ForcedFirebird's m20 dyno thread.

[RobE30]

This thread is great. Thanks to everyone who's contributed. After reading through it, I'm amazed that my engine (284/272) on a stock b25 has held up d/t my severe lack of knowledge with tolerances/clearances. Round 2 is going to be much better.

How many miles should a Schrick 284/272 cam last? I think I'm around 40k, regular oil changes Castrol GTX 20/50

[dvallis]

Hey Varg, that's a good way to look at it. We've got a nice study of HP for M20 turbo stroker builds.

[varg]

Thanks for that, dvallis. It is very rare that someone posts a dyno printout that good. Usually it's one or two runs just to brag about the peak hp number when the comparison is the real value of a dyno in the first place. I had a little fun with your numbers since I don't get to see this kind of comparison with turbo cars too often. Of course it's not gospel, just for comparison, and forcing linearity is only way to easily display what kind of power increase your build is seeing per added psi of boost (the slope of the line).

[dvallis]

It's really well behaved, drivable and fun. I'm getting 5-10 psi boost at partial throttle, so maybe 200-250 HP. At WOT 19 psi the boost comes on like Mike Tyson punching you in the face. Make sure you're pointed in a straight line, hold on and try not to scream like a little girl. :-)

[gnmzl]

That's a curve I'd love to see in any of my cars. How does it drive, did you get a chance to test it?

[dvallis]

Das Beast 2.8L turbo stroker M20

See Build Thread page 1 for specs

BLACK : 6 psi
RED : 10 psi
BLUE: 16 psi
GREEN: 19 psi

[ForcedFirebird]

I'm not sweating it Keith, it's relevant. What did you do for the CPS?

Right on dvallis.

[dvallis]

'Bird this is a great thread. Will be sure to post my dyno run here.

[whodwho]

yes there is only one but i'm against incorporating additional idlers, tensioners into the Vee belt system for the additional cost, points of failure and maintenance.

You threw me on the 'timing belt'. You could run without the tensioner and idler and just use the manual adjusters and would be 100% stock BMW non maintenance parts. it allows to run a newer damper and one that's tuned (if there is any real difference) for the 84mm crank that I am running. I also have a ATI damper for my S54 that I am seeing what I can do for a hub.

it would make more sense on an M30 which needs the extra space

Or a supercharger setup 8^)

(ignore the alternator holding up the SC, that was just to hold it while checking the SC > plenum > throttles alignment)

Only options ATM are using a 24v damper, which is larger in diameter and has the OlT mark at 2 o'clock vs 10 o'clock (easy fix), will require custom CPS bracket and either change to vee belt damper, or serpentine alternator other oprtion is totally a custom /adapted unit.

Sorry for derailing your thread I though it was relevant to your post, I will make a new thread

[digger]

yes there is only one but i'm against incorporating additional idlers, tensioners into the Vee belt system for the additional cost, points of failure and maintenance.

it would make more sense on an M30 which needs the extra space

[whodwho]

one tensioner on the timing belt is more than enough....

I don't understand your statement?? There is only one

[digger]

one tensioner on the timing belt is more than enough....

[whodwho]

Funny timing, here is a recent project that might be relevant 8^)

[digger]

i just want to see which part is rubber and some basic dimensions will probably do if it is cut up a bit

i think i have a solution for the ATI option for the M20 that retains all the pulleys locations with little more than some modified front covers. there are a couple of options i came up with based on ATI's initial work to fit their recommended Inertia ring.
- one option allows the stock OE crank gear (albeit the new version) and 24V 95mm long centre bolt used for a typical stroker which is ideal. will be discussing with them in coming weeks.
- another options a new gear that integrates to the damper but means the big M18 bolt needs to be removed to change the timing belt which is not ideal. this will add a fair bit of cost to the already expensive price so fingers crossed the first option can be taken from concept design to a detail design.

[ForcedFirebird]

any chance you could cut it up and measure the rubber bits and steel so i can model in CAD and do some calculations? you could always send it to me

Not likely as he is about 1300 miles away, but can ask.