Query on setting up turbo on NA 4BD1

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Originally Posted by The Mutt

Where is the best spot to hook up a boost gauge?

I'm putting the EGT probe into the exhaust today, and am looking at getting a boost gauge next.

Glenn

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The outlet of the compressor housing if it is already tapped, tap a hole in the inlet manifold, or anywhere in between (perhaps weld a socket in crossover pipe).

At the manifold will give a little higher reading than at the compressor, because of pressure drop - pressure drop is greater if you have an intercooler.

But anywhere mentioned above will indicate how the turbo is boosting. The main advantage in measuring boost at the manifold is that it will let you know if anything has happened inside the hoses between compressor and manifold.

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Originally Posted by rijidij

Yep, it is wastegated. 9psi is the max it goes to. I have'nt touched the turbo except for spinning the compressor housing around.

What are you referring to with these figures......
If I want to fit a turbo to my 120 NA, is there a particular model I should look out for, eg T25, T28 etc etc and I presume each model comes in differing specs ?

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The A/R describes the geometry of the scroll housing. Turbos like the T28 came in a variety of configurations, from ones made to boost to higher pressures and lower flows (those fitted to the twin turbo skylines) to ones made to flow more air at lower boost pressures.
The A/R ratios on the compressor cover can be used to identify which one you've got.

But besides that, a given family of turbos (say T25 family) can have an assortment of different sized turbine housings (different A/R ratio) for different applications. Smaller builds boost at lower revs but chokes of a little higher end power. Bigger loses the low end but provides less restriction at the high end for more power.

But you can only use it to compare if you've got exactly the same wheel sizes inside. Otherwise it gets complicated.

There are a whole range of turbos that'll work on the 4BD1's depending on your goals. I'm using a T25 with a turbine A/R of 0.49 which is as small as you can really go.
It builds boost really early, I can have 17psi at 1500rpm.
The biggest I'd want to go is the T28 which Isuzurover has fitted with the 0.86 A/R turbine housing.

In between we have T25's with a 0.64 A/R, T28's with a 0.64 A/R and a lot of other options (T3's, IHI turbos, MHI turbos, Schwitzer etc).
I like the T25/T28 series because they have a high degree of interchange and they are dirt cheap to rebuild. There is also big support for them through the ricer crowd.

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Originally Posted by Dougal

I'm using a T25 with a turbine A/R of 0.49 which is as small as you can really go. It builds boost really early, I can have 17psi at 1500rpm.

I like the T25/T28 series because they have a high degree of interchange and they are dirt cheap to rebuild.

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I like the idea of building boost earlier in the rev range of an engine not known for high revs, so I should look for a T25 A/R 0.49 or similar.

Can you buy rebuild kits for them, and is rebuilding straight forward to do yourself, or should you get them rebuilt by a turbo specialist ?

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Originally Posted by rijidij

I like the idea of building boost earlier in the rev range of an engine not known for high revs, so I should look for a T25 A/R 0.49 or similar.

Can you buy rebuild kits for them, and is rebuilding straight forward to do yourself, or should you get them rebuilt by a turbo specialist ?

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My T25 is from a Nissan bluebird with the CA18DET engine. Shouldn't be too hard to find that or an equivalent in Aus. The ricers throw them away because they think they're too small.:D

Rebuilding is fiddly, but not hard. A rebuild kit from ebay will cost you about $US50 plus freight, so under $100 on your doorstep. Took me 2 hours to do mine because I forgot the heat shield the first time around.
I had to do mine because the oil line feeding the turbo came apart. Interestingly the turbo took another week to finally die.