Hey Russ, I just emailed Nick @ v/f for my dyno sheet. pm me your fax number and I will send it to you if I get a response sooner.

 

Thanks Billy.

Just post it here if you can, since our cars are essentially identical. I'll see if I can get my stock graph if yours doesn't have baseline. Thanks, Russ

 

still waiting for the dyno... I'll try them again on Monday

 

Cool.

IIRC, boost on centrifugal blowers is exponential relative to rpm. Redline = max boost, and at half max rpm, boost is 1/8 max (or around there). Given the low boost nature of centrifugal units at under half redline rpm, it's always good to see an actual dyno to assess area under the curve.

 

The actual way to calculate boost at half maximum rpm is to take the square root of the maximum boost. For example, if your boost at 7000 rpm is 10 psi, then it is 3.16 psi at 3500 rom. NOT 1/8th like you stated.

 

Couldn't remember exactly the equation, only that boost is not linearly proportional to rpm. One of the reasons why some consider positive displacement blowers, and particularly twin screw blowers, to be superior to centrifugal units. I suppose that's a moot point since there isn't a twin screw alternative in the market for these cars, perhaps due to packaging.

 

Biggest disadvantage (besides heat) in a positive displacement SC is that the power gets flat after about 3/4 rpm. A centrifuge keeps pulling all the way to redline.

 

Excellent Write-Up Blue. Your machine sounds awesome and looks beautiful. Enjoy in good health and spirtis, Who needs warranty anyway?, just another reason for them to say it was abuse and not spirited use!!!

 

Not true on a properly configured twin screw setup, at least not from what I've seen. Coming from bmws, both compressors are used by the aftermarket. At the same psi, the twin screw puts out more tq and more hp at every rpm. Twin screw dynos can look like they die at high rpm, but in reality they don't. Rather, it's b/c the twin screws have sledgehammer tq in the low and midband, making the high end tq look weak by comparison. You'll also note that no car manufacturer sells cars with centrifugal blowers; they are pretty much for the aftermarket due to cost and packaging ease. If they were superior to twin screw units, they'd be used by Benz, GM etc. I'll grant you they don't have the adiabatic effeciency of the centrifugal though, particularly the Roots type blowers. But the twin screws from Lysholm and Eaton are notably better than the old Roots style.

Anyway, I don't want to get into a debate about blower units, since this has been debated on many a forum, and it's a moot point on these cars.

I'm just interested in seeing low rpm numbers on the evo setup.

 

i have my before and after dyno charts in the big supercharger thread. i'll see if i can dig them up.

from what the way i understand it, even though the centri units don't build much low end power, the big advantage is that doesn't change the characteristic of how the car delivers power, there is just more of it.


i have been in a TPC'd 996. very different from my car. it didn't really drive like a 996 anymore. it wasn't bad at all, just different. much torqier (spelling?) down low. probably even a bit faster than the Evo setup. almost felt like the car had a v8 stuffed in there

 

ah shoot, didn't realize tpc was a PD unit. Perhaps it's not a moot point.

anyway, definitely interested in seeing the low rpm power delivery from an evo customer's dyno.

 

I really down know what you mean by "low rpm power" since you are never shifting into a low rpm range from redline. In my case, shifting from 1st, to 2nd near redline puts me in the sweet 4200 rpm area and delivering a cooler charge than does the roots style.

 

Very nice! Congrats!

 

I tend not to drive my car around bumping into redline frequently. Rather, a lot of the time, I'm shifting at 4k rpm or so or am accelerating under part throttle from 2.5k or so under normal traffic conditions.

Low rpm power matters to me since my C2S is my street car.

Among the various reasons why I consider my C2S to be a better street car than my prior GT3 is the midrange torque delivery, which is useful under normal driving conditions.

As they say, 'area under the curve'.

 

While I drive my car around town quite a bit too, I'm with 1999Porsche911 on this one. Unless I'm just puttering between lights, in which case I really don't care whether my car is supercharged or not, I tend to keep the car above 4,000. It's much more fun up there, even if just to pass, take a curve, or just listen to, and feel, the engine. Area under the curve doesn't matter much to me if I'm at 2,500 rpm because I'm pbviously not trying to accelerate at that point anyway. Otherwise I would downshift. And all of my shift points leave me at 4,000+ in the next gear anyway, at which point my blower is rolling . . . So maybe I chose the right type of supercharger for my style of driving?