Thread: 4BD1T Turbo Sizing and Performance Prediction.

Originally Posted by Dougal

Compound turbos.

Ah. Of course, I should have known that, there's been a lot of chatter on here about them lately. Think that might be a bit of a struggle to fit that kind of package in a Td5 engine bay, but I should do some reading up on them.


Resume normal transmission....

Well dougal I turned the fuel down (out 2 turns), wound the boost back (2 turns), its smoother to drive now, but hit 4th up hill and it runs out of steam. So after I get it registered I will turn it all up a little at a time until I get it right.

Forgot, boosting to around 20psi now

Well after taking mine camping this weekend, I am very very disappointed with it towing, definitely no better than the amarok.
Towing the camper it struggled on hills, egt's got to 728max, mainly around 650, boost got to 27psi, would feel like it would lose power after 18psi, was a tad Smokey but not rediculous.

Cruising on flat road at 100, egt was 450ish, 10-14psi boost.

So need a little help with tuning this thing!

Originally Posted by Vern

Well after taking mine camping this weekend, I am very very disappointed with it towing, definitely no better than the amarok.
Towing the camper it struggled on hills, egt's got to 728max, mainly around 650, boost got to 27psi, would feel like it would lose power after 18psi, was a tad Smokey but not rediculous.

Cruising on flat road at 100, egt was 450ish, 10-14psi boost.

So need a little help with tuning this thing!

So what weight are you towing, what altitude and what rpm?

Losing power at higher boost suggests your intercooler might not be keeping up. At 20psi and 3000rpm you need to shed up to 18kw of heat through the intercooler to keep intake temps around 40C.
But do you also have a restriction gauge on your air cleaner to show how much vacuum it is sucking against?

Towing about 900kg, close to sea level, mainly at cruising rpm in higher gears, hits a slight incline and starts dropping back, put the boot in and doesn't get any better, drop back a gear and get the revs up is a bit better, but starts dropping off again. is OK in 1,2&3 when taking off, seams to be when under load

Originally Posted by Dougal

So what weight are you towing, what altitude and what rpm?

Losing power at higher boost suggests your intercooler might not be keeping up. At 20psi and 3000rpm you need to shed up to 18kw of heat through the intercooler to keep intake temps around 40C.
But do you also have a restriction gauge on your air cleaner to show how much vacuum it is sucking against?

What tune do you have on yours dougal, as I wonder if yours struggles like this, in particular with no inter cooler?
If I back it off to 22psi, turn the fuel screw in a bit and see how that is, may do all my tuning with the camper on though as that will be the cars main purpose.

Forgot to say, it got hot coming up one hill, back to 3rd, doing 60 (can easily do over 80in my work van towing on same hill), plenty of smoke, cooled straight off and was fine after that
Also struggles to keep up with mates zd30 patrol and 1hdfte 100 series towing the same campers