I have my setup pullied for 14psi.. im only seeing about 10 psi maybe 11 every now and then.. Setup is trick flow heads on a 383.. They flow pretty well but should i still see about 12 psi or 13 psi? or is what im seeing ok?

 

You need to get the idea of "xxlb pullies" out of your head. For two identical setups, the same pullies will produce ~the same boost, provided everything is right. You are asking if your result of 10psi with "14lb" pullies is right. The only way anyone can answer would be if they had EXACTLY the same setup that you do, which seems unlikely. But if specify in more detail what you are running, maybe there is someone with a setup that is close. You should ignore any answers you get that aren't based on a nearly identical setup.

Rich

 

10# on a 383 w/ decent heads is about the limit of the P series blower

It is a ratio of blower flow vs. engine flow.
The ATI p-series flow 1200cfm, a 350 @ 6000 rpm flows approx 600cfm
(1200/600 *14.7) - 14.7 is roughly 14.7# boost

14.7 is atmospheric pressure.....

a 383 flows approx 660cfm @ 6000 rpm
(1200\660 * 14.7) - 14.7 = approx 12#

These are based on the blower being maxed at 6000.

Pulleying the blower to max at a higher RPM means less peak boost. The 14# kit maxes at 6600 if I remember correctly. A 383 @ 6600 = approx 725cfm. This would be (1200/725 *14.7) - 14.7) or approx 9.6# boost.

This calc is generic as it does not account for heat expansion of the air, flow restrictions of the engine, intercooler pressure drop, or cam overlap...... but it generically proves the point.

This is why a charger is rated for 30# boost, but may not provide that boost on your engine.

 

What size pullies do you have?

 

6.66 crank and a 2.75 blower.

 

In that case, I think you are missing out on a few lbs. I also have the 6.66/2.75, T-trim, 383, AFR 210's, 224/236 cam, and am making 12 - 13 psi after the intercooler.

Try installing the bypass valve backwards. If it picks up boost, then the valve is leaking. Do you have a ported MAF? Also, a hard intake pipe?

Mike

 

Another thing to check is your boost gauge accuracy. Personally, I'm running a fairly cheap autometer boost gauge and it shows about 2 pounds less boost than the DFI readings that I get from the MAP sensor.

 

I think I have the same problem speedmiser. I'm running a Phantom mechanical Vac/Boost gauge 30in vac/20 PSI boost. Stock it pulled 20" of vac. at idle, and 7-8 psi boost at WOT. With my 224/236 cam, ported heads and the same blower setup, I see 9-10" vac at idle, and 4-5 PSI at WOT. The wierd thing is my MAP reads about 15 inches at idle. All the lines are tight and it's all connected the same way it was when it was stock, only difference is that I'm using a copper line. Oh well.

Oh, I'm going to run the electric version of that guage on my truck, so I'll get to see if it's more accurate. Some time in the near future.

 

Bringing this back to life.. I talked to a buddy of mine with the same pulley setup and he is seeing 16psi @ 6300 RPM on the t trim with no intercooler. He has a solid roller 355 with afr 195cc heads (non ported). I really think im loosing out on some boost..

I installed the valve backwards and it didnt pick up any boost. I have a ported MAF and the stock plastic intake pipe.