Less power at lower revs?
11-14-2009, 11:10 AM
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Less power at lower revs?
Hey everyone,
I've been looking at a lot of Dyno charts of supercharged S2000s, and I was wondering why they all seem to make less power at lower RPMs?
I always though the S would really be the PERFECT car if it had 290~310whp but the idea of having less power at lower revs just seems unappealing.
I like being able to overtake others without scaring everyone. Any thoughts?
I've been looking at a lot of Dyno charts of supercharged S2000s, and I was wondering why they all seem to make less power at lower RPMs?
I always though the S would really be the PERFECT car if it had 290~310whp but the idea of having less power at lower revs just seems unappealing.
I like being able to overtake others without scaring everyone. Any thoughts?
11-14-2009, 11:23 AM
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Main reason is that you are refering to centrifugal superchargers. They build boost as the RPMs increase. You do not see full boost until about redline. As superchargers are belt driven it takes power to make power. You are putting a load on the motor by running a belt driven blower, so at low are rpms the blower is just robbing power not making any. If you want down low torque take a look at the SOT kit, or turbo set up. KW I think makes a bit more down low power then the Vortech, SOS, CT Engineering set ups.
11-14-2009, 07:23 PM
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I'm still pretty confused, can you guys not use any abbreviations? 
What is a positive displacement blower? What type of blower does the Science of Speed kit use?
What is a positive displacement blower? What type of blower does the Science of Speed kit use?
11-15-2009, 03:24 PM
#6
Comptech (CT), Vortech, Kraftswerks, and Science Of Speed are all centrifugal superchargers. Centrifugal superchargers have a linear boost curve where they only hit maximum boost at redline and below that their boost is proportional to their RPM. An example of their boost profile is something like this:
1000 rpm 0 psi
3000 rpm 2.5 psi
5000 rpm 5 psi
7000 rpm 7.5 psi
9000 rpm 10 psi
The SOT kit is a roots type supercharger. Roots type superchargers aren't quite as efficient as centrifugal, but are positive displacement superchargers. What that means is that every revolution of the supercharger passes roughly a constant amount (volume) of air. This leads to a flat boost curve (and hence a flat torque curve). These superchargers make full boost low in the RPM range. An example of their boost profile is something like this:
1000 rpm 0 psi
3000 rpm 6 psi
5000 rpm 7 psi
7000 rpm 7 psi
9000 rpm 7 psi
More info here:
http://www.superchargersonline.com/content.asp?ID=76
http://www.superchargersonline.com/content.asp?id=5
http://www.modified.com/features/0504_sccp...wers/index.html
Tim
1000 rpm 0 psi
3000 rpm 2.5 psi
5000 rpm 5 psi
7000 rpm 7.5 psi
9000 rpm 10 psi
The SOT kit is a roots type supercharger. Roots type superchargers aren't quite as efficient as centrifugal, but are positive displacement superchargers. What that means is that every revolution of the supercharger passes roughly a constant amount (volume) of air. This leads to a flat boost curve (and hence a flat torque curve). These superchargers make full boost low in the RPM range. An example of their boost profile is something like this:
1000 rpm 0 psi
3000 rpm 6 psi
5000 rpm 7 psi
7000 rpm 7 psi
9000 rpm 7 psi
More info here:
http://www.superchargersonline.com/content.asp?ID=76
http://www.superchargersonline.com/content.asp?id=5
http://www.modified.com/features/0504_sccp...wers/index.html
Tim
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