Quote: Originally Posted by
ptperformance 
Actually the top 8 of the top 10 fastest here on the forums have mid length exhaust on them. I don't see how the dump DP's don't work either but there are several that have stated lost power on the dyno with them. Try a search and see what you come up with. The only thing I can come up with is the exhaust pulses are still moving for and aft with that short of a dump on it. Temp vs exhaust gas velocity? At this point I would simply be guessing but we have tried it on 4 different cars with a short dump then a longer dump, all the longer dump cars made more power then the short dump and pulled harder in the 1/4 mile with better numbers. Why, no idea. Does longer work for our car, yes proven by more then just one vendor.
I ran a 11.56 open and a 11.7 closed. Same night, same tune, same 1.67 60'
Open I made 30psi, closed I only made 27-28. The only reason I closed it up was because at PIR you can't run past 10pm if you are above 90db... which I was closed too, but oh well. The reason 8 out of 10 of the fastest cars run a mid length system is because of twin scroll turbo's and their need for a little bit of back pressure to keep the pulses separate. Also, open raises your egt a lot... not sure why, but it does.
I think a reason people loose power on open dump with stock turbo is you are spinning the turbo up too soon. You get the spike sooner then with the stocker its all down hill. who knows.
