Diesel Truck, Tubo outlet temp, Intercooler ducting

Can anyone advise. I have a non modified Isuzu 4BD1T truck diesel. It has a 2" diameter thin wall steel pipe going directly from the standard turbo (about 5 psi boost I believe) Directly to the inlet manifold.

Aim is to get this to go up hills better with out having to change down as many gears.

Can anyone advise/guess the likely MAX teperature of the pipe going between the turbo and the inlet manifold? (Just a rough guess would be OK.) keeping in mind this is a low pressure trubo installation.

The reason for asking is that I am thinking about adding an intercooler and I have been looking at using some non silicon flexible pipe work. Rigid pipe work would be a real mission to get to an intercooler in front of the radiator. I have found some rubber hosing that wil take 150 degrees celsius and wondering if this will survive?

Can anyone advise if I intercool this with out changing the fueling am I likely to see any gain in power? and if so what woudl be a real rough guess in percentage terms?

I would advise against using rubber or any other week materials for a boosted vehicle. you could probably get a mechanic or muffler shop to bend the pipes for you if you bought them. also, that way, you're not worrying about one of your pipes breaking off when you go full, or close to full, throttle. it might cost you a bit more but it will be alot safer.

Thanks for your feed back. I was thinking that with only 5 psi of boost if the intercooler hosing were to break I am not really going to have a major problem (I should be able to drive to the next garage OK albeit with unfiltered air going in the intake).

...and maybe the temperatures will be a lot lower on the tubo/induction pipe than on a higher pressure install so a lower temp hose (150 degrees celcius rating) is unlikely to fail in the first place?

The other reason I ask is that I am trying to work out if an intercooler will actually give me a gain in power with ths little pressure. I am likely to see a 1.5 psi drop in pressure through the intercooler and I am wondering if the lower air charge from the intercooler will gain me more than I lose from the pressure drop of the intercooler?

I am pretty new to this (although I have modified lots of normally aspirated engines in the past), so any help appreciated.

You can buy silicone hose joints for turbos. I would say that the worst case scenario is that your compressor outlet temps are ambient temp times pressure ratio divided by efficiency of the compressor.

A guess: 90* ambient, times your pressure ratio of 1.33, divided by efficiency which at worst is at least 70%. That is a worst case scenario of 141 degrees for short bursts, but I suppose the real killer might be underhood heat.

Thanks Curtis for the excellent response.

Now with only 140 degree celcius max temp in the charge and with a 1.5 psi pressure drop in an intercooler and 5psi pressure from the turbo am I likely to see any power gain with the intercooler or does the pressure drop negate the benefit of the intercooler?

Whoops correction I just loked at Curtis calculation again and note temp is in Fairenheight so thats 140 degres fairenheight.

are you canadian?

anyways, if the hose did break, your engine wouldn't suffer much, if any, harm. the onyl thing is that it might be running really rich and you'd notice a huge decrease in gas mileage and power. that is if it would even start.

a great and cheap way to increase horsepower on a diesel is to retune your chip, if you can find a chip tuner for your car. most diesels dont use as much fuel as they can, this means you dont get as much power. if you retune your chip to give you more fuel, your gas (or diesel) pedal will be more sensitive and you'll have more power, so have a lighter foot and you wont lose any gas mileage.

No not Canadian, I'm a Kiwi.

A broken pipe from the intercooler to the inlet won't stop it starting or idling because the turbo is doing nothing at low revs. I tested, it starts and idles fine with this hose temporarily removed (I had to remove it when I replaced the injectors recently.

beef_bourito I think that your right chipping to increase the fueling would work, except in my case I am not sure if this 1991 Isuzu 4BD1-T engine has a chip. I kinda think that it may use some more primative technology? In an old fashioned car the speed of air going thru the carburettor venturi pretty much determines the AF ratio. I've not a clue what determines the AF ratio in an old diesel?

Thanks for the information provided at this point. It woud seem that given the temps Curtis thinks this piping will reach (10 degrees celcius) cheap and flexible rubber hosing (rated at 150 degrees) will survive for a reasonable period and would also be very easy to install - but would also unfortuanately be an effective insulator. So if I go ahead with this project, I think I will use mandrel bent aluminum 2" tube and silicon joiners. Whidh addresses the construction.

But what I still don't know is will I actually get a net power gain given an estimated pressure drop of 1.5 psi through the intercooler an piping?

I'm a Kiwi.



