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Originally Posted by Genetic Cesspool
Paolo,
You have probably mentioned it somewhere but I couldn't find it.
Why are you going the twin turbo route over your current setup? I know the easy thing would be to say 'it is better', but what sort of gains are you looking for? What are you and Heffner shooting for as far as numbers go?
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Genetic Cesspool, There are many reasons I am going to the Heffner Twin Turbo setup: The biggest reason is they make the ultimate power and offer the ultimate flexibility.
As you probably know, the turbos are driven off the exhaust gases while the supercharger is driven off the crank pulley through a belt. To spin the supercharger, it robs horsepower and more importantly, torque(parasitic loss to spin the blower).
With superchargers, once you get past a certain power level, you are driving all that power through a belt. When the supercharger pulleys get small past a cetain point, especially on slicks and skinnies, the belt is not consistent and starts to slip.
Don't get me wrong, for the regular guy who has around 750 RWHP and drives his supercharger on the street on street tires the belt will last a long time no problem. My belt with the bigger pulley on street tires is still fine after the Texas drag racing event and numerous 200+ MPH runs.
But here is where the flexibility comes in:
Whatever power you have got with the supercharger, that's all you've got and sometimes the whole nine yards of power is not what you need.
Take the road course portion of the Ultimate Street Car Challenge, I had not gotten a chance to test the car on the road course and found the almost 900 RWHP with the cats off to run way too hot on the road course. 550-600 RWHP would have been much better and would make so much more less heat than 900 RWHP.
So for this year, if I get in, I hope to be able to turn down the boost so I can get the chance to run some full out laps to get a real feel for the road course instead of last year's 5th and 6th gear laps(to keep the heat down) to get the feel of the course.
Some more benefits of the turbos are the following: you can use the boost controller to limit how much power/boost you can run in each gear or for different speeds ==> This way you could possibly run just enough boost to break the tires loose in 1st-4th gear and have almost idiot-proof driveability to boot!
You could also have a high boost-low boost setting. So for cruising, you could run some minimal 550-600 RWHP(less wear and tear on the engine not to mention much better gas mileage!)
Due to the parasitic loss of spinning the blower, I have read that superchargers are 30% less fuel efficient than a comparably powered engine/car with turbos. Most people here, myself included, did not buy Vipers for gas mileage. But I can tell you that after 10-12 full tanks(19-20 gallons topped off) of gas @ 85-90 miles/tank, you start to think back to the time when you used to get 160-180 miles/tank. Even with 93 octane, that starts to add up fast!
Superchargers are difinitely Bad-Ass, but Turbos are Badder yet.
If anybody here has not gone to Heffner's website and downloaded the video of Sal's Heffner Twin Turbo car, you are definitely missing out!
I went for a ride in Sal's car in Texas. My car makes 100+ more RWHP and has a built motor and the whole nine yards....... I went for a ride in Sal's car and all I can say is that as hard as my car pulls in any given gear at it hardest, Sal's STOCK MOTOR, 11 PSI Heffner Twin Turbo pulls as hard in that gear INSTANTLY! Un-F'ing Believable! The sound of the blow off valves is incredible you have to see the video!
As far as #'s are concerned, I am hoping for 1000+ RWHP and 1100+ RWTQ. We will see shortly.
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