WG tests
 

Its been a while since I looked at my WG. So decided to do some tests. (its original with 250 K plus on it).
First after removing I saw that the soot pattern on the valve was distinctly asymmetric, all the bypass was coming out of one side. See pic.

http://forums.pelicanparts.com/uploa...1576951879.jpg

So the valve was not seating evenly.

http://forums.pelicanparts.com/uploa...1576951958.jpg

Cleaned the valve and the housing where it seats.
Next the shims I had been using (supposedly stainless steel ) had rusted and there was rust between the WG diaphragm housing and the base.

http://forums.pelicanparts.com/uploa...1576952180.jpg

Cleaned this up. Reassembled the WG without shims and tested the gate by applying pressure to the input nipple of the WG.

-Starts to open at 3 psi.
-Can see clear opening all the way around the valve and housing at 5 psi.
- Fully open at 10 to 11 psi.

Next I built an adapter to test the gate spring under simulated exhaust pressure.

PLEASE NOTE THIS DOES NOT INDICATE ANYTHING OTHER THAN A RELATIVE SPRING PRESSURE AT VARIOUS SHIM WIDTHS.



http://forums.pelicanparts.com/uploa...1576952617.jpg


http://forums.pelicanparts.com/uploa...1576952639.jpg

-No shims the WG will hold 20 psi.
-0.1 inch shims the WG will hold 23 psi.
-0.2 inch shims the WG will hold 25 to 26 psi.

Again the numbers are just that, a relative stiffening of the spring force by shimming it.

Next I am planing a test with the waste gate being controlled by applying vacuum to the nipple (to hold it closed against the exhaust ) and then switching to pressure when the car hits the required boost point to hold it.
Kind of a dual WG but without the modifications to the diaphragm chamber.
Will keep y'all posted.
Sox

Interesting because my WG operates approximately at the same pressures as yours. I had no idea it holds 20 psi tho. Since most think my low boost problem stems from too much backpressure, that means BP could be well over 20 psi. Hope to get a gauge on the crossover pipe in this week.

Mike G.

That is not holding pressure it is just the point at which it stabilizes for the amount of air I can supply. If I had a bigger compressor these numbers would be higher.
The point was to show the relative difference the shims make.
Sox

For me 1/8 shim increased approximately .2 BAR or 2.9 psi on the stock gauge. The second 1/8 shim did nothing.

Mike G.

Mike are you talking about the boost? I was talking about pressure at the WG to turbo side.
Sox

Yeah Boost!

But I am interested in the amount of turbine inlet pressure it would take to open the WG Valve.

Thanks
Mike G.

I am in the process of testing this diverter as a replacement for the CV.
Have to play with the PWM duty cycle to tune it, but seems to work.
Important: you need to introduce a leak on the down pipe to the WG, as this device will switch but not release pressure on the WG and WG will stick open.
Sox

http://forums.pelicanparts.com/uploa...1577488249.jpg

Hey, that's some awesome testing! Your WG spring might be slightly soft as Mike's doesn't start opening until 5psi. But still within spec as it doesn't open fully until 10-11psi, which is fine.

Using with check-valve manual-controller with bleed-hole should give you any boost you want, 20psi+

Electronic solenoid shouldn't need bleed hole as both NC/NO ports will connect to COM. With fast duty-cycle signal back & forth, any residual pressure between valve and WG will be bled off. Look up various Supra MKIV forums on how to connect solenoid in push/pull configuration. With EBC, such as Apexi AVC-R, you can get any boost-level you want. I've gotten 25psi with unmodified stock WG when solenoid is configured in push/pull with connection to vacuum source on one side.

So....
further testing, replaced the O2 sensor with an old busted one. I drilled a hole through it to attach a hose to it. (The ceramic in the sensor is a really hard one, busted a few drill bits on it ).
did some road tests:
-hose to WG is pinched off, so no boost control by the KRL.
-Car gets 11 psi at about 22psi at the inlet to the turbo/WG connection. (this agrees with my static finding above, 22psi is when the WG starts to leak past the valve).

