Query on setting up turbo on NA 4BD1

[will@montlaur.com.au]

Hi All,

long time watcher of the isuzu-landy forum (it was how I discovered them in the 1st place) but haven't had much to contribute to date. Thanks to all for the background as I'm a fan of the set-up.

I've had a NA4bd1 running in a ratty old 82 range rover for a couple of years now (conversion was done around '92, two owners before me) and I've finally got around to getting it seen to.

I've found a 93 vogue and the process of moving the engine, 4 speed and a bunch of other bits across and refurbishing anything that's r**ted has started (I'm not doing the work myself).

Naturally the subject of turbocharging has come up. The general consensus on this forum seems to be - if the engine's in reasonable nick, do it - but don't go too nuts on the boost.

The bone of contention with the chap doing the work (who's reluctant to turbocharge an old motor to start with - fair enough) is that the NA motor injector pumps cause the engine to smoke like blazes when it's off boost - bad enough to attract the attention of the fun-stoppers.

There's been no mention on this forum of belching smoke when turboing a NA4bd1. Has anyone had any issues in this regard? or is there a way to set up the turbo/exhaust and fueling to compensate?

any further info would be greatly appreciated.

cheers,

will

[Larns]

Can't say that mine blazed smoke out the rear at low revs, there was a little under hard acceleration but that was about the extent of it. If it dose it then look at other problems like haveing your injectors cleaned and having the timing checked. And a new air filter dosen't go astry either.

:twobeers:

[Bush65]

AFAIK, Isuzu trucks released in Australia with the 4BD1-T, did not have the boost compensator fitted to the injection pump (but some other countries did).

The purpose of the boost compensator is to reduce fuel/smoke when boost pressure is low.

Although there are some differences between the injection pump on the NA and turbo engine, the main ones are calibration (disregarding the boost compensator).

[will@montlaur.com.au]

Sounds good to me.

current thought is for a garret GT2560, which I gather mounts to a standard isuzu turbo manifold (westar quoted $230 new).

Should these two bolt straight up?

W

[Dougal]

Sounds good to me.

current thought is for a garret GT2560, which I gather mounts to a standard isuzu turbo manifold (westar quoted $230 new).

Should these two bolt straight up?

W

If you pick the right turbo, you'll have very little time off-boost and so the smoke won't be a problem.
I have a JDM engine which has a boost compensator (reduces fueling when there's no boost), I suspect the pumps without boost compensators restrict fuelling based on rpm, this would be the torque plate's influence.

The GT2560 (basically the new version of the old T28) is a good place to start, but I went even smaller on mine (GT2252 is the new equivalent of my T25).

It won't bolt straight up, but I have an adapter design which will make it fit. See this thread http://www.aulro.com/afvb/isuzu-landy-enthusiasts-section/63176-budget-4bd1-turbo-install.html for pictures, PM me if you'd like a copy of the drawings.

[will@montlaur.com.au]

If you pick the right turbo, you'll have very little time off-boost and so the smoke won't be a problem.
I have a JDM engine which has a boost compensator (reduces fueling when there's no boost), I suspect the pumps without boost compensators restrict fuelling based on rpm, this would be the torque plate's influence.

The GT2560 (basically the new version of the old T28) is a good place to start, but I went even smaller on mine (GT2252 is the new equivalent of my T25).

It won't bolt straight up, but I have an adapter design which will make it fit. See this thread http://www.aulro.com/afvb/isuzu-landy-enthusiasts-section/63176-budget-4bd1-turbo-install.html for pictures, PM me if you'd like a copy of the drawings.

Thanks Dougal,

I'm trying to stick to the 'keep it simple' principal given I'm not doing the work myself, so off the shelf would be preferred.

Am I correct in assuming that any turbo from the GT25 family will mount straight up to a stock turbo manifold? 2nd assumption being GT22 or smaller won't mount straight up?

