and windage trays aren’t worth it IMO

Quote:
Originally Posted by mulishaflesh969 View Post
23. Clutch/flywheel - Should one upgrade their clutch/flywheel while they are at it? would a oem stand up to the challenge? i know i like to do a burnout or two already, and clutch slip will be a bitch, so upgrade, or not upgrade?
lighter flywheel is nice (not too light though) and you would want a uprated clutch by the sound of it

Quote:
Originally Posted by mulishaflesh969 View Post
Overall, how much power would someone really get from a build like this? if its a full rebuild, or if its just slapping parts together, what numbers should we expect?
180-280hp depending on budget and the type of power delivery you wnat

Last edited by digger : 10-27-2012 at 02:06 PM.
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