88mm supercharger pulley

Jinxx

That's waaaay to small for gtm kits

pokeyl

Falls on the 70% line and makes more power on the way to 7K than the other pulley at 7500.. I shift at 7 and have more HP and torque sooner.

I like it and have over 25K miles on this set up. All based off a dyno tune done at Z1 on another car with a 88mm pulley making 517 RWHP boost at 11 PSI.

current set up, GTM 1.5 kit 750cc injectors and some day digital NOS.

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Jinxx

Maybe I'm not looking at this right .....from my understanding the 88mm will be at 11lbs at around 7k rpm and would be just over make for the supercharger........and the 84mm is 14 lbs at the same point and even overspinning more .....so a 82mm would be like 17lbs at 7k and way above max range of supercharger .....I realize you are getting boost sooner in the rpm range but should be limited on how high you can run the engine rpm without risk of blowing supercharger/motor ......also if you don't rev to the upper limits of the rpm range would torque be lost even at a higher boost ?

Jinxx

Also I have the 38-91 stage two supercharger not the 1.5

pokeyl

OK, I don't do math, I just works for me. I even ran this with my 1.0 set up. That system made only 8 PSI due to restriction in the intake. 38-81 compressor

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Jinxx

Hmmm that sounds strange for a 82 mm pulley .... I'm at 8lbs with my 92mm pulley now ....at what rpm did you hit 8lbs and how high did you rev to ?

pokeyl

I had 8 @ 5000 and it stayed at 8 until 7500. All with the stage 1 intake and the small charge tubes

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Jinxx

That's strange ... Either super charger was maxed out or something was wrong ... Super chargers are based on engine rpm so the rpm increase should have increased the boost from 5k-7.5 k .... Sounds like supercharger was over spinning and couldn't produce anymore boost .... Killing the life of the charger and borderline blowing it.

theDreamer

Not exactly, the stage 1 SC by GTM has a pretty terrible intake design.
There are 2 intake filters with a sharp bend along with a couple other 90+ turns before hitting the SC unit. It ended up restricting even the smallest pulley from going over 8PSI because of airflow restrictions.

And actually, the 1st design which I had we were topping out at 6-6.5PSI and they made some quick changes and sent out a new piece and we finally hit 8PSI.

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Zat_Zuma

I know of a 88mm pulley from GTM, like new.
How much is it worth to you and I'll present the offer

Might even have a 84mm too

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Jinxx

Even still ....with intake restriction I can see the boost not going past a certain point ...but the supercharger is still spinning with rpm wouldn't it be still overspinning well over the maximum for the supercharger and running the risk of damaging the charger ?

pokeyl

I found Rotrex compressor maps as high as 115K for compressor speed still in the 65% or better range at our air flow, 38-81 compressor.

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Jinxx

I don't know how to read them ...but from the rotrex website they all say 90k is max for them ...so I was using that as a reference for overspinning....I like the idea of boost sooner in rpm range as I don't like to redline the car .....was wanting to try to balance the pulley size to have maximum effiecincy of charger around 6800 rpm ......so I'm not sure which pulley size would be best or what the negative issues it would cause.

EVOHUNTER

man you can really spin those rotrex's, my vortech is being over spun at 54,000rpm.

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pokeyl

PR------Air Flow----RWHP Tgt------Stock HP
1.53------0.35----------400------------------300
1.73------0.38----------450
1.92------0.43----------500
2.01------0.44----------525
2.11------0.46----------550
2.20------0.48----------575

I don't do math, Excel is my friend.

This is using the Rotrex install information.
There are many other factors but it is a start
Use the compressor maps and find the intersection of the lines, that is the speed you have to spin the unit.
There is heat energy loss (that is % in the compressor map), intercooler pressure drop, intercooler temp drop

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