If that's the case any reduction in turbine size takes me outside the "mount straight up" requirement; ie into the GT22 family. A GT2554 will provide a smaller compressor but I don't see that providing any benefit in making boost at the lowest revs possible. (correct me if I'm wrong here)

I know I'm just fishing for an answer I want to hear but if a GT2560 meets my needs, ie;

a) mounts straight up to a stock manifold
b) wastegated, ball bearing & water cooled
c) quick spool (I'll keep the exhaust as large as possible)

I think I'll probably stick with it. What do you think?

W

[isuzurover]

Thanks Dougal,

I'm trying to stick to the 'keep it simple' principal given I'm not doing the work myself, so off the shelf would be preferred.

Am I correct in assuming that any turbo from the GT25 family will mount straight up to a stock turbo manifold? 2nd assumption being GT22 or smaller won't mount straight up?

If that's the case any reduction in turbine size takes me outside the "mount straight up" requirement; ie into the GT22 family. A GT2554 will provide a smaller compressor but I don't see that providing any benefit in making boost at the lowest revs possible. (correct me if I'm wrong here)

I know I'm just fishing for an answer I want to hear but if a GT2560 meets my needs, ie;

a) mounts straight up to a stock manifold
b) wastegated, ball bearing & water cooled
c) quick spool (I'll keep the exhaust as large as possible)

I think I'll probably stick with it. What do you think?

W

The factory manifold has a T3 flange. Very few turbos of the correct size have a T3 flange. AFAIK all the turbos you mentioned above have a T2 flange, which is why an adaptor is needed.

The turbo I fitted (in the thread Dougal linked) is the same as a GT2560R except that it has journal bearings. IMHO, you wouldn't want to go smaller than a T25, and it won't help with the flange issue.

Water cooling offers no benefits, and some disadvantages in a diesel. Have a look at the turboglide website for the reasons. Many people (Dougal and myself included, run water cooled turbos with the water lines disconnected/blanked.

If you are paying someone to do the job, the turboglide kit may be a good way to go.

[rovercare]

. Many people (Dougal and myself included, run water cooled turbos with the water lines disconnected/blanked.

If you are paying someone to do the job, the turboglide kit may be a good way to go.

I don;t run the water cooling either

Turboglide will do a full kit for you

Mine smokes off boost and sharp throttle openings in low range, but you don;t need to fuel it up that much

[will@montlaur.com.au]

excellent. thanks heaps guys.

I'll give turboglide a call on Monday and see how I go.

cheers

W

[rar110]

I fitted a GT2560 (GT28R ?) to mine on a genuine Isuzu top mount T2 manifold. It spools up fast, engine doesn't smoke, so I don't think it is over fueling. As with Ben my compressor had to be rotated requiring some modification to the actuator arm. I had mine fitted by a Brisbane turbo specialist with a long and good reputation. The result was excellent but cost a lot more than Ben's. Two things the installer insisted on was an over boost safety valve and new injectors. I went 3" mandrell pipe with a lukey muffler.

[Dougal]

I fitted a GT2560 (GT28R ?) to mine on a genuine Isuzu top mount T2 manifold. It spools up fast, engine doesn't smoke, so I don't think it is over fueling. As with Ben my compressor had to be rotated requiring some modification to the actuator arm. I had mine fitted by a Brisbane turbo specialist with a long and good reputation. The result was excellent but cost a lot more than Ben's. Two things the installer insisted on was an over boost safety valve and new injectors. I went 3" mandrell pipe with a lukey muffler.

How much boost do you have and what rpm does it arrive? The factory overboost relief valve was set to 15psi on my engine. It went years ago.:)

[dylan gover]

I fitted a GT2560 (GT28R ?) to mine on a genuine Isuzu top mount T2 manifold. It spools up fast, engine doesn't smoke, so I don't think it is over fueling. As with Ben my compressor had to be rotated requiring some modification to the actuator arm. I had mine fitted by a Brisbane turbo specialist with a long and good reputation. The result was excellent but cost a lot more than Ben's. Two things the installer insisted on was an over boost safety valve and new injectors. I went 3" mandrell pipe with a lukey muffler.
besides the obvious ,a overboost safety valve, ????????
i no see no hear nothing of,
please explain?

