Boost Bypass!?

[Wings65288]

i was just reading a very interesting post in the how-to section, i wanted to see what EVERYONE is doing so i'm posting it in the most popular section. heres what TDUPREE said

what are some thoughts on the bypass mod. Does this actually do anything. If so do you have to have a chip tune or is it safe to do on a stock vehicle?
http://www.rpmoutlet.com/boost bypassc.htm
those are the instructions I have for it. I just got my car not long ago so any info would be appreciated

check out that link he put there, have all you guys done this or is this bad for your engine? thanks

 

[Bluedot_26]

http://svtperformance.com/forums/showthread.php?t=91349&highlight=boost+bypass+valve

 

[CobraBob]

Here's a very good summary of the information you're looking for found in the link that Bluedot 26 provided.

OK- some info here:

Basic boost bypass action consists of a vacuum operated bypass valve, which you need and want. The bypass valve is not the same thing/concept as "the bypass-mod" which would be more accurately described as "preventing manual override of the bypass-valve".

1. Boost drop-off at higher RPM's. This is caused by the increasing inefficiency of the blower itself. The Eaton does this, KB & Whipple (different design) do not, but they all have bypass valves. The boost bypass valve or boost bypass mod have absolutely nothing to do with this- zero.

2. The bypass is a safety valve. It GIVES nothing. It REMOVES some boost (by ~3psi I believe) by manually opening a (otherwise closed) vacuum control valve on the side of the blower.

3. When the bypass is open, incoming air bypasses the blower and DOES NOT get compressed. When the bypass is closed, the air is forced through the blower and is compressed. When the valve is partly closed, some intake air will bypass the blower while some percentage is compressed. This is why you get the variation in boost with throttle pressure- through the blower or around it. This is good since you don’t necessarily want to be under boost with grandma in the back seat.

4. The "boost-bypass" valve can be overridden if a particular parameter is exceeded. I don't recall all of them, I believe there are 3; one of which is blower discharge temperature. As you up the boost via smaller pulley, those parameters are more easily exceeded.

5. When a boost-bypass condition is triggered without the mod, the computer can step in and back off the boost, even under full throttle by opening that bypass valve up a little via the bypass solenoid (boost-wise i'd be like taking your foot off the throttle a little).

6. When a boost-bypass condition is triggered WITH the mod (no matter how it's done), the computer can't step in and bleed off boost. Well, it still tries (unless you chip-disable it) but either you a) rerouted the vacuum lines so that the solenoid still opens as it always did, but now has no mechanical effect on the vacuum-operated valve (that way the computer is "faked" into thinking everything is ok so no code is set) or b) you unplug the solenoid so it's basically dead (which causes the computer to issue a soft service code).

You WANT the vacuum operated bypass valve; you just don't want the fun police stepping in whenever they want. Without the valve, the air coming in is compressed 100% of the time, so the eaton is chugging away compressing (and heating) air even when you're idling at a traffic light. The intercooler never cools itself off completely, so when you punch it, it's ALREADY hot and does a much poorer job = less power. That means less power overall and much worse mileage (the compressor is under load 100% of the time). The bypass lets you drive around as basically a n/a car would until you smash it (and the valve closes).

 

[Wings65288]

thanks for that bob, sounds like it's pretty much not worth it then. thanks a lot man