reno808

ahhhhhhhhhhhhhhhhhhhhhhhhhhh i see

lart951

That's another good point while intake pressure can be relative low, exhaust pressure can be MUCH higher.

67King

It is a rebuilt stock one wiht a LIndsey diaphragm, and to the best of my ability to tell, a dual port with the second port plugged (and of course, anodized a different color to help the scruts). But to the point, I worded it along the lines of "OEM style" because that included the Lindsey option. It is also $440, which is, IMHO, overpriced. Not a criticism of Lindsey, given the volume, I'm sure it is not a case of them taking advantage of the literal monopoly PCA has handed them. Just a case of cost driving the sales price, rather than normal market forces. But, given the rest of the rules, it just seems silly to box people into a corner like that.

I will test my wastegate as soon as I build a plate to be able to do that with - which I'm planning on doing regardless given that something on my race car broke this weekend where I was only getting 1.2Bar of boost. But, it should operate like an intake valve in a turbocharged application. OEM's typically have to run heavier springs, because the boost pressure makes the effective rate of teh spring lighter when tested against atmospheric. So while the valve may crack open at say 5 PSI on a bench, it may actually only take 4 PSI of boost to crack open on the car because of the pressure behind the valve. The diaphragm "pushes" on the top of the valve, whereas the exhaust pressure "pulls" from the head of the valve. But they are additive forces (in the OEM style - and subtractive forces in the aftermarket style).

I don't know for certain, but looking at it, that is the behavior I would expect.

Chris White

Amazing. I come back 12 hours later (+/-) and there is four more pages of 'stuff'. If we could channel all the hot air in this thread it would open up any wastegate!
The funny thing is that you guys are missing one very important element in the one area that you are disagreeing on - or at least that's the way I am seeing it.
Pressure in the cross over pipe, also known as back pressure, and can it open a wastegate?
The proper answer is "knida, sorta, maybe". Keep in mind that the back pressure is a number that fluctuates with a lot of factors. In a well designed and fresh system you want the back pressure to boost ratio at or under 1.5:1. A K26/6 can get to 2:1 easily and if you run it to high boost (20pis) you could get to 3:1. That would mean there is 60psi of back pressure at 20psi of boost. since most people that try to run 20psi on a K26/6 also have lots of old parts, inefficient bolts ons and other non-stock or worn out parts this number can vary wildly!

If you really want to get a grip on wastegates pick up ANY wastegate and try to open the valve with your hand. Good luck with that. The various springs that come with a Tial are not rated by actual "spring" pressure, they are rated at the pressure the wastegate should open with the control line attached to the intake manifold. A 10psi spring does not physically compress with 10 lbs of force against the valve - as Harry pointed out there is a serious mechanical advantage due to the size of the diaphragm....and bonus points for using the word "tranche"!

Finally - I can attest to the fact that a stock system in good condition will boost well over 20psi with the control line removed. Its one of the rare cases where Porsche did not design something that would fail to a safe functioning mode!

Chris White

That is 'limp mode' - when the stock ECU sees anything that it deems incorrect input from various sensors it will go into limp mode and open the CV to 100% duty cycle allowing only .2 bar of boost (or 1.2 bar atmospheric).
That can be a major pain to track down since there are a number of sensors it is relying on and its more likely a wiring harness issue....

67King

And that is why I pulled out of the Club Race in a couple of weeks. Interesting, my father-in-law had an "overboost" but it behaved very differently. Sad thing is, I completely rebuilt the wiring harness specifically to try to avoid these kinds of issues. Then I removed the fusebox, and basically rewired the whole car. It is probably a self inflicted wound. Ug.

reno808

use a EBC and create the fail safe that way. I did the same. so my fail safe will be running the spring.

Paulyy

How does your fail safe work? Mine just shuts off until WG spring pressure. But i haven't reached that properly ever. I usually hit the DME overboost first as it's lower.

I should try my overboost properly on the eboost.

lart951

So i wasn't wrong about back pressure a ratio of 3:1 = 60psi on the crossover DAMN, ok here is my test project, I will get a stock wastegate, install the tie pipe(crossover to wastegate inlet) sealed, have a welder install a fitting so I can fit a pressurize line from a compressor, let's see how much psi will i need to open the valve, for those techs here would that be an accurate test?

mahoney944

I agree the insults are not needed, however when figures like lart and paulyy are giving people advice on a system, and that advice is particularly harmful someone needs to chime in. Even after chris and turbotommy gave a proper review of the wastegate operation which mirrored what i was saying they continue to insult and act like children.

The issue that seems to be the main concern here is will the exhaust pressure push open the valve with no boost pressure to the diaphragm? And if you look on page 1 of this my answer was slightly, and as chris echoed "kinda, sorta, maybe". lart and paully argued that if you clamp the wastegate feed line that the exhaust pressure would force the gate to open regardless and would boost at spring pressure rate. This is absolutely false. As chris and I explained, the exhaust pressure has the potential to slightly crack open the valve under a high boost condition. however this slight crack of the valve is not enough to regulate the boost properly and leads to an over boost condition(limit of the turbo).

I'm not calling anyone an idiot, except those who cant read the paragraph above and understand its meaning. I supply help to those who need it based on facts not assumptions. I may not be a paid member but the assumption that you need to be in order to be knowledgeable about 951's is sad. anyone can buy a membership not everyone can be well informed. Time is a factor that that can bring experience and knowledge opportunities, however this doesn't mean time reflects knowledge.

reno808

Well my stand alone tells the solenoid the boost max and min. if the solenoid where to fail it will run like 7 or 9 psi max.

67King

I can't for the same reasons I can't run an aftermarket style wastegate - SP3 rules do not allow.

67King

If you read what I posted, I gave a pretty thorough synopsis of how it works, which pretty much aligns with what you and Chris said.

And then I go back to page 1, and I read Pauly's stuff. And he says pretty much the same thing. That exhaust back pressure pushes against the valve trying to open it, and boost pressure into the diaphragm pushing down on the valve trying to open it. That simply cannot allow the gate to open at spring pressure rate. I did not read anywhere where he said the crap you say he said.

Both of you are guilty, but you are doing it a lot more. What is that? COMPLETELY misrepresenting what the other is saying. Completely misquoting him. That's why I said I don't see much disagreement. Y'all are both arguing for the mere sake of arguing. Instead of trying to understand each other, you are both operating in the mindset of trying to find a "gotcha" quote. Sheesh, if you'd stop doing that, you'd realize y'all are more or less saying the same thing.

Just chill out, man. Trust me. You are reminding me of another guy who used to post here who was a complete know-it-all, and managed to throw insults around like sailors do profanity.

Chris White

Harry - you are going to ruin it for the rest of us.....while they are arguing here they don't have time to argue in other threads....

Chris White

Easier to make a plate that bolts right to the wastegate inlet (with gasket) and thread in an air line quick disconnect fitting. 10 mins of fab and you are ready to go.

You have about 1.25 sq inches of valve area - so at 60lbs of air pressure you will get 75lbs of force on the valve.....might be getting close to enough force, especially if the spring it a little tired.

But to be able to use this info on the forum you will need 6 witnesses, 4 youtube videos, notarized statements with altitude, air temp, humidity reports and at least one fiery explosion of some sort.