when should I see boost?
02-27-2009, 12:48 PM
#11
3rd Gear Member
Join Date: Mar 2006
Location: West Virginia
Posts: 563
You're not always going to see boost when driving around. You're bypass valve will be opening in a vacuum situations allow the boost to escape when you're not on the throttle.
The boost also will increase as the rpms raise. You're only going to probably start will 1-2lbs around 3500rpms. And you won't see full boost until redline.
The boost also will increase as the rpms raise. You're only going to probably start will 1-2lbs around 3500rpms. And you won't see full boost until redline.
02-27-2009, 12:53 PM
#12
5th Gear Member
Join Date: Nov 2005
Location: MN
Posts: 4,412
02-27-2009, 01:34 PM
#15
4th Gear Member
Join Date: Jul 2006
Location:
Posts: 1,495
your bypass valve is what allows boost to start building. The bypass valve is always open when the engine is under vaccum. That means any time you arent giving it wide open throttle. Whenever you give it wide open throttle the bypass valve closes and that allows the supercharger to make boost. The stock 3.60 pulley makes 8psi on a non intercooled setup. Adding a front mount intercooler will normally lose 1-3lbs of boost depending on the setup. Adding a powerpipe may only increase boost by .5 - 1lb. It in most cases wont make up for the loss caused by the intercooler. So at redline I could see you possibly only making 6psi. But you did say that at one time you saw 8. Need to be sure on that. I suggest putting on a 3.3 pulley and installing a KB boost a pump.
02-27-2009, 02:12 PM
#16
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Join Date: Aug 2007
Location: Shelbyville, Indiana
Posts: 1,088
According to the dyno (and my boost gage at WOT), my car has 1.8 lbs of boost at 2500 rpm but just crusing down the interstate the vac/boost gage will show around 10 in. of vacuum not boost. The butterfly valve in the throttle body has to be open before the boost from the supercharger can reach the engine.
02-27-2009, 07:09 PM
#19
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Join Date: Jul 2006
Location:
Posts: 1,495
as long as the car has enough fuel to support it an increase in boost shouldnt affect the a/f ratios as long as the tune has been set up correctly. With a 3.33 pulley I ended up having to buy a KB boost a pump with my focus pump to get enough fuel. Its a good idea to buy a wideband a/f gauge so you know for sure how its running all the time. With a stock motor I wouldnt go past 10lbs of boost though...
02-27-2009, 10:31 PM
#20
5th Gear Member
Thread Starter
Join Date: Mar 2008
Location: PA
Posts: 2,825
I am running a blow through setup with a BOV...I am replacing the bov because its a piece of crap and not opening...ever...So its possible it maybe stuck slightly open, but not opening completely when it should. I have a new greddy on the way. My car is stock with the exception of an h pipe and exhaust. I am going to the dyno on wednesday, what do you think the I'll make when hes done tuning it? I was hoping around 360rwhp. I have seen people make 370 on a 3.6 pulley and no intercooler but they had an aftermarket tb/plenum. I have the stock tb and plenum but have an intercooler which should allow me to pull a little bit more timing. So what kind of numbers am I lookin at..