Thread: Max. EGT and probe position

Hi Murray,

I now have wound my fuelling back as it is MORE than adequate with a max of 550/600 degrees, turbo intake is the way to go as this ensures accuracy. Downstream in the dump pipe can be 150 to 250 degrees difference depending on losses across turbine/ housing efficiency etc. I was at 650 to 700 for a while, made for some great acceleration with the autobox behind the Isuzu, but after 3 trans breakages and a change to manual, these fuel settings were silly, I now get plenty of torque and 11 to 14 l/100km consumption at the lower settings.

Anyway, a Defender/ County shape is different enough for some different cruise figures to mine, so I would just be experimenting with your installation. Definately mount the probe upstream though.

JC

That is the spec for the turbo's max egt. I know my engine has been living at 750C max for about 20 months now.

Apparently those IHI RHB6's are good for a pressure ratio of 2.8, that's 26psi at sealevel.
Anyone want mine? Only problem is it needs a new compressor wheel.

Originally Posted by justinc

Hi Murray,

I now have wound my fuelling back as it is MORE than adequate with a max of 550/600 degrees, turbo intake is the way to go as this ensures accuracy. Downstream in the dump pipe can be 150 to 250 degrees difference depending on losses across turbine/ housing efficiency etc. I was at 650 to 700 for a while, made for some great acceleration with the autobox behind the Isuzu, but after 3 trans breakages and a change to manual, these fuel settings were silly, I now get plenty of torque and 11 to 14 l/100km consumption at the lower settings.

Anyway, a Defender/ County shape is different enough for some different cruise figures to mine, so I would just be experimenting with your installation. Definately mount the probe upstream though.

JC

G'day JC,
Yeah, I've got my probe pre turbo. 660 degrees is commonly the highest temp I reach.....more if I deliberately load it up a lot. I don't think I'll be tempted to tweak the fuel and boost any more. I'd like this engine to last a long time. Your fuel consumption figures are the same as I can get from mine too.

Cheers, Murray

Originally Posted by Dougal

That is the spec for the turbo's max egt. I know my engine has been living at 750C max for about 20 months now.

Apparently those IHI RHB6's are good for a pressure ratio of 2.8, that's 26psi at sealevel.
Anyone want mine? Only problem is it needs a new compressor wheel.

Are the IHI's a good turbo ? Can you get parts for them ? I'll be fitting a turbo to my 120 when I do it up. I've limited my search for a turbo to a GT25 because I'm not really up with what other turbos suit the Isuzu.

Murray

Originally Posted by rijidij

Are the IHI's a good turbo ? Can you get parts for them ? I'll be fitting a turbo to my 120 when I do it up. I've limited my search for a turbo to a GT25 because I'm not really up with what other turbos suit the Isuzu.

Murray

Yes they are good turbos, but I had problems getting parts for mine. Since the perenties seem to use them they should be easy to get in Aussie.

GT25's are a solid choice and the easiest to get parts for.

From memory the IHI model fitted to 4BD1T motors was RHB5. Small a/r Garret T3s and T25s were also fitted. IHI turbos are fitted to some subaru models. IHI's seem to be at least as robust as Garrett I understand. My impression was that Garrett was more aimed at performance and IHI turbos were more often applied to industrial/commercial applications. Fitting IHI to subaru WRX's does not really fit the industrial label.

From looking at this option it seemed there was possibly two flange types for IHI's.

I went with Garrett as the flange type was much more common. Also, I found a t25 Isuzu manifold.

At the time I was looking for a turbo on a budget, Garrett T25's or small A/R T3's were the go.

I sourced a cheap T3 manifold, so was looking for suitable T3's.

I found the following cars that were fitted with the same spec'd T3 Garrett (turbo A/R 0.48, intake A/R 0.42):

- Pre 98 Saab 900's and 9000's (900's were oil cooled, 9000's some were oil, some both oil and water),
- Late 80's/early 90's Volvos (these mainly came with a split T3 flange)
- Mercedes 300TD and 350TD made between '88 and '95 (W124's) (not many in Aus, but quite a few in the US)

Of course, if I had more money to play with, I would have just bought one of the (wastegated) turbo's that was factory fitted to 4BD1-T's

Originally Posted by rar110

From memory the IHI model fitted to 4BD1T motors was RHB5. Small a/r Garret T3s and T25s were also fitted. IHI turbos are fitted to some subaru models. IHI's seem to be at least as robust as Garrett I understand. My impression was that Garrett was more aimed at performance and IHI turbos were more often applied to industrial/commercial applications. Fitting IHI to subaru WRX's does not really fit the industrial label.

From looking at this option it seemed there was possibly two flange types for IHI's.

I went with Garrett as the flange type was much more common. Also, I found a t25 Isuzu manifold.

No, the IHI fitted to the 4BD1T's is a RHB6, bigger frame than the RHB5/RHF5 series which are fitted to subarus and other small petrol and diesel japanese engiens.
The RHB6 was fitted to virtually nothing else, hence the parts shortage. There was only one flange option.

Later there were three garrett turbos. A high mount T25 which fits the manifold you have, then two other T25 variants which fit the later style side mount manifold with a T3 mounting flange.
The early side mount turbo was non-wastegated and arrived around 1988. Turnbine A/R is 0.89.
The later side mount turbo is wastegated and has a smaller turbine A/R of about 0.67
All these T25's use the same compressor wheel and 0.48 A/R cover.

I have photos of all of them, I have the RHB6 and non wastegated T25 in my parts bin.