Different Pully Sizes= Different PSI ???

[Schweppe23]

Those who have used different size pullies on your superchargers, what kind of boosts levels did you see w/ each pulley. I know that this is gonna vary...depending on headers, different size tb's, headwork, etc, etc. Post what mods you have done. I'm just trying to get some idea of numbers in my head. Also if you have used a scan tool to check you IAT post your temp readings with the different pullies.

Thanks,
Pat Lavanty

[jaketuff]

2.8 Stock.... 4-6psi

2.7 Pulley... 4.5-7.5psi

Estimating
2.6 Pulley...6-8.5psi
2.5 Pulley...7.0-9.0psi

2.4 Pulley.... 9-12psi Varies it seems with winter / summer temps. Car runs lean on stock PCM. Fuel enrichment from ASE NA chip/4.2L injectors overcomes this issue.

JOUT

[SPAZ]

I have no guages, so i couldn't tell ya.........

[AaronGTR]

2.8" pulley - 6psi
2.8" pulley after raised rev limiter - 9psi
2.8"pulley after headers - 6psi

2.5" pulley - 9-10psi

[aleroboy]

2.2" pulley 13 psi with stock exhaust manifolds and a 62mm TB
9 PSI with TOG headers at 5000+ feet above sea level
boost may be higher at sea level
I've yet to go with the 2.2" pulley

[Schweppe23]

Has anyone checked their intake air temps with the sc. Swapping to a smaller pulley will put the superchargers out of their efficiency zones and create higher intake temps right?

(Pulling numbers out of my a$s)
Example: 2.8 pulley putting out about 5psi and giving intake temperature readings of 145 degrees

then you change the pulley to a 2.4 pulley and boosts levels go up to 9psi but intake air temps also rise to 180 degrees

These numbers are just guesses cause im just trying to understand if the direct relationship between higher psi's and higher IAT cancel out the horsepower that one sees.
Am i making sense?

Thanks,
Pat Lavanty

[SPAZ]

Sure it makes sense, but i have not checked the temp with different pulleys.

[aleroboy]

Originally posted by Schweppe23


These numbers are just guesses cause im just trying to understand if the direct relationship between higher psi's and higher IAT cancel out the horsepower that one sees.
Am i making sense?

Thanks,
Pat Lavanty

You're VERY correct and very close on the temps.
why do you think I did the intercooler?

2.2" pulley will create temps from 210-230 degrees
the larger and less restricted the inlet to the sc is, the lower this number will be.
but hp increase is minimal with the high temps
iat resistor mod works for about a day then the computer learns arround it all pulls tons of timing.
with the intercooler in play the temp dropped to 150 under full boost with my intercooler pump off and the core being heat soaked.
pump on and ice in the tank, temps in the upper intake manifold are 70 degrees.
I'm ceramic coating the intercooler pipe since it goes over the exhaust to help keep the intake charge cool.

[PontiacGT2K]

John, you're a madman.

[aleroboy]

Originally posted by PontiacGT2K
John, you're a madman.

why?? its fun to have an alero lay down more hp at the dyno than a 96 TA with minor mods.

[PontiacGT2K]

Originally posted by aleroboy
why?? its fun to have an alero lay down more hp at the dyno than a 96 TA with minor mods.

Oh yeah I totally agree with you, I meant "madman" in the best way possible.

[aleroboy]

Originally posted by PontiacGT2K
Oh yeah I totally agree with you, I meant "madman" in the best way possible.

And to think I'm not done yet

[AaronGTR]

You are right that increasing the boost will increase the air temps, but that doesn't necessarily put the blower out of it's efficiency range. An increase in air flow will still equal an increase in power along with the appropriate fuel increase. The increase in air temp just takes away a little of the power gain (one reason intercoolers are good). Blower efficiency has more to do with the amount of air it's capable of moving, usually expressed in cfm (cubic feet per minute). If you reach the blowers max flow rate, and continue to turn the blades faster, all you are doing is causing heat thru air friction and drawing more mechanical power from the engine. In an extreme case the blower will draw more power than it makes. The other cause of the heat increase is the increase in compression. That's why adding headers is one of the best mods for a boosted car. If you remove flow restriction you can decrease compression (less psi) while flowing the same amount of air, since boost pressure is only a function of air resistance. From the flow charts I've seen on the M62 blower, on a 3.4 liter engine with the appropriate increases in flow ability, the blower would be at peak efficiency at 10-12psi and would reach 14psi before beginning to lose efficiency.

[Schweppe23]

Thanks Aaron. Does anyone have any information or can direct me to where i can find out more about the m62 unit. With proper headwork,headers, larger tbs, pnp gasket matched upper and lower intake manifolds....what size pulley would one need to achieve 14psi...(2.0???) Also having the computer tuned to have the rev set at 7k...that would also increase max boost potential...psi build with rpms???right.

[aleroboy]

Originally posted by AaronGTR
The increase in air temp just takes away a little of the power gain (one reason intercoolers are good).

Maybe on close to stock pulley sizes its a little but 60 hp is quite a bit to me.
once you drop below a 2.4" pulley the iat temps start to get into the 190+ range.

Schweppe23, to get 14 psi with all the mods you listed you will need a bigger supercharger.
according tot he max rpm of the E/M I'm allready a tad higher than the recomended max on the top end.
my power is not falling off or suffering yet but to get as high as 14 psi with even my setup would require a bigger supercharger.

[Knappy1]

John is right about needing a bigger SC to hit that kind of boost with all of that work listed. I''m running a 2.5" pulley with S&S headers, high flow cat, and SLP and only getting 6 psi. If you added all of the porting and polishing that you listed along with my exaust set up, you would drop to an even lower boost level. You couldn't spin the M62 fast enough to get 14psi. But, instead of worring about getting more boost, we need to worry about getting a properly tuned computer to run the boost that we can get. Trust me, there is a huge difference in performance with the DHP versus the stock computer.
Rob

[AaronGTR]

That's strange because I'm running a 2.5" pulley with headers, no cat, SLP exhaust, and I'm getting 9psi at the 6,300rpm redline. Anyway, I agree that with that amount of flow work done on the engine to push enough air to get 14psi you'd need a larger blower. You could get 14psi if the flow was restricted, but what's the point in doing that right. You could probably get to 12psi though (which would be pretty good IMO) but you'd be aproaching the limits of the engine's internals. If you planned on revving to 7,000 rpm as well you would need to do extensive engine mods. Balanced crank, forged pistons and rods, and stiffer valve springs would be the minimum. Not a cheap proposal.

[Schweppe23]

I don't understand....you guys both have the 2.5in pulley and aaron is seeing 9psi and rob is seeing 6psi. How could this be?

[Knappy1]

I haven't had it to 6300 rpm, so maybe there is a bit more boost there...other than that, I don't know. Aaron, do you have a larger TB?

[Schweppe23]

You could probably get to 12psi though (which would be pretty good IMO) but you'd be aproaching the limits of the engine's internals. If you planned on revving to 7,000 rpm as well you would need to do extensive engine mods. Balanced crank, forged pistons and rods, and stiffer valve springs would be the minimum. Not a cheap proposal.

Sounds like a plan.