turbodisplay
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| posted on 10/6/10 at 04:49 PM |
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Diesel turbos in a petrol engine
Is it possible to use a diesel turbo in a petrol engine? I know that in the past the heat was ment to be too much, but heard that nowdays most diesel
turbos can cope with a petrol engine.
With diesel turbos pushing 150+ hp from 2l engines, more if chipped I cannot see the exhaust temps being much lower.
Of course there is the issue of the compressor maps, different rev range etc.
Darren
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austin man
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| posted on 10/6/10 at 04:57 PM |
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is there something that requires doing for the wastegate ? as they are slightly different to petrol units
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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turbodisplay
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| posted on 10/6/10 at 05:04 PM |
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Most modern units have varible vane technology - effectively like swiching the turbine fitted on the fly. I guess they might not cope well if the temp
is much higher.
I think there are sill a lot of normal wastegate types as well.
Darren
[Edited on 10/6/10 by turbodisplay]
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Stott
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| posted on 10/6/10 at 08:24 PM |
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I don't think it's viable as they are all a bit small, they can push the pressure out alright but only really for an engine requiring
5Krpm max, when you're on about 7k and maintaining the boost level they can't cope.
You should see the size difference between my tdi unit (approx 3.5"diam) making 1.63 BAR and my workmates Celica GT4 unit running 1.35 BAR
(approx 6" diam) !!  
And they are both on the limit as far as boost goes
I guess if it was a low boost app though it might work, but it's to do with CFM IIRC
HTH
Stott
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hobbsy
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| posted on 10/6/10 at 11:00 PM |
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You could run them as twins but longevity would still be an issue
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bi22le
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| posted on 10/6/10 at 11:04 PM |
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my mate is supercharging a rover v8. The supercharger is a massive turbo from a very large mariene engine. It must be about 200mm in diameter
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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turbodisplay
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| posted on 11/6/10 at 06:59 AM |
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Regarding heat I can see that he higher compression ratio of a diesel will reduce exhaust temps, but the rich mixture of a petrol turbo should lower
temps.
It would probally require two 2l diesel turbos to power a 3l petrol engine.
Darren
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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alistairolsen
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| posted on 11/6/10 at 07:16 AM |
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First of all, twins are pointless. Find a single turbo to suit your application.
With ref to temps, variable vane geometry is generally accepted not to stand u to the heat. Its not CR and mix related, diesel just burns cooler than
petrol be a couple of hundred degrees.
I looked at it because the most suitable turbo for what i wanted (160bhp) tended to only be available on diesels. If youre fitting to a 3l, why would
you want to use one? use one of the many commonly available petrol turbos in that size range!
Turbos are rated by efficiency, limited on flow and pressure. a bigger engine will consume more air and therefore the pressure will drop at high rpm
if the turbo cannot flow enough to meet demand (this is how most OE engines are setup) a bigger turbo (selected correctly) will make more boost high
up and if correctly controlled a more linear torque curve
My Build Thread
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turbodisplay
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| posted on 11/6/10 at 02:00 PM |
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I am planning on a sequential setup as I really hate lag, my 2l turbo just is too slow until it gets going, thinking that a diesel turbo will give me
boost quicker through the lower reve range.
As far as temps go burning 1 mole of diesel will produce a similar amount of power as 1 mole of petrol, so the difference in heat must be the thermal
efficiency of the engine. As the compression ratio is higher, more energy is absorbed from the gas before being released.
Darren
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sebastiaan
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| posted on 11/6/10 at 02:49 PM |
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quote:
Originally posted by turbodisplay
As far as temps go burning 1 mole of diesel will produce a similar amount of power as 1 mole of petrol, so the difference in heat must be the thermal
efficiency of the engine. As the compression ratio is higher, more energy is absorbed from the gas before being released.
Darren
Partly true (the compression ratio bit). The lower temps are caused by a higher lambda (i.e. a diesel runs much cooler than a petrol engine). The 911
turbo used variable geometry turbine turbos and those were specced at 1050 degrees C. And mega expensive.
A standard diesel turbo on a petrol engine will not work for long. It WILL either destroy the turbine housing or the turbine wheel. It's simple
physics...
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turbodisplay
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| posted on 11/6/10 at 03:08 PM |
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At full throttle isn`t the lambda ratio about 1? I`ve seen some chipped diesels that pour smoke when the throttle is opened. Also seens a narrrowband
lambda sensor on a diesel also pointing to lambda 1 being used at some point in the cycle.
Darren
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