[isuzurover]

besides the obvious ,a overboost safety valve, ????????
i no see no hear nothing of,
please explain?

It is just a valve on either the inlet manifold or the pipe between the compressor outlet and the manifold. It is set so that if the wastegate sticks closed (etc), causing the turbo to overboost, then the valve will pop open and vent the excess pressure.

There are a few pics floating around of genuine 4BD1T setups which show them.

[rovercare]

It is just a valve on either the inlet manifold or the pipe between the compressor outlet and the manifold. It is set so that if the wastegate sticks closed (etc), causing the turbo to overboost, then the valve will pop open and vent the excess pressure.

There are a few pics floating around of genuine 4BD1T setups which show them.

A blow off valve...acheewww achewwww:D

[EchiDna]

A blow off valve...acheewww achewwww:D


fully sik bro!:o

[isuzurover]

A blow off valve...acheewww achewwww:D

I am sure there are some people with BOVs on diesels... You would have to install a throttle butterfly to get it to actuate though :D

I know someone with an automatic rotary who installed a BOV :D :D :D :D

[rovercare]

I am sure there are some people with BOVs on diesels... You would have to install a throttle butterfly to get it to actuate though :D

I know someone with an automatic rotary who installed a BOV :D :D :D :D

SD33 comes with a throttle butterfly, well the turbo equivelant does:)

[Dougal]

SD33 comes with a throttle butterfly, well the turbo equivelant does:)

So do the Toyota B, L and KZ series.
But that's not all, you get free head cracks too.:D

Some diesels use a pneumatic governor, the butterfly pressure difference is what sets the fuelling. One advantage is reduced NOx emission due to less excess air. One big disadvantage is the pumping loss that goes with that.

[The Mutt]

While our Rangie isn't on the road yet we got a turbo kit from Turbo Glide in Wollongong, they are very helpful, we did the install it ourselves, a friend who is a pro welder brazed the oil feed to the designated nut and added the connector to the removable panel on the left side of the Isuzu.

The turbo itself is based on the Garrett T25, if I heard John correctly Garrett added an internal wastegate which the standard T25 is missing, he said it is made for the army 6wd Landies.

I asked a diesel mechanic we know about adjusting the injector pump to match the turbo, he told me to get the motor going and adjust fuel flow till we get the standard boost pressure, I'll try it his way first.

John also told me to get my EGT probe and meter from Wadeair at Spring Hill near Orange, from memory I had to ask for the meter from China and a 8M X1 probe, I rang up and ordered the parts they were in our PO box the next morning. Talk about great service.


Glenn

[Dougal]

The turbo itself is based on the Garrett T25, if I heard John correctly Garrett added an internal wastegate which the standard T25 is missing, he said it is made for the army 6wd Landies.

The T25's cover a whole family of garrett turbos with similar wheel sizes. The most common type (found in petrol japanese cars and sold aftermarket by garrett) do have an internal wastegate and usually have exhaust turbine housings with either 0.49 A/R or 0.64 A/R.

But the T25 that Isuzu fitted to many of their 4BD1T and 4BD2T engines doesn't have the external wastegate, it's also fitted with the inlet flange from a T3 turbo. This will be the one that you are talking about above.

Other turbos factory fitted to the Isuzu 4BD1T include a wastegated T25 with a T3 flange (these seem quite rare) and a wastegated IHI turbo that was used on the early 4BD1T's which came out in the mid 80's.

My 4BD1T came with the Wastegated IHI, a good turbo but I had a crappy aircleaner cause dust erosion of the compressor wheel and found parts impossible to get.
I now have a wastegated T25 with the 0.49 A/R turbine housing, this turbo came from a Nissan bluebird with the CA18DET engine.

