best m20 stroker combination.

[ForcedFirebird]

Just starting to research this for my own build. My eta came with the “i” head, header, and a few other bits to do the swap. I thought I read you could get pretty close to 200hp just putting the head/header on without tearing the motor apart. Realistically how much hp am I looking at without racing pistons & rods & all that?

maybe 155whp....

all of those setups above have much higher compression than yours.

Closer to 140

I did this years ago and hit the dyno (ignore the 200tq number, that was a fluke with the ignition pick up)...





Since then we played around with various combinations, most ever made was 145whp/170tq, stock eta bottom end with 885 head/cam, open headers, eta intake manifold and 325i throttle. Great for TQ, but a stock m20b25 is still more powerful.

[ForcedFirebird]

If you are looking close to 200 you will need atleast a 2.8l or a 2.7 with ITBS.

Im running 524td crank, CP pistons, 86mm bore, 135mm Eagle H-BeamRods, BimmerHeads cam and racesprings and 19lb injectors with stock intake, stock AFM, no head porting and ebay headers.

[IMG][/IMG]

This a little before and after for kicks and giggles. This was a few days after the build was done. I had it re-dynoed at it makes closer to 198hp and 215ftlbs. You can see where the intake definitely limits the power in the upper RPMS.

How much compression? We just did a budget stroker using eta crank/rods stock b25 pistons (~9.7:1), block shaved 2mm, stock cam and it made 180/178 at the wheels. Also no porting, just a good valve job...

[digger]

Closer to 140

[2mAn]

maybe 155whp....

all of those setups above have much higher compression than yours.

[cornchip]

Just starting to research this for my own build. My eta came with the “i” head, header, and a few other bits to do the swap. I thought I read you could get pretty close to 200hp just putting the head/header on without tearing the motor apart. Realistically how much hp am I looking at without racing pistons & rods & all that?

[CamE30]

yep stock ECU, stock AFM, no head porting, stock throttle body.

[cavpilot]

If you are looking close to 200 you will need atleast a 2.8l or a 2.7 with ITBS.

Im running 524td crank, CP pistons, 86mm bore, 135mm Eagle H-BeamRods, BimmerHeads cam and racesprings and 19lb injectors with stock intake, stock AFM, no head porting and ebay headers.

So, these numbers are with a stock ECU?

[CamE30]

Already in the works, cant wait to see how it will respond. The ITBS just showed up today.

[digger]

Time for RHD, ported head, MS pnp etc....

[CamE30]

If you are looking close to 200 you will need atleast a 2.8l or a 2.7 with ITBS.

Im running 524td crank, CP pistons, 86mm bore, 135mm Eagle H-BeamRods, BimmerHeads cam and racesprings and 19lb injectors with stock intake, stock AFM, no head porting and ebay headers.

[IMG][/IMG]

This a little before and after for kicks and giggles. This was a few days after the build was done. I had it re-dynoed at it makes closer to 198hp and 215ftlbs. You can see where the intake definitely limits the power in the upper RPMS.

[ClassiE30]

Just did a nice stroker build for a customer.

2.7 Eta Crank
S50 135mm Rods
Metric Mechanic Pistons
Metric Mechanic Prepped cylinder head with Race/Rally Cam
Bav Auto style Headers
Stock Intake 19lb injectors
WAR Chip/MAF

With dyno tuning we pulled 197hp to the rear wheels.

Damn! Thats what Im looking for. Are you SoCal local?

Sent from my Note5

[digger]

this is a 1 5/8" header on a stock B25 still works pretty good though doesn't mean the same design in a 1 3/8" or 1 1/2" wouldbnt be be better

http://www.e30zone.net/e30zonewiki/images/6/62/Btb12.jpg

pipemax recommends 1 3/8" incase anyone was curious for a decent 2.7L

[digger]

as for not needing a tuned set of headers i think that is not true ive never seen any M20 make respectable numbers without a good header it doesn't just bump up hp more so the midrange power (torque).

[digger]

A S50 crank and bigger bore places significantly more demand on the head and if you use a 272 cam you aren’t increasing the flow capacity enough to compensate. I think you will be lucky to make 200whp with a 272 on a 3L it’s going to peak too low. It would have good midrange though.

[SkiFree]

I agree with your methodology and theory, however the real world results aren't quite so concise. What I'm telling you is based from the results of a dyno-comparo did between long tube 1.5 vs 1 3/8 primaries (on a mildly modified M20). Yes, the 1 3/8" pipes didn't lose power, but they did not gain near as much as the 1.5's. And while its convenient to say, I simply don't have the slightest clue where that graph is anymore. Rather not argue on a message board.

I'm sure if the OP called MM where his pistons cam from, they'd tell him something similar.