Turbo vs. S/C
07-19-2006, 05:38 PM
#76
Under the Lift
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An open road racing friend has blown up two stock Z06 motors just driving TO the race.
Last edited by Bill Ball; 07-20-2006 at 12:50 AM.
07-19-2006, 05:44 PM
#77
Captain Obvious
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In all honesty, out of all the SC’ed 928s here, I believe my planetary drive Paxton system is the least efficient of them all. I’m limited to only a maximum of non intercooled 6psi and that’s it. Unfortunately if I to install an IC (which I have in the past) the resulting pressure loss can not be compensated by a smaller pulley cause the SC impeller speed is already running at the maximum recommended safe level. Saying this, I am still 100% satisfied with what this old design supercharger delivers. My estimates are to be around 100hp or around 125hp with the cats removed. I think this shows how small the margin between the more efficient Vortech and the less efficient planetary drive Paxton centrifugal SC really is.
I’m fully convinced that all these arguments about SC efficiency are pretty irrelevant. Anything 928 over 400hp will be limited to the driver and how well they can keep the tires from spinning out of control. I’m yet to see any other boosted 928 with stock tires (225s) turn a 2.06sec 60” and a 12.8sec ¼ mile.
If one really wants to boost their 928, just buy whatever they can afford. I guarantee they will be happy with even a base kit.
I’m fully convinced that all these arguments about SC efficiency are pretty irrelevant. Anything 928 over 400hp will be limited to the driver and how well they can keep the tires from spinning out of control. I’m yet to see any other boosted 928 with stock tires (225s) turn a 2.06sec 60” and a 12.8sec ¼ mile.
If one really wants to boost their 928, just buy whatever they can afford. I guarantee they will be happy with even a base kit.
07-19-2006, 05:45 PM
#78
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Originally Posted by blown 87
Thanks for the heads up, we are thinking of doing a blower on a C5 and he wanted a twin screw, i will show him this.
07-19-2006, 05:50 PM
#79
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Originally Posted by Imo000
If one really wants to boost their 928, just buy whatever they can afford. I guarantee they will be happy with even a base kit.
07-19-2006, 08:24 PM
#80
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Oh, the old super-turbo debate. If you want the most usable power for a car like the 928 then the turbo is the answer. Few people have ridden in a turbo 928 let alone seen a turbo 928. I've built three and I am onto number 4.
Here is some food for thought...a recent article compared a Ford V8 with four forms of forced induction applied:
Vortech Centrifugal
Eaton-Roots
Kenne Belle Screw
Twin Turbo
The results are as follows (engine dyno numbers)
Vortech: 532 ft-lbs/667HP
Eaton: 533 ft-lbs/572HP
K-B: 525 ft-lbs/629HP
Turbo: 679 ft-lbs/750HP
All engines ran the same boost level, same fuel, same ignition timing. Don't beleive it...I have the article should anybody want to read it. You have to consider the power curves, not just the peak numbers. For example, the area under the Eaton curves is substantially more than under the Vortech curves, even though the Vortech makes higher peak numbers. The Eaton out guns the turbo to 3000 RPM, where the turbo then outguns anything in sight. The 2,500-6000 RPM range is where a car like the 928 should have power.
For me the turbo is the clear choice for the following reasons:
Boost where I need it...up the middle (remember the 928 is not a drag race car)
No load on crankshaft, no belt to slip
Cockpit adjustable boost (run 87 octane and turn the boost down)
Power delivery is smooth
No noise
More efficient
Useable power, not just off idle grunt or peaky power delivery
Longer lasting (look at diesel rigs and how long they go)
It is also the choice of forced induction by the industry leaders...Audi, Porsche, Ferrari, VW, BMW, Saab, Volvo, Lotus....Cummins, etc.
Here is some food for thought...a recent article compared a Ford V8 with four forms of forced induction applied:
Vortech Centrifugal
Eaton-Roots
Kenne Belle Screw
Twin Turbo
The results are as follows (engine dyno numbers)
Vortech: 532 ft-lbs/667HP
Eaton: 533 ft-lbs/572HP
K-B: 525 ft-lbs/629HP
Turbo: 679 ft-lbs/750HP
All engines ran the same boost level, same fuel, same ignition timing. Don't beleive it...I have the article should anybody want to read it. You have to consider the power curves, not just the peak numbers. For example, the area under the Eaton curves is substantially more than under the Vortech curves, even though the Vortech makes higher peak numbers. The Eaton out guns the turbo to 3000 RPM, where the turbo then outguns anything in sight. The 2,500-6000 RPM range is where a car like the 928 should have power.
For me the turbo is the clear choice for the following reasons:
Boost where I need it...up the middle (remember the 928 is not a drag race car)
No load on crankshaft, no belt to slip
Cockpit adjustable boost (run 87 octane and turn the boost down)
Power delivery is smooth
No noise
More efficient
Useable power, not just off idle grunt or peaky power delivery
Longer lasting (look at diesel rigs and how long they go)
It is also the choice of forced induction by the industry leaders...Audi, Porsche, Ferrari, VW, BMW, Saab, Volvo, Lotus....Cummins, etc.
07-19-2006, 08:38 PM
#82
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Originally Posted by Herr-Kuhn
The 928S4 Twin Turbo is coming soon...
Follow up the build with a trip to Green Bay - maybe we can get Andrew Olsen to meet us here and we can have a huge boosted party!
Why Green Bay and not your locations? Easy, less cars to travel - four - five boosted 928's in Green Bay, easier if you two come here.
Date to be set once John is finished with his install.
07-19-2006, 10:06 PM
#83
Three Wheelin'
I think that the comment in the article about not just focussing on peak numbers is a good one. Area under the curve is very important, especially for a road car. A good tool, this article plus the results that folks here have posted, to help people decide what is best for them.
07-19-2006, 11:05 PM
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Hacker, if it wasn't for this pesky 4.7 Euro Hybrid twin turbo build and all the associated headaches I would already be driving the 32V car...I'm just finishing the dial in on the 4.7 this weekend. The ball bearing turbos and big charge air coolers have been waiting for my attention.
07-19-2006, 11:15 PM
#86
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Originally Posted by Herr-Kuhn
I'll agree to come to Green Bay...but only if Lag and Z come out of hiding. 
07-20-2006, 12:41 AM
#88
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Originally Posted by Hacker-Pschorr
Well it's about damn time!!!
Follow up the build with a trip to Green Bay - maybe we can get Andrew Olsen to meet us here and we can have a huge boosted party!
Why Green Bay and not your locations? Easy, less cars to travel - four - five boosted 928's in Green Bay, easier if you two come here.
Date to be set once John is finished with his install.
Follow up the build with a trip to Green Bay - maybe we can get Andrew Olsen to meet us here and we can have a huge boosted party!
Why Green Bay and not your locations? Easy, less cars to travel - four - five boosted 928's in Green Bay, easier if you two come here.
Date to be set once John is finished with his install.
07-20-2006, 12:43 AM
#89
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Best cheese curds are at the DyckesVille Bowl (not kidding on the name) 1/2 mile from my parents house on the water just south of Door County. Damn good excuse for a road trip.
Sharks in Dyckesville - has a nice ring to it.
Sharks in Dyckesville - has a nice ring to it.