[The Mutt]

So what amount of boost can I look at getting from my turbo without going over the top? We will be towing a large sailboat on a regular basis, at other times the Rangie will be topped with a ShippeShape and the back loaded with gear.

Glenn

[isuzurover]

So what amount of boost can I look at getting from my turbo without going over the top? We will be towing a large sailboat on a regular basis, at other times the Rangie will be topped with a ShippeShape and the back loaded with gear.

Glenn

The main issue is keeping EGTs down. Fit an EGT guage and set it up based on that.

Stock (4BD1T) boost is 16/17psi. <20 is probably fine. But whether you can achieve that depends on the turbo and fuelling.

[rijidij]

The main issue is keeping EGTs down. Fit an EGT guage and set it up based on that.

Stock (4BD1T) boost is 16/17psi. <20 is probably fine. But whether you can achieve that depends on the turbo and fuelling.

The 4BD1T that I fitted came from a truck and the turbo only boosts to 9psi max according to my gauge. I was led to believe that standard boost was even less than 9psi, so I have'nt 'played' with it. 16/17psi sounds more appealing. Are these figures mentioned in an engine manual anywhere ? I would like to try more boost, but one of my main aims is to get a long life out of my engine.

It's interesting to see that a company like Turbo-Glide set their turbo kits to 9psi.........

Q. How much boost and power do you set up for along with Max EGT?

A. We use 9lb and a torque gain of no more than 30% and an EGT of no more than 500°Celcius under prolonged full throttle usage. My staff and I have seen many turbo kits installed exceeding these parameters resulting in severe engine damage. Use of chassis dyno is mandatory before and after fitment of turbo.

Turbo-Glide: Turbo FAQs (http://www.turboglide.com.au/index.cfm?fuseaction=category.display&category_ID=11)

[Dougal]

The 4BD1T that I fitted came from a truck and the turbo only boosts to 9psi max according to my gauge. I was led to believe that standard boost was even less than 9psi, so I have'nt 'played' with it. 16/17psi sounds more appealing. Are these figures mentioned in an engine manual anywhere ? I would like to try more boost, but one of my main aims is to get a long life out of my engine.

It's interesting to see that a company like Turbo-Glide set their turbo kits to 9psi.........

Q. How much boost and power do you set up for along with Max EGT?

A. We use 9lb and a torque gain of no more than 30% and an EGT of no more than 500°Celcius under prolonged full throttle usage. My staff and I have seen many turbo kits installed exceeding these parameters resulting in severe engine damage. Use of chassis dyno is mandatory before and after fitment of turbo.

Turbo-Glide: Turbo FAQs (http://www.turboglide.com.au/index.cfm?fuseaction=category.display&category_ID=11)

Someone (maybe Isuzurover) found factory figures of around 13psi. My 4BD1T turbo wastegate was set to about 20psi, not surprisingly it never opened until I cut the arm and welded in an adjustable section. It was doing about 18psi max back then, but didn't need it. Dropping the boost to 15psi gave it more top end (if you call 3000-3600rpm top-end) and gave me EGT's of about 600C at full load and moderate revs. I could get them up above 700 by red-lining it.

I suspect turboglide are basing their 9psi on their experiences with fragile stuff like toyotas with indirect injection. Their figure of 500C suggests post turbo.
With 9psi and a boost/backpressure ratio of 2 (what I get under acceleration) that gives you a preturbo EGT of around 630C. Plenty hot enough for many IDI engines.

Boost by itself does not hurt an engine. It's the combination of boost, fuel loading and injection timing that determines the stress on an engine. It's possible to put a lot of extra stress on and get little extra power if you're doing it wrong.

I've been running 20psi with no intercooler and EGT's to 750C (occasional accidental excursion past) for just over a year now. 12,000km.

[Bush65]

I 2nd what Dougal posted.

They probably had in mind the indirect injection toyota and nissan engines. Indirect injection engines typically have compression ratios about 22:1 to aid starting in cold climates.

