CALL911

I've got a D1SC on my 95 Z28 in my Sig. I usually see about 14ish pounds of boost. I currently have the black metal Procharger BOV that attaches via the 1 inch hose and vacuum line to circulate.

I have reason to believe the BOV is failing on me, and I have heard that the model I have is not the best. I don't really want to drop the big $ on the Procharger red race BOV that I will have to weld to install.

I want a good replacement that goes in place of what I have on the hose. I know Tial makes a 50mm BOV that is in my price range, but don't know which one best suits my application.

Could anyone point me in the right direction?

Alex94TAGT

The stock Procharger "pro-flow" valve is definitely not the best. If you shine a flashlight, you can see light around the butterfly valve -- it obviously leaks. Sometimes you can realign the butterfly valve to make it seal better.

I currently run the Tial Q -- venting to atmosphere with the 3 psi (0 to -7"Hg) supercharger spring -- but be aware that it does require welding (comes with its own weldable mounting flange in either aluminum, mild steel, or stainless). I think that's generally going to be the case with any aftermarket BOV, and I'm not certain how many aftermarket BOVs are supercharger-friendly (-need a light spring for it to be open at idle). Without welding, you might be stuck with the stock pro-flow valve.


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I have the corresponding "recirculating" base if I ever decide to quiet things down -- which you'd need if you've still got the MAF on the low-pressure side -- but I've no idea how much that cuts down on its flow capabilities (shown to the right in the following photo). If memory serves, the I.D. of the recirculating base is a hair smaller than the stock pro-flow valve I.D. Not entirely certain, but I believe that Procharger's "Big Red" recirculating valve has a larger outlet -- but again, it requires welding for the flange.


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At any rate, I'd stay away from the knock-offs -- they're know to fail.

CALL911

Thanks for the input. I know that ATIs big red one is good, but honestly I think it's a bit more expensive than it should be. Tials is almost half the price and still good. But I was really hoping to stay away from welding if I could.

Does anyone else know a good BOV (recirculating one for a supercharged application) that does not have to be welded?

onefastmx5

First off, you keep using the term BOV = Blow off valve.. and your supercharger uses a Bypass valve to relieve intake pressure. Do not buy a BOV because it is not open at idle, which your D1SC is still pressurizing the intake. The pro-flow is horrible, as mentioned above, and cheaper knock offs aren't a good idea either. Save yourself the headache and just spend the money on a good bypass valve and be done with it. Big red is a good option, as is the Vortech Mondo. I personally have tried- standard vortech bypass, aftermarket BOV, ebay bypass valve, Pro-flow (along with converting plumbing for the flanges)... and finally wised up and bought the Vortech Race bypass (only running 10psi max). After spending all that cash on testing numerous products I could have bought 2 'big red' bypass valves... live and learn.

mzgp5x

I use two (2) bosch style by pass valves re-calibrated for my engine vac/ pressure. The valves (alum) are 1" inlet, exit. The spring was not correct for my engine vac/ pressure. Every engine is different based on cam and flow. I took data during road tests and sized a spring rate that would hold the valve closed for max pressure build. It worked.

I tried many valves with no solution. (Procharger/ HKS, off the shelf Bosch). The Bosch valve was lowest cost (~$105.00 ea.)

I did an excel sheet to determine the spring force, based upon the valve piston areas, and, engine vac to offset the piston for bypass. I machined some spring boss mounts (delrin) and found a spring from enco that fit. Cut the coils to match the required excel calculated spring rate.

I do not think an off the shelf valve works well on a major modified engine. I have a D1 ATI prochrger and see 14~15psi of boost max. The valve is sized for 18 psi @ the pressure side seat. Any pressure side excess will overcome the spring force and bypass boost with WOT. If the TB modulates closed, the added manifold vac on the vac side of the valve piston will bias the piston open, and, bypass boost.

Hope this helps. B.

CALL911

Actually, I think it might help. You said you are running two bypass valves? Did you have to weld them into the piping? Do you have any good pics of your setup? What springs did you use? Any links?

