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Discussion Starter · #1 ·
While looking at regular superchargers (say Weiand or BDS) used in "muscle" cars, I noticed that none of them seem to even have any sort of provision for a boost bypass valve. I've also noticed a lot of people that do the boost bypass "mod" to their L67/32 say they get better boost response at the loss of some fuel economy. I was wondering if the quicker boost response would increase even more if the boost bypass system was disabled completely (valve locked in the closed position obviously). Also, do any of the high end GTPs, m112 or m90 run with a disabled or blocked off boost bypass valve? Just curious if this would totally kill fuel mileage and also if someone does it, does it make the car have the slight blower "whine" at idle like the previously stated blowers w/o the boost bypass do.
 

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It is pretty easy to "disbale" the boost byapass. The result is of course is constant boost throughout any driving condition. This is pretty "cool" to watch on the gauge as you are stacking boost at rpm levels where the boost is SUPPOSED to fall off for our motors. All in all...not a good idea.
 

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The Eaton supercharger system incorporates a specially designed bypass valve, which is actuated by a vacuum motor near the throttle body, and recirculates the supercharger air flow when boost is not required. During typical driving conditions, the engine is under boost around 5% of the time, which means the remaining 95% of the time the engine is under vacuum, allowing for better fuel economy and a quieter ride.

When the boost bypass valve is closed under vacuum, the engine has to turn the supercharger just to get outside air. With the Bypass valve open the engine can draw in air with out having to go through the supercharger which lets the rotors free wheel. This increases fuel mileage by reducing the amount of power required to turn the rotors in the supercharger.
 

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Discussion Starter · #5 ·
I understand what its function is completely, I was just wondering if it has ever been experimented with to see if you do get into boost quicker. Looks like Rooty copyed that directly from the eaton site, and it says the bbv helps the engine yield better fuel mileage and also have a quieter ride, so I'm guessing there would be some minor blower whine at idle then. Anyone ever try this to see how much fuel economy is actually lost and if there would be a performance gain if it were disabled say just at the track or at a dyno run. I realize it would be completely stupid to try this before running on the highway for a trip or something since you wouldn't need to be forcing boost in all the time for any reason, but for short local trips and any race times would it be beneficial at all?
 

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we bypassed the s/c @IDD IV and gained a whopping 50 ponies... :D
drove it around town and then back to Tn. w/ no big difference in the mpg. it does respond a little faster!!!! (but keep in mind GM put it on there for a reason)
 

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Discussion Starter · #7 ·
So was yours stuck open or something? That seems like a huge difference. Did yours sound any different at idle then?
 

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Our bypass valves are also electrically operated also. It disables boost under certain conditions, one is trans in reverse.
 

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next version of our s/w will have some tables to control the boost valve opening under high load conditions, the scanner also logs the % open.

Hope you guys don't mind me posting this stuff. Just let me know if you do...

Chris...
 

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next version of our s/w will have some tables to control the boost valve opening under high load conditions, the scanner also logs the % open.
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""we bypassed the s/c @IDD IV and gained a whopping 50 ponies...
drove it around town and then back to Tn. w/ no big difference in the mpg. it does respond a little faster!!!! (but keep in mind GM put it on there for a reason)""

im having trouble determining if you're joking or not. help me out.
 

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if anyone can tell me how to change the "boost bypass" i'll give it a shot and i'll try and see how lt goes. i check all the differences in the engine as well. let me know.
 

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Just take out the BBV Solenoid, slightly reroute the vac lines, and then disable the codes in the PCM. Simple way to negate the PCM from having any effect on the amount of boost you are able to achieve. Now, do NOT remove the Boost Bypass Valve Actuator itself, or disable it with a zip tie or some such, it's honostly pointless to do so and is likely to cause more problems than what it's worth. I've "fixed" a few peoples cars who decided to do this and ran into tuning issues because their car ran like crap, wouldn't idle and suffered from bad part throttle KR. Put a BBV actuator back on and in working order....poof things were much better.
 

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does it work? sounds like a big headache..
 

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Discussion Starter · #15 ·
10-05-2004

10-02-2007


Holy 3 year old thread batman!
 
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