Thread: Reclaiming factory boost level

Originally Posted by rijidij

Yeah, with the shortened rod the waste gate opens when it should now.
It's the original factory turbo, but I don't know the specs.

Your turbo appears to be the rare wastegated T25 with the T3 flange. Same compressor as the T25 I'm running (mine from a nissan CA18DET bluebird) but a larger exhaust turbine.

I just got back from a few days in the Vic High Country around Dargo. The mountain roads up there confirmed that tuning your diesel is really worth it. I am very happy with the performance, on and off road.
The only down side is, there's so much torque that I'm getting a bit of clutch slip (new turbo p-plate) in 3rd and 4th in certain conditions under heavy acceleration and heavy load, up hill on the road usually.
Off road though, no problem. In fact I was even more happy with performance. We climbed Randal's Track off Crooked River Road mostly in 3rd low with what seemed to be a good reserve of extra power/torque.

Murray

So tweaking the fuel and the extra turbo boost was worth it. How did the pyro temp go. Any noticeable increase? .......Brian

there is a bit of a trick you can do with your pressure reference line to your wastegate, if you put a longer hose in there (eg 2-3m coiled up so its not messy) the turbo will come up to full boost slightly quicker than if it was just connected via the shorter hose, the same thing can be achieved with a reservoir eg 1L metal bottle of some kind with two nipples in it, you put it inline with the wastegate

the theory behind it is it takes slightly longer for the wastegate to see the inital rise pressure and hence it stays closed until it reaches its mechanically determined level, therefore more exhaust pressure goes to driving the impeller, this process eliminates what is called 'wastegate creep'. it is common in internally wastegated turbo's

dont get me wrong its not a HUGE difference but it is definately noticeable

i have used this technique when in my younger sillier days i used to own a vl turbo, that had a t3 turbo with an internal wastegate similar to yours (the wastegate i mean)

if you want more boost, i can tell you about a bleeder valve setup to 'fool' the wastegate in a way, ill post details if anyone is interested, it is alot less permanent and easier than shortening the rod to try boost levels above standard

Originally Posted by Bearman

So tweaking the fuel and the extra turbo boost was worth it. How did the pyro temp go. Any noticeable increase? .......Brian

No big difference in pyro temps from when I first tested the new setup. I was pulling a fairly heavy camper trailer. On the way home I deliberately loaded the engine up on some decent hills. The highest temp I acheived was approx. 660*c. This was in mild to cool air.
It hit 700* very briefly the other day just after I left home (no trailer), but once everything's up to operating temp I don't seem to be able to push past 660*.
I haven't tried it in really hot conditions yet. I'll keep you informed.

Murray

With 15psi, a decent intercooler and just touching EGT's of 700 you must be close to my power levels.
I'm running 20psi with no intercooler and EGT's that can get way too high if not watched.
I use a section of viaduct to determine power and torque output, because I know the slope, speed and engine weight I can get a pretty good figure on it. Using that I put my torque output at around 520Nm on a good cold day. Less on a warm one.

That's enough to light up tyres on dry tarmac in second gear and damp tarmac in third, my clutch still isn't slipping. I'm using the original Isuzu pressure plate (dating from 85/86 I think) with a clutch plate that's about 10,000km old.