Turbo vs Supercharger
12-01-2004, 04:35 PM
#34
Originally Posted by Geo
All that other stuff about backpressure, etc. is a red herring. You have backpressure with a supercharger as well. .
This was your statement. The backpressure is the same with a Belt driven Supercharger as without. The Backpressure with a TURBO however, is NOT at all small.
12-01-2004, 04:45 PM
#35
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so it seems like the general verdict is that the SC is better for low RPM power and the Turbo is better for redline RPM power.
So for road racing the Turbo is better and for drag racing the SC is better.
I was just thinking it would be cool to make a 951 SC (not centrifugal) for some low end power for around town.
So for road racing the Turbo is better and for drag racing the SC is better.
I was just thinking it would be cool to make a 951 SC (not centrifugal) for some low end power for around town.
12-01-2004, 04:48 PM
#36
GEO -
I am very real. Forced induction on a belt driven suprcharger WILL rely on exhaust scavenging. I will assume you were keeping your perspective narrowed to Turbos, which usually would not use scavenging as the piston must PUSH the air into the header. Heat and pressure are what drives the turbines.
I will. Thank you for this source. Hopefully he will not be as scewed as some in the direction of turbos being better for ALL APPs.
... Well we are BOTH using second hand knowledge at best.
...That could be true. Where the RESIDE DOES. Do they reside in an area with little or no cooling air? Then the compressor side WILL get hot. I heater works in the same way. Blow air through a metal apratus (that is heated itself) to heat the air on the outlet.
Are you for real? Backpressure in the exhaust is backpressure in the exhaust. If you pump more air into an engine, it still has to flow out. Both forms of forced induction benefit greatly from increased exhaust size. Since forced induction does not rely on scavanging like an NA, you cannot go too large on a exhaust (per a Garrett engineer who happens to be a friend of mine).
Go read the forced induction portion of Mike Kojima's "Suck, Squish, Bang, Blow" series in Sport Compact Car a few years back (before it became a punk talking ricer mag). I understand it's in book form now as well.
You're disputing things being written here, but I don't see anything backing up your claims either.
Oh, and BTW, from the Garrett engineer, the heat of the exhaust has very little impact on the discharge temps of a turbo.
12-01-2004, 04:52 PM
#37
Race Director
Well, to add a tidbit of interesting history to this thread, the Lancia Delta S4 in the mid 80's had both a supercharger and turbocharger. One of these cars ran over my foot when I was at the Olympus WRC Rally in Washington State back in the late 80's. 
The supercharger took care of the early turbo lag, and the turbo was for the high rpm muscle. Boy was that a complicated engine compartment!
The supercharger took care of the early turbo lag, and the turbo was for the high rpm muscle. Boy was that a complicated engine compartment!
12-01-2004, 04:52 PM
#38
Nordschleife Master
Originally Posted by 944J
so it seems like the general verdict is that the SC is better for low RPM power and the Turbo is better for redline RPM power.
So for road racing the Turbo is better and for drag racing the SC is better.
I was just thinking it would be cool to make a 951 SC (not centrifugal) for some low end power for around town.
So for road racing the Turbo is better and for drag racing the SC is better.
I was just thinking it would be cool to make a 951 SC (not centrifugal) for some low end power for around town.
I would think since the turbo has lag the throttle modulation would suffer a great deal when it came to handling.
12-01-2004, 04:54 PM
#39
Originally Posted by Geo
BTW, what are your credentials and/or what is the source of your info?
My credentials to try and highlight some misinformation regarding the outlet temps on turbos? Or to highlight the "same boost pressure" power difference statements that sound a bit "chat room fact" based? I've read and continue to read (thanks again for that source) 100s of articles and books (which I can only refer to as *semi* unbiased) about FI. Do I manufacture my own turbos or superchargers? Nope. Do you?
I've taken apart (and nearly put back together
) three 928s and one 944. Much of my info comes from Smokey's book and A. graham Bells two books on performance tuning and Forced induction.
I'll be looking forward to getting into reading that source you mentioned.
12-01-2004, 04:59 PM
#40
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Originally Posted by Rich Sandor
talking about post compressor temps:
how many supercharger setups do you see with intercoolers?
how many supercharger setups do you see with intercoolers?
12-01-2004, 05:12 PM
#41
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I dont think its that much heat in a turbo. I ran 18psi of boost on a murker once with NO INTERCOOLER and it didnt asplode. harharhar. I would powerslide it in 2nd gear on pavement at like 6500rpms bouncing on the revlimiter at 18psi. I did this for around 2 months with my friend. The car didnt exlpode lol.
Why isnt this on the 928 forum, ill tell you why. The CS Supercharger guys constantly bicker and flame about turbos like they are the devil. Except for andy i like his roots type blower kit since its cheap and works well.
I was doing some research on superchargers once and turbos, have read sevral books and they all come to the conclusion that roots and CS chargers loose effiency over 14psi of boost. Hell a roots blower 12 is like pushing it.
If superchargers are so good and so much better how come the 18 Wheeler truck market uses turbos? Hell my dads semi has like 800,000 miles on the turbo... I guess that means turbos are better to me.
I would like to twin turbo my 928 but im too poor. So im going to make a rear mount turbo for it myself. It may be laggy but i found a used nitrous kit for cheap so i can shoot like a 25hp shot in 1st gear to spool it.
Why isnt this on the 928 forum, ill tell you why. The CS Supercharger guys constantly bicker and flame about turbos like they are the devil. Except for andy i like his roots type blower kit since its cheap and works well.
I was doing some research on superchargers once and turbos, have read sevral books and they all come to the conclusion that roots and CS chargers loose effiency over 14psi of boost. Hell a roots blower 12 is like pushing it.
If superchargers are so good and so much better how come the 18 Wheeler truck market uses turbos? Hell my dads semi has like 800,000 miles on the turbo... I guess that means turbos are better to me.
I would like to twin turbo my 928 but im too poor. So im going to make a rear mount turbo for it myself. It may be laggy but i found a used nitrous kit for cheap so i can shoot like a 25hp shot in 1st gear to spool it.
12-01-2004, 05:27 PM
#42
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Originally Posted by TarHeel 944S
Yep, I've seen numerous 944 N/A engines with superchargers on them before, I was asking to see a 951 engine supercharged as 944J stated.
I'm pretty sure that would be pointless to perform, having a perfectly good turbocharged engine and taking it all off to slap on a sugercharger...doesn't make much sense to me at all...
I'm pretty sure that would be pointless to perform, having a perfectly good turbocharged engine and taking it all off to slap on a sugercharger...doesn't make much sense to me at all...
12-01-2004, 05:27 PM
#43
Race Director
Originally Posted by BrendanC
This was your statement. The backpressure is the same with a Belt driven Supercharger as without. The Backpressure with a TURBO however, is NOT at all small.
12-01-2004, 05:31 PM
#44
Race Director
Originally Posted by BrendanC
I am very real. Forced induction on a belt driven suprcharger WILL rely on exhaust scavenging. I will assume you were keeping your perspective narrowed to Turbos, which usually would not use scavenging as the piston must PUSH the air into the header. Heat and pressure are what drives the turbines.
12-01-2004, 05:32 PM
#45
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Originally Posted by Rich Sandor
talking about post compressor temps:
how many supercharger setups do you see with intercoolers?
how many supercharger setups do you see with intercoolers?