[astr]

I'm finally getting my '89 4BD1T back together. My plan is to run it in the Isuzu NPR truck for a while to get some experience with it before pulling it to swap into an FJ62 Landcruiser. I have three turbos that I can install: 1) the original setup which is a non-wastegated, watercooled housing turbo in a non intercooled configuration 2) An older turbo, also from a 4BD1T but has a wastegate but no watercooled housing, also in a non-intercooled configuration, 3) a turbo from a 4BD2T which appears to be exactly the same as 1) except that the turbo outlet is rotated to line up with the intercooler plumbing. I also have the intercooler.

I'm leaning towards 3) but was wondering if there would be any real advantage to using the older turbo with the wastegate. With a little work (breaking loose the rust), it also could be reconfigured to line up with the intercooler plumbing.

Any input would be appreciated.

 

[Dougal]

I've got an excellent idea.
How about you try both of them and tell us how they compare back to back?bounce

I also own both (IHI-RHB6 and T25 without wastegate which fits the angled T3 manifold), but have no plans to run that particular T25 as it'll sit too close to the bonnet (hood) in my truck.
I have run a wastegated T25 (and will again shortly) which has the same compressor as the 4BD2 type turbo. It pumped air around 20 deg C cooler than the IHI at 15psi (120degc, 140 deg C) and boosted just a fraction later.

 

[astr]

Sounds like a good idea! Since I won't have access to a dyno, what would you suggest be a good way to compare the two, other than gut feel?

 

[Dougal]

Sounds like a good idea! Since I won't have access to a dyno, what would you suggest be a good way to compare the two, other than gut feel?

Find a hill suitable and run the truck up it with each. Start at the same speed at the bottom and see what it gets to at a set point up the top. That's what I do anyway.

Have you got a boost gauge? The minimum rpm needed to get say 5psi boost is another good benchmark.

 

[astr]

I have a boost gauge, plan to get an EGT gauge and will try to rig up a tach. I also will measure air temp, pre and post turbo. No hills in the immediate area and, since the truck is not licensed or insured, I'm limited to driving it on a 1/4 mile of private road adjacent to the shop. It wil be interesting running time trials on the 1/4 mile with an NPR truck!