M20 dyno results (knock limited)

[zaq123]

Just dyno'd this 2.9L 10:1 with Schrick 284/272, ITBs and completely original AMC head with Supertech valves and OEM springs/rockers. This engine is knock limited for whatever reason on 93 octane (98 ron).
Timing table is the max it wanted to handle without knock. I know AMC head isn't ideal. But my freshly rebuilt 885 had a crack and I just wanted to enjoy this car already hence was like F' IT and bolted AMC head to it. Have new 885 and maybe will drop it off to be machined and bolt it over the winter.
What's your thoughts on this timing and dyno?

[digger]

I’d be looking at the cam timing with adjustable cam gear as a couple of members either here or old e30tech forum found a bunch retarding the cam . The cylinder head is definitely not ideal and likely restricting things somewhat.

[DesertBMW]

first why even waste all that time and money on M20 just to have the same power as bone stock M52B28? It is well known that M20 has poor chamber design, that is why the engine stock comes with 9.3:1 compression ratio, and then even with that it will knock on hot day.
If your project is limited with knock with 93 octane. I would try some 117vp racing fuel, just to see what can your engine do with that.

[zaq123]

I’d be looking at the cam timing with adjustable cam gear as a couple of members either here or old e30tech forum found a bunch retarding the cam . The cylinder head is definitely not ideal and likely restricting things somewhat.

cam was set to Schrik Spec with adj. cam gear, 4deg. retarded.

[zaq123]

first why even waste all that time and money on M20 just to have the same power as bone stock M52B28? It is well known that M20 has poor chamber design, that is why the engine stock comes with 9.3:1 compression ratio, and then even with that it will knock on hot day.
If your project is limited with knock with 93 octane. I would try some 117vp racing fuel, just to see what can your engine do with that.

M52B28 is 193HP. This Dyno is more on par with N52B30, 231HP (196WHP with ~15% loss for the drivetrain). 60HP gain from stock M20B25( about 35% jump) is not exactly WAR chip kind of mod.

[AWDBOB]

This is too funny- I've known KP since like 2008 lol. He sent me a pic of your car on the dyno!

Jak Stoll in Louisville had issues with his AMC head. The chambers were smaller than a genuine 885 and they varied by up to 4cc due to poor machining.

Cinnabar325is owns Mission Motorwerks in Bechtelsville and might be able to get the head right

[88Sedan]

Results are not bad. I wonder if there would be more area under the curve w/slightly less duration on the cam. With the amc head on it might be more optimized since max head flow would be less than an 885. 200 whp sounds fun though.

[MrBurgundy]

first why even waste all that time and money on M20 just to have the same power as bone stock M52B28? It is well known that M20 has poor chamber design, that is why the engine stock comes with 9.3:1 compression ratio, and then even with that it will knock on hot day.
If your project is limited with knock with 93 octane. I would try some 117vp racing fuel, just to see what can your engine do with that.

lol people who come in just shit on other people are truly insufferable.

first, this m20 is making more horsepower than a stock m52.

secondly, m20s sound way better

third, its the original or at least, period correct motor.

24v swapped cars are played out and nothing exciting, especially a m52 swap.

an almost 200whp m20 is fucking cool.

[digger]

cam was set to Schrik Spec with adj. cam gear, 4deg. retarded.

the power numbers are pretty good.

If you are confident the cam is dialed in to spec then it’s likely the head that’s holding you back a bit. The un modified amc is rough on the chamber and ports. I seem to recall it flows like 15cfm less than the 885 bmw casting and the shape is rubbish but I don’t know where I saw that. I haven’t cc the stock amc but as above the variation in cc seems plausible

What was piston to head clearance ?

[zaq123]

This is too funny- I've known KP since like 2008 lol. He sent me a pic of your car on the dyno!

Jak Stoll in Louisville had issues with his AMC head. The chambers were smaller than a genuine 885 and they varied by up to 4cc due to poor machining.

Cinnabar325is owns Mission Motorwerks in Bechtelsville and might be able to get the head right

haha, this is awesome. Karl was like "what is Alpina?" . Unfortunately my 885 head was machined, 3 angle valve job done all that but was never pressure tested by the shop before all that work. It had a small bubbling invisible crack in the usual spot. I sourced new (to me) 885 head ready to go but was itching to drive this car this summer hence AMC on it now. Pressure tested new 885 head myself and it's ready to go. Unfortunately machine shop lead times are months, KP dyno appointment took me a month from when I booked it as well. So I had it road tuned and had KP to fine tune it for me. Once this winter is here, thinking about swapping the head but for now, it's what it is I guess and there is definitely plenty of power to have fun with it.

[zaq123]

the power numbers are pretty good.

If you are confident the cam is dialed in to spec then it’s likely the head that’s holding you back a bit. The un modified amc is rough on the chamber and ports. I seem to recall it flows like 15cfm less than the 885 bmw casting and the shape is rubbish but I don’t know where I saw that. I haven’t cc the stock amc but as above the variation in cc seems plausible

What was piston to head clearance ?

just over 0.9 mm smallest clearance to just over 1mm largest (measured different from cyl to cyl). I'm not sure what those small dips are near peak on the dyno, tuner din't mention it nor I've seen his log. Wonder if it's knock threshold he set in Haltech he set pulled the timing away.