SPRAYED 01

iTrader: (22)

I know the obvious answer would be yes. Im tring to understand exactly why. The way i think about it,if the diaphragm was ripped the referance off the turbo would not be able to push the spring down causing max boost.

I experianced an issue on the dyno where right at 13pounds and 4800rpm the boost would drop to 3lbs right away. It did this about 10 times. I only got one ok pull to 5500rpm. I checked the diaphragm and it was torn badly.

Can anyone explain the internal workings of an external wastegate in order to solve my lack of boost.

Thanks
Alex

black98ws6ta

iTrader: (77)

Its preety simple, esp if you already have it apart. The diaphram is connected to the "piston", so to speak. When the pressure connected to the side port of the wastegate excedes the spring pressure the pressure will push on the diaphram and the bottom on the "piston" and the valve will open fully.

The most common use for the top port of the wastegate is with an electronic boost controller. It adds pressure to the top as the boost is rising in a aid to help keep the valve closed untill it is at the target boost.

Typically wastegate instructions tell you to reference the side port of the wastegate to a boost only pressure source. If the diaphram is torn it means that it will not open the valve correctly and should make tons of boost depending on how big the rip is. If you dont have anything hooked up to the top of the gate it would just leak into the atmosphere, but I am not sure if thats a big enough leak to cause the drop in boost, fix the diaphram and find out.

SPRAYED 01

iTrader: (22)

Thats exactly what i was thinking. It would make alot of boost with it ripped. Mine is almost doing the opposite. It will make 13-14pounds like its supposed to and then all of a sudden drop down to 3-4 for the remainder of the run. I know i have to replaced the diaphragm because its ripped but i would still like to understand what is happeing to my boost. Ive checked for any and all leaks and there is nothing.

ddnspider

iTrader: (26)

i had the same issue when i dyno'd it would boost fast to 10psi and drop back to 7 and hold there.did it do this b4 the diaphram ripped?somethings not hooked up right if it did.

SPRAYED 01

iTrader: (22)

I bought the kit used so im not sure if it did this before. This is the first time i took it past a couple pounds. It did the same thing 9out of 10 times. I tried using a manual boost controler,tried completly leaving the boost referance off for max boost, i tried hooking it up every way possible with the exact same results.

ddnspider,what ended up fixed your issue?

MECHAM

iTrader: (4)

i bet the answer is he got another WG

SPRAYED 01

iTrader: (22)

MECHAM,
Im sure when its all said and done the wg or fixing of the wg will fix my issue. But I am really curious to exactly why. This is my first FI application and i really just want to learn as much as possible. Is there any reason why you think i should replaced the entire wg as opposed to replacing the diaphragm?

black98ws6ta

iTrader: (77)

Did you do a pressure check to cheak for leaks? I have taken piping apart and put it back together several times but a pressure test will always show leaks. Small leaks at clamps, leaks at injector o-rings, leaks through the iat sensor. I assume its possible that the leak through the wastegate is large enough to cause a boost loss, but if you ran it without a reference line completely then that tells you its not it. If it were my car I would pressure test the complete system(going as far as pulling the rockers so it is pressure tested up to the valves seat seal), and fix the wastegate.

ddnspider

iTrader: (26)

my wastegate was fine,by boost controller was the issue.i was using an eboost2 and couldnt get it to hold the specified boost value throughout the rpm range no matter what i tried,i assumed i wasnt setting it up correctly.i sold it and got a $10 ebay manual boost controller.hooked it up using the side port of my Tial wastegate leaving the top port vented.check here for more info
https://ls1tech.com/forums/forced-induction/627348-vacuum-lines-gauge-install-help-newbs.html

SPRAYED 01

iTrader: (22)

Thanks,thats how i had it hooked up also. I left the top open to atmosphere and the side as referance. I spoke to hks today and they said that is sounds like a wastegate issue. Im looking into getting a rebuild kit that includes the diaphragm,and all gaskets. I really hope that fixes it.

SPRAYED 01

iTrader: (22)

This is why i think i have ruled out any cold pipe,intake or sensor leaks. Or any after boost type leaks. When the car was on the dyno i was basically under the car. When i took the referance line off the turbo i put my finger in front of the port on the turbo for the boost reference. When he made the run as soon as the boost fell off to almost nothing the pressure from the turbo port also fell off. So even if there was a huge leak in the intake or cold pipes the boost off the turbo wouldnt change. This is why i believe it is an issue with exhaust not getting to the turbo to spool it. Which points at the wastegate. I did pressure test every thing for about 1 hour with 3 people and we found nothing. Let me just say again this is not a slow boost leak issue. This is an immediate drop from 14lbs to almost nothing. Im rebuilding the wastegate on friday just for the hell of it and because the diaphragm is ripped. But the way is see it,it should not help at all.

Brady

iTrader: (3)

Is it a possibility that the inlet plumbing to the turbo (from filter) is collapsing?

SPRAYED 01

iTrader: (22)

its hare plastic tubing so i dont think so. i even tried taking all of that off for one run.

SPRAYED 01

iTrader: (22)

Okay just rebuilt the wastegate,check if the valve was sealing. Everything was perfect. Same thing happens. It will hold 5lbs all day through the entire rpm band. Its once i put that 14lbs spring in that around 8-10psi it just instantly goes to 0 boost. I am freakin out,i have no clue what is going on. Is there anything in the tune that could cut off injectors or spark for some crazy reason. Please help!!!!

LASTLS1

iTrader: (7)

Are you losing spark? Are your coils and plugs in good shape. Does the motor sound clean when the boost falls off? Does a/f stay steady?

ddnspider

iTrader: (26