1.45 bar too much?

[IMR-Merlin]

We are seeing good AFR readings with 80# injectors throughout the range. Is 1.45 bar too high for cylinder pressure in these old sleds?

[turbo owner]

Fuel quality could be an issue, what will you be using for fuel? Quality of the build as well.

1.4 is a lot, not recommended as far as I'm concerned.

[IMR-Merlin]

93 octane pump gas. AFR's are good, plenty of duty cycle left in injectors, EGT's are withing range and zero detonation.

[T77911S]

just curious, when does the intake valve close. head studs? case work? timing? dual plug?

the 935's and other turbo cars ran 1.45bar. but of course you are talking about the best parts and lots of machine work on the case. i also think they ran lower compression

[turbo owner]

Originally Posted by IMR-Merlin

93 octane pump gas. AFR's are good, plenty of duty cycle left in injectors, EGT's are withing range and zero detonation.

So far so good.

Did you use high quality head studs?

Aluminum is soft but the studs do screw in pretty deep, did you install helicoils or case savers? It could cause pulled head studs if doing it a lot and that's bad news.

[IMR-Merlin]

Twin plug, 964 cams but unsure of timing.
Others unknown.

[GJF]

I've ran 2 bar on stock nikasils. If your turbo is only efficient to 1.2 or 1.4 then don't exceed the threshold. More boost past a given turbo's map will only add excessive heat to the charge even though boost numbers are up. More boost does not always mean more HP. When your timing is too advanced at the upper mid range then the heads can lift. The reason why fire rings are useless. Regardless, if you do lift a head you simply back off timing at that point and proceed. If you have CE rings it's a different story. If your lean with any method of sealing it could be a different story. But as long as you are at AFR's of 11.5 on boost and no detonation, your good. And just to be clear for others........ this is for aftermarket EFI twin plugged engines, NOT CIS.

[IMR-Merlin]

Internals are untouched from PO who was running undersized injectors with 22degree advance and 1.0 bar spring (1.1) actual. With baseline time we had some knock up high and pulled 5degeee of time off the top. Cured bing but also ran out of injector.

So if the car held fine with previous tune. Detonation brings cyl pressures WAY up. Or thought is. Under better management and no knock. Pressures should be lower.

Originally Posted by turbo owner

So far so good.

Did you use high quality head studs?

Aluminum is soft but the studs do screw in pretty deep, did you install helicoils or case savers? It could cause pulled head studs if doing it a lot and that's bad news.

[IMR-Merlin]

Originally Posted by GJF

I've ran 2 bar on stock nikasils. If your turbo is only efficient to 1.2 or 1.4 then don't exceed the threshold. More boost past a given turbo's map will only add excessive heat to the charge even though boost numbers are up. More boost does not always mean more HP. When your timing is too advanced at the upper mid range then the heads can lift. The reason why fire rings are useless. Regardless, if you do lift a head you simply back off timing at that point and proceed. If you have CE rings it's a different story. If your lean with any method of sealing it could be a different story. But as long as you are at AFR's of 11.5 on boost and no detonation, your good. And just to be clear for others........ this is for aftermarket EFI twin plugged engines, NOT CIS.

Thanks. I always assume people know it's twin plugged EFI and I am using an EBCS to control boost!

[lite75]

Watch the intake charge temps, after some hard pulls on a dyno they will increase fast. Move alot of air through the intercooler.
What RPM are you making peak torque at?

[JohnJL]

COuld I ask for your ignition map?

[IMR-Merlin]

Hitting peak around 4k

[lite75]

Nice!

[IMR-Merlin]

Originally Posted by JohnJL

COuld I ask for your ignition map?

On my mobile app. But I can post later

[IMR-Merlin]

Originally Posted by lite75

Nice!

Forgot to add. We are allowing g some time between pulls to let the engine temps and IC to keep up. No insurance pulls for sure.

[IMR-Merlin]

Wish we had E85 up here!

[kenikh]

Originally Posted by lite75

Watch the intake charge temps, after some hard pulls on a dyno they will increase fast. Move alot of air through the intercooler.
What RPM are you making peak torque at?

Water mister

[IMR-Merlin]

Scaling it back a little. Looks like we will settle around 1.25 for reliability and longevity.

Should have a solid 400/400 at the wheels.

[xbmwguy]

Merlin what static fuel pressure are you running? My base pressure is 50#s with e-85 and 110 lb injectors. I run 1.4-1.5 regularly in the cooler months and am at 1.2 in the warmer(Africa hot) summer here still waiting on jerry to invite me up to check out the slant from hell and swap tuning ideas 😜

[IMR-Merlin]

static 50# climbs up to 70# under boost with 60# injectors.

Settled on running 1.25-1.3 bar and the ARF is 11.5 +/-.3 from 4000-7000 with the injectors hitting about 65-70% duty cycle.

timing is pulled back a little and we pulled an honest 400/400 on my buddies dyno that is a total "heartbreaker" for the usual dynojet numbers.

Originally Posted by xbmwguy

Merlin what static fuel pressure are you running? My base pressure is 50#s with e-85 and 110 lb injectors. I run 1.4-1.5 regularly in the cooler months and am at 1.2 in the warmer(Africa hot) summer here still waiting on jerry to invite me up to check out the slant from hell and swap tuning ideas 😜