spoolup is determined by alot of other factors. Most notable is exhaust and portwork. Other things can have effects too. Cams, even fuel control. What ELSE did you have with that 14b? Alot of people also dont' realize that wastegates tend to slip their bushings after time and get off center on old internal gate turbos. It's easily remidied by pushing the bushing back in but it requires turbo removal to do it. A new turbo obviously wouldn't have this feature yet...YET.
Pauleyman, how do cams effect spoolup? I have heard from TTMKIV guys that cams usually increase spoolup by about 500 rpms on their cars but I would have thought that cams would help spool time by increasing flow through the head.
I don't actually know... My car just feels slow on the low end since I installed cams. The cams might allow more air and exhaust by, but the car isn't making as much HP on the low end as it did before. So, I would just guess that there would be less exhaust overall and might actually take a little longer for the RPMs to get going. My turbo is a bit big and slow spooling to start with though anyways...
Not true, Ecoli. At least not always. It depends on what the cams are designed for. Most cams are designed for high RPM horsepower and therefore sacrifice a little on the low revs. It doesn't have to be this way. My GUESS is that the TT Supra guys greenstreak was talking about got some cams with longer duration on the exhaust side. Longer duration=exhaust valves open longer=more exhaust gases per engine stroke=faster spool for your turbo. Right? If I am in error (which is entirely too possible) someone feel free to tell me I'm a big dummy! :p
[This message has been edited by Talonted (edited September 15, 2000).]
On the cams issue:
If you were to get an exhaust cam to keep the exhaust valves open longer, you would end up using the intake charge to help remove all the exhaust gases. (both sets of valves would be open at one point). If you were to mash the go pedal and start boosting, your pressurized intake charge would push any extra of the exhaust out in addition to a small amount of that intake charge leaving the cylinder. Hense, spooling the turbo quicker. Wouldn't this significantly decrease spool up time or the time to reach full boost pressure? Just a thought. Someone set me straight if I've messed up here.
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