don16

Any real noticeable difference?

Dark_horse

I was actually surprised to see a difference. I noticed a consistent power and the shifts were more better along with the sound of the exhaust had changed a little while hitting redline. My wife noticed a difference too and asked what I had changed on the car. I’m not sure how it made the exhaust/headers/sport cats sound even more aggressive but it did. I have a tune and maybe my stock diverter values were bad, they were pure plastic and felt super cheap. More boost definitely over worked the cheap plastic stock ones.

Pb Pedis

Always a good idea to upgrade the diverter valve when running more boost. From an OEM perspective, I'm not surprised the stock valve would leak under higher then OEM pressure....it's probably designed to do that in the event of an unforeseen overboost situation. Here is the Forge valve sold/re-branded by Champion Motorsports:


991.2 Turbo S

spdracerut

The stock diverter valve is the same basic Bosch design used for two decades on every VW/Audi/Porsche on the market. OEM diverter valves on any car are typically designed to blow open at a high enough boost pressure as a mechanical fail safe against overboost in case of wastegate failure. Of course, this is bad when you intentionally increase the boost pressure. As these valves are made by the millions, they are made very cheaply and tend to fail when used in a performance application. If a car is just a daily driver going to the grocery store its whole life, the valve will probably last 10 years. On a track car, not so much. Also, if they are leaking, then your turbos have to spin faster which means more heat and more back pressure on the engine, so less power.

don16

Thanks. And what mileage do you have and what boost are you running?

​​​​​​I just wonder if say brand new OEM valves would give the same affect for another 50k.

Tier1Terrier

I would like to re-ask this question perhaps differently @4 Point 0

Can a stock valve simply be weak and not completely fail or is it all or nothing. In other words, if you have a weak valve (not completely failed), then you would have a slower boost response (not completely eliminated, just slower)? So if the valves are held closed by more pressure, then the boost response should be quicker. And then, wouldn't that result in faster response to increased throttle?

4 Point 0

If your stock valves are brand new and working correctly, then there is zero performance gains by changing them.
But they are prone to fail if you track or drive the car hard.
So you are doing a stitch in time. They will fail.

You are loosing power. By replacing them with the reverse setup, they are helped by more boost not weakened by it.

So if your stock ones were not holding, then you could feel the restored power. But I doubt it. The turbo’s were probably compensating.

Its a cheap fix and a no brainer.

I would not replace with OEM. The design is faulty. It is not if, its when they fail.

Yes, it can be gradual leaks. My mechanic put them on the bench and and blew compressor air through them and one had failed. He said it is extremely common.

Let me put it another way. You are restoring lost boost. You are over engineering for future increased boost.
It can only add lost power. If the OEM had not failed yet, then the only difference is, these won’t fail. The more pressure, the harder these close. Where as, as OEM age, the slightest pressure opens them, even when they are meant to be closed.

4 Point 0

When i was on Stock turbo’s, I got a Protune.

That ramped boost up to 24psi but tapered off to 21.

Now with TiAL M800’s, I run 27psi all the way to Redline.

OEM valves never handled the 24.

Tier1Terrier

This is what I'm driving at. My C2S is about 5 years old. I recently had a Softronic tune which bumps me up to 17 psi according to the gauge on the MFD. I realize this is not a huge increase but I figure if I'm getting even a small amount of leak from the valve, getting the reverse mechanism after market model might show an immediate improvement.

D2M

I did this mod about 2 years ago in hope of increasing the blow off noise slightly. There was no increase in noise but at certain load and RPM there is a slight difference in blow off tone when lifting off he throttle sharply. I did this install without removing the rear bumper or heat shields. I was able to sneak them in just by removing the rear portion of the fender liner.

spdracerut

There's a rubber diaphragm inside the diverter valve that starts to degrade and tear over time. So you can think of it as a garden hose with a hole in it that will get larger over time. I'm sure your Softronic tune is running much more than 17psi. I'd say at least 20psi. The first COBB OTS Stage 1 maps ran 24psi if I remember correctly. The MFD is limited to showing 17psi even though the true value is higher. I imagine you can datalog using the Softronic hand held device? The datalogs would show you the actual boost value.

don16

What do you mean they never handled 24? The tapering was probably the tune more than the valves, no?

​​​​​​Did you notice any difference with shifting before and after changing valves? I sometimes experience a delay/lag which I attribute to boost pressure drooping considerably between shift's.

don16

Are the APR valves installed in the same orientation as stock valves?

4 Point 0

The stock turbo’s fell off up top, and had to be tapered off. Nothing to do with valves. I was just answering questions as to what boost i was running.

The stock valves failed long before i was any where near the current 27psi.

Wujohn

I guess this is my next project - I am running stock boost but after 4 years with 2 good years of hard abuse, I am likely due.

QQ - if as 4Point0 says, with these after market valves, more boot pressure forces the valves closed (more). Is there an issue or risk of too much pressure causing some other failure because these don't blow off when needed?