Comparing Petrol to Diesel Turbo'd Engines
Turbo Mini Forums

A recent discusion on the GT15 got me thinking about the one I have in the garage. After a bit of digging it seems to be off a 90bhp 1.9 diesel.

I'm now trying to find out it's suitability for use on my 998 (say 110 to 120bhp)

I have a spreadsheet that I use to work out all the airflow and pressure requirements for a petrol engine, but surely this won't work for a diesel engine. the BFSC will be completly different for example.

Also, asuming my impellor has the same dimentions and trim as that listed on the Garrett website, is it fair to assume the comp map is pretty close to that listed?

Any thoughs?

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

There are too many variables to make a direct comparison.

1. Peak hp may only be at 3000rpm on the diesel. Torque may be more appropriate.

2. Boost. How much boost does it run on the diesel?

3. BSFC, AFR and Hp per Lb/min of air may all be different.

As long as the compresor dimensions match the map, then just use your spreadsheet and plot the results.

If it is the larger of the two GT1544s, then it looks a good selection.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

bung it on !

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Obviously I'll bung it on it was free(ish).

Worst case it'll be an easy swop for another GT15 of a different spec with the same flange.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

i.e. I paid for it", it was cheap though.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

you two crack me up.....

In return rebuilt GT17, shouldn't complain really.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Was that the deal? First I have heard of that. Your are right though a good swap.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Hi wil_h,
Remember I built my low boost 998 with the VNT15 coming from a 110hp VW 1.9TD.
It was an interesting but negative experience. Diesel turbos are built to run with a much lower gas temperatures. This "big" VNT even with wide open VNT control spins like hell from 4000RPM, it's just too much for it. So the compressor is in surge.
This may have worked with a huge external wastegate, but it makes a quite complex system with 2 wastegates, not to mention that VNT must be controlled in a very special way (I have an RC servo for that).
For my next (and coming) 1bar setup I just bought a Subaru Legacy 2.5 biturbo turbos (ball bearing), they costed nothing in the US on ebay.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Cheers for that, what was the compressor spec of the turbo you used?

Looking at the garrett website the GT15 looks ideal, but I suspect that the 15s available direct from garrett are not the same as those off TDs.

Only one way to find out!!

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Coming back to this question.
I've started working on my "stage 2". Removed the VNT15 and compared it with the Legacy twin-turbo (2L ~250hp) second stage turbo. Compressors look very similar, I mean the case has the same size, the compressor wheel as well (did not measure though but anyway specs of both are unknown). Turbines are quite similar.

So now I'm back to my old idea of adding an external wastegate to this VNT which works great at low RPM, I even bought the WG last year.

With VNT15 (which comes from a 115hp VW 1.9TD the problem was that it got uncontrollable from 4000RPM, it was spinning like hell and pressure was going to 500mbar even at light load. So probably temperature, as the gaz flow of my 998 is lower than in a 1.9L TD.

So I have a question to experts: will the VNT stand the high gas temperatures of the petrol engine if I bypass most of gases to make the turbo consume just the necessary to give me 100hp ? The VNT is just oil cooled. I understand without numbers it's hard to say, but still what do you think ? Once again, turbine and compressor sizes are very similar.
Thanks

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

How about a remote turbo on the clutch, exhaust gases should get cooler by the time they get there ?

(I hope so, my DCi turbo is rated at 700°C tops ...)

Rusty by nature

No no, would expose the turbo too much. Up to know my car had an original look and it should stay like that, MOT guys don't notice the turbo.
My idea is that if the diesel turbine extracts more energy and thus needs only a fraction of the flow, perhaps it would heat less than a petrol one ?

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

I think that these days the diesel and petrol turbos are generally the same in terms of temperature rating.

In days gone by, they probably used inferior materials in turbos for diesel cars, but I don't think they do anymore.

Garrett certainly quote their turbos for use in petrol or diesel engines without distinction.

There are a number of 200hp plus turbo minis running on just oil cooling as well.

When it comes to the VNT, there may be issues with temperature on the moving vanes. You will just have to suck it and see.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

shurly a diesel turbo can withstand the high temps.

just for comparison ( i am no expert)

I have used a Td5 landrover discover often to haul hevvy trailers ive seen the turbo glowing red after towing a 3 ton trailer up a 12% 2 mile long gradiant.

I also remember years ago while collecting a classic landrover from switserland good 2.5 - 3 tonnes behind a 300 tdi discovey that that to was glowing wel in the dark when we got to the to of a high pass in the alps we stope then just to let the turbo cool douwn as it must hab been 3 of four miles up hill and boy was the doscovery tdi pulling hard in 3rd gear and just making the top doing less than 40 MPH after hitting 70 befor the start of that graidiant

If the metal of the turbine is glowing red hot then that must be som serious heat, the 300 tdi discovery is still going strong on the original turbo and still used to pull a 1.5 tonne tractor with about another ton of machienery on a flat bed around the west coast of scotland.

EGT's on desels can get up to 800 c after fiddleing with fuleing most are over fuling before boost and still over fuling even on full boost discovery 300tdi run between 0.8 and 1.2 bars of boost under full load.

Cheers, Andrew

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Little car Little power........... For now That is!!!!!

1983 mini down paid, must collect soon and get welding!
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Petrol EGTs can hit 1000 degrees C (you should be aiming for less than 900 though.

Diesel only gets to about 800 degrees C and thats the most - typical temps are more like 400.

Thats the problem with VNT on petrol - to my knowledge the only people running VNT on a modern petrol engine are Porsche in the 911 turbo. They state the turbo uses "space age materials" lol but I can't find any more info than that.

Alex

AlexF