The Project Pad

With my setup, I have no need for a diverter/bypass/recirc valve, but honestly, the BOV I have is getting kind of annoying. After about 30 minutes of driving, I can't stand it anymore. I'm looking at taking a 4 hour drive in January, and would be nice to not draw so much attention every time I shift as well. I found a stratmosohere for pretty cheap, and was wondering if anyone has run them, and would recommend it, or going with another brand. Let me know what you guys think.

When I was in the B5 world they were all running forge DV’s and many people starting doing back to just the plastic 710N . It’s cheap and does the job. You won’t hear it outside the car but a little from the inside . I guess the reason people were switching is because they felt the plastic ones were faster and worked better , and also the metal ones do require some maintenance - they need to be taken apart and greased To make sure they move freely (removing a diverted is not that hard though)
I have always wondered about the recirculating blowoff valves as opposed to then diverters (is there any difference ?) like the one pictured below . I would love to run one of these but they’re expensive

Leave your ovaries at home and just run without any kind of bypass valve. It's only there for NVH reasons on OE cars.

Noisy Cricket wrote:Leave your ovaries at home and just run without any kind of bypass valve. It's only there for NVH reasons on OE cars.

Noisy Cricket wrote:Leave your ovaries at home and just run without any kind of bypass valve. It's only there for NVH reasons on OE cars.

Srsly... There's literally been millions of turbo cars produced without them. It's only there so the driver doesn't hear a little chee-chee-chee noise when they let off throttle. (Funny story: I was on the phone with Jonathan a few years ago. I realized he was driving somewhere when his cell phone completely failed to noise-cancel the turbo giggle from the T3 in his XR4Ti as he was upshifting. Ford 2.3 Turbos never had recirc valves)

One of the upgrade mods people in the Volvo community do to the K24-7400 is make the bypass valve spring so stiff that it doesn't do anything... Food for thought.

Yes, there have been many cars made without them, including the 5000q that my engine came out of. The blow off/diverter valve is mainly put into cars now to increase the life of the turbo. The "giggle" you speak of is the turbo stalling, which causes premature wear on the thrust plate and the bearings in the turbo. The diverter valve can also have the added benefit of helping to keep the turbo spooled up better if the return is aimed properly.

It stalls even with a diverter valve. If anything, the turbo slows down faster with a valve than without, since it is still flowing air and thus is still under load, but there's no exhaust flow to drive it. You can install a turbo tach and see this for yourself.

Turbos are not positive displacement devices. They are dynamic flow devices. Stick your hand over a hair dryer or leaf blower exit and note that the thing will actually speed up instead of load down. No flow means less load, not more.

Totally love my 710 from bosche. Handles 30 lbs of pressure, fast-acting diaphragm construction, and zero maintenance. Can make them much louder too by cutting away the "discharge" pipe (and also running a shit loud of boost lol). It's a a dream come true!

Noisy Cricket wrote:It stalls even with a diverter valve. If anything, the turbo slows down faster with a valve than without, since it is still flowing air and thus is still under load, but there's no exhaust flow to drive it. You can install a turbo tach and see this for yourself.

Turbos are not positive displacement devices. They are dynamic flow devices. Stick your hand over a hair dryer or leaf blower exit and note that the thing will actually speed up instead of load down. No flow means less load, not more.

Counter-intuitive, but I like it. Might have to play with that

audifreakjim wrote:

Noisy Cricket wrote:It stalls even with a diverter valve. If anything, the turbo slows down faster with a valve than without, since it is still flowing air and thus is still under load, but there's no exhaust flow to drive it. You can install a turbo tach and see this for yourself.

Turbos are not positive displacement devices. They are dynamic flow devices. Stick your hand over a hair dryer or leaf blower exit and note that the thing will actually speed up instead of load down. No flow means less load, not more.

Counter-intuitive, but I like it. Might have to play with that

This makes sense really. Pretty easy to see this effect with centrifugal pumps of any kind. Less load on the shaft when the air is just swirling around inside the housing instead of actually getting pushed out by the blades.

audifreakjim wrote:

Noisy Cricket wrote:It stalls even with a diverter valve. If anything, the turbo slows down faster with a valve than without, since it is still flowing air and thus is still under load, but there's no exhaust flow to drive it. You can install a turbo tach and see this for yourself.

Turbos are not positive displacement devices. They are dynamic flow devices. Stick your hand over a hair dryer or leaf blower exit and note that the thing will actually speed up instead of load down. No flow means less load, not more.

Counter-intuitive, but I like it. Might have to play with that

I'd be really interested to see some data logs with turbo speed

I agree regarding compressor stall,f never thought about it, but it makes total sense. However, I think this misses the other benefit of a diverter/blow off which is to avoid excessive pressure spikes. Using the famous 20vt intercooler as a case study, I could pop end tanks at 12psi but with the addition of a valve 20psi was no issue. Obviously we all have welded end tanks these days, but I feel like it could still cause some side effects.