The c.r in a 4BD1 is more suitable for turbo engines.

[rovercare]

I 2nd what Dougal posted.

They probably had in mind the indirect injection toyota and nissan engines. Indirect injection engines typically have compression ratios about 22:1 to aid starting in cold climates.

The c.r in a 4BD1 is more suitable for turbo engines.

More suitable? at 16:1 it should NEVER of been naturally aspirated:D

[Dougal]

More suitable? at 16:1 it should NEVER of been naturally aspirated:D

I've seen figures which go right up to 17.5:1. The highest compression ratio I've seen on a direct injection diesel is 18.something.

Unless you want to look at Scanias ethanol burning diesels, 28:1 static with a decent amount of boost on top of that.

[The Mutt]

Thanks guys, I came across info a while ago saying that the factory setting for the 4BD1 turbo was 5psi and never go over 12psi, it is going to be interesting to see what I can get out of this engine/turbo setup.

Firstly I'll get our Rangie back on the road with the Isuzu running a basic setup, iron out any bugs from the conversion then start to tweek the settings to improve performance, this is going to be interesting.

Thanks Again Guys ............ Great Forum

Glenn

[Dougal]

Thanks guys, I came across info a while ago saying that the factory setting for the 4BD1 turbo was 5psi and never go over 12psi,

Name and shame.:o

[The Mutt]

I'll go through the research info I compiled over the last 2 years and see who told me.

Glenn

[justinc]

Hi Glen,

I have had great success with my installation, it is in a 1992 RRC, LT95 box and 33's. Matt(Rovercare) and I both have the same turbos 'kits'etc from Turboglide, and we are both using front mounted intercoolers.
The efficiency of having an IC when boosting above 10psi or thereabouts is better, Less smoke and lower EGT's.
I'm getting around 12litres/100km around town, and 15l/100 towing a camper trailer at 100km/h. At these hiway speeds on a flat road, my upstream mounted pyro measures around 350deg, and up to 450deg if into a headwind. When pushed to the governor up hills etc, it will peak at 550deg.

I have 15psi on full noise at the manifold, I have disconnected the wastegate and have set it up using the fuelling to control max boost. With the .48A/R housing I am getting almost zero lag, and have wheelspin/ traction issues when climbing hills around corners on dry bitumen even under moderate throttle use:o No Dyno figures yet, I'm working on it!

IMHO these engines are overengineered in a TRUCK, so turboing a N/A engine in a RR or 110 etc is chickenfeed for this iconic Isuzu engine:D:D:D
In trucks, at a MUCH higher duty cycle, these engines are good for a million K's. I'm hoping for at least that from mine, as it now has about 550k up and shows no signs of stopping:) It initially came from a 1988 110 that fell apart from rust at 420K, the engine outlasting the vehicle. I DO take care of it, oil and filters regularly, shut down ONLY sub 180deg temps, and I DON'T let it idle all the time.

In Short, it is very hard for you to hurt one of these engines:twisted:

JC

[isuzurover]

The 4BD1T that I fitted came from a truck and the turbo only boosts to 9psi max according to my gauge. I was led to believe that standard boost was even less than 9psi, so I have'nt 'played' with it. 16/17psi sounds more appealing. Are these figures mentioned in an engine manual anywhere ? I would like to try more boost, but one of my main aims is to get a long life out of my engine.

It's interesting to see that a company like Turbo-Glide set their turbo kits to 9psi.........

Q. How much boost and power do you set up for along with Max EGT?

A. We use 9lb and a torque gain of no more than 30% and an EGT of no more than 500°Celcius under prolonged full throttle usage. My staff and I have seen many turbo kits installed exceeding these parameters resulting in severe engine damage. Use of chassis dyno is mandatory before and after fitment of turbo.