Since we are running almost the same procharger unit (D1 vs D1SC) and almost identical boost, it would seem that I would need pretty much the same as you. I just would like some more info first though.

mzgp5x

I run two (2) Bosch type valves.
They are mounted in parallel.
Each has a 1" tube inlet/ exit.
Bosch type valves are aluminum. Body and internal. They also make plastic. I don't like the plastic.
Bosch valves have a piston that is spring loaded on the pressure side seat. The pressure side area is less than the suction side area of the Bosch valve.
I made a manifold to mount each valve on exit side on intercooler. They are secured with hose clamps.
The D1 Procharger does not have SC oil internal source.
The D1 has an internal step-up aio of 4.44:1 (DISC...~ 4:1?)
I use a 7/6 to 3.4"pd pulley ratio.
An F1A is better @ 5.4:1.
I believe spin-up rate is everything on a SC. So, larger ratio is good.
I have tuned the max SC rpm to match the cam high limit basic rpm.
Each by-pass valve is triggered off vac source locate @ intake manifold after the throttle valve.
The exit side of each valve (1" tube) vents to the SC intake. I use a clear PVC with nylon braid fiber (also had @ enco by the Ft.)
I run all metal tube on the inlet side of the SC, and, most every where else. I run my MAF on intake side of the SC inlet. I know... this works for me. Not popular with the people.
Spings can be had @ use-enco.com. I used a 3/4 OD spring about 3 inch long free length. I think I cut coils to achieve a ~ 15.5#/inch rate. Spring is preloaded in the Bosch valve about 0.25 inches.
I machined a delrin sleeve to center the valve in the 1" piston bore.
Bosch valves seal 100% on the pressure side with the proper seat load.
Sorry of the response length.
Hope this helps. B.

CALL911

Do you have any detailed pics on your setup? I think in this case a picture may be worth a thousand words. I really need to just see how you have yours setup to get a good feel of what I may need to do.

Alex94TAGT

The distinction you draw is no longer accurate. Perhaps I wasn't very clear in my previous post.

I run the Tial Q BOV (read:blow-off-valve) on my supercharged car, and the valve is indeed wide open at idle and low-load (vacuum) conditions / cruise. It only closes under boost. The reason for this is because I swapped in a low-pressure spring Tial makes, which allows the use of their BOV on supercharged applications. Swap in a stiffer spring, and it's all set for use on a turbo. You must use the proper spring for the application.

As far as I can ascertain, the Tial Q BOV is functionally and mechanically identical to the Procharger Race bypass valve -- both of which are available in open or recirculating designs. Just different names stamped on the casing, perhaps different dimensions / flow ratings, and I believe the Procharger Race valve has a built-in spring pressure adjustment nut. On the Tial, you have to unbolt and separate the casing to swap or shim the internal spring.

That said, this does not infer that ALL blow-off-valves are suitable for use on a supercharger, but the Tial Q is one such valve.

CALL911

How much boost and vacuum are you seeing with your setup? What exact spring are you using on your Tial Q (specifically what psi spring)? If your setup is similar enough to mine, I may just end up going the same route you have.

I "used" to see around 8 units of vacuum at idle. It has dropped to only 4 units of vacuum.

mzgp5x

Posted some pics on...
photobucket.com
search under users.
then, my ID... mzgp5x.
Hope this helps.

Ultra_Dog

I also installed a 2nd BPV on my Procharger setup. (car has since been sold).

The original BPV was fine until I increased the boost, then it would whine incessantly everytime I let off the gas. Instead of a bigger single, I simply added a second unit just prior to the throttle body. I used a cheapy Bosch model.

The difference in sound was tremendous, the power...identical.

CALL911

There are lots of different choices out there, and different sounds associated with them.

I ended up going with the Tial 50mm BOV, and got the spring they reccomended for the supercharger. I haven't installed it yet as it is a weld in model.

canbaufo

Anyone run both, a BOV and a bypass valve? Always thought that would be nice because you'd get the constant recirc of the BPV and then some additional blow off (and nice sound) from the BOV at higher pressures.

MysticBowtie

Speed Inc. put my setup together. They used a Vortech Mondo on my Procharger D1SC @ 16lbs. It was designed for high boost and works great!