Bypass valve (blow off valve) ????

So I had a leaking injector so I changed 'em all(just stock brown tops for now). I removed the upper intake to ease the installation - everything went back together good except over about 8-10 lbs of boost the intercooler blows off! I cranked down the clamps, now after a few squirts through the gears it still manages to pop the IC out of the TB hose! never had this problem till I did the injectors. I've been thinkin' about a Bypass or BOV anyway, so what's everybody using?

Do you have the bracket that bolts the IC to the exhaust manifold stud on, and is it tight? That bracket does quite a bit to hold the IC in place. Last year, I forgot to tighten down the nut that secures the bracket to the stud, and blew hoses off a few times at 20 psi boost until i found the nut loose. Also, be sure there isnt any oil film inside the hose or on the outside of the IC or TB where the hose fits on.

I am just running the plastic Bosch bypass valve that most here and over at TF are running. Got mine from Performance Techniques when I got my new turbo from them last year. It cost about $40, but that was before I found out there are other sources for about $25 new.

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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)

A bypass or blowoff valve won't cure that problem. Did you reconnect the intercooler support bracket?

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88 TC X 2, 86 SVO, Main TC with K&N, 3"DP to 2.5"duals through Dynamax, Ric valve at 17+ and disconnected KS.
Elite Bodega 16" chrome wheels. Autometer pod w/ A/F and Vac/boost gauges.140 mph Motorsports Speedo New engine: Total Seal rings and TRW pistons, ported and polished head w/ cc'd chambers,1.59"exhausts, SS valves, gutted upper, knife edged lower, A-230 cam, Race Engineering Adj Cam Sprocket, Crowlers, ARP head studs, and rod bolts. Walbro 255 HP pump and Kirban adj FPR, T-3. Centerforce II, KB subs and jack rails.

I could've blown off a couple of punks in a RS camaro today - but the IC blew off between 1st and 2nd(not much of a race when it just whooshes after about 5 lbs of boost) So I got under the hood shoved it back on and tightened it down and realized the only thing different was leaving off the bracket! I listened to a guy that told me it transfers a lot of heat to the IC! True, but if it won't stay on it doesn't do any good!!! I've still got the bracket, but I'm gonna start on the front mount IC pretty quick.

no, put the bracket back on! You really need it, or so I've found. Never heard it transfers heat, I think the IC in its stock location is beyond help anyway [Image: smile.gif]

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'88 Thunderbird TC
ATR 3" cat back, Sac. Mustang 3" DP, Tiny Avenger boost controller, K&N cone in fenderwell, Walbro 255 lph fuel pump, Perf. Techniques T03/T04E turbo, KB Trac Kit
'86 Mustang GT
usual bolt on stuff

Hey Jeff K,about the valve you have,does it earn it's keep,as far as you are concerned?I mean is it worth it?$40 bucks(or $25 for that matter)doesn't sound like too serious of an investment,does it really do it's job?

weird, on my old thunderbird i only had one of the bolts haphazardly bolted in and it never gave me any problems....i cant imagine the IC "blowing off" !!!

about the blow off valve....as far as fuel economy and driveability around town goes, is it better to have it or to not have it?

Originally posted by sean:
about the blow off valve....as far as fuel economy and driveability around town goes, is it better to have it or to not have it?

A Blow Off Valve (vents to atmosphere) or Bypass Valve (vents back in front of the turbo) is used to keep the air charge from slamming back into the spinning turbo when you lift (close the throttle's butterfly valve) in between shifts. It prevents damage to your turbo and keeps the turbo spooled up between shifts. Perhaps the latter fact would improve gas economy, but that's not the main purpose.

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Dan Eaves
88TC 5spd, Crower 5.5" Sportsman Rods, Short Wiseco Pistons bored .030" Over, Ported Head with Polished Combustion Chambers, Gutted & Polished Upper, Ported & Polished Lower, Polished T/B, Ported E6, SVO T3 .63AR Turbo, 3" DP w/No Cat, 2 1/2" single cat back w/DynoMax Super Turbo Muffler, RR Cam, K&N in Fenderwell, Gillis Boost Valve, Centerforce I Clutch, Removed A/C, Polished Wheels, Polished Valve Cover, Polished Crank and W/P Pulleys, Walbro 255LPH HP Pump, Kirban Adj FPR, and the DAMN Heater Core is new too !

[This message has been edited by Dan E (edited 09-12-2001).]

well if anything i thought having the turbo constantly spooled would use MORE gas...

[QUOTE]Originally posted by sean:
[B]
well if anything i thought having the turbo constantly spooled would use MORE gas...


I think "spooled" and "spinning" are two separate things.

Spooled up is when it's under boost.
Spinning is just that.
If you slow the turbo down when shifting , you have to use more effort to get it going again.Therefore using more gas to get things going again.
Thats my theory anyway.