alxdgr8

How did you delete the cat? With an aftermarket test pipe or cut off of the stock one? Sounds like it could be a collapsed downpipe/cat-pipe.

mahoney944

your definately wrong. i respect you 2 in the porsche community. but the fact is. the pressure from the j pipe is used to push the diaphram which opens the valve. the valve opening releases exhaust from getting to the turbo controlling the speed of it. if you clamp the wastegate line the wastegate doesnt receive any pressure and directs all the exhaust through the turbo creating over boost.

Paulyy

And the way the valve stays closed it via a spring. Which has a specific pressure rating. In this case a stock 944 turbo has 7 psi. over time it weakens so it'll start to bleed 2-3 psi. The wastegate is shimmed so it puts more pressure on the spring so it opens at a later time.
So the back pressure from the turbo opens the wastegate and it bleeds out. like any other wastegate.

mahoney944

This is also a good point, a collaped downpipe though usually pinches the exhaust flow though and wont allow the car to boost at all. this is all dependant on how much the pipe is collaped. in my experiences once the inner wall collapses they pinch completely quickly.

mahoney944

it wont start to bleed if youre not sending any pressure to it. since the boost line that he is clamping is what works against the spring pressure. the spring is strong enough to stay closed all day. when you refer to "bleeding early" this means the spring has weakened and the boost pressure can now easily push the valve open. the sooner this valve opens the less exhaust flow gets to your turbo creating lag. this is why racers opt to use a heavier spring to keep the wastegate closed right up until the desired boost level. however if no pressure is working against the spring it stays closed, closed wastegate = over boost

lart951

You are confusing a dual port design wastegate with the stock 951

mahoney944

heres a free lesson from the "noob"

single port / stock / clubgate
The pressure from the j pipe is used to open the wastegate by sending pressure to the top of the wastegate diaphram, to raise boost you restrict this flow with a mbc. Less boost pressure to the wastegate means its stays closed longer and boost higher. this setup utilizes boost pressure only on the top side of the diaphram.

Dualport
Dual port is very similar to a single port except you "T" into the supply line that pushes from one side of the diaphram and use a mbc to regulate pressure to the spring side which basically allows you to change the total net pressure of the spring side. this setup utilizes boost pressure on both sides of the diaphram.

on a single or dual port if you direct a line from the j pipe to the top of the wastegate (the side port if you are using a tial) not using any mbc / cycling valve (if your using the stock setup) the car will boost at the spring pressure. if this line is clamped the wastegate wont open and over boost will occur.

If you clamp this line and over boost doesnt occur (over boost as in the boost shoots way above normal, not the factory over boost protection of the ecu/ klr)then the wastegate has seized and is stuck open.

Paulyy

Wow.

Seriously, have you ever looked at a 944 turbo's wastegate?

Let me educate you:

This is a factory wastegate (picture from clarks garage)



As you can see, the exhaust inlet side, doesn't have a valve facing it. In fact it's on the "wrong" side. So you'd think the exhaust is pushing on the valve to keep it closed?
No, It doesn't Because if you notice that the valve has no room to go inside the wastegate itself. The valve actually goes outside the wastegate (unlike an aftermarket wastegate that the valve goes inside the chamber)
So the exhaust is actually pushing the valve open there for, it bleeds. That means the turbo is getting less exhaust which means less boost.

Notice how the boost line pushes down on the wastegate spring to open it?

lart951

I wouldn't waste my time anymore, I bet my last ball he has never hold a stock wastegate in his hands, or has any idea of the gases flow.

mahoney944

Please post a statement where i said this? I never said exhaust holds the valve closed. i said without a boost supply line to the wastegate it wont open properly creating over boost. boost pressure is used to open the valve not exhaust pressure. if what you were saying was correct what would be the use of having boost pressure sent to open the wastegate? because opening the wastegate is what slows down the turbo. so looking at your thoughts, if the exhaust is pushing the valve open by adding boost pressure youd only be opening the valve sooner slowing the turbo, reducing boost.

I have 2 stock wastgate, a LR dual port and a tial dual port.

Paulyy

This is my last post!





YES.

the reason it has regulated boost pressure going to it is for overboost protection. Thats why people shim the wastegate to stiffen the spring up then send regulated boost to open the wastegate sooner

lart951

The design of the stock wastegate is unconventional too. it is one of the reasons it will never be able to compare to an aftermarket wastegate.On a stock wastegate, the valve is pushed out of the valve body (just like a cylinder head) which is opposite of the Tials,Synapse,etc......which have a valve that is pushed into the valve body of the wastegate.

The stock wastegate is a single port unit which relies solely on the light spring to keep it closed. It WILL bleed boost to a certain extent no matter how new it is. A new stock wastegate will bleed off less boost then a worn one of course and with a large turbo running a lower PSI, it may not be noticeable.

It is also difficult to dial in a single port wastegate as shown above. A dual port design is far better in every way and does not require modifying pipes to "mask" boost issues. The dual port use the turbo's own boost pressure to keep the wastegate closed along with the spring, this allows boost to hit much harder.

A single port with gradually open over a longer period of time as boost rises.

A dual port will stay closed until you want it to open, making the opening time much shorter and thus more power earlier on. All of this is dependent on how you set up the boost controller.

If comparing a stock wastegate to an aftermarket run in single port mode, then there will still be some gain from something like a Tial due to the design of the valve and direction of movement. Tial's also allow you to easily swap springs.

mahoney944

Youre trying to tell me that exhaust is opening the valve. lets just say this is true (which it isnt). so you have a stock 7 psi spring, with the boost supply line pinched, your saying the wastegate will open at 7psi. as you stated in another post the boost pressure is used to open the valve directing exhaust out of the car(agreed). so tell me this. if using a stock wastegate with the supply line clamped(in your words) will make 7psi and by sending boost pressure to the wastegate only opens the valve which bypasses exhaust to the turbo(slows the turbo). how would you raise the boost level?

game winner.

mahoney944

lart, I can also say that i have tested the stock wastegate, tial 38 dual port, and LR dual port. tial though made of quality parts has an extremely bad design flaw, since the valve opens opposite, the supply line is sent to the opposite side of the diaphram(the valve guide side). this actually allows for a small leak to occur from the supply side chamber through the valve guide and into the exhaust. tial relys on expansion of the valve guide to seal the chamber. obviously the valve guide sleeve cant be completely sealed or the valve could not slide up and down. on a stock or lr wastegate the supply pressure is sent to the top side of the diaphram sealed between the cap of the wastegate and diaphram. allowing no leaks to occur from a supply side aspect.

Paulyy

Are you actually kidding me?

Have you studied physics? serious questions, because i did physics though out highschool.

You're telling me (and Louis AKA Lart) that the backpressure (which is a 1.1 - 1.5:1) cant push the wastegate spring open but the boost pressure can?

They're both working in the same direction. they both push the valve down.

The pressure on the factory spring is 10psi (0.75 bar. It's in the damn manual).

***I did say 7 psi before, which i was wrong, it's actually 10 psi. I meant 0.7 bar. But it doesn't change the theory behind how it works.