What's wrong with superchargers?
07-02-2012, 06:48 PM
#41
I'm just following TNTUBA around posting on anything he's been posting on, since we have similar SSM goals in mind. Also, I'm completely unable to leave a thread alone with people crapping on superchargers. It's a personality fault of mine.
This is my twin-screw supercharged power curve:
It's about as flat as you can get, and makes it much easier to drive since it's predictable, linear power all the way through the curve, and it modulates with the throttle pedal in a predictable, linear fashion.
A turbo will never do that. Turbos are great for the track where you're just modulating mid corner and then flooring it on exit from a high RPM, but when you need to constantly go on/off gas and get the most power you can (i.e. autocross,) a twin screw supercharger is unbeatable.
A normal (M/MP) roots is okay, but tends to fall flatter on its face at higher boost at higher RPMs. For low boost they're fine. A centrifugal is all the worst parts of a turbo (power lag), without any of the advantage (laggy but still AVAILABLE torque at low RPMs) and is only useful for a track car with a VERY close ratio gearbox to keep it up in the boost. In that circumstance I'd still choose a turbo over a centrifugal SC since you can get so much more maximum power without parasiting it all away. Centrifugal is mostly just cheap and easier to plumb since it's small and can drop in a spot that has an A/C compressor or power steering pump...
This is my twin-screw supercharged power curve:
It's about as flat as you can get, and makes it much easier to drive since it's predictable, linear power all the way through the curve, and it modulates with the throttle pedal in a predictable, linear fashion.
A turbo will never do that. Turbos are great for the track where you're just modulating mid corner and then flooring it on exit from a high RPM, but when you need to constantly go on/off gas and get the most power you can (i.e. autocross,) a twin screw supercharger is unbeatable.
A normal (M/MP) roots is okay, but tends to fall flatter on its face at higher boost at higher RPMs. For low boost they're fine. A centrifugal is all the worst parts of a turbo (power lag), without any of the advantage (laggy but still AVAILABLE torque at low RPMs) and is only useful for a track car with a VERY close ratio gearbox to keep it up in the boost. In that circumstance I'd still choose a turbo over a centrifugal SC since you can get so much more maximum power without parasiting it all away. Centrifugal is mostly just cheap and easier to plumb since it's small and can drop in a spot that has an A/C compressor or power steering pump...
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07-02-2012, 08:07 PM
#47
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Join Date: Jul 2005
Location: Anacortes, WA
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I got my *** handed to me. But we put miatas on top of the fleet of vetts vipers and RX7's.
I think Race logic traction control, Quafe Transmission so you can go fast enough in second gear, and a better rear wing were an advantage for David. I also think I got some suspension setup issues. maybe half of the differance could be chocked up to that. The other half he just out drove me.
Another thing was it was Goodyear vs Hoosier but I dont know what the differance there is.
Bob
I think Race logic traction control, Quafe Transmission so you can go fast enough in second gear, and a better rear wing were an advantage for David. I also think I got some suspension setup issues. maybe half of the differance could be chocked up to that. The other half he just out drove me.
Another thing was it was Goodyear vs Hoosier but I dont know what the differance there is.
Bob
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07-02-2012, 08:17 PM
#52
I got my *** handed to me. But we put miatas on top of the fleet of vetts vipers and RX7's.
I think Race logic traction control, Quafe Transmission so you can go fast enough in second gear, and a better rear wing were an advantage for David. I also think I got some suspension setup issues. maybe half of the differance could be chocked up to that. The other half he just out drove me.
Another thing was it was Goodyear vs Hoosier but I dont know what the differance there is.
Bob
I think Race logic traction control, Quafe Transmission so you can go fast enough in second gear, and a better rear wing were an advantage for David. I also think I got some suspension setup issues. maybe half of the differance could be chocked up to that. The other half he just out drove me.
Another thing was it was Goodyear vs Hoosier but I dont know what the differance there is.
Bob
BTW, We should spend some time Friday figuring out how to tune our wings. I bought a giant spool of pink twine from harbor freight for the purpose.
The goodyear vs hoosier thing is really interesting, and I think a lot of it comes down to driving style. I wish there was a good way to get really good data on the two tires, but the setup changes for the two tires on an SSM car to optimize them differently are huge...
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07-02-2012, 08:26 PM
#56
Powertrain details for the build: Engine - DestinationSSM
Motor: Around 4500$ all done, half of which was the machine shop labor charge. In the end, I still think I overbuilt it, but I'd probably do about the same thing again if I had to start over. I'd spend a little more money on it if I were going turbo (stronger rods probably,) but it's a very very similar build to a high power turbo build.
Supercharger head unit: 2000$
SC crank pulley from FFS: 150$
Manifold from Corky: 860$ + infinite headache
Intercooler: 80$ + maybe 100$ of fab time
Intercooler piping: 100$ + maybe 100$ of fab time
RB header: 425$
Custom 3" stainless exhaust: ~1500$
AEM: 950$
In the end, the motor build, exhaust, and AEM are identical to what I'd do/have to pay for on a higher end turbo build. So, the SC "kit" is around 3000-3500$, depending on how much you can do yourself and how much you have to pay a welder to do.
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07-02-2012, 08:28 PM
#57
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Join Date: Jul 2005
Location: Anacortes, WA
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Bob: Are you running a 6spd? The quaife set really is perfect for autox... I think autotech has 2 kits left -- you should pick one up, especially if you're talking about building an XP miata.
BTW, We should spend some time Friday figuring out how to tune our wings. I bought a giant spool of pink twine from harbor freight for the purpose.
The goodyear vs hoosier thing is really interesting, and I think a lot of it comes down to driving style. I wish there was a good way to get really good data on the two tires, but the setup changes for the two tires on an SSM car to optimize them differently are huge...
BTW, We should spend some time Friday figuring out how to tune our wings. I bought a giant spool of pink twine from harbor freight for the purpose.
The goodyear vs hoosier thing is really interesting, and I think a lot of it comes down to driving style. I wish there was a good way to get really good data on the two tires, but the setup changes for the two tires on an SSM car to optimize them differently are huge...
Bob
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07-02-2012, 08:30 PM
#59
I think the courses were terrible for any cross class comparison, though. There were very few sections to use any power. I think our cars were basically overweight CSP cars for most of this weekend, especially on Sunday. I was just happy to stay ahead of Scott overall by 3 tenths for the weekend.
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07-02-2012, 08:32 PM
#60
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Location: Chattanooga, Tn
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Awwww that's the sweetest thing anyone has said about me in years
Not all us blower guys are douches. I will freely admit I'm a jack ***....but not a douche.
David's car is breaking my heart. I had been thinking all winter I was going to have a bad Autocross Miata......and he had to come along a take it up a few notches.
Not all us blower guys are douches. I will freely admit I'm a jack ***....but not a douche.
David's car is breaking my heart. I had been thinking all winter I was going to have a bad Autocross Miata......and he had to come along a take it up a few notches.
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