I measured up my pulleys and I have a 6.66" (I think) crank pulley and a 3.12" sc pulley... I am seeing 8psi with the aftercooler... now I want to see 12-14psi... what size of supercharger pulley must I buy???

the other thing... how do you measure the pulleys??? on the grooves or total diameter? I believe its on the grooves since the belt is what touches... The crank measures close 7" overall so it shuold be a 6.66" pulley right?

LMK

Thanks

 

What rpm are you turning the motor to?

Rich Krause

 

6000-6200...

224/236 cam

Do you remember I had some fueling problems.. well it turns out that i found the face plate of the superfueler and i had my additional injectors set to OFF

Now I have enough fuel... I sent an email to ASP to order a 2.75 pulley that should max out the S-trim at 6200rpm more or less...

14psi boost I should hit 560rwhp easy... with the intercooler and say 120IATs .... it should be possible...

Let me know what you think... THANKS

 

Glad you solved your fuel problem. You are on the right track wrt the pulleys. You will need max flow from the S-trim to generate ~14psi. If your crank pulley is 6.66 and your blower pulley is 2.75 the impeller speed will be 50,000rpm at 6,000engine rpm. 6,000rpm is just about right for your cam. I might spin the blower just a bit slower to allow a couple of hundred more revs though. The blower gets less effieicent above 45,000rpm and much less efficient over 50,000rpm. Spining it much faster than 45,000rpm will not really produce much more hp, maybe even less. You will see more boost, but the IAT will skyrocket and the air mass will level off or start to fall. Don't believe anyone who says different. I have seen this many times on the dyno.

Vortech lists 50,000rpm as an "absolute max". There are many people spinning them faster. I know of one who grenaded the impeller. Not pretty. I don't recommend over 50,000rpm max impeller speed.

Let me know how how it works.

Rich Krause

 

So you recommend a 2.95 then?

LMK

Thanks

 

I dont get it.. I am making 44krpm right now... So i shouldn't change pulleys???? I only see 8psi with the aftercooler... means I need a bigger supercharger???

Im a bit confused now... I want a bit moreboost or better said.. airflow out of it...

What difference does 2000rpm make on a supercharger?

If I use the 2.95 pulley it would be 46krpm, 2.85 would be 48k

BTW.. the car runs like CRAP without the supercharger...

 

The 2.95" would be as small as I would go with a 6.66" crank pulley. Rev it to 6,200 and see what you get, that will be 48,300rpm at the impeller. Beyond that, you can gain up to 2psi by eliminating inlet restriction. Are you running "dryer hose" or a solid intake? I saw a 2psi gain with my S-trim going to solid, smooth intake piping.

Remember, it's not how much pressure you see on a boost gauge that determines hp, it's the increased mass of air entering the cylinders that allows you to make hp. So, the other thing you can do short of better heads is to cool the intake charge with either water injection and/or an intercooler. Of course, the combustion gasses must also get out of the cylinders. So exhaust mods can also add significant hp to a SC car.

I was running a 2.95/7" combo with the S-trim, but only revving to ~5,800. At 5,800 the impeller speed was 47,500.

I am aware that you have thought about a lot of this already, but I am posting it in the hope it will be of use to others reading the thread.

BTW: if the car "runs like crap" w/o the blower, I wonder if there are some other problems. It should run ok. What's up with that?

Rich Krause

 

I will go with the 2.95... I am running the vortech aftercooler.. it has made a huge difference... I am in the process of installing some computer fans to have them ON on an additional copper radiator that I added which made a HUGE difference too...

Its better to follow advice.... if not.. why post and ask? I will have results this week or so.. I think...

How much PSI should I net???

I am not using the dryer hose.... its my own fabbed solid intake...

I dont think my heads flow that well.. I had to run the the car without a tube of the supercharger and the car felt like a 200HP car... damn.. and the MAF was being used... Maybe since the tune is totally different.. There is a lot more fuel going in and a lot less timing??


Anyways... Let me know what you think.