Do I need a by-pass valve?

chobracobra · Sep 18, 2006

I finished the install of a novi 1000 blower kit on my car. The instructions dont really go to deep into the by-pass valve issue. Do I need one? I know exactly what it it used for, just not sure if it is necessary. The kit makes 5-6 psi. thanks

poneypower89 · Sep 18, 2006

with 5-6 psi you do not actually NEED one.

They are usually recommended at 7-8psi and required at 9psi or more.

One way to tell if you actually need one is to get on the car real hard.. then left off suddenly.. if the car bucks noticeably hard it could be because of compressor surge.. IE you need the by-pass.

I just installed a new BOV on my car, its nice to have that little extra insurance to protect to the blower in any case.

chobracobra · Sep 18, 2006

their also used when downshifting; closed throttle deacceleration? can anyone reccomend one?

spierce · Sep 18, 2006

BOV

PUT IT IN!
I've blown all my hoses off several times and had to limp the car home because it blew the clamps out from under the car while doing about 65.
just pony up and put it in.. it's easy.

JChalfan · Sep 18, 2006

chobracobra said:
I finished the install of a novi 1000 blower kit on my car. The instructions dont really go to deep into the by-pass valve issue. Do I need one? I know exactly what it it used for, just not sure if it is necessary. The kit makes 5-6 psi. thanks

Everything I've heard says you don't need one at 5-6 psi. I'm running about 6psi and haven't had a problem without one.

spierce, what kind of charger/turbo do you have? How much boost are you running?

Jeff

Blk91stang · Sep 18, 2006

Why would boost have anything to do with needing a bypass valve? I can have 3psi in a 600ci motor but when the throttle body shuts closed, thats a huge amount of cfm trapped in the inlet tube that cant get out. CFM should be meaured instead of boost since when you shut the throttle, there is no more boost in your manifold anyways. It's all about cfm!!

Understand what i'm saying? I would use a bypass valve no matter what boost I'm at. It's worth the extra $100 or so it cost to put it together.

JChalfan · Sep 18, 2006

Blk91stang said:
Why would boost have anything to do with needing a bypass valve? I can have 3psi in a 600ci motor but when the throttle body shuts closed, thats a huge amount of cfm trapped in the inlet tube that cant get out. CFM should be meaured instead of boost since when you shut the throttle, there is no more boost in your manifold anyways. It's all about cfm!!

Understand what i'm saying? I would use a bypass valve no matter what boost I'm at. It's worth the extra $100 or so it cost to put it together.

In general, we're talking about 302ci motors. Many people may not know the cfm their blower flows, so it's easier to talk about psi. While you have a good point, most people go by psi "rules of thumb".

Just my $.02.

Jeff

Blk91stang · Sep 19, 2006

JChalfan said:
In general, we're talking about 302ci motors. Many people may not know the cfm their blower flows, so it's easier to talk about psi. While you have a good point, most people go by psi "rules of thumb".

Just my $.02.

Jeff

That is a good point, I just wanted to clarify, not confuse. I guess if your running 7 psi on a 427 Dart small block, you should know the difference by now.

fidstang · Sep 19, 2006

That trapped pressure over time will damage the compressor and bearings from backpressure. Doesn't matter how much boost. Boost is boost and it will put strain on the compressor, turbo or supercharger.

chobracobra · Sep 19, 2006

where can i find myself a good kit?

Blk91stang · Sep 19, 2006

I would find a regular bosche Bypass valve from something like an S-trim kit and rig it up yourself.
If i'm not mistaken you have an aluminum discharge tube so just get a bung welded in or drill and tap it for a 1" hose fitting. You are also going to need to do the same for the intake tothe supercharger. If it is plastic, drilling and tapping still works except I would use some epoxy to seal it up real well. After this, use some 1" hose and connect it all.

It will take a little engineering but should work great.

91ghp5.0 · Sep 19, 2006

is there a huge performance difference between a bypass valve and a BOV? as far as i have learned, a bypass valve just relocates the air back infront of the supercharger instead of "blowing it off" or releasing it to the atmosphere. is a BOV something i could have rigged up on a paxton 1000? it goes between the charger and the TB, correct?

Stangdriver627 · Sep 20, 2006

Yes, a BOV/Bypass will go after the boost is created and before the TB, that way you will not have "boosted" air sitting, it allows for the air to vent. whether you choose BOV or a Bypass, it's a good investment.

S/C or Turbo->->->->BOV/Bypass->->->->TB

~Alex

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