North American Turbocoupe Organization



Bosch Bypass Valve
SteveX82 Offline
Posting Freak
#1
After looking at no less than 15 or so pages detailing how to install a Bosch bypass valve, I still haven't found a clear answer in regards to which port should connect to what. Some pages say that the side port should connect to the low pressure side and the bottom port to high pressure, other pages claim exactly the opposite. Does anybody have any input (possibly some "official" Bosch instructions?). Thanks for any insight.
Estoril blue 1987 TC 5spd, 148k mi, a237, Bailey BOV, spec stg3 clutch, spearco FMIC, 50 trim t3/t4, 3" exhaust, Bamafuel, LM1, 55pph
Best 1/4 mile: 12.31 @ 110mph on 25psi
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Pete D Offline
Administrator
#2
I got my short side to the intake system ahead of the compressor and it works fine. I have no idea if that is correct. And I have seen the same inconsistencies in information.

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NATO Member. it's not a vice, it's an obsession
"The nice thing about each new day is nobody ever used it before" Barnaby Jones
88 TC X 2, 86 SVO, mods list at
http://www.turbotbird.com/showroom/pd_88tc.htm

[This message has been edited by Pete D (edited 07-27-2002).]
Pete Dunham


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SteveX82 Offline
Posting Freak
#3
After a bit of inspection with a flashlight and a vaccuum pump, I've decided that I've had the valve hooked up backwards the whole time. It turns out that the spring-loaded / vaccuum assisted diaphragm is a contained vaccuum system in itself that stays open while the car idles. By making the side port on the valve the high-pressure side, you can eliminate the little boost-battle when it sees boost in both the small vaccuum port and on the bottom port. With my BPV hooked up this new way, I no longer see the old 2-3 psi drop is boost pressure that I did with the old setup. Maybe Bosch should release some sort of instruction manual to set the record straight?
Estoril blue 1987 TC 5spd, 148k mi, a237, Bailey BOV, spec stg3 clutch, spearco FMIC, 50 trim t3/t4, 3" exhaust, Bamafuel, LM1, 55pph
Best 1/4 mile: 12.31 @ 110mph on 25psi
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Jeff K Offline
Administrator
#4
I have seen it hooked up both ways. I have mine hooked up with the side port to the pressure side (the IC in my install) and the end port hooked to the hose between the VAF and turbo. My reasoning: hooked up this way, both sides of the rubber valve thingy inside see the same pressure (boost pressure), and the rubber valve wont blow itself out. If you connect it the other way, the inside of the rubber valve sees boost pressure and the outside sees atmospheric pressure, abd the rubber valve can balloon out, and be damaged, which I understand is fairly common, especially if running high boost. It might act a little slower hooked up my way, but from what I can tell, it still works just fine.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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natmac3 Offline
Administrator
#5
I haven't hooked mine up yet, but when I do, it will be done as illustrated in the diagram. I know it's crude, but it's the best I could do on short notice...
1987tc
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r3lic76 Offline
Member
#6
i just got my bosch and i have no idea how to install it (other than knowing that it goes into my IC)

any linkage to how i can do it?

and can i use it as a blow off valve instead?
88 Turbocoupe - T3 conversion - bbk255 - kirban FPR - open 3" dp - ported lower intake
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Jeff K Offline
Administrator
#7
Quote:Originally posted by r3lic76:
and can i use it as a blow off valve instead?

You CAN NOT use it as a BOV! Under high vac conditions, like idle and cruise, the Bosch valve is open, and if used as a BOV, it would amount to a HUGE air leak under those conditions.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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SteveX82 Offline
Posting Freak
#8
Quote:Originally posted by r3lic76:
i just got my bosch and i have no idea how to install it (other than knowing that it goes into my IC)

any linkage to how i can do it?

and can i use it as a blow off valve instead?

Here's some "linkage" for you: http://natoubb.turboford.org/Forum1/HTML/002586.html
Please note that the way I have my BPV routed in this picture is, in my opinion, backwards. I'll try and create a super-fancy-schmancy rendition of the BPV's internals sometimes to help defend my opinion.

You could use the BPV as a blow off valve, but I wouldn't recommend it. TC's use a closed air metering system that pays relatively close attention to how much air enters / leaves the engine. With a blow off valve, some of the air measured by the VAM will be vented to atmosphere entirely unaccounted for, thereby creating a temporary rich condition. You'd also have to put a large one-way check valve on the outlet side of the BPV since the BPV's internal valve stays open during idle and would create a vacuum leak.

[This message has been edited by SteveX82 (edited 07-28-2002).]
Estoril blue 1987 TC 5spd, 148k mi, a237, Bailey BOV, spec stg3 clutch, spearco FMIC, 50 trim t3/t4, 3" exhaust, Bamafuel, LM1, 55pph
Best 1/4 mile: 12.31 @ 110mph on 25psi
Reply

Scott Evil Offline
Senior Member
#9
Quote:Originally posted by natmac3:
I haven't hooked mine up yet, but when I do, it will be done as illustrated in the diagram. I know it's crude, but it's the best I could do on short notice...


I have replaced the BPVs in my Audi about 6 times in two years, so I have way more experience with these than I ever wanted.

Your diagram is backwards. The vent should be under the vacuum line. Otherwise you have constant pressure on the diaphram. This will wear it out quicker (the longest life I have had on these is about 5 months as it is).

What Bosch part number is everyone using? I am running 0-280-142-110 on the Audi now and they last about 5 months under 17-18 psi of boost.
1986 SVO 1D <19,000 miles
2001 Audi S4 Silver (the fastest color)
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Pete D Offline
Administrator
#10
The number on mine is 280 142 102

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NATO Member. it's not a vice, it's an obsession
"The nice thing about each new day is nobody ever used it before" Barnaby Jones
88 TC X 2, 86 SVO, mods list at
http://www.turbotbird.com/showroom/pd_88tc.htm
Pete Dunham


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