Re-read his statement. You will make useable boost above 2500, past 3500 is when you really feel it

I think you misunderstood my statement. I was trying to tell you to disregard Black_Z28's statements, then said that I, myself do not have a powerdyne, so I could not answer your question.

 

oic sorry i thought you was trying to say i didnt deserve an answer because you thought i didnt have a s/c . . sorry for the misshap

 

Mongse... you probably had a huge problem there... maybe your throttle blades were not closing entirely and you had a problem with your bypass valve or a big vacuum leak... at idle I see 14" vacuum...

You must have had a lot of problems braking then...

 

No problems braking and the car ran fine. 12.4s @ ~117ph is OK on a stock motor I suppose. Right around 3200-3400 I would start to see pressure.

Don't remember what I was seeing for vaccuum @ idle. Wish I still had the charger on the car...it hasn't run in over a year.

 

My gauge never goes below 0. should I see vacuum. mine alsodoesn't build much of anything until @3000maybe a lb, once I open up the TB then it shoots up with the RPM's. Tell me if you think I have anything wrong.. Thanks

 

Something IS wrong... does your gauge read vacuum? if it does?? do you feel your brakes hard??? If you are always reading 0 it should be, like if the car is turned off or something... Where are you measuring your boost? on the manifold or on the intake pipe???

Let me know... Thanks

 

Man you don't even have a supercharger first of all... second of all, you list things like "valve seals", "air foil", and "skip shift" as mods to your car so I would not be talking with such confidence about a subject that you obviously know diddly squat about (making boost at idle??? ). Yes you might be able to make some boost under 2500 but the load on the engine at that low of RPM would be way too much... I never go WOT until probably around 3k. I will start leaning into it from 2000 and by the time I'm at 3000 i'm goin WOT and boost flows freely. I mean how many drag racers do you know that spend time at WOT under 3k... when you launch you are already almost past 3k, especially if you have a stalled auto. WOT is not meant for such low RPM. And besides, unless you are running a very small pulley setup you won't make that much boost under 2500 RPM anyhow... For the supercharger to be able to boost the engine with any significant amount of boost is by using a bypass valve to control the airflow into the engine during normal driving so the blower can be spinning faster than is needed so when you do need boost it can kick in. When you go into boost, the boost pushes the bypass closed and all the air goes straight to the motor. When you are driving, the vacumn opens the valve. Still does not mean you can boost at idle if you floor it, that would be ridiculous.

 

There are a number of variables that determine how much boost a given combo will make at various rpms. To talk about this intelligently requires some assumptions and defining of terms. First, the whole discussion assumes WOT. Then, we have to define "boost". Usually, that refers to manifold pressure above atmospheric. But in the context of this discussion, it might make more sense to define it as "a higher manifold pressure than would be seen without the SC" at a given rpm. By that definition, a centrifugal SC will make "boost" from right off idle.

Most combos will see some degree of positive manifold pressure quite early. Mine is a fairly high boost setup (17psi) and things happen pretty quick when you crack the throttle. So it's hard to watch the boost gauge. But from looking at logs, dyno runs, and the boost gauge as best as I can see it, there is positive manifold pressure by ~1,200-1,500rpm. I see 4-5psi at 2,500rpm.

Rich Krause

 

Yes, boosting your life could be a way of difining it...

I start to see some SORT of boost.. .1 .2 psi maybe 1300rpm or sooff idle.. but its so insignificant that it doesnt deserve to be called boost... I see one psi about 2000rpm... etc etc... 3psi at about 3000rpm.. i dont know why I have such a non linear boost curve though... anyways... I dont have time to see the boost gauge all the time... I use the superfueler as my boost gauge though...

 

If you're not seeing any vaccuum, I'd say the gauge is hooked up wrong.

I think the difference in blowers would affect when you see actual boost as well. For instance, I had a P600B (3.xx:1 ratio) and Rich has an F1 (4.xx:1). He not only makes a LOT more boost than I even could on my P600B, but would make it quicker.

 

This could go either way. But in my opinion, "boost" in this discussion should be used as higher than atmospheric pressure. "Higher manifold pressure than would be seen without the SC" could also be used, but the man asked how to make his boost (ie - power gains) come in at an earlier RPM. Having higher than normal manifold pressure while still being under vacuum would have very negligible/miniscule power gains, which is not what the original question inquired about. This "higher than normal" pressure would build more quickly the sooner positive manifold pressure comes about (duh). JMHO, sort of a stupid thing to argue about, I know.

 

i plumbed it into the plastic tube coming right out of the blower at the elbow.I read on here that that would work fine and easier than trying to tie into the intake. I do see about 7lbs at WOT but only for a second and very little below 3500. Let me know what you think. I appreciate the help!!

 

terrysblownss you need to hook your gauge into the intake for it to read vac, im pulling 22 lbs of vac at idle I dont see any boost till about 3000 RPMs at 6000 im making 9 lbs normal driving you never even know the blower is there, you sure do when you put it to the floor

 

with a 4.41:1 step-up on a paxton head unit, I see 6-7psi at 6k rpm. I already have 2-3psi of boost at 2500 rpm. It's pretty linear all the way up.

I have the MAF on the pressurized side and a bypass valve dumping to air (might as well call it a blow-off valve). Even at partial throttle, I see vaccuum on the boost gauge. It's not until I crack the throttle blades open enough to flow tons of air (1/2 throttle or better usually) that it goes to the boost side. That's what makes the centrifugal blowers so streetable...

 

Hey guy's, thanks for the input. Leaving it there is fine right ? I really don't care about vac. just boost pressure..I wish I was like some of you and could get 7lbs at mid rpm range. Once I build it I'll be there !!!