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JohnJL's Avatar
 
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Supercharged 3.4L Results

I have a summary thread over on the general board (Supercharged Race Car Build) but I thought I'd post here for the more focused boost crowd.

Here are the results....I'm going to take a break from it now and just drive it (when it lands in Toronto.) I'd be interested in what the next move might be...I'm getting good power for .8 BAR but even on the smaller pulley I cant get more than that and I built everything with 1.2 BAR in mind.

Anyway, I'm happy with 337hp at the wheels through a G50 in a 1000kg car...to the track!

Smaller pulley, bigger charger, call it done...for now...

All figures are at the wheels, no drivetrain corrections. 30degC ambient temp, IATs maxed at ~40degC with the coolers going.









I think it needs a better exhaust and heads to get much more.
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Old 02-09-2010, 02:53 AM
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Wow!!!

Lots of work and time what I could see in your pics.

Enjoy!

Walt
Old 02-09-2010, 05:08 AM
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Well done on getting it finished, very impressed you can keep the IAT within 10degC of ambient, those fans are really doing their job by the looks of it!
Out of curiosity, i assume a super charger keeps intake temps much lower than a turbo anyway, being that the compressor isn't next to anything red hot, is that logic correct?
Top work by the way!
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87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
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Old 02-09-2010, 09:28 AM
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Quote:
Originally Posted by JBL930 View Post
Well done on getting it finished, very impressed you can keep the IAT within 10degC of ambient, those fans are really doing their job by the looks of it!
Out of curiosity, i assume a super charger keeps intake temps much lower than a turbo anyway, being that the compressor isn't next to anything red hot, is that logic correct?
Top work by the way!
Incorrect logic, proximity to a heat source has barely measurable impact.
The centrifugal compressor is significantly more efficient at compressing gas than lobed type type blowers so the compressed air is cooler from a turbo than a lobed supercharger.
Old 02-09-2010, 11:06 AM
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Originally Posted by copbait73 View Post
Incorrect logic, proximity to a heat source has barely measurable impact.
The centrifugal compressor is significantly more efficient at compressing gas than lobed type type blowers so the compressed air is cooler from a turbo than a lobed supercharger.
Wow, that's even more impressive then!! I've actually ordered a pair of Spal fans to go under my stock 993 intercooler, i will be doing some tests soon to see whether they help reduce IAT. It was looking at this build that made me decide to experiment! People pay fortunes for better intercooling, if i can get my intake charge even within 25 degrees of ambient at WOT i'll be seriously happy
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87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
Old 540 BMW, XB12S Modified, for being a total hooligan
Old 02-09-2010, 11:31 AM
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Quote:
Originally Posted by copbait73 View Post
The centrifugal compressor is significantly more efficient at compressing gas than lobed type type blowers so the compressed air is cooler from a turbo than a lobed supercharger.
I am no scientist but I understand this is still a hotly debated topic. I am not sure there is 100% consensus on the point of efficiency.

centrifugal compressors (usually exhaust-driven turbos but also belt-driven units) and screw/lysholm compressors function very differently. One difference is that the turbo "crams" air into the manifold where the buildup of air creates the measurable "boost." On the other hand autorotor superchargers compress the air within the unit as the "pocket" of compressed air travels down the lobes. The air then exits into the manifold "pre-compressed." The air sometimes then "pops" out (that distinctive supercharger sound) and in that "pop" is the expansion of that air pocket. That expansion absorbs heat (cools the charge) somewhat from the high temp it was while inside the supercharger.

Their impact on driving behavior is also significant. Lots of time and money has been spent on anti-lag strategies but there is still something to be said for the instantaneous off-idle power you get in a well-executed supercharged application.

As far as which delivers a cooler charge I am not in a position to opine, but I can share that I'm seeing a total 10 degrees C above ambient on 12.5lbs boost with an air-air Bell intercooler.

Anyway, there are there are ever more super- and turbocharged cars out every day which is a good thing. It is interesting to point out that neither turbocharging nor supercharging has developed into a monopoly...and I love the fact the new Audi RS4 with its supercharged 3.0L is faster, more powerful and MORE EFFICIENT than its 4.2L NA predecessor.

j
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1982 911 3.2 Indiash Rot Track Supercharged track toy
1978 911 3.0 Lichtbau toy "Gretchen"
1971 911 Targa S backroad toy
Old 02-10-2010, 02:24 PM
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I can assure you there is no debating that turbocharger centrifugal compressors are mechanically more efficient than lobed type superchargers or that installed turbochargers are more efficient in the engine system than superchargers.

However, what is debated is the importance of boost response and predictability in the intended driving cycle. Each machine can make boost and the differences in efficiency can be rectified, to some extent.

The supercharger is mechanically tied to the crankshaft so it’s responsive and predictable. Both of these are traits the vast majority of Porsche guys who prefer N.A. engines will tell you are critical to precision driving. Those who are somewhat more freestyle, like the feel of power generation under their foot and appreciate a surpise from time to time like the turbo. Plus, at the extreme turbos make more HP.

I was hooked on turbos at a very early age when my uncle drove me around in his new early 60s Corvair Turbo Spyder. I can still remember him say “wait for it”. Supercharger guys don’t wait for it.
Old 02-10-2010, 05:21 PM
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What I find interesting is the torque/hp intersection. It's much earlier than our turbo cars (5150). If I'm reading it correctly, that's impressive. I would like to see more torque in relation to HP (like squared numbers) in a 3.4L motor though.
Old 02-10-2010, 05:27 PM
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Quote:
Originally Posted by DonE View Post
What I find interesting is the torque/hp intersection. It's much earlier than our turbo cars (5150).
This is just due to different scales on hp/torque. If you use same scale for both (assuming imperial units), they will always cross on same RPM point regardless of engine.
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Old 02-11-2010, 12:07 AM
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Quote:
Originally Posted by JohnJL View Post
Anyway, there are there are ever more super- and turbocharged cars out every day which is a good thing. It is interesting to point out that neither turbocharging nor supercharging has developed into a monopoly...and I love the fact the new Audi RS4 with its supercharged 3.0L is faster, more powerful and MORE EFFICIENT than its 4.2L NA predecessor.
j

Isn't that the S4? Maybe different down under but yes, very nice engine. I test drove one of these and the power is right there, no lag. Audi underated that engine - no chance that car gets 0-60 in 4.7 seconds with 330hp. It has much more power than that.

Was wondering what they are putting in the RS4 for 2010...nother V8?

Anyway, sweet car but will not haul 3 car seats and three boys worth of gear...maybe in a few years. I recently unloaded a Jeep SRT8 with a 6.1 HEMI - talk about power...quarter mile in 12 sec with car seats and sub 4 second 0-60...12 miles to the gallon :-(
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Old 02-11-2010, 04:54 PM
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