M20 Stroker FAQ for newbs such as myself?

[digger]

everyone always talks about 8k M20s, but I've never heard of one.. really, how long would a motor like that last? 24 hours of run time? :p

it would never we worth revving to 8k as it wouldn't make any power unless it was a 2.0L m20, the other bigger capacity m20's would make power much earlier in the rpm range and it would be a pointless and expensive exercise going to 8k.

the cast rockers will never handle 8k all day long no matter what you do as its still cast, you need billet rockers to achieve this and it would be more economical aswell with the billet ones

[Andreas]

i dunno really.. i just think its cool to rev that high i guess. just one of those meaningless goals.

Well said man. For some reason I also have that "meaningless" goal for my 3.1 liter M20 stroker. I've already purchased billet rocker arms, 304 deg Schrick and ITBs.

I also own a E46 M3 CSL and can tell you that it is no earth shaking experience to rev to 8,000 rpm and I hardly ever do it even though max power is somewhere at 7,900 rpm and it does pull all the way.

I suppose one just wants to rev the M20 because others say that you cannot. You will probably hardly ever rev that high to avoid frequent engine rebuilds but on the rare occassions you can show off if you want to.

[moatilliatta]

yeah, and i also though it would sound pretty bad ass to hear that engine rev up that high while tearing it down the track... but it it would be pointless if there is no power up there....

[MrK]

If you want to make power around 8k rpm, you'll have to remove the main choke-point that makes revving that high pointless: The stock intake manifold. With ITBs I don't see any reason why a useable 8k rpm wouldn't be possible.

[digger]

If you want to make power around 8k rpm, you'll have to remove the main choke-point that makes revving that high pointless: The stock intake manifold. With ITBs I don't see any reason why a useable 8k rpm wouldn't be possible.

a 2.8 M20 with 288 + ITB peaks at 7000rpm so even 8k is worthless. As i said on a 2L it is achievable to rev to 8k and still make power

[Andreas]

a 2.8 M20 with 288 + ITB peaks at 7000rpm so even 8k is worthless. As i said on a 2L it is achievable to rev to 8k and still make power

Probably anything above 7,500 rpm is useless, even with a 300+ deg cam and ITBs, due to the 2 valves per cylinder and the ports on the head. I suppose one also has to start questioning the timing belt at those rpm - will it strip its teeth or jump a few teeth when it possibly oscillates too much.

Do you have info / pics on that 2.8 you're referring to, or is that your car ?

[digger]

Probably anything above 7,500 rpm is useless, even with a 300+ deg cam and ITBs, due to the 2 valves per cylinder and the ports on the head. I suppose one also has to start questioning the timing belt at those rpm - will it strip its teeth or jump a few teeth when it possibly oscillates too much.

Do you have info / pics on that 2.8 you're referring to, or is that your car ?

player6's car from e30zone, a member here aswell. Car was also featured in total bmw feb 06 issue.

http://www.r3vlimited.com/board/showthread.php?t=71055

http://www.e30zone.net/modules.php?name=Forums&file=viewtopic&t=27412&start=0

[digger]

I suppose one also has to start questioning the timing belt at those rpm - will it strip its teeth or jump a few teeth when it possibly oscillates too much.

i think you'd atleast be changing it at smaller intervals or you could get non interferance pistons

[Andreas]

Thanks for the links digger.

One would also have to open a high-revving engine on a more regular basis to replace all the bearings.

[winstontj]

MM's posted HP figures

what exactly don't you agree with and what have you based that on?

I've seen a few MM m10's that have been dyno'd right out of the box at 20whp lower than promised. Also the math involved to calculate rod ration isn't that hard. Some of the early m10 strokers they put out were really bad. I don't have figures in front of me but I'm sure you can find them if you do a little reasearch (if you want to). I don't like bad mouthing anyone but you have to notice that when guys like IE put up statements saying they no longer post HP ratings because they feel their competitors grossly overstate their HP ratings it gets obvious after a little while - only one company really boasts HP numbers for their motors.

[digger]

I've seen a few MM m10's that have been dyno'd right out of the box at 20whp lower than promised. Also the math involved to calculate rod ration isn't that hard. Some of the early m10 strokers they put out were really bad. I don't have figures in front of me but I'm sure you can find them if you do a little reasearch (if you want to). I don't like bad mouthing anyone but you have to notice that when guys like IE put up statements saying they no longer post HP ratings because they feel their competitors grossly overstate their HP ratings it gets obvious after a little while - only one company really boasts HP numbers for their motors.

i doubt MM ever quoted rwhp to begin with so saying it was lower by 20whp says nothing about the engine itself dyno's can be off (up or down) by this amount easily.

Korman also give hp numbers ( SO THAT MAKES TWO) for their m20 strokers and the numbers are inline with what MM claim and both these companies are probably more reputable than IE. They also actually sell engines not just kits so they are entilled to give hp numbers and would actually know the rael hp, but a stoker kit byitself from IE adds nothing until all the other bits and pieces are included such the head/cam is properly rebild and all the bearings and clearances are pproprelty speced these can make or break an engines performance so thats propbably the real reason why IE don't add a hp number when marketing their products.

What do you expect a MM 3200 240hp rally engine to make at the wheels?

[winstontj]

What do you expect a MM 3200 240hp rally engine to make at the wheels?

I would expect a ~15% loss in the drivetrain (maybe less in a properly prepped car) so if 240@ flywheel that would be 204whp if my math is right.

We are all entitled to our own opinions - My opinion is to look for the shop that actually uses (races with) the product you are looking for. I'm not going to start badmouthing any shop (more than I already have) because it's not smart or productive. I simply have my convictions and believe what I believe based on information I have.

The e30 world is new to me but you guys seem to be against IE and for shops that don't seem to race the stuff they sell. Maybe I'm wrong again here too... Dunno... Just trying to figure things out so I can build a decent motor.