The blowoff valve doesn't control over-boost - the compressor pulley size is the only thing controlling the boost upper limit. The blowoff valve only vents when the delta pressure between the manifold and the compressor outlet exceeds 10 inches Hg, which tells it that the throttle blades are closed and that the pressure needs to be dumped. Essentially, it prevents overboost of the carb bowls when you slam the throttle closed at high rpm.

This thing would actually run much better with a stout automatic. With over 600 ft/lbs of torque, the last thing this car needs is a 5-speed... I drove it around a little today, and it will rip the rear tires right off the car in any gear - it's ridiculous and absolutely insane...

 

Okay so its a delta P across the the throttle blades that opens it other wise the outlet would overpressure once the throttle closes at hi rpm. And the pulley is sized for your engine/rpm range/supercharger size.
But doesn't the volute style blower have a much greater efficiency at high rpm where the roots style blowers are more linear with rpm?

I'd like to try one on my 4th gen camaro with GEN II LT1 and EFI but its got an 4L60E auto. That and a smog legal ProCharger is $5K still in the box is the show stopper. But man, what a toy.

cardo0

 

Everything you state is completely correct. On the dyno, when we were plotting boost versus rpm and power, you can really see the thing come on when the rpm comes up. Of course, that's what makes this like a drug rush: You keep wanting more, and when you see how the engine responds to more - and how much power is coming on so incredibly fast - you don't want to stop... Driving the car around on the street, the power is absolutely instant from idle and on up: Once rpm goes past 1500, the rear end simply lights up at half throttle from the massive torque output, and things go crazy... All you can see in the rear view mirror is tire smoke and chunks of rubber flying through the air. I call this the "Happy Machine," because you just can't stop laughing from the insane amount of over-power. And it idles like a "normal" performance car with no blower whine or any indication of the crazy power: Your mother could drive this thing around town (as long as you put a block of wood under the gas pedal as a throttle limiter).

The guys with the 4th Gen Camaro/LS combo (and the Mustang guys) with automatics and the Vortec are producing absolutely whacko amounts of power. With the "kit" and all the parts needed for systems upgrades, we easily have $5K into this thing. And then we added the Tremec... What the heck... it's just money. And you CAN buy fun...

Lars

 

For some reason the GEN II LT1s run with converted single planes for intakes and i don't really know why as they have to fab the down turn plumbing as well. I'll have to research that on the camaro forums but watching your build is so similar it got my attention and i can see why the EFI crowd embraces the vortec blowers already with an electric fuel pump and electronic fuel delivery. I read of quite a few plumbing leaks on those conversions. But not much on the blowoff valving setup. I think every supercharger uses a blowoff valve except the smallest like the 141ci roots. No roots blowers for the GEN II motors - none. But the sbc has such a broad variety of parts available to complement any configuration - draw through or blow through, EFI and of course NA.

That's enough for tonight,
cardo0

 

Too cool man, wanted to buy one of those kits since they came out.

 

These are fun numbers to look at... here are the peak dyno numbers we achieved with this silly thing before I got chicken and dialed it back just a tad: (I can't make the table come out right, so you have to look at it right to align the numbers with the columns - the last column is volumetric efficiency)

EngSpd VolEff
RPM Clb-ft CHp %
3000 510.1 291.4 109.2
3100 522.2 308.2 107.8
3200 538.1 327.8 107.7
3300 555.1 348.8 108.7
3400 569.8 368.9 110.7
3500 579.2 386 113
3600 586 401.7 115.1
3700 592.3 417.2 117.4
3800 598.9 433.3 119.5
3900 606.9 450.6 121.6
4000 616.8 469.8 124.3
4100 627.2 489.6 127.2
4200 636 508.6 130
4300 643.2 526.6 132.8
4400 649.3 544 135.7
4500 654.3 560.6 138.2
4600 658 576.3 140.7
4700 659.6 590.3 143.4
4800 658.6 601.9 145.6
4900 657.2 613.1 147.8
5000 655.8 624.3 149.8
5100 654.5 635.6 151.9
5200 652.8 646.3 153.9
5300 650.8 656.7 155.6
5400 648.5 666.7 157.5
5500 645 675.4 159.6
5600 638.6 680.9 161.2
5700 630.1 683.8 162.8
5800 622.4 687.3 163.9
5900 615.3 691.2 164.7
6000 607.7 694.2 165.5

With some sticky tires, we should be able to break every component in the driveline...!

 

Yummy supercharger goodness

 

Ah. So 700hp is your limit lars. I bet 500hp would spook me. Man thats some bragging rights for a street car. Modern technology mated to old school muscle. And for a lot less than a new ZR1 ($112K)or ZL1 ($55K) or even a Viper ($100K).

cardo0

 

just stumbled across thread could someone let me know where engine specks are? Thanks

 

Me Too!!!