Was searching around, and had a thought. Right now, the setup going on my motor is a 7.65 crank pulley and 3.40 blower pulley, which should max the D-1SC impeller at about 6500-6600 RPM.

Would there be any benefit to moving down to a 3.2" blower pulley and maxing the blower earlier, or keeping with the higher rev limit and maxing the blower later. This is kind of an all out effort with what I've got.

My thought is that the 3.4" combo would make better peak power with boost coming on later, but the 3.2" combo would have a better under the curve area with a tad less peak power given less RPM's.

 

I would say spin the blower up sooner in the rev range...and keep the peak RPMs down

however...that being said.. I put on a smaller blower pulley to make more boost below 4500rpms ...and I still rev the crap out of mine,so the idea could be flawed

 

I thought a 3.4" pulley was the smallest one made for a D1SC. I believe they make smaller ones for a D1, however.

 

I saw someone mention a 3.2" pulley. Way I figure it, with the 7.65 crank pulley I have now, I can max the impeller at about 6600-6700 RPM with the 3.4" pulley, or at about 6300 RPM with the 3.2" pulley. A 383 with TFS heads and a 230's/240's low .600's lift cam is what I'm trying to figure our. Whether it's going to want to pull higher than that or not. Crap, I just need to do an F-1A and forget about it.

 

Something else to keep in mind...it will be harder to avoid belt slippage when you go smaller than 3.40".

Impellar speed with a 3.40" pulley @ 6500 engine rpm = 59,962
Impellar speed with a 3.20" pulley @ 6500 engine rpm = 63,710
ATI says the amx impellar speed on a D1SC = 62,000

I can't imagine creating a problem by spinning it an additional 1700 rpm.
Maybe Ponyhntr will have something to add to this.

 

I'm not talking about overspeeding the blower impeller. I'm talking about pulleying the blower to bring max impeller speed a little sooner (we're talking 400 RPM here) and bringing my powerband down to there.

I've got the 12 rib pulley setup and will switch to a SCDE tensioner if necessary (going to see how the ATI tensioner holds up first).

Here's another thought -- given the extra cube setup, what if I was to go with a smaller crank pulley than the 7.65 and run a larger blower pulley and max the impeller closer to 7K RPM. still get the same boost, but more RPM......

 

I have my build up setup for a 3.2 Blower pulley shifting at 6200, IMO with FI on a street car why Rev the hell out of it, just speed up the blower.
There are a Few reasons I do this.

 

So here's the real question. Has anyone actually tried a back to back setup doing this (dyno, track, ect) and made note of the effects???

 

I like this idea. But you would need a bigger blower to do it. I very rarely run it all the way to 15 psi but spinning the blower faster at lower rpms in the mid range give you loads of torque down low.

 

For a street car the it's a good thing to spin the motor slower, like everyone says, it will give you more power under the curve.

The bad thing with LT1's is that ATI doesn't make a pulley smaller than a 3.40.

If you really wanted to, you could run a 8.5" crank pulley with that 3.40 blower pulley and it will max the blower at about 6050 engine rpm. If you wanted to stay with the 7.65 crank, the 3.40 pulley will max it out at 6700.

 

I almost feel like 6050 is going to be too low to cut the motor off. We'll see what happens with the 7.65/3.4 combo. I'm using Ben's car as a benchmark here to base my estimations off of.

 

You could run the 8.5" with a 3.70 blower pulley and spin the engine to 6500. That will also redline the blower.

 

Sean, keep in mind your setup is a little more agressive than mine, and you will probably be making more power/boost. Ultimatly you need to ask yourself what your goal is here? Is it a RWHP dyno number? Is it a ET at the track? Is it just to be faster than CALL911 ? If you are mearly just interested in the setup of the power curb, I think you have answered your own question on this one. Go with peaking the power lower. With the combo Ponyhntr listed above, that should be perfect. If you want another 80 RWHP and to be sliding all over the place, listen to the inside your head and just go for the F1. I really think the D1SC on your motor should make the power level you are looking for though.

 

I want two things. A number, 700+, and 9's once she's set up.

 

Yank the seats out, along with the A/C, buy a truck to trailer it to the track, along with all the drag suspension, yank the stereo, and add nitrous!

If you have to have a for sure 700+, just go with an F1. I think you'll be close, if not a snidge over with the D1SC, but if that is something you'll be upset about with only 685 or so, just stop thinking about it, and go for it. As for the 9's. Honestly, you might have to do some of the things listed above. I'm not saying it isn't possible to have a street car that is capable of 9's, but most are really gutted out, and are a "drag car" that drives on the street (especially for a 6-speed).