QuickSilver2002

I have an ATI d-1 setup and I want to run more boost, but want some protection to keep if from going too high in the upper RPMs. This has been talked about before, but I think I’m ready to start experimenting.

Anyone tried one of these. http://www.greddy.com/products/blowoffvalves_frame.htm

Look down towards the bottom where it says Relief valve. What does .08-2.0 kg/mm^2 convert to? I tried converting but my numbers look way off.

Also, HKS has something called a race valve that they claim can be configured as a blow-off and pop-off valve in one.

BIGBOS

When I decide to upgrade I'm going to go with an ATI race ready BOV... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Lost Time

Blow-off valves (BOV) and pop-off valves have nothing to do with each other and perform entirely different fuctions. Pop-off valves are used as a last resort to keeping your max boost under a certain level. It is NOT designed to be the only form of boost control you have. If you're relying on a pop-off valve solely to keep your boost under (x)psi, you're asking for a blown motor.

That being said, GReddy makes some good products. For the person planning on using a "race ready" bov, I'd stay with the street versions and not the "race" versions that are available. Unless you're running >15psi the type-s will work just fine. Other good suppliers of BOVs etc. are HKS, Apexi and Blitz just to name a few.

If you're converting Kg/Cm^2 to psi, it is 1:14.2, so the range you gave above is 1-28psi (roughly).

Hope that helps.

<small>[ February 17, 2003, 11:09 PM: Message edited by: Lost Time ]</small>

QuickSilver2002

I understand that a blow off valve has a completely different function than a pop-off valve. After reading a bit more about the HKS valve, it sounds like it can perform one or the other, but not both at the same time. http://www.hksusa.com/products/more.asp?id=761

I just want to run a smaller pulley and get more boost in the lower RPM range, but have a safty device that will bleed off anything over xPSI in the upper RPM range. It seems like a simple enough concept.

AzzHauler

iTrader: (3)

I'm looking for the same thing. I found that greddy one and the hks deal, but didn't want to spend a lot of money. I'm trying to fabricate something myself that does the same thing. If it works out great, if not I'll just buy one of those I guess.

Lost Time

I promise you, if you rely on a pop-off valve to limit your boost, you'll be rebuilding an engine.

They are designed to compensate for the occasional boost spike, not as a device to limit max boost. If you consider the size of the vent on a pop-off valve, it can't expel enough boost to be effective. If you attempt to run a setup that you "know" for sure is going to produce more boost than you want in the higher rpms, you're going to have boost creep problems using a pop-off valve.

It is basically nothing more than a diaphragm with a pressure spring on it. When the springs sees (x) amt of boost, it opens. When the boost it's seeing is less than its spring pressure, it closes. Problem is, it's only designed to bleed off a small amount of boost for a VERY short period of time (such in the case of a boost spike).

Don't entrust your $6,000 motor to a $0.35 pressure spring.

QuickSilver2002

That is exactly what I was afraid of and why I thought the HKS valve was intresting. It seems like it would be hard to purge enough air yet still have a solid seal, but then again flow dynamics are very difficult to speculate on. Has anyone actually tried this?

I just want to bleed off a # or two of boost, nothing major.

Boost control downsteam of the compressor does not seem impossible; I wonder why the concept is not more developed.

MIGHTYMOUSE

iTrader: (59)

not blow off not pop off but a wastegate is what i would try on a s/c car in the intake tubing.

a wastegate opens at a set boost point.. also if you use one of these you can have it controlled by a boost controller and run exactly whatever boost you want as long as you have enough pulley for it.

Lost Time

Naturally you would want to use a wastegate of some sort for boost control but it's not as easy as it sounds. Standard turbo wastegates are designed to bolt onto turbo manifolds, not into intercooler or intake piping. To modify it to attach onto intake piping would take a good bit of custom work, but it would give you the most tuneability. ANY of the aftermarket boost controllers would be able to limit boost to exactly where you set it. Hell, you could even set up rpm-specific boost, or have hi/low boost settings.

You just have to find a way to plumb it in there, that's the trick.

1slowCamaro

I have wanted to do this for so long. You would think somebody would have invented something like this by now. You know how much money they could make? We should figure out how to do this exactly.

How many holes are on a wastegate. The place you would connect to your supercharger plumbing and then when the spring compresses does it release excess boost out another hole? Trying to figure exactly how these things work. You could make that hole vent to the atmosphere. If thats how they work you could just connect a boost control to it and thats it? That cant be it because that wouldnt be that complicated. Somebody tell me what I'm missing or screwin up.

Justin

Justin

<small>[ February 19, 2003, 04:48 PM: Message edited by: 1slowCamaro ]</small>

MIGHTYMOUSE

iTrader: (59)

slowcamaro yea thats all there is to it, as long as the maf is AFTER where you put the wastegate on the pressure side of the blower.. then you just release it to atmosphere.. seems easy to me but wastegates are too espensive to give it a shot i guess..

Blackbird

you also accomplish this by getting the throttle body before the blower....

Basically it would act a lot like a wastegate. You could control the amount of air coming into the engine independent of the blower speed (never more, only less). The result is that you could pulley the blower to make 20psi and limit it to 10psi but due to the pulleying the boost would come in MUCH faster then if it were truly pulleyed for 10psi. Its output would look a lot like a roots style blower. You'd have a very fast ramp rate to the target boost and then boost could remain exactly the same the rest of the RPM range. You could even dip it a little at your torque peak (peak cylinder pressure) and then put a little boost back in. This would allow you to theoretically keep your cylinder pressure constant across a large range of the RPM band making it extremely easy to tune the car and avoid detonation.

It's less work on the blower too. Picture your vacuum cleaner. If you put your hand over the inlet and "starve the impellor" the motor spins faster because it's doing less work.

1slowCamaro

Sometimes you can find new ones priced allright on Ebay. Only sometimes though. So theres a vacuum hookup and a place to connect a boost control?

Justin

1slowCamaro

I think putting the throttle body before the blower would be a little more complicated.

Blackbird

didn't say it would be easy <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

but I think I may have a very clever idea to accomplish the goal outlined in this thread.

still looking into it before spilling the beans.

99GMC Can

There is a device built exactly for what you need. It 'restricts' air flow in relation to boost. I can't remember what it is called. I found it in a turbo book. They used them instead of wastegates. The only danger was overspinning the turbo. This restrictor was installed on the preasure side of the turbo. A pop off or blow off valve won't work because the change in preasure is dramatic. You need to regulate the preasure. Pop off valves will rattle and self detruct if used as continuous relief. When I find the book (it's hidden in a pile) I'll post the name/manufacturer. Also, why not feed the relieved air back to the blower. That way you can keep the MAF upsteam.

1slowCamaro

Yeah you should find and post that thing 99GMC. The reason I wouldnt vent it back into the intake is because the blower would be spinning faster so it will be heating the air more. It would be better to pull in fresh cold air rather than compress and heat air thats already been compressed and heated. Make sense? I would probaby pulley mine to make like 15 psi so I would have good boost right way and then could bleed the rest off. That would be great cuz then when you didnt want to run the car hard you could just turn down the boost control. <img border="0" alt="[driving]" title="" src="graemlins/gr_driving3.gif" />