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Discussion Starter #1
For you guys with turbos when you say you crank up the boost, you are actually closing down the blow off so that it doesn't let out as much air? right? So on a centrifical SC can you do the same thing with the bypass valve? Also when you do adjust the boost have you compensated for it in the tunning on the ECU and if so how? Say you had it tuned for 10psi and then you crank it up to 12psi how do you compensate or are the safeguards(knock sensors) doing it for you?
Thanks, look forward for the reply's.
 

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They are doing it with a boost controller and/or a different spring. If they are smart they will either have enough fuel to make small changes safely or be able to access another program with different fueling and spark if needed.

Messing with the diverter valve on your blower won't change your boost. If you're ready for stage 2, I'm going to finalize that next week. And then obviously, we're wrapping up the intercooler kit in a day or two.
 

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Discussion Starter #3
Just cuious on how they get away with it. I kind of knew the diverter wouldn't do anything. hey can you call me on my cell I have some questions for you. 480-226-5892
 

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They are doing it with a boost controller and/or a different spring. If they are smart they will either have enough fuel to make small changes safely or be able to access another program with different fueling and spark if needed.
i'm not quite sure that another program would be necessary. If you can keep your tune the same at different loads, that should be fine right??

Like if at 9 psi your load is N, so you get your a/f good, timing set etc...then you make sure your tune is fine for up to like 15 psi or whatever (provided you have high enough octane gas to support that much boost), you should be able to have a tune that works between 9-15 psi, right?
 

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you can run more boost with higher octane as long as your a/f is still with in acceptable limits like Randy said above. Todd you can adjust the turbo boost output by adjusting when the wastegate opens. The blow off valve only opens for a second or less to let off the excess pressure when the throttle plate is closed.
 

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Boost is not controlled by a divertor or BOV it's controlled by the wastegate of a turbo system or the pulley of a supercharger.
 

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Yah Todd for us, the valve is closed as soon as we hit 0 vacuum.... so there is no boost going through there.

The only route for us is to change the crank pulley or the blower pulley.

And in reality... you never wanna raise your boost.... a boost controller is best used for dialing down the boost when you're detonating ot there is the potential to damage your manifold by having your floor boards falling out and yelling shut-up! at your laptop.
 

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Discussion Starter #11
I know how to adjust the boost on the SC system I was just wondering about how the turbo guys do it without blowing up their engines. So if the diverter vavle see's 0 vacuum it is closed and the SC puts full boost to the intake? So if the vacuum line broke or fell off for some reason you could have 10PSI or more going into the engine and do some serious damage? That would not be good.
 

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on an SC... you know what your max boost will be. its a finite number. X psi at Y RPM.

Wheras with a turbo... if your boost controller gets whacky... yes in theory you could overdo the boost (Overboost) and run into major problems.

One of the few advantages of superchargers
You always know what boost level you're gonna have.
 

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Discussion Starter #13
So even with the diverter valve closed the max PSI will only happen at max RPM. So you can't get max PSI at idle. The that would be safer. So the diverter valve just relives the back pressure when you slam the throtle closed so the SC doesn't get spooled backwords. Kind of like the blow off valve on the turbos. thanks Todd
 

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AFAIK, the bypass valve is used mainly for drivability purposes and to prevent compressor surge. If it fails, you won't over-boost the engine, but you might lose some throttle response.

Under vacuum, my bypass valve is open, and air can flow directly from the airbox to the throttle body, as if the turbo didn't even exist. But as I lose engine vacuum (from the turbo spooling and/or the throttle opening wide enough), the valve closes and air can only get to the throttle body by first passing through the turbo and intercooler. So if I unplug the bypass valve from its vacuum source, it will stay closed under vacuum, and the engine may lose a bit of responsiveness because air will have to flow through the entire system to get from the air box and MAF meter to the throttle body. In theory, a blow-through MAF meter would solve that problem by metering the air AFTER it has already passed through the turbo and intercooler. But the nice thing with a bypass valve is that, if the turbo hasn't spooled at all yet, it won't present any restriction to airflow because the air will be bypassing it.
 

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I know how to adjust the boost on the SC system I was just wondering about how the turbo guys do it without blowing up their engines. So if the diverter vavle see's 0 vacuum it is closed and the SC puts full boost to the intake? So if the vacuum line broke or fell off for some reason you could have 10PSI or more going into the engine and do some serious damage? That would not be good. [/quot]

"DAYUM! THIS CAR FEELS FAST FOR ONLY 170WHP!!!" ::Looks at guage to see he's running 15psi instead of 6psi::

what? over boosting never happens.....
 

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LOL, yeah it's no big deal if the bypass valve's vacuum line pops loose. But if one of the boost controller's lines pops off, you could be in real trouble if you don't have an eye on your boost gauge.
 

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Good AFR still does not necessarly mean it is safe to crank boost... excessive timing could still create massive deto.
 

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Good AFR still does not necessarly mean it is safe to crank boost... excessive timing could still create massive deto.
Right, that's why we're saying that you can add a little more boost with more octane.
 
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