2.8 td boost pressure?

[Tomato]

Hello guys, i want to ask how big pressure i can set on my 4M40 engine...
I made some experiments and i raise my pressure to 1,5 bar, and my head or head gasket gone...
I dont know if it is caused because of raising pressure...but i dont know
To everybody, every raising of pressure was done together with raising of fuel amount...

[Pauly]

1.5 bar(21psi) is miles to high for the 4m40. I used to run 14psi which is about 1ish bar and that was probably too high. Ended off dropping it back to 12psi(0.82 Bar) and upped the fueling slightly and its been happy ever since. I did a full rebuild and made a custom 3" turbo dump pipe and fitted 3" straight through exhaust. Totally different car

[Goodsy]

That boost with the compression ratio over 20:1 you are really pushing it!
I'm running a peak boost of 22psi with a compression ratio on 17 to 1.
It settles fast to 6-14 psi.

[Goodsy]

1.5 bar(21psi) is miles to high for the 4m40. I used to run 14psi which is about 1ish bar and that was probably too high. Ended off dropping it back to 12psi(0.82 Bar) and upped the fueling slightly and its been happy ever since. I did a full rebuild and made a custom 3" turbo dump pipe and fitted 3" straight through exhaust. Totally different car

Agree there. 10-12 psi would be safeish.....

[pajeroman3lt]

My NJ has been at 15psi for 6 months now and is running great.

[Pauly]

But Goodsy you're running a 4m41 which is designed to run at those pressures. Even if we lower the compression ration the old 4m40 are not very good on cylinder heads so adding pressure is just asking for trouble.

I agree you can run them at 14-15 PSI for a long time and there are no adverse side effects in the short term but what about in 1 or 2 years time? After spending over $4k on a rebuild(and that's with me doing everything except the machining) I'm not really keen to see how far it can be pushed.

Just be careful. Up to 15psi is probably safe and do-able in the old 4m40's but beyond that you're really asking for some problems

[Goodsy]

I thought I said that. I'm running a higher boost because of the lower compression rato of 17:1
The 2.8's have a compression ratio of over 20:1 meaning a lower boost is safe.

[schnitzel]

My 4m40t In the delica has been running 15 psi since I bought it 7 years ago. Previous owner had fuel adjusted as well.

[Pauly]

Didn't mean for it to sound like that goodsy. Was more referring to the fact even if we dropped our compression ratio to match what your 4m41 runs I dont think our heads could take the pressure

[Betz]

Having done a head I am a bit terrified to seek more power out of my 2.8

My plan is;

Boost & EGR gauges in place (for reference values)
Delica ecu mod + tune (not sure what items needed for this yet)
Bigger or second IC & port match intake
Extrude Hone & port match exhaust manifold
Hybrid turbo, dump & 3" system


Before I do any of the above I'm going to get another car to get to work so I can pay for all the failures

[Goodsy]

Didn't mean for it to sound like that goodsy. Was more referring to the fact even if we dropped our compression ratio to match what your 4m41 runs I dont think our heads could take the pressure

Got you now. All good.

[Jonos]

My plan is;

Delica ecu mod + tune (not sure what items needed for this yet)

Would love to know more info on this mod? did a quick google search and could not seem to bring any info up on it.