Supercharged diesel engine

[nivaman]

What are the pros and cons of fitting a supercharger to what was formally a turbo charged diesel.
I am aware the majority will say leave it as a turbo but am wanting to investigate this seeing as both the turbocharger and supercharger are effectively a supercharger .
Will the s/c require separate boost control or could the original turbo boost control be used.
I assume the heat output would be less with the s/c as with the turbo, bearing in mind psi pressures used.
Has anybody had experience with the Toyota SC14 s/c or Garrett turbo's?.

[badnuz]

Read bulletproofs thread

[andrew007]

wot sort of engine are you looking at doing this to?

[nivaman]

Fiat Tipo 1.9 turbo diesel.

[Nivapulledout]

theory says should be fine. If you get your gearing right with a supercharger you can not overboost anyway, just a matter of playing around, should give really nice torque.
you could even keep the turbo and just have a bypass valve on the supercharger, so you are using supercharger down low and the turbo up high bypassing the charger. this is how all turbo detroit diesels run and the old ones are all running with no relief valves or electronic controls. just the a diaphram which adds fuel when under boost.

[Nivapulledout]

oh and on the heat output I am guessing you mean charge air temp.
it will not be much difference between the two at a given pressure as most of the increase in air temp is from the compression of the air, not heat transferred from turbine to compressor.

[darinz]

The big thing you need to remember is that a turbo uses waste energy to create the boost where as a SC draws energy from the crank to produce the boost. So from an effeciency point a view a turbo wins hands down.
As far as lag goes, with a diesel and the correct sized turbo this is very minimal so not really a factor.
There has been plenty of comparison tests done on Nissan TD42's so quite different due to size and older design but the end result was that on a deisel turboing was cheaper and produced better results. This isn't saying more hp or torque, it is saying better performance. Don't get dyno figures mixed up with real world results.
Also as was stated above, the majority of intake heat in a turbo is from compressing the air not heat transfer so the same intake temps will be achieved with a SC.
Normally a SC runs less boost than a turbo but it produces it lower down so it feels like more overal power.
I like turbo's with lowish boost as they produce a more predictable power curve so makes it easier to actually put power to the ground. Think of it this way, with a SC all the power hits instantly low down which is either exactly what you want or exactly what you don't want. With a turbo th power comes on smoothly so you have far better control of it and traction. If you need it all instantly then you either dump the clutch or (with an auto) load the torque converter by applying the brake.
Look at it this way, 10psi will basically achieve the same hp whether turbo or SC but with the turbo the power is gradually applied.
Personally I think a turbo achieves better overal performance on a 4x4 for offroad.
Now if you talk high boost, then you are talking large turbo's, lag etc and that is a different story.
(But alot of that is opinion and observation)

[Bulletproof]

I have been running a SC 14 on my 5L for years with a dual air system worked manually and it is far superior to a turbo with lots of control.

Because I have boost at idle I can pick a line at idle and then floor it with instant pickup.

On steep hills I can shut off and gain traction without dropping out of the turbo range and not being able to get back into it like the turboed trucks.

1KZs with there turbos which are the same cc as mine just don't have the the instant pickup for standing starts on steep hills. They just have not got the pickup to spin the wheels.

Cheers Richard

[Nivapulledout]

and yours is a mean truck man I have seen your vids. sounds great as well

[nivaman]

Thanks Bulletproof
I like the idea of instant boost, with your engine are you still running the turbo?.
How many psi is the S/C running?.
What is your dual air system and how did you design it?.