Next, the Cat is just a thru pipe, so I will check the pressure pre Cat and post Cat.
I don't have any data for how high the inlet to the turbo runs on these cars. Any info is appreciated :)
If the pressure is still in the 20's past the turbo, then I will look at my muffler. It is a flow master series 40.
Sox

Pressure in downpipe and exhaust after turbo should be very low.

Pressure-ratio between turbine-inlet and intake-manifold boost-pressure is not direct or linear. At low-RPM and low boost-levels, ratio will be < 2:1. At high-RPM and high-boost, it will be > 2:1. Also varies by turbine-size with larger TurboS K26/8 turbos operating at lower ratios than K26/6.

For high-power high-boost builds greater than 300rwhp, even larger turbines are used. At stock 10-12psi boost-levels, they will operate at < 1.5:1 ratios.

When going from factory exhaust to straight-pipe config, you'll typically see an extra 1-2psi boost. IF exhaust is not too restrictive.

Tested pre cat....negligible pressure, so will not do post cat.
As it stands:
Pre Turbo 22 to 24 PSI for a 10psi boost.
WG seems to be letting go at a combination of 8psi on the gate barb and 22psi on the Valve side. (KLR is starting to divert at this point).
Pinching off the WG control line increases the 8psi to 10psi and the 22psi to 25psi.
Next will mechanically hold the WG and test. (briefly :) )
Sox

Seems like my 9 psi boost to 22 psi to crossover doesn't seem to be too far out of the ball park?? So does a stock turbo S actually achieve 11.6 psi???

Thanks

Mike G.

Yup max boost on stock TurboS is 12psi in mid-range and trails off to 8-10psi at redline.

So what was the boost pressure when the WG line was pinched off. Most state that it could go extremely high?? Mine didn't really go that much higher.

Thanks
Mike G.

Hey can you do a bleed down test? Apply 10-15 psi to the WG line sealed off and see how much or how long it takes to bleed off pressure? I'm going to give that a try too hoping that I can determine if my diaphragm has a slight tear and bleeds off at higher pressures.

Thanks
Mike G.

i'm pretty sure that vac line is supposed to be air-tight and not bleed off at all.

Yeah "if" everything is working as it should!! :D

Thanks
Mike G.

Tested pre cat....negligible pressure, so will not do post cat.
As it stands:
Pre Turbo 22 to 24 PSI for a 10psi boost.
WG seems to be letting go at a combination of 8psi on the gate barb and 22psi on the Valve side. (KLR is starting to divert at this point).
:)
Pinching off the WG control line increases the 8psi to 10psi and the 22psi to 25psi.
:)
Next will mechanically hold the WG and test. (briefly )
Sox

Geez that's it 10 psi? Even my turbo re-builder said it should completely over boost!

Thanks
Mike G.

It should but the WG is likely letting go, so that's my next step.
Your and my issues may be the same.
-low boost.
-no real back pressure post turbo outlet.
-Isolating the KLR from the WG does not increase boost significantly.

So next step for me is to prevent the WG from bypassing and make sure the Turbo has the oomph to make enough boost.

I had a similar problem years ago and IIRC it turned out to be the knock sensor telling the KLR that the engine was knocking. The KLR then retarded the ignition which ended up in low boost. Will look for that thread.
Sox

Well update on waste gate testing. I made an adapter to see how much pressure it takes for the gate to start opening. The pressure was applied to the exhaust in side of the gate. First the adapter shown in the first pic is not going to work I had an explosive pop out of the tube before the gate opened (very exciting ) J. So the second picture shows the adapter with the hose bolted down. As an aside before I get to the actual numbers, the waste gate was very dirty with a lot of soot caked in to it. (the car is a 1986) so 20 years of it. This prevented the gate from ever closing all the way. So I cleaned the gate lip and the valve ( simple green, tooth brush and steel wool se next pic). After it was seating well, I took my readings and here they are:
1) stock 20 year old gate. The gate leaks a little around the valve, but it holds till 20 psi then a rush of air comes out.
2) With 3 mm of shims installed the gate holds till 30 + psi and then there is a rush of air. (the small leak at any pressure remains).
3) The diaphragm starts to open at 5 psi and full open at 8 psi (stock old gate).
4) The diaphragm starts to open 7 psi and full open at 9 to 10 psi (with shims) I did not expect that much difference in the diaphragm numbers as the aperture and the chamber in the diaphragm housing is quite small and the pressure difference is comparatively large ??