Its a desputed fact, but we actualy run the internet :)


Where in the Country are you?

Your little Izuzu use's good old fashioned mechanical injection.
You put your foot down and it pumps more desiel into the engine, this makes it run faster drawing in more air, etc etc etc.

I think you might find it runs a little more than 5psi to, most comecial deisel applications run a quite high boost levels.


Instead of adding an intercooler you might want to look at increasing the boost first, and even doing both.
If they are like the Mitsubishi Canters then your truck will have a very ordinary off the shelf turbo that is probably used on a few cars from the same period. That means you should be able to use an off the shelf extrenal wastegate, or adjust the existing internal one to control your boost levels.
A boost guage is of course a good first place to start, as you then know whats going on :)


And what hills are you climbing that you want to go up them faster?
I know the Izuzu Turbo Desiels are pretty damn quick, certianly on par with a Turbo Canter, I know from personal experiance that they are quite capable of doing 100kph up the bombays when empty :smokin:

oh well, you used celsius so iwas hoping there would be another canuck on here.

Moppie thanks for you comments.

I live in Auckland. When emptyh I certainly can't get over the bombays hills in 5th. Travelling south I have to change to 4th and travelling north I am down to third. I have just chucked some refreshed injectors in it today so it will be interesting to take it for a test ride tomorrow. The old ones were apparently in pretty poor shape after 320,000 km apparently without a service on them.

My truck has been converted to a motor home and weighs about 4400 kgs empty.

Your suggestion of a boost guage is probably a good idea. I also welded up a new pipe from the turbo to the inlet today. Key reason to make it easier to service. The old one went over the cam cover and the injectors and was very awkward to remove. The new one is sectioned with silicon joiners.

Should be very easy to fit a boost guage fitting in this. How easyis it to adjust the internal waste gate? Is there some sort of sping in there that can be uprated?

Seems it's not worth increasing the amount of air going into the engine (with and intercooler or modified waste gate) if I don't also increase the fueling. Is there an external adjuster on the fuel pump to increase the fuelling?

Iv never really played with Desiels, and unfortunatly my Turbo knowledge is limited.

However, fuel supply to the injectors will be controlled by the regulator, which has the throttle connected to it.
Its usualy on the side of the engine, and will have hard fuel lines running to the injectors.
If its anything like the old BOSCH mechanical system then I think they use a sliding pin with a spring behind it to control pressure.


Its nice to find a Motorhome owner looking to increase the performance of thier truck, to many of them travel to slowly with out any regard for whos behind them.


Since your in Auckland you might want to check out some of the Desiel turbo specialists. I know of one in Penrose, on the corner of the South Easter Arterial and Gt South Rd that Iv heard good things about.
They should know about whats needed to get a little more power out of your little truck.

your truck will respond to an increase in boost. diesels usually run really lean. when you increase the boost, you increase the temperature, this increases exhaust gas temperature so in a high power machine it can be worrisome to increase egt's too high but in your little diesel i don't think it will be a problem, you might want to make sure you have an exhaust gas temperature gauge just in case though, every diesel should have one. anyways, when you increase the temperature, the diesel burns better and gives you more power. not only that but you increase the concentration of oxygen in the cylender, this makes the reaction faster and more efficient. all these effects will give you more power.

if you got your engine to add fuel at the same time, you would see even more of a power increase, but i think increasing the pressure will be easier. it will also give you better gas mileage, becuase it will increase the power without increasing the fuel consumption.

Moppie I know who you mean they are called Diesel and Turbo and they rebuilt the injectors for me. Two were apparently so bad that they couldn't be rebuilt. The nozzles on the other two were replaced.

Anyway I went for a test drive this morning up my test hill/rise on the North Western motorway. Outcome is that it the engine runs much smoother at low revs and has more more power in the mid range. However it is no better at going up hills in top gear. Using my normal set speed at the bottom of the hill/rise (100km/h my speed at the top was still 92 km at the top). My target is to be able to maintain 100km/h all the way to the top of this rise in 5th. The intersesting thing is I did two runs up the hill and the second one (with the engine a little bit warmer was definitely better)

Lifting the engine cover while running, The temperature of the pipe from the turbo to the inlet gets just hot enough that I don't want to keep my hand on it.

I think the next step is take a run up the same hill with the air firltes removed and see what effect this has before upgrading the turbo/fuelling.

