Thread: turbo vs gas injection in 3.9 isuzu!

FWIW I have a GT2560 (water cooled ball bearing T28) on my 4BD1 fitted to top mount Isuzu manifold, cost $1200 for the turbo. No lag, spools up quickly. It has the same diameter turbine as T25 and same compressor diameter as T3. It has an exhaust AR of about .64. This turbo and the T3 were recommended by the specialist that fitted my setup. I was looking at a few turbo options including the T25, T3 (with small exhaust AR), IHI RHB5, Mitsubishi TDO516G. However, I stuck with Garrett as the Isuzu manifold I had suited a T2 flange. I was happy to go with a larger turbo as I was told it would suit intercooling if I wanted to do that down the track. The dyno done before and after indicates the setup resulted in a lot more power and torque. The wastegate is set at 12psi.

The oil is fed from the same point on the block as the alternator. The coolant is fed from the block. The oil drains to the cover on top of the oil pump and the water to the thermostat housing. There are a few hoses running from the wastegate to the turbo and air feed pipe that I don't understand. The compressor faces out with a 90 deg bend, matching in with a steel pipe that travels around the back of the motor under the air cleaner to the intake. It has a backup pressure release valve that prevents boost exceeding 25psi. It has a custom made 3" dump pipe that is much the same as factory. The 3" exhaust travels down between the engine mount and the starter motor and travels down the inside of the chassis rails to a Lukey mufler then finishes in the same spot as the original exhaust. The exhaust uses the v8 mount points on the chassis.

The T25 from Nissan 180SX with CA18DETT has an exhaust AR of about .48 from memory. As Dougal says these come up for sale pretty frequently ranging from about $150 to $350. Quite a few recommended this turbo when I was doing research.

Originally Posted by rar110

The T25 from Nissan 180SX with CA18DETT has an exhaust AR of about .48 from memory. As Dougal says these come up for sale pretty frequently ranging from about $150 to $350. Quite a few recommended this turbo when I was doing research.

I think 0.47 A/R on the turbine side and the exhaust wheel is a few mm smaller than your one as well.
The T25 is a very fast spooling turbo, but I expect your one would provide a bit more top end. The old T25 is fine for up to 15psi, beyond that the T28 (now GT2560 that you have) is a better choice for a single turbo.

I'm whipping my T25 quite hard with 20psi boost, running it outside the limits garrett intended. It hasn't died yet but I don't recommend other people boost that high.
I also left the coolant water lines unhooked on mine. IMO they're a legacy of this turbo being fitted to many petrol engines and aren't necessary on a diesel.

Bilby

If I change over turbos I'll still need all my feeder and drane lines, I may ditch the manifold and make my own. So I'm really only looking at getting rid of the turbo, and manifold maybe. I did set up mine from scratch however, so if it's Pt no's for all the req parts to change over for the turbo your after, then I should be able to help you out.

Cheers

Originally Posted by Larns

Hay Dougal, where is the easiest place to pick up a T25? New and cheap, I've been quoted around 12-1400 bare. And is the T25 got a water cooled housing?
For those out there I might be selling my factory turbo kit.

Cheers

pm sent

Originally Posted by long stroke

Hi
I'm shore you have discussed this many times before but just need to know which one you would go for out of a turbo or gas injection!
which one ends up cheaper!
which one would give more power and fuel efficiency!
and which makes it run smoother.

CHEERS
REGARDS
TIM.....

gas will be cheaper due to government rebate, engine will run smoother and EGT wont change, turbo will increase power but use more fuel, the way to go is turbo it then gas it!