BLWR PWR

So, I have a 89 Iroc with a 350. Trick flows, Large tube runners, Ported plenum, 52mmtb, Edelbrock base, etc. The intake is well opened up for a LTR setup. I am getting 5 lbs of boost@5500rpm with my Vortech S trim. 4lbs@5000, 3lbs@4500 down the line. My point is I dont see boost till about 3200-3500rpm and then it starts at 1lb. I rrealize that centrifical superchargers work this way, boost in relation to rpm. My question is , how can I get the boost to start/kick in at a lower rpm? Smaller pulley? I guess I want more grunt at about 3500 rpm. Dont say gears, I have 3.54s, dont say stall, I got a 2800, dont say superram, dont like the looks, dont say miniram, not smog legal. Dont get me wrong, the car is quick at 12.5-12.7s and 111. But I want more. Any ideas on boost at lower rpms?

Willie

iTrader: (1)

To get more boost, you'll need to spin the impeller faster relative to engine rpm. But before jumping in feet first, you need to calculate a few things. What is your impeller rpm at your shift point? What is maximum safe impeller rpm for your Vortech?

BLWR PWR

Using the formula crank pulley dia. x 3.45 x rpm @shift/sc pulley dia. I come up with a impeller speed of 40500. Thats 7.50x3.45x5400/3.45. Vortech says max efficient impellr speed is 45000, max speed period is 50000. So it looks like I have a little room to play. Is it better to go smaller blower pulley or larger crank pulley? Which is easier? I have a forged steel crank, but stock pistons and rods. Will I be pushing my luck? The blowers been on about four years and 20000 miles now.

Willie

iTrader: (1)

Using the formula crank pulley dia. x 3.45 x rpm @shift/sc pulley dia. I come up with a impeller speed of 40500. Thats 7.50x3.45x5400/3.45.

Confirmed.

Vortech says max efficient impellr speed is 45000, max speed period is 50000. So it looks like I have a little room to play.

Keeping in mind that the blower efficiency graph is somewhat parabolic, I feel confident saying you can turn it close to 50,000 for the highest average efficiency.

Is it better to go smaller blower pulley or larger crank pulley? Which is easier?

I don't know. Can you get both a larger crank and smaller blower pullies? With my ATI, I can only get a smaller blower pulley. I would think it would be easier replacing the blower pulley, but I'm not familiar with the Vortech, so.....

I have a forged steel crank, but stock pistons and rods. Will I be pushing my luck?

I think you'll be fine. I was pushing 10.5-psig with my old Paxton on my stock 305 and never had problems.

Willie

NTChrist

It seems like a lot of guys have belt slippage issues.

Can you rule out belt slippage as a problem?

BLWR PWR

Willie, thanks so much for your input. I will check with Vortech on the pulley issue. You might be right as far as only being able to get different blower pulleys as opposed to crank pulleys. Ive got to do something, I've got some friends with n/a 3rd gens getting close and it could get embarassing if they catch me!

ATOMonkey

Not to change the topic a lot, but... Isn't the whipple charger a positive displacement blower(similar to roots) that mounts like an accessory? Positive displacement gives lots of low end boost.

88GTAinRI

Do Superchargers use waste gates similiar to turbos?

nitrobreth

i have a whipple on my 454ss. boost all the time! i have boost at idle like i do at 2500. does not mount like accesory. sits right on top of your manifold. twin impeller. just awesome.

B4Ctom1

no, but they do use a bypass valve (a blow off valve of sorts) mounted in the boost line, like turbo cars do. a waste gate is used as the limiter on a turbo and the engines rpm is the limiter on a supercharger. without a wastegate, over rpm of the turbo impeller, over boost, and a few other small things can happen. I saw a subaru with a wastegate that had a jammed/modified pushrod, when it granaded the shrapnel went through the motor causing a short trip on a long hook to a junkyard for the whole car (not worth fixing). saw a similar event on a 2.2 chrysler lebaron (damn, it was fast for one day)

BLWR PWR

Whipples are nice, however they do not make one for the TPI induction system.