No Boost??
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Le Mans Master
Joined: Feb 1999
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From: levittown pa. usa Even a bad day with my `Vette, is better than a good day at work
St. Jude Donor '10
No Boost??
I finaly got around to playing around a bit with my Procharged `90 that I got last year, & it seems to have a few problems. The car runs fine & I can hear the supercharger whining, however the boost gauge does not move much & it seems that the bypass valves stay open at all rpms. I removed one of the valves & put vacuum to it, & it does open. It just don`t close as I step on the gas. The vacuum line to the valve was 35-40 lbs with the car running. It a P600b with the intercoolers. What should I be looking for? Thanks
Thread Starter
Le Mans Master
Joined: Feb 1999
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From: levittown pa. usa Even a bad day with my `Vette, is better than a good day at work
St. Jude Donor '10
I don`t think they are closing at all (there are two). Does it matter where you put the vacuum lines on the engine?
PS: when I took one of the valves off to look at it, it was closed with no vacuum.
PS: when I took one of the valves off to look at it, it was closed with no vacuum.
Instructor
Joined: Feb 2011
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From: harrison twp mi
they should be closed w/no vacuum(just checked mine to be sure). i plumbed mine into a open port on the manifold that was not shared with anything else.had to gang a couple other things together to free one up.
Thread Starter
Le Mans Master
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From: levittown pa. usa Even a bad day with my `Vette, is better than a good day at work
St. Jude Donor '10
Le Mans Master
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From: Windermere FL
Disconnect the vacuum line from both BOV and if you feel any air coming out of either BOV then they are not closing properly and you need to replace.
If you get no air coming out of the BOV with the line disconnected, then your problem is that you have a leak somewhere in your intercooler setup. This was a problem with mine at one time. Turns out the clamp was not on good and the hose came loose and all the boost was being dumped. Should be easy to find as you will feel air coming out of the joint at idle.
But if your setup preformed like my 90, you will only get a couple of pounds of boost anyway. That setup is just too restrictive. I ditched both intercoolers and all the associated plumbing and really cleaned up the engine compartment. I went with Meth Injection instead.
If you get no air coming out of the BOV with the line disconnected, then your problem is that you have a leak somewhere in your intercooler setup. This was a problem with mine at one time. Turns out the clamp was not on good and the hose came loose and all the boost was being dumped. Should be easy to find as you will feel air coming out of the joint at idle.
But if your setup preformed like my 90, you will only get a couple of pounds of boost anyway. That setup is just too restrictive. I ditched both intercoolers and all the associated plumbing and really cleaned up the engine compartment. I went with Meth Injection instead.
Thread Starter
Le Mans Master
Joined: Feb 1999
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From: levittown pa. usa Even a bad day with my `Vette, is better than a good day at work
St. Jude Donor '10
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Instructor
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From: harrison twp mi
someone correct if thats not correct.
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From: harrison twp mi
Safety Car
Joined: Aug 2009
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From: Melbourne, Victoria, Australia
Re intercoolers
Disconnect the vacuum line from both BOV and if you feel any air coming out of either BOV then they are not closing properly and you need to replace.
If you get no air coming out of the BOV with the line disconnected, then your problem is that you have a leak somewhere in your intercooler setup. This was a problem with mine at one time. Turns out the clamp was not on good and the hose came loose and all the boost was being dumped. Should be easy to find as you will feel air coming out of the joint at idle.
But if your setup preformed like my 90, you will only get a couple of pounds of boost anyway. That setup is just too restrictive. I ditched both intercoolers and all the associated plumbing and really cleaned up the engine compartment. I went with Meth Injection instead.
If you get no air coming out of the BOV with the line disconnected, then your problem is that you have a leak somewhere in your intercooler setup. This was a problem with mine at one time. Turns out the clamp was not on good and the hose came loose and all the boost was being dumped. Should be easy to find as you will feel air coming out of the joint at idle.
But if your setup preformed like my 90, you will only get a couple of pounds of boost anyway. That setup is just too restrictive. I ditched both intercoolers and all the associated plumbing and really cleaned up the engine compartment. I went with Meth Injection instead.
Re intercoolers and blow of valve (bosch blow of opens @12psi)
I am running 8 psi boost @ around 5,600 rpm with a large air to air intercooler.
My vette runs a standard maf (leaving intercooler) and ecm, does have a adjustable Fuel Management Unit to force more fuel thru the injectors to keep air fuel ratios good.
The engine is a high mile one and still runs strong and trouble free without the need of retarding ignition (and loosing performance)
Originally tried running without the intercooler, had lots of issues to get it running with the standard ecm and maf. It needed a lot of retard to stop the pinging even with a pulley to drop the boost to 6 psi.
My (since supercharged) vette has done many miles with only a injector connector fail ...only found out after fitting new Bosch 3 injectors .. but they are nice
My next step will be a engine rebuild, (when it starts feeling tired)
AFR heads, steel crank, forged pistons, nice super tough rods and a 4 bolt block. then at least 15 to 20 psi boost 
Last edited by gerardvg; Jul 22, 2011 at 05:59 AM.
Pro
Joined: Dec 2010
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From: Shillington PA
Are you sure, I think it is open with vacuum, closed once you hit 0 vac and move into boost...
Thread Starter
Le Mans Master
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From: levittown pa. usa Even a bad day with my `Vette, is better than a good day at work
St. Jude Donor '10
Would it hurt anything if I disconnected one of the Bosch valves & just ran with the one in my intercooler? 
Safety Car
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From: Houston TX
The BOV will only close under significant throttle and when there is a load on the engine. The BOV will not close fully by "blipping" the throttle while the car is stationary.
Leave both BOVs connected, as there tends to be a large amount of air that needs to be vented under vacuum and the Bosch BOVs are quite small.
Put a guage on the intake, drive the car, make some WOT runs and you will see if there is any boost. I suspect you will see that you have some boost; probably 5-8psi.
Good luck.
Leave both BOVs connected, as there tends to be a large amount of air that needs to be vented under vacuum and the Bosch BOVs are quite small.
Put a guage on the intake, drive the car, make some WOT runs and you will see if there is any boost. I suspect you will see that you have some boost; probably 5-8psi.
Good luck.
