Thread: Turbos that work on a 4BD1.

Originally Posted by Lotz-A-Landies

I spent 2 hours looking at T3 flange turbos including for Nissan RB20 last night. The prices vary from a couple of hundred to a couple of thousand and I'm still no wiser about which one to buy.

Diana

What do you aim to achieve from the car ??

Also be carefull there are Garrett copies that are cheap but not good...there is also cheapies like XSpower etc etc that from what I can gather are of a lesser quality... As for my above question I will assume your going to say you want more top end and highway driving for towing etc , I will probably say look for something around a gt2554 or gt2560 or a vnt such as Vern and rover care..

RB20 turbos should be all the same. The only difference would be old, original and used vs new equivalent.

Anything sold aftermarket for ricers is probably a lot bigger than the stock one.

Originally Posted by c.h.i.e.f

What do you aim to achieve from the car ??

It's a 6x6 so heavier than a 110 or 130 with a 4.7T GVM and legal GCM of 7.5T. The vehicle will be used mainly on road, towing car trailers with series LR on the trailer etc and some off-road but not interested in regular extreme rock crawling etc.

Would like the turbo to come in reasonably early for loaded starts and off road but would also like reasonable highway speeds and longevity of the turbo plus engine so not boosts around 20 or above.

Asking a lot aren't I?

You are correct about the variety of turbos for the tuners and drifters in the Nissan Skylines. Many of the turbos had small inlets 2.5" where I thought I should be looking for something with a 3" inlet. Most seem to have an outlet around 2" which I thought is too small.

Am even thinking of going for the OEM turbo fitted by Isuzu for the trucks as that is similar to the main use the vehicle will get.

Diana

Originally Posted by Lotz-A-Landies

It's a 6x6 so heavier than a 110 or 130 with a 4.7T GVM and legal GCM of 7.5T. The vehicle will be used mainly on road, towing car trailers with series LR on the trailer etc and some off-road but not interested in regular extreme rock crawling etc.

Would like the turbo to come in reasonably early for loaded starts and off road but would also like reasonable highway speeds and longevity of the turbo plus engine so not boosts around 20 or above.

Asking a lot aren't I?

You are correct about the variety of turbos for the tuners and drifters in the Nissan Skylines. Many of the turbos had small inlets 2.5" where I thought I should be looking for something with a 3" inlet. Most seem to have an outlet around 2" which I thought is too small.

Am even thinking of going for the OEM turbo fitted by Isuzu for the trucks as that is similar to the main use the vehicle will get.

Diana

In addition to what dougal said about aftermarket turbos for ricers you will notice most are running around the 0.86 hot side AR In my opinion is useless for us ... Sorry if I have not noticed but is yours a 6x6 perentie ?
Well in my eyes the gt2260v (think that's what Vern etc etc are running) will best suit your needs...
Also the inlet and outlet on the compressor of most turbos will be small most inlets will be 2.5" and outlets around 2" my new turbo has 4" inlet and still a 2" outlet so this is not a problem

Originally Posted by Lotz-A-Landies

....

Am even thinking of going for the OEM turbo fitted by Isuzu for the trucks as that is similar to the main use the vehicle will get.

...

Turbo technology has improved a LOT since they were made. Although you may weigh the same as an isuzu truck, unless you use an isuzu box and 4.7 diffs, the isuzu will ahve a much lower first gear (in high range) and probably still a wider spread of gears.

Originally Posted by c.h.i.e.f

...

Well in my eyes the gt2260v (think that's what Vern etc etc are running) will best suit your needs...
...

I tend to agree. An option like this will give you the best combination of early boost but not be strangled on the highway.

Also agree re the compressor intake size. Don't worry. Just make sure you use transitions in the pipework that are as smooth as possible.

Originally Posted by c.h.i.e.f

<snip>... Sorry if I have not noticed but is yours a 6x6 perentie ?
Well in my eyes the gt2260v (think that's what Vern etc etc are running) will best suit your needs...
Also the inlet and outlet on the compressor of most turbos will be small most inlets will be 2.5" and outlets around 2" my new turbo has 4" inlet and still a 2" outlet so this is not a problem

No mine is a Land Rover Special vehicles Defender - Reynolds Boughton (Scottorn Trailers) 6X6 conversion till now a carby 3.5V8. Temporatily it will be running an LT85 5 speed over a Disco 1 LT230 and 3.54 diffs. Later it will likely get one of Grubb's MSA conversions. The suspension is 6 coils which I'm looking to replace with active air suspension.

The GT2260v is a T25 flange isn't it?

Originally Posted by Lotz-A-Landies

Hi John

Sorry a long time away from this thread. Once upon a time, I thought I was smart, but maths always does my head in as my thoughts accellerate off at tangents to the focus of the issue!

In my limited experience of this issue, I was under the understanding that manufacturers are getting better/more efficient results by modifying the shape of the turbine vanes rather than the crude calculation based upon A/R or are you suggesting that the A/R actually calculates the vane design?

And

How can one determine the efficiency of a particular design?

Wouldn't it be good if we could merely punch in some parameters like flange, engine capacity, vehicle weight and RPM band into a calculator and the result would come out as a part number including the vendor with today's best price!

Diana

The vanes on the turbine impeller are not so critical like the compressor, and there is little that has improved there for many years, perhaps since turbos were created for aircraft.

A/R (cross section area divided by radius to centroid of area) relates to the housing and are values that are changed to produce different results with the same turbine to match engine requirements.

The Squirrel Performance online calculator will do pretty much what you are asking. The difference is you select up to 6 turbos at a time and the calculator plots the results on their compressor maps. It doesn't give much for the turbine side.

BorgWarner also have a good online calculator.

Originally Posted by Lotz-A-Landies

I spent 2 hours looking at T3 flange turbos including for Nissan RB20 last night. The prices vary from a couple of hundred to a couple of thousand and I'm still no wiser about which one to buy.

Diana

T3 flanged turbos will be mostly too large for what you want. You will probably need to use a T25 to T3 adaptor.

Originally Posted by Lotz-A-Landies

It's a 6x6 so heavier than a 110 or 130 with a 4.7T GVM and legal GCM of 7.5T. The vehicle will be used mainly on road, towing car trailers with series LR on the trailer etc and some off-road but not interested in regular extreme rock crawling etc.

Would like the turbo to come in reasonably early for loaded starts and off road but would also like reasonable highway speeds and longevity of the turbo plus engine so not boosts around 20 or above.

Asking a lot aren't I?

You are correct about the variety of turbos for the tuners and drifters in the Nissan Skylines. Many of the turbos had small inlets 2.5" where I thought I should be looking for something with a 3" inlet. Most seem to have an outlet around 2" which I thought is too small.

Am even thinking of going for the OEM turbo fitted by Isuzu for the trucks as that is similar to the main use the vehicle will get.

Diana

From information which came to light in this forum recently, for the 4BD1T, it appears that Isuzu changed (2nd half of 1988) from the earlier IHI waste gate turbo to the free float Garrett with large T3 turbine housing, mainly to reduce exhaust manifold pressure for better efficiency.

A waste gate also serves the same purpose as well as controlling turbo speed. A VNT (variable nozzle turbine, or VGT variable geometry) is another approach to address both of these issues and does better than the earlier mentioned approaches.

20 psi on a diesel is not going to hurt the turbo (or 4BD1), as long as the compressor is operating at a reasonable efficient point on the compressor map. Driving a small compressor at a higher speed that is outside an efficient point on its map is futile and is the compressor equivalent to spinning tyres with lack of forward motion.