Turbo-Glide: Turbo FAQs (http://www.turboglide.com.au/index.cfm?fuseaction=category.display&category_ID=11)

Sorry - 16/17 is Tdi spec... Getting the numbers mixed up. This is what I posted earlier - taken from my isuzu WS manual:


A few people have asked about this in the past and I think there has been a bit of misinformation (some may have come from me :o ).

I finally got my ISUZU WS manual back in my hands, and it says:

1988 and Earlier engines were fitted with an:
IHI RHB-6 (with wastegate). The wastegate opening pressure (boost pressure) was: 680mmHg = 13.15 psi = 0.91 Bar

1989 and Later engines were fitted with a Garrett T-25 with NO WASTEGATE. Maybe this is where the erroneous 5psi boost figure came from, but I don't see why these would run lower boost than the earlier engines.

Murray - which turbo do you have?

[rijidij]

Murray - which turbo do you have?

This is the tag off my turbo. The engine came from a 1988 NPR59, and it does have a waste gate. I haven't really got into the turbo side of things yet, because I haven't had to, but if there is more potential there for more performance without over doing things I would like to investigate it more.
If anyone can give me more info about my turbo from the numbers on this tag I would appreciate it. I presume TF 0424J is the model.

https://www.aulro.com/afvb/images/imported/2008/11/581.jpg

[isuzurover]

This is the tag off my turbo. The engine came from a 1988 NPR59, and it does have a waste gate. I haven't really got into the turbo side of things yet, because I haven't had to, but if there is more potential there for more performance without over doing things I would like to investigate it more.
If anyone can give me more info about my turbo from the numbers on this tag I would appreciate it. I presume TF 0424J is the model.

https://www.aulro.com/afvb/images/imported/2008/11/581.jpg

You can plug those numbers into the garrett/honeywell website and they will give you the specs.

My manual was published Sept 1988. I think some people have said that the IHI-turboed engines never came here.

[Dougal]

This is the tag off my turbo. The engine came from a 1988 NPR59, and it does have a waste gate. I haven't really got into the turbo side of things yet, because I haven't had to, but if there is more potential there for more performance without over doing things I would like to investigate it more.
If anyone can give me more info about my turbo from the numbers on this tag I would appreciate it. I presume TF 0424J is the model.

https://www.aulro.com/afvb/images/imported/2008/11/582.jpg

That'd be the rare wastegated T25.

I have a non-wasteged T25 from a 4BD2T in my parts bin. Garrett #466898-6
Here's the wastegated T25 from a 4BD2T from a guy in the US Garrett #466409-1
Both of these fit the T3 flanged manifold like Isuzurover has used in his conversion.

Which manifold do you have Murray?

[justinc]

That'd be the rare wastegated T25.

I have a non-wasteged T25 from a 4BD2T in my parts bin. Garrett #466898-6
Here's the wastegated T25 from a 4BD2T from a guy in the US Garrett #466409-1
Both of these fit the T3 flanged manifold like Isuzurover has used in his conversion.

Which manifold do you have Murray?

Said in your best 'David Attenborough' voice:D:D:D:D


JC

[rijidij]

Which manifold do you have Murray?

I don't know how much you can tell from these pics.

https://www.aulro.com/afvb/images/imported/2008/11/453.jpghttps://www.aulro.com/afvb/images/imported/2008/11/454.jpg

[Dougal]

I don't know how much you can tell from these pics.

That's the latest style manifold, the same one that Isuzurover bought and fitted his turbo to.
It has the T3 flange, but I have adapters to fit T25/T28s on them (Isuzurover is running one).

Is that a wastegated turbo? It'll have an actuator can with the rod running to a lever underneath the exhaust outlet if it is.

[rijidij]

Is that a wastegated turbo? It'll have an actuator can with the rod running to a lever underneath the exhaust outlet if it is

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......
A/R 0.48 on the turbine and 0.42 on the compressor
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 ?

[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

[Bush65]

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
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.

[Dougal]

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 ?

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.

[rijidij]

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.

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 ?

[Dougal]

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 ?

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.