Diesel Turbo, Petrol Engine

[D-Angle]

Can anyone tell me if there is any reason why you can't fit a turbocharger from a diesel engine to a petrol motor? Obviously you have to fit lower compression pistones etc, but are there any fundamental differences between a diesel and petrol turbo that I don't know about?

[slinky]

I seem to remember reading in PPC that the materials used in turbo's designed for diesel engines are different to those used for petrol, as such they aren't interchangeable..

[wheeljack888]

Gasoline exhaust temperatures are upto 300deg C more than diesels, and have to be designed to suit.

A diesel turbo wouldn't last long on a gasoline.

[PJR]

Also, petrol engines generate vacuum in the inlet tract, where as diesels generally do not. I believe. This means turbo's on petrol engines need a special oil seal, or the vacuum would draw oil out of the turbo, and cause quite some smoke.
Im not an engineer however, but its something very much along these lines!

Cheers, P

[stevieturbo]

Id say for most applications, they would work just fine, as long as they are sized suitably.

I doubt the seals are any different in modern turbos, and it would be extremely rare for a turbo to be mounted in a suck through application these days for it to matter.

[thong]

PJR said:

Also, petrol engines generate vacuum in the inlet tract, where as diesels generally do not. I believe. This means turbo's on petrol engines need a special oil seal, or the vacuum would draw oil out of the turbo, and cause quite some smoke.
Im not an engineer however, but its something very much along these lines!

Cheers, P

theres more oil pressure than vac,so seals will be the same as use'd on petrol motors.

[Marquis_Rex]

wheeljack888 said:

Gasoline exhaust temperatures are upto 300deg C more than diesels, and have to be designed to suit.

A diesel turbo wouldn't last long on a gasoline.

What he said.
As an aside it's a reason why Variable Geometry Turbines are more common on diesel engines: The lower temperatures mean that tighter tolerances can be specified without having to worry as much about thermal expansion limits.
The Porsche 997 Turbo uses VGT on a petrol but it uses very expensive ceramic turbines.

A bit of a sore point for me as I've just had to change both Turbo chargers on my Porsche, but I reckon the Turbos on a Petrol engine have a harder life in terms of durability too due to the heat.
A guy here from Diesel development disagrees though, saying that the oxygen rich exhaust gases of the diesel engine don't do the Turbines any favours in terms of high temperature corrosion. Wheeljack- do you have any thoughts on that?

Edited by Marquis_Rex on Monday 13th November 09:42

[GavinPearson]

Assuming that the material in the turbine could take the heat the next hurdle is matching the turbo to the engine. It's not an easy task. I would doubt that you would find something on a diesel that matched the petrol engine correctly. Drive a car with a well matched turbo and you will understand what I mean.

[wheeljack888]

Marquis_Rex said:

A guy here from Diesel development disagrees though, saying that the oxygen rich exhaust gases of the diesel engine don't do the Turbines any favours in terms of high temperature corrosion. Wheeljack- do you have any thoughts on that?

I can definitely see that being a problem. Also more recently you have DPF regeneration cycles which chucks burning fuel at the turbine blades, that must cause a few problems too.

Just to add on the diesel temperature comments, when I designed an turbo exhaust manifold, I had to put in a 'tight' fixing hole on the manifold and slots in the other fixings (increasing in slot-pitch the further away from the tighthole) to account for thermal expansion. What we didn't want is the assembly expanding against a hardpoint and causing undue stress. The tighthole was to provide a 'relatively' geometrically stable part for the turbo, which was bracketed to the cylinder block. I would guess that the turbo assembly would designed with a similar principle in mind, and therefore a gasoline turbo would have 'sloppier' fixing locations. The other thing is turbo efficiency is probably dependant rotor to housing clearance so the tighter you can make it the better, and this is probably more possible on the diesel turbo.

Cheers

Phil

[chuntington101]

well a turbo suppkier (one of garretts no the less) has used a VNT turbo form a deisel on his Scooby for a while now! to great sucsses! the only problem was getting the a crontroler for the VNT but he got around it in the end. tuyrbos still working great i think.

but yes they do use a diffrent iron to what the petrol ones do, but then if the turbo your looking at fitting on your car is half the price and lasts 80% as long you may as well go for the deisel turbo!

thanks CHris.

[wheeljack888]

OK, I concede!

I do probably come across all doom & gloom, and you probably would be fine for 30000+ miles using a diesel turbo on a gasoline (depending how benign the usage is of course).

But I do believe that it is very hard for the pro-am enthusiast (even engineer's close to the industry) to appreciate the mind-blowing detail and complexity that's involved in modern engine design. It ingrains a very deep circumspection that to many may seem unnecessarily pessimistic.

[Marquis_Rex]

chuntington101 said:

well a turbo suppkier (one of garretts no the less) has used a VNT turbo form a deisel on his Scooby for a while now! to great sucsses! the only problem was getting the a crontroler for the VNT but he got around it in the end. tuyrbos still working great i think.

but yes they do use a diffrent iron to what the petrol ones do, but then if the turbo your looking at fitting on your car is half the price and lasts 80% as long you may as well go for the deisel turbo!

thanks CHris.

Was it in the UK? Then, yes it's possible this set up may last if you're lucky, trundling around at your low speed limits with the possible odd temperature peak during transients, but you;re playing a game of chance.
OEM stuff is tested to the limit regardless of which country it's going to, the turbo compressor characteristics are matched fastidiously.

That's why when I see supposedly knowledegeble people on forums peddling the latest "hybrid" set up on some Porsche Turbo which gains low speed torque and top end I'm ALWAYS weary. How was it optimised? By the seat-of-the pants dyno? You cant even match turbo-compressor characteristics on an engine dyno properly.Someone like Borg And Warner or Garret will make sure the turbine and compressor efficiencies are finely tuned and matched containing for aspects such as high altitude overspeed compensation.

[chuntington101]

Rex, no it was a guy in the states that was doing it. he used a GT32 equvilent (i think). it was a garrett turbo and it was deffinatly VNT. as i said worked very well on his motor, and may still be once he got the problems ironed out (VNT control).

Thanks Chris.

PS. if anyone wants a link ot his site then feel free to ask and i will mail it to you. dont want to p!ss of the mods