Which hill are you running up the North Western?
If its the one near the end of the motorway then carrying 4,500 tones with a final speed of 92kph is pretty damn good.
Especialy that your not supposed to do more than 90kph anyway :)

Which hill are you running up the North Western?
If its the one near the end of the motorway then carrying 4,500 tones with a final speed of 92kph is pretty damn good.
Especialy that your not supposed to do more than 90kph anyway :)

Yes the hill at the end of the motorway.
Of course I was only doing 100km/h in the interests of research and science...its a bit like the way Japanese count whales!

At last a site where I might find some info. Good to see a fellow campervanner trying to get his van up hills at 100k. My goal too!!. 4400kg, 178 mitsi canter 4dr5 engine. I am trying to find out if I can turbo it. Some said no it only a handgrenade anyway, however, they are turboed in mitsi jeeps overseas. I also saw a guy who had one in Fuso that was going to turbo it. The power rating of the turboed, intercooled jeeps goes from 176 nm torque to 225 nm torque. Now my question is, does anyone know if teh 4dr5s have oil spray jets going up into the underside of the crown of the piston. And are the conrods tough enough to take the extra strain put on if it is turboed. 100km is fast enough for me, I just want to climb hills easier.

Mitsi makes a turbo'd version of the canter, and I know they will pull 4,000kgs gross up the bombays at an easy 100kph. But thats an empty box truck, so either you have a very light weight camper, or a very small canter.

If your another Kiwi then I know roadlife in Manukau can do turbo conversions, otherwise you might want to find a Japanese Used parts wrecker who can import a turbo'd enigne out of a 155, it should drop right in.

7.5 meter campervan, not much room to put another engine in there except maybe a 4dr7. It is the old version of Canter (78), narrow front wheelbase, wider rear wheelbase. Yes a kiwi, Riverton NZ. And this engine was rebuilt, pistons rebore etc 40 000 km ago, just before I bought it. So not too keen to trow it away even though it is underpowered, 80 ps at 3700rpm (so far as I can tell)

80 ps at 3700rpm (so far as I can tell)

Yikes, thats not a lot, althought it would have been state of the art in 1978.
All the new model canters start 120hp for that size chassis, and go up to about 160hp.


You might get away with some low pressure turbo charging, prehaps only 4-5psi.
You would need to build some custom parts, like exhaust manifold.
The turbo would be easy to sourse, the turbo canters use an off the shelf Garret unit, very similar to whats on the Mitsi Evolution lance.
You will need something in size.

Yes you are right, it is not much at all!!, and you don't have to drive it!!

I have seen a car turboed that had the turbo after the flange on the exhaust manifold, so in effect it was mounted in the ehaust pipe. So no change to the Ex manifold. I cant see why I can't do it. I though the biggest issue would be attaching the inlet pipe to the inlet manifold. The turboed 4DR5s in the jeeps didn't lift the hp much only the torque. I figured if I could get away with it, without blowing the engine it might be worth it.

One person suggested if I was putting in another engine I should put in a 4D31T. Another reason for not wanting to change the engine is I don't want to change the gearbox. It is a column change which is real good for the camper. It has swivel front seats and a floor change would just get in the way. The front section is all living space, not like some vans where it is only driving space.

A column change would be very nice.
An increase in hp normaly requires an increase in RPM as well, which you can't do. Its the increase in torque you want.

Turbos work of a differnce in heat and pressure accross the manifold, in theory the closer they are to the exhaust ports in the head, the better they will work.
You can plumb them in further down the exhaust stream, but they become less and less efficant. However, since your only looking for a low boost aplication that might not be such a big problem.

thnx already for the comments, yes exactly right, more power, (torque) not hp needed. Yes the column change is nice. Our van started as a truck, then it was stripped to a chassis, cab thrown away as well, and they started to build it from scratch. so it is 2.3 wide outside, 2.2 inside, and as I said the front is usable like a bus campervan is. The engine box is not very big either. So I figured that if I can turbo it without blowing it up it will make nice van to drive as well as live in.

Can anyone advise. I have a non modified Isuzu 4BD1T truck diesel. It has a 2" diameter thin wall steel pipe going directly from the standard turbo (about 5 psi boost I believe) Directly to the inlet manifold.

Aim is to get this to go up hills better with out having to change down as many gears.

Can anyone advise/guess the likely MAX teperature of the pipe going between the turbo and the inlet manifold? (Just a rough guess would be OK.) keeping in mind this is a low pressure trubo installation.

The reason for asking is that I am thinking about adding an intercooler and I have been looking at using some non silicon flexible pipe work. Rigid pipe work would be a real mission to get to an intercooler in front of the radiator. I have found some rubber hosing that wil take 150 degrees celsius and wondering if this will survive?

Can anyone advise if I intercool this with out changing the fueling am I likely to see any gain in power? and if so what woudl be a real rough guess in percentage terms?
I have a range rover with the same engine.
Mine runs 15psi boost and I have had the joy of instrumenting several parts of it (intake temps, exhaust temps, exhaust pressure etc).

With 15psi boost on a turbo with rooted compressor blades, the air temp at turbo outlet reaches around 150 C.
With 15psi on a turbo with good compressor blades the charge temp is down to 120 C.

Rubber radiator hose will handle these conditions for a short while, before oil degrades it.
Fuel hose will handle these conditions almost indefinitely. Silicon turbo hose will do the same job as the fuel hose for about 5 times the cost.

The formula for working out charge temps
Temp rise = compression ratio^(1.4-1/1.4)
Adiabatic outlet temp = inlet temp in kelvin (i.e 293K=20C) x temp rise
actual temp rise = adiabatic temp rise divided by efficiency

To save you some work, I have a spreadsheet.
5psi boost (I think you're running more) = 53 deg C outlet temp (20C inlet) with a 65% efficient turbo compressor.

I've just finished fitting a TD05 turbo to my 1994 Canter Motor home. (I too want to go up hills a bit quicker) I am amazed at the difference. A local hill I used to struggle up in 4th and just hang onto 60 klm on, I now fly up in 5th and can maintain 75klm,very happy with that. The truck feels much stronger and as if it wants to pull, rather than 'please don't make me go up another hill, I'll die" its really worth the effort. I am running 7.5 PSI boost and we ran the diesel pump adjusting screw in 2 full turns. It blows a bit of smoke if you pump the pedal down hard, but clears after a second or two right out to 3200 revs. Very happy if you just press down evenly and run along, no smoke. I am fitting an Exhaust Temp gauge and looking at a boost gauge just to be able to monitor whats going on. its interesting. Another bonus is it takes that un earthly sucking sound from the air cleaner under the passengers feet away. Very happy so far :iceslolan

Sorry, my motor is a 4D31NA. I fitted a turbo to it and will keep the fingers crossed re longevity. Does anyone know what Temp I should be looking for at the exit from the Turbo. I have fitted the sender unit in the first curve directly after the Turbo. Thanks

Sorry, my motor is a 4D31NA. I fitted a turbo to it and will keep the fingers crossed re longevity. Does anyone know what Temp I should be looking for at the exit from the Turbo. I have fitted the sender unit in the first curve directly after the Turbo. Thanks

750C is the limit for turbo inlet, put your own safety factor on that. More boost (and better intercooling) lowers EGT's, more fuel raises EGT's.
Unfortunately your probe in the exhaust down-pipe isn't much use, the temperature across the turbo continually changes, rough rules of thumb (100C drop, 200C drop etc) either drop performance un-necessarily or endanger your engine. If you really need to know, you need the probe in the manifold.

Make sure the probe is long enough to reach the centre of the gas stream.

The probe is about 75mm away from the outlet of the turbo. The EGT gauge came with instructions and this is where it indicated the sending unit could go.
I was wondering about the length of the probe, thats cleared that up, thanks.
So if 750c is the inlet temp of the turbo, If I allowed maybe 50 to 100c drop across the trubo and try and keep it around the 650C max area? I have fitted an intercooler . Thanks for your comments, so far I am very happy with the result.

The probe is about 75mm away from the outlet of the turbo. The EGT gauge came with instructions and this is where it indicated the sending unit could go.
I was wondering about the length of the probe, thats cleared that up, thanks.
So if 750c is the inlet temp of the turbo, If I allowed maybe 50 to 100c drop across the trubo and try and keep it around the 650C max area? I have fitted an intercooler . Thanks for your comments, so far I am very happy with the result.

650 post turbo is too hot, especially for a previosly non turbo engine which is unlikely to have piston oil squirters and alfin (steel reinforced) pistons. In the worst conditions you'll have over 200C across the turbine. 550C is a better figure, but post turbo is a guessing game.

The EGT gauge makers say post-turbo because they can't instruct the average muppet to drill and tap their exhaust manifold or turbo housing. They are protecting their own skin. I run a 3mm probe in the exhaust manifold and it's been perfectly good for the last 6 years.