During a recent visit to the local junkyard I spotted an F150 Custom Turbo Diesel from the 80s with a single turbo that spun freely when I attempted to turn to the turbine with my finger.

Its a little rusty but would it be possible to rebuild it and use it on a small block chevy? the guy said he would sell it to me for $20.

The truck was wrecked, side impact, so the engine might still have run.

 

It shouldn't be a problem if the diesel engine is twice the size of the gas engine you're putting the turbo on..

Cheers,

 

the type of combustion specific to diesels also raises the amount of exauhst gasses.

 

Thats exacly what i wanted to do so did you ever do it??

 

Looking at this theoretically....

Since diesel has an cetane rating, I'll assume that diesels burn a hydrocarbon molecule that can be represented as

CxHy -- where y is usually equal to 2x + 2

Oxygen (O2) is the oxidizer for the fuel and the products after the reaction is

H2O and CO2

If you look at carbon dioxide, there is no change in volume of gas because there is the same number of oxygen atoms in oxygen and carbon dioxide. With water, the volume of gas doubles because there is only one oxygen in water.

So the actual combustion in a diesel and gas engine is about the same (I do understand in thermodynamics that diesel and otto cycles are a little different), just ignited differently. One would conclude that exhaust gasses for both engines should be the same.

I do agree that the WAY higher compression of a diesel would have some affect on the exhaust gasses like giving it more energy and raising the temperature of the exhaust gasses greater than gas engines.

 

so then what gives with people using turbos on 5.0 to 5.8 liter gasoline engines to make 8-12 pounds boost when they were originally on a 6.5 to 8.0 liter diesel engine making 28-30 pounds of boost?

 

The wastegate is set to 8-12 psi boost. Also there are compressor efficiency maps to consider.

 

yeah but why dont they have horrible lag if they are so mismatched then?

how does a 7.3 liter engine and a 5.0 liter street motor end up needing approximately the same turbo?

 

I can't say anything about the lag since I have never seen a side-by-side comparison, but I'll take your word for it. I can only guess at an answer and I won't waste brain matter on that one.

 

Diesel uses heat produced by compressed air to ignite the diesel.

Just incase anyone wanted to know

 

Man that be a rigid idea! That turbo combined with a small block chevy, a Dodge tulip, & a Ford patunia would make for a wicked combination. However, you have to watch the overall maximum boost, due to the inflation of bologna. Mamma always said its better to blow than suck. Inflate that baby until the spleen stimulates the prostate causing the urge to POOP!

 

budda,

Dont do that, you're just making people dumber.

 

 

doesnt diesels use a 4" exhaust system

 

B4Ctom1 – you’ve made that statement before and I replied before that that was wrong. Diesel does not have any different effect on sizing then gas.

Airflow = (displacement/2) * rpm * VE for both types of engines.

Typically, many diesels may be designed to work at below 3000rpm, where gas engines typically work up to 6000rpm or more… looking at the above, you’ll see that at 2x the rmp you’ll have the same airflow with half the engine.

Assuming similar use, when trying to find a diesel turbo to use on say your 5.0 or 5.7L gas engine, you’re looking for a 10-12L diesel. The thing is that until recently, you couldn’t assume similar use. Diesel’s were typically designed to spend a long period of time at a steady load, where we (gas engine guys) often look for quick, instantaneous changes in load and response. The end result is that that turbo off an engine that is 2x the size will be a little on the large side for a gas engine because when it was matched to the diesel they didn’t worry about how fast it would spool since it had all day to do it. Because of that, you would actually be looking for a turbo off a slightly smaller diesel.

The reason that I quantified that with “until recently” is that diesels are not starting to come under some emissions regulation, and in an effort to get them to run cleaner, they are now being run with leaner mixtures and OEM’s are now starting to worry about how fast the turbo will spool. The result is that most more recent designs use turbos with smaller turbines and wastegates to spool faster which would better match that gas engine that is ½ the size.

Of course, all of this is just a rough rule of thumb… you’ll get a much more accurate answer by looking at the NA powerband of the engine, the intended max hp for then engine under boost, and then matching a turbo with a matching compressor map…

 

I could buy that.

So what if:

A) the turbo diesel wasnt maxing out the turbos capabilities in its normal operations...

B) I did, but didnt expect alot from it...

For example. A 6.0L to 8.0L Diesel (in a newer truck) making like 300 hp at 25 psi all day long. This same engine as a given would, if you maxed the turbo out it made 400-500 hp full boost 32-35 psi (Im not looking for figure accuracy on this side of the equation).

Then You took the same turbo and say wanted to make like 400 to 450 hp at 10-12 pounds in our 350 in your camaro.

Is that beyond the bounds of what could be made to happen?

 

Can you clarify what you’re asking? I reread what you wrote a few times and I wasn’t positive I was understanding what you were asking.

From what I think I’m following:
WRT to (A), OEM setups almost never ‘max out’ a turbo’s capablilities on the compressor side, but are usually sized somewhat small on the turbine side.

WRT to (B), I’m not sure what you’re saying.

To a great extent, the amount of boost you need to run to make the power on that engine does effect the size of the turbo. The more boost you have to run (within the limits of what the compressor can do) the smaller the compressor could be and supply the volume of air necessary to make the power.

To make 400hp (at the crank) out of something like an L98, a well tuned/well designed setup would only need around 7psi, possibly less, and you could get 400-450hp of air out of most turbos used on diesels, certainly out of something like what is used on a Powerstroke (FWIW, the new, smaller powerstroke comes with a larger turbo on it then the older 7.3L ones). OTOH, the Holset used on the Cummins 5.9 is probably too small.

 

I guess following that process that if a deisel can make in the 400-500 hp range with the turbo then could I?

 

typically, you could use a turbo off a diesel to feed about 2x the HP on a gas engine compared to the HP of the OEM diesel setup. It's difficult to compare it to "what it could do on the diesel" because turning up the boost on one doesn't give you more power, adding fuel does.