That was from my testing in 2007....

So my current numbers are quite a bit worse.
Sox

I applied vacuum with a hand vacuum pump to the WG control line and boost did reach 2 bar on the stock gauge. Which I guess should have told me that the WG is not working properly :eek:


That would suck!

Thanks
Mike G.

I am going to test mine with the vacuum on the WG and also test if the WG is still letting go at the same time.
Sox

Mike have looked through this thread ?
http://forums.pelicanparts.com/porsche-944-turbo-turbo-s/343134-boost-problem-again.html

Well what are you waiting for? SmileWavy

Thanks
Mike G.

Xmas ??

Ran the vacuum on WG and pressure monitor on the turbo inlet (header side) test.
-With no CV to WG hose had 11psi boost and approximately 25psi on the turbo.
-With 10 inches of vacuum to WG had 15psi boost and 31 to 33 psi on the turbo.
-With 20 inches of vacuum to the WG had 17 psi and 44 to 47 ish psi on the turbo. Chickened out as the boost was headed north at a very fast clip...don't want to do head gaskets at the moment :).
Sox

Was the top of the WG open to atmospheric pressure or was the line blocked off?

Thanks
Mike G.

P.S. Thanks for getting that done before xmas;)!

Top was connected to my vacuum source...
Sox

So after further pondering helped along with a little tequila...
I have devised a way to help the spring in the WG that does not require surgery of the OEM WG, or loosing the protection of the KLR.
Before y'all pile in and tell me my mechanical skills are lacking..:) this is just a proof of concept.
It does increase the the pressure needed to start opening the valve by 3 psi for my out of the junk box spring.
I will neaten it up so it fits in the WG outlet to the exhaust.
Sox

http://forums.pelicanparts.com/uploa...1580085910.jpg

That there spring on that there position in that there exhaust flow is gonna gets purdy dang hot!

Thanks
Mike G.

Yah, but it only gets heat during boost bypass. Normally the valve is closed. Secondarily a stainless steel spring meant for exhaust valve should be able to handle it.
If not "such is life". :)
Sox
Ps. I did say the idea was born out of a shot or 10 of tequila....

as that spring gets hot and the metal expands and gets softer the spring pressure will change, and then change even more when the wg opens and temperature rapidly rises. it might be unpredictable.

Nize, yah...true. Need to use pressure/vac combo.
Was trying to think outside the gate (pun intended).
I am going to test with this version of the spring. WG starts to open at 9 psi and fully open at 14psi.
Sox

http://forums.pelicanparts.com/uploa...1580151542.jpg

Put it in the normal spot like a beer drinker would not a tequila drinker.

Thanks
Mike G.

Mike, too boring....no tequila no excitement :)
Sox

Nize, if you are reading my other concurrent thread KLR part2, I am going to use the KLR to control the boost. So if the spring changes, the sensor along with the control loop in the KLR should handle it and keep my boost in the range I want. I am planing on setting it to 10 to 13 psi at this point.
Sox

This question isn't exactly pertaining to WG testing but what are you doing for fuel/ign mapping with the added boost?

Thanks
Mike G.

Mike at this time I am not planning to go past 14 psi, so I will have plenty of margin with existing fuel/air. As you see at 13.32 psi I am still well below 12 AFR (I would not want to go leaner than 12).
Sox

http://forums.pelicanparts.com/uploa...1580231998.JPG

Geez that's still super rich! Stock ECU/Chip FPR and all?

Thanks
Mike G.