I have a 02Z06TT and it was worthless in 1-3 gears on the street until I stepped it down. I seems to me now that with a supercharger it would be easy to do the same thing simply using a boost controller before the MAFS. Is this common or does the cam, headers and more extensive parisitic losses associated with a supercharger install through the tune off to much? Or something else? Just curious with the new production supercharged cars coming out.
It's an STS with high flow cats, B&B shortie headers. I can still blow the tires off at 450rwhp, 430rwt of the 560rwhp and 540rwt available for 4th and 5th gears.
You dont need a boost controller. You need way better tires.
I have 335 Nitto 555 R's and had to back down the boost on my D-1SC. The shop that I was working with had talked to the Tech. guys at ATI about a boost controller. If you had one you could run higher levels of boost and bleed it off using the boost controller where it(the boost/torque) is not needed.
You actually do need a boost controller. The objective isn't so much to limit top boost (which of course it does anyway). The objective is to get more boost down low. Unlike with a turbo, with a centrifugal blower the peak boost is normally unregulated. So to keep the blower from over-boosting, the gearing is chosen so the maximum Boost level is achieved at peak RPM. That means the blower doesn't make much if any boost at low RPMs. If you have a "wastegate" mechanism that allows you to regulate the boost level, you can gear the blower higher and make more boost down low, while protecting the engine from too high a boost level at peak RPM.
I've always thought this was doable, but I haven't had the motivation (or b*lls, to be honest) to try it on my car. But I would definitely like more boost down low. The car pulls like a mo-fo above about 4K RPM, but it's a little doggy off idle. The Mustangs article, above, is pretty good information. Thanks for the pointer!
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Interesting, I thought superchargers works earlier then turbos and ended earlier because they couldn't spin faster then the engine, but I don't have any first hand experience and I was curious with the new ZR1 happening.
I also heard that Magnusen makes a boost valve kit.
In a Turbo, the boost is proportional to engine load (the HP the motor is putting out, sort of), not engine RPM (though load is dependent on RPM). A turbo will make good boost even at low engine RPM, and very high boost at high engine RPMs (provided the engine is under load). You limit a Turbo's maximum RPM, and so it's maximum boost level, with a wastegate, a pressure operated proportional valve that diverts excess exhaust gas around the turbine above a certain level of boost.
In a centrifugal Supercharger boost is driven by engine RPM alone. The supercharger's maximum RPM is limited by design (through gearing), at some multiple of peak engine RPM. The RPM the compressor is turning when the engine is at red-line is the speed that produces the maximum desired boost level for that engine. Peak boost is always at red-line. And because boost is proportional to RPM, this means the boost goes down as RPM decreases. Below a certain RPM, the blower isn't moving as much air as the engine actually demands and it makes no boost at all.
Magnusons (Roots type) or Whipples (which are similar to Roots) are constant displacement pumps. They produce the same amount of additional air per engine RPM regardless of engine RPM. This is also a function of mechanical gearing.
All types of mechanical superchargers need bypass valves. When you close the throttle, you don't want the pressurized air to dead-head against the butterfly. This can damage the throttle and also cause "compressor stall". But because the air was already metered by the MAF, you can't dump it to the outside. So when the engine pulls vacuum, systems like my Vortech use a BOV to recirculate the air from the high-pressure side of the compressor back to the low-pressure side of the compressor. But a BOV isn't a proportional valve (like the wastegate on a Turbo is). It's either open or closed with no in-between. So the plumbing is already there. If you replaced the BOV with a wastegate-like valve that was proportional, you could use a boost controller to limit the supercharger's boost. That'd let you set the mechanical gearing for a much higher maximum boost. For a centrifugal blower, that moves the entire boost curve "up" giving you much better boost lower down. And even though the boost now gets to maximum at a lower engine RPM (because of the higher gearing), when that happens, the boost controller starts to open the valve to limit boost to that level and all is well.
Like I said, I've given this a lot of thought, I just haven't have the "chops" to try it on my daily-driver. I'm a wuss. But it'd suck to blow it up...
Interesting, the centrifugals boost climbs to its max with the RPM. The GM roots more similarly to a turbo makes the same boost all the way through the RPM range, but, starts like GM claims at low RPM, and its torque peak ends about 900rpm sooner then my turbo, and doesn't twist as much because a turbo spools, but longer term consitent power. The ZR1's AFR is probably 12 so simply putting a wastegate on the intake with a 11 AFR possible would yield a significant power reduction, and adding an extra 50-75rwhp and torque with simple mods for some drag radials, is doable. We've seen the stock C6 Z06 do 10.8 with drag radials before, maybe more now. Low 10's for sure for the ZR1 with one day of mods.
Also I think my turbos BOV vents before the MAF to atmoshere as it trys to equalize to the closed intake, but, yes the metered after butterfly intake air simply initiates the movement of the BOV and evacuates the unmetered air before the MAF and butterfly. Seems like this would work on a supercharged car!
Thanks!
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