Turbo or not???

[constapa]

Hi, i have an old track (petrol) i i'm about to do a turbo conversion. Here is my question. I'm i going to have problems with the turbo lag? Truck is used for off road at most. I know that many have done it but i need some opinions for the specific use. I don't see any factory off road trucks with turbo and i don't know if this means something...
Thanks

[crunch]

What Truck is it? What motor is in it? Is it used onroad aswell? Whats the on-road/off-road ratio? I think a bit more info in your post will benifit you.

But in short- A small Turbo will eliminate most of the lag, whereas a larger Turbo needs time to wind up (lag).

Supercharging an option instead? On-tap power....

[just cruizin']

Lag shouldn't be too much of a problem in a 4WD as the rev range isn't too big normally. On ricers where revs go 6000 and above tubos are sized to handle that sort of through put so at 1000-2000 they tend to suffer. Most and I say most there are always exceptions, of 4WDs would never be run over 5000 for any length of time and the turbo can be sized to operate at well between 2000 - 4000 rpm

[AussieCJ7]

old truck implies old engine implies worn I would expect a turbo to accelrate the wear rate

is this really the most econmical way to meet your goal of more hp ?? particulary if you have to add a engine rebuild into the cost

[-Scott-]

Is this a comp truck? Comp trucks seem to use full throttle a lot more than I do, so you may want more high RPM power than a recreational 4wder.

If you go small turbo for minimal lag you won't get as much top end power. Large turbo for top end power won't spin up as fast, so more lag.

Variable vane turbos can help, more $$$.

Cheers,

Scott

[constapa]

Thanks for the replies guys, so i have to give some details...
The truck is Gen1 2.6L Mitsu Pajero, the engine is recently rebuilded and is in excellent condition. It is used most for off road (80-20). It's not a competition track. I know all (???:lol:) the theory behind turbo and turbo lags but i need some feedback from someone that has a turbo on a petrol engine. As you know there are situations that you drive through passages that require low rpm's because some power more means loosing traction. So is it difficult to handle this with a turbo? The turbo that i'm goinf to fit is really small (from a 1.8L car that has peak torque at 2.500 rpm). I expect it to start boosting from very low in my truck because the flow is much greater. And yes it's a variable vane turbo... (it's going to have a boost controller that operates remotely from a button on the steering wheel'')
Thanks again

[-Scott-]

Sounds good! So, what happened to the 2.4i?

If your engine becomes too "peaky" for delicate work, turn the boost off?

Good luck,

Scott

[constapa]

Sounds good! So, what happened to the 2.4i?

If your engine becomes too "peaky" for delicate work, turn the boost off?

Good luck,

Scott

Thanks Scott. The 2.4i was an option because of two things.
1. The 2.6 has not the power i need (...or i like
2. I was sick with the Mikuni carb.
These days i'm finishing an EFI convertion (not Magna) and as you may understand my appetite is growing
That's the thought behind the boost controller, lowering the boost as possible for the "delicate" work (nice word Scott!) and hitting the button when horses needed!
I'm still wandering though, why any factory don't use something like this (small turbo) - is there any problem i don't know???
Cheers

[ISUZUROVER]

I'm still wandering though, why any factory don't use something like this (small turbo) - is there any problem i don't know???
Cheers

If you fit a small turbo to minimise lag it will be a bit strangled at the high end - at peak revs you will be out of the optimum "efficiency map" of the compressor. If you mainy use the vehicle off-road and don't need high revs very often I don't see why it wouldn't work.

[Zute]

The best set up would be twin turbos. Like on Nissans Skylines and Mazda rx7. Small turbo for low rev's. Larger one cuts in around 4000rpm.

[Zute]

OR, twin charger. Roots type blower takes care of low revs, with turbo feeding the top end rev's.
This has been used on MR2's in Japan.

[constapa]

I'm still wandering though, why any factory don't use something like this (small turbo) - is there any problem i don't know???
Cheers

If you mainy use the vehicle off-road and don't need high revs very often I don't see why it wouldn't work.

That's exactly my opinion Ben, anyway the 2.6L engine doesn't like to rev above 4.500 rpm.

Zute, you're right but i don't want to get 200+ hp from my truck. Besides that when it's going to be the day of the bill i'm sure gonna have a stroke...

[ISUZUROVER]

That's exactly my opinion Ben, anyway the 2.6L engine doesn't like to rev above 4.500 rpm.

Zute, you're right but i don't want to get 200+ hp from my truck. Besides that when it's going to be the day of the bill i'm sure gonna have a stroke...

4500rpm is a lot for a small turbo.

A mate of mine fitted a small turbo to his 3.9L ISUZU 4BD1T. This engine redlines at 3200rpm. He found that above 2000rpm it didn't produce any extra power and torque because the turbo was limiting it. He then fitted a turbo from a subaru WRX and has been happy since.

[def90]

i have a turbo off a rb20 skyline, 2L motor, is great for 3.9 oiler as it spools up well under 1000rpm but doesn't give much over 2100-2200rpm. don't need to take motor any further then that as ben said is limited to just over 3G. there are plenty of import turbos you could adopt and cheap 2nd hand without many k's on them...

[constapa]

4500rpm is a lot for a small turbo.

A mate of mine fitted a small turbo to his 3.9L ISUZU 4BD1T. This engine redlines at 3200rpm. He found that above 2000rpm it didn't produce any extra power and torque because the turbo was limiting it. He then fitted a turbo from a subaru WRX and has been happy since.

Well,Ben, the turbo that i'm going to fit is from an Audi 1.8T. An engine that redlines (if my memory serves well) at about 6500 rpm. Most important is that the car has a really linear way of produsing power. Ok, i know, that is another engine, but fitting a turbo like this on a 2.6L engine is going to limit it a bit but i expect to be ok for my use. 3.9L with a small turbo??? This is really another story. This is an engine that i would'nt think to fit a small turbo. There must be a balance in everything. You wrote that redlines at 3200rpm? What engine is this, a diesel?

[DamTriton]

A supercharger off a Toyota import 2 litre engine (4age series - can't remember offhand exactly which one) would be a better bet. You can adjust your level of boost by varying the pulley diameters, and this will give you your aim of smooth increase in power with revs to whatever you set it up to.

Lag is always going to be a problem with a turbo. The more you do to reduce the lag, the less net effect you will gain from the turbo. Variable vanes are an attempt to resolve some of these issues, but still have their technological problems.

VV technology does not reduce the need to look at the inlet tract volume and flow rate as a part of the overall lag problem. Runners that are too long going around to a large intercooler can cause the lag time to be too high from having to pressurise a large volume of gas. This is a situation which is OK for ricers (full throttle, 6500rpm gear changes, only causing a blip in inlet press changes with gear change), but not OK if you are on-off the turbo at low revs.