P38 turbo or supercharger?

jarmin2610 · Mar 25, 2011

Just been told by a bloke that superchargers are more economical than a turbo due to less lag and instant power.
Is there any truth to this and can you get a supercharger fir the p38 2.5 BMW lump?
Discuss!!!!!

wammers · Mar 25, 2011

Power from a supercharger is there all the time true. But they take a lot more power from the engine than a turbo does. I don't see how a supercharger can be more fuel efficient than a turbo. Turbos use free energy superchargers need to be driven by the engine.

jamesmartin · Mar 25, 2011

i agree the whole point of turbo is the economic way of getting more power but with the down side of lag

Steve_R1979 · Mar 25, 2011

jarmin2610 said:
Just been told by a bloke that superchargers are more economical than a turbo due to less lag and instant power.

Complete bollocks!!!!!!!!

As said above, a charger is belt driven, and takes power in order to give power.

A turbo runs of waste exhaust gasses that are free!!!!

dogsbody · Mar 25, 2011

Unless you run the supercharger through a clutch, usually electromechanical, so that it is only powered when you want it. Means a bit of lag as it spins up but it saves on fuel the rest of the time.

It would mean a custom build that would cost more than your Rangie, you probably wouldn't be able to see over the bonnet and the engine would self destruct the first time you used it. But apart from these minor points I look forward to seeing the photos.

jarmin2610 · Mar 25, 2011

Ha.
Guess he was talkin out of his arse then.
Thanks for the replies anyway.

zen · Mar 26, 2011

actually he is not...kind of right in a way...thats why you may have noticed lots of s/c on modern cars..(mercs,bmw's etc)

modern supercharger setups dont always run the supercharger on load..ie on tick over,crusing,over run they are not on load and draw no power(well bugger all)..this is due to the boost being vented into the intake thus unloading the s/c and hense very little power required to spin it...
when on load though power is sapped as my 112 eaton draws upto 50hp to give max boost..the control for this is mechanical and vacum from engine controlled (vac opens valve,valve unloads s/c)

however..turbo's use "free energy"..ie exhaust.but even that is not free,for example as just bolting on a turbo without proper research,as too big turbo =massive lag..too small=restricted exhaust,no top end power..most turbo setups ,even moderm oem setups are a compromise..

so yes a supercharger will work on your engine..but you got a turbo ..so why ever considering s/c??

also..a supercharger is good in economy issue over a turbo at low boost as its instant..and hense you have more bottom end torque..if used wisley can give improved mpg,espically over a n/a engine(really applies to petrol lumps more as dieasels tend nt to suffer from lack of low end torque..)

wammers · Mar 27, 2011

zen said:
actually he is not...kind of right in a way...thats why you may have noticed lots of s/c on modern cars..(mercs,bmw's etc)

modern supercharger setups dont always run the supercharger on load..ie on tick over,crusing,over run they are not on load and draw no power(well bugger all)..this is due to the boost being vented into the intake thus unloading the s/c and hense very little power required to spin it...
when on load though power is sapped as my 112 eaton draws upto 50hp to give max boost..the control for this is mechanical and vacum from engine controlled (vac opens valve,valve unloads s/c)

however..turbo's use "free energy"..ie exhaust.but even that is not free,for example as just bolting on a turbo without proper research,as too big turbo =massive lag..too small=restricted exhaust,no top end power..most turbo setups ,even moderm oem setups are a compromise..

so yes a supercharger will work on your engine..but you got a turbo ..so why ever considering s/c??

also..a supercharger is good in economy issue over a turbo at low boost as its instant..and hense you have more bottom end torque..if used wisley can give improved mpg,espically over a n/a engine(really applies to petrol lumps more as dieasels tend nt to suffer from lack of low end torque..)

So he fits a modern supercharger and saves a couple of mpg. He will have to use the car for the next 500 years to even pay for the convertion.

juiceyv8 · Mar 27, 2011

Bad enough trying to keep a stock p38 running let alone running any sort of boost.

bison4x4 · Mar 27, 2011

zen said:
however..turbo's use "free energy"..ie exhaust.but even that is not free,for example as just bolting on a turbo without proper research,

Exactly, for example, a turbo engine has a different cam giving altered valve timing from a normally aspirated engine.
The exhaust valve opens earlier at the end of the power stroke to recover waste heat/exhaust gas pressure to drive the turbo, thus causing a loss of driving power, but it increases the efficiency of the turbo, which would then give hot compressed air to the inlet manifold.
So that then needs cooling in the intercooler to increase the volumetric efficiency.

So - as you said, not exactly free!

Sorry, had to cut that ^^^ down a bit - I was getting too boring.

P38 turbo or supercharger?

jarmin2610

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wammers

No longer with us, RIP

jamesmartin

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Steve_R1979

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dogsbody

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jarmin2610

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zen

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wammers

No longer with us, RIP

juiceyv8

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bison4x4

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