lart951

Look at the design, the wastegate starts to bleed around 7psi, (not fully open) and it will fully open at 11-12 psi if the wastegate spring is not too worn out, by adding shims you add resistance to the opening process, that's why he is getting 15psi,.

mahoney944

you obviously cant read so ill post it again..... Im not saying that the exhaust doesnt assist opening the valve, but it surely doesnt open properly without the supply line pressure. the key part of this post is highlighted for you, respond to this.

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 by exhaust pushing open the valve 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?

If your saying exhaust will hold the spring pressure open at 7 psi and boost pressure will only open the valve more reducing exhaust through the turbo, then your saying with no pressure sent to the wg youll get 7psi and with full pressure your get 7psi because opening the wg more only slows the turbo

Paulyy

You dont...
To raise the boost level, you need to shim the wastegate first. by shimming it, as lart has said, it adds resistance to the spring holding so the wastegate can open later.

On a stock car. All that line does is it stops it from overboosting, or boosting at all by sending boost pressure down that line. Otherwise it's not doing anything.

I'm not sure what you're not understanding about it.

How many times do i need to repeat my self. The spring in the wastegate is rated at 10 psi. Which means. It takes 10 pounds per square inch of force to push it down.

lart951

Yes, in the 944 turbo design the exhaust pressure presses the valve out, it partially opens (bleeds around 7psi) boost pressure keeps building up but bleeding keeps occurring once you reach the boost controller desired pressure the valves open fully, if you set your mbc to a higher pressure the turbo will work harder to keep the desired boost the wastegate will be limited to the mechanical resistance of the spring

lart951

there are plenty of threads do a search

mahoney944

ok lets clear one thing up there are two ways to raise pressure on the stock wastgate,

1. you can shim the wastegate, this works because the boost pressure from a stock configuration will stay the same but with added resistance to the spring it says closed longer and directs more exhaust to the turbo. (this boost side pressure remains the same and the spring side is raised)

2. (personally did this for years) choking the boost supply line with a mbc. this metthod reduces the amount of boost side pressure being sent to the wastegate. (boost side is lowered and spring remains the same) the turbo has to work harder to push the valve open. raises boost.

clearly keeping the valve closed raises boost by directing more flow through the turbo

mahoney944

This doesnt make sense on a single port setup, raising the pressure opens the valve sooner and lowers boost.

The more pressure you send the sooner the valve opens and that causes more exhaust to bypass the turbo, if exhaust is bypassing the turbo its not spinning as fast.

This quote is true on a dual port setup because adding more pressure raises spring side pressure. and this keeps the wg closed longer.



its a simple science, on a single port to lower boost you send more pressure to the wg opening it sooner and a dual port you send less pressure to the spring side lowering resistence opening the wg sooner.

to raise boost on a single port you use a mbc to choke pressue to the wastegate keeping it closed longer. and on a dual port you send it more pressure to the spring side raising resistence keeping the wastegate closed longer.

lart951

https://rennlist.com/forums/944-turb...-worth-it.html

Paulyy

Yes which in this case, the MBC will be fully closed. just like pinching the line. The turbo is limited to the wastegate spring pressure.

mahoney944

your completely contradicting yourself. sending pressure to the wastegate opens it sooner, so clamping it would keep it shut longer. raising boost.

mahoney944

paulyy, you use a tial, do me a favor, run a line straight from the j pipe to the side port on the wastegate with no mbc, just a stright line. youll see that your car will run about 13 psi max if running the stock tial spring. then use vise grips to crush this line and watch your boost gauge get maxed out.

Paulyy

Oh wow.

Then explain how the KLR kills the boost with out shutting off fuel or ignition? Because that is a feature in the 944 turbo.

lart951

when the line is pinched you will have surges the valve does NOT stay open all the time it closes and opens creating those choppy dyno charts, so boost will raise to the point that the valve stays open through a series of surges.

mahoney944

when the stock klr determines an over boost condition it does two things, a fuel shut off (often refered to feeling like someone putting on the brakes) and the cycling valve is sent the signal to direct all the pressure to the wastegate fulling opening the valve, bypassing as much exhaust to the turbo as possible. no fuel, no exhaust spinning the turbo, no over boost.

this is exactly why when you upgrade to a mbc you remove this feature in the klr by use of aftermarket chips so your car can boost higher without getting the fuel cutoff and you are able to delete the cycling valve and run a line straight to the wg using a mbc to choke the feed supply, keeping the wg closed longer raising boost.

mahoney944

more contradictions

first you say the car will boost at the spring pressure and next you say it raises. pick a side.

test this and get back to me because i have personally tested this and have done so on 3 stock wastegate, 1 lr dual port and a tial 38 mm all run in single port mode.

do me a favor, run a line straight from the j pipe to the side port on the wastegate with no mbc, just a stright line. youll see that your car will run about 13 psi max if running the stock tial spring. then use vise grips to crush this line and watch your boost gauge get maxed out.