Thread: DIY T2560.

Ha ha, that gauge alone will get all four spinning

While the T2560 had great top end, it was slow to arrive (16psi at 2000rpm, 21psi at 3000rpm) and the hole off idle with no boost was starting to annoy me. It couldn't spool fast enough to burn clean on acceleration either, leaving some black smoke in the gap between the boost compenstor opening at around 7psi and the turbo needing 15psi to burn clean.

So I swapped the turbine housing yesterday, removing the 0.64 A/R turbine housing and fitting a 0.49 A/R. So the turbo is now the hot end from a CA18DET bluebird T25 and the cold side from an RB26DETT T28.

Initial impressions are excellent. Off idle it's only a fraction slower to build boost than the T25, I have around 19psi on tap at 2000rpm with around 8psi boost at 2000rpm/100km/h cruise. It hit 22psi at higher rpm.

I've got to finish my provent install before I test it out further.

Another update

With the new intake pipe: http://www.aulro.com/afvb/isuzu-land...take-pipe.html
I am now running 24psi max, have 20psi at 2000rpm and around 8psi at 100km/h cruise. EGT's at cruise are around 400-420C where they used to be 430-450C.

I get the feeling the exhaust side is choking with this much boost and the wastegate clamped shut, power is dropping around 3000rpm. I plan to hook up my exhaust drive pressure gauge again and see just where the pressure is at. I've added a pressure tap in the downpipe too.

Still running a 2 1/4" exhaust.

Interesing.....is there a max figure you would be looking for when measuring drive pressure ? Would you have any details on what instruments you have used to measure drive pressure? i would have like to compare the choking that the gt2052 caused compared to the tb28 etc etc

With high load and low rpm (2000rpm ish) you should see drive pressure below boost. The drive pressure will increase from here as rpm rises. At lower loads about 1.5 times boost, hard acceleration up to 2x boost.

If you are seeing 3-4 times boost, then you've got a bad restriction somewhere or your turbo is way to small.
I was using a section of copper line from the manifold to get away from the hot bits, then into rubber tubing to the cab. I use a cheap pressure guage with about 60psi capability. Most boost gauges don't go high enough, an oil pressure gauge should be okay. I also put a shot of grease up the line to cut out gauge chatter.

My old copper line (supercheap auto pressure gauge line) came apart at the join, I need to replace it with some 1/8" copper tube.

Thanks dougal...so the length of the tubing drops the temp enough not to cause any damage to the guage im asuming ? interesting about the shot of grease trick actually!

Oh and in regards to the adaptor plate we discussed i found that T3 flange which is what i ordered for the flange on my new turbo fits straight onto the manifold even though i was under the impression they were a t25 flange....i must have misunderstood info in my investigations.

There is no flow through a pressure gauge line, so you only need to worry about heat conducting along it. The gauge end is cold, it's just the tubing you need to worry about.

The later style compact manifold is T3 pattern, the only T25 pattern is the top-mount garret manifold that is quite rare. I have an IHI pattern which isn't quite T25, I slotted the holes in the turbo housing to make it fit.

auh thanks
so i would probably need to use say 1.5-2m of copper tubing surely that wouldnt conduct a dangerous amount of heat that far would it? i would think the heat would disipate quite quickly.

oh i see well i was happy to see it fit to the manifold but unfortunately i still had to get my friend to hydro cut a spacer plate to space turbo away from manifold to stop compressor housing touching the manifold