Smaller pulley but no more boost?????

[WELTERRACER]

O.K. here is the speal....

#1 i had a 5"pulley on my procharger and i was getting 6psi

#2 i changed to a 4.75pulley and was up to 8psi.

3# i added an intercooler and a bypass valve and psi dropped to around 6-7psi

#4 i added 4.5"pulley and a extreme velocity carb bonnet and my psi is still in the 6-7psi range (when it should be in the 12psi range)

My car is only running 1 5/8 headers and single 3" exhaust with a exhuast dump just after the headers!

Is my exhaust the reason my boost isnt going up??? At 6psi i gained 1/2 a second at the track when i upbolted the dump, but it didnt change the boost!

[Texas Hotrod]

Restricted i'cooler???? Can you connect a pressure gauge after the s.charger and before the 'cooler and compare the 2 readings.

Make sure the carb is opening 100%.

[WELTERRACER]

Im not sure if its the intercooler.. here are the specs

core length 24"
core height 12"
core thickness 4"
inlet / outlet size 3"
end to end length 31"
airflow 800cfm per minute,rated to 1000 HP
pressure drop .2-.5psi @15psi

[blown69nova]

Not an expert, but not all intercoolers are created equal. Make sure it is not a restriction.
Does your blower flow more than 800cfm?
Steve

[WELTERRACER]

the P-1SC flows up to 1200cfm at 30psi.. (im no wear near that)

I was getting 10psi back when i had 10.3-1 compression,, once i changed out to 9-1 compression i actualy lost 4 psi due to the compression (procharger said it is nature of the beast)

It could be possible the belt is slipping although i dont hear it..

I guess an easy way to tell would be to uncap the exhaust and run it at the track (if only i could find the time)

[69Bbird]

It could be all the 90deg fitting you have in you piping. The more 90s the more restrictions. You might want to try to replum using bigger raduis 90s. An easy way to see if its your intercooler is to stick a straight piece of pipe in place of your intercooler and see if you pick up any more boost.

[JMarsa]

I was getting 10psi back when i had 10.3-1 compression,, once i changed out to 9-1 compression i actualy lost 4 psi due to the compression (procharger said it is nature of the beast)

That doesn't make sense to me. If you had 10.3 CR in chamber and modified the motor (pistons/heads/head gasket) so that you're now 9:1 CR, how would that affect the output of a pulley driven assessory?

--JMarsa

[ProdigyCustoms]

It may very well be that you are limited on the intake side of things, try removing the air cleaner / plumbing just for a test.

[Blown353]

1. Check for belt slippage. Look at the belt for signs of glazing and belt dust on components near the pulleys. If you're running the stock procharger tensioner arrangement this is a very likely problem.

2. Have you changed your air filter/intake since the intercooler install? What Frank suggested is a good first try. A restricted air filter or intake plumbing will really hurt performance.

3. If it's easy, try bypassing the intercooler and make a pass. If the boost comes back then it's your IC & plumbing that is the restriction. I see a lot of tight radius 90 degree bends in there-- that's not good.

4. You can also perform a pressure drop test across your IC and plumbing, but you'll need another pressure gauge to install right at the outlet of the supercharger. Comparing that gauge to your manifold vacuum/boost gauge will tell you the pressure drop across all your IC plumbing.

[WELTERRACER]

That doesn't make sense to me. If you had 10.3 CR in chamber and modified the motor (pistons/heads/head gasket) so that you're now 9:1 CR, how would that affect the output of a pulley driven assessory?

--JMarsa

Prochargers are setup to your exact engine specifications.(compression/cam specs etc). more area in the compression chamber the less boost you have.. (theres probobly more to it than that)

Thanks guys.. I might try bypassing the intercooler and see if that helps, if not i will look for belt slippage..

[JMarsa]

Prochargers are setup to your exact engine specifications.(compression/cam specs etc). more area in the compression chamber the less boost you have.. (theres probobly more to it than that)

Please don't take this the wrong way, but I find that hard to believe that ATI modifies each unit. My understanding is that ATI has several models that are standard and as mentioned in this thread and in many others over LS1tech.com thier tensioner performs less than sufficient for many people.

I understood your PSI reference to be describing boost. Most peope refer to boost as what's measure out of the discharge outlet of a forced induction unit. Otherwise your talking about cylinder pressure.

As stated, the best way to understand pressure drop is to measure at the begining of this path and at the end just prior to entering the intake manifold.

--JMarsa

[olitei]

hi i think your pressure may not be going up because the intercooler is working, when you compres air there is the by product heat and when you cool the air charge with an intercooler the the density increases but you may lose some of the of pressure, a true test would be to measure air temp and pressure before and after the intercooler, if you have a pressure drop with no drop in air temp the intercooler is not very efficent, but if you get a 50%-75% temp drop with only a 2 psi pressure drop i'd think your doing ok also small headers would cause a increase in boost there a restirction a good header will help to scavange the cylinder and may actualy suck some of your boost out with it, rember an engine is a air pump hope this helps, orin also is the bypass valve adjsuted properly i assume this is like a blow off valve it should be set so it opens when blower surges when throtle is lifted if it opening to low of pressure may be bleeding off some of your boost,

[josh@scotts]

do you have a blowoff valve thougth maybe it was leaking through there? did you check with procharger about the size off the piping between none intercooled to intercooled (diameter) you might need a smaller pully to fill 3" 3 1/4" pipe that is much longer than before when it just went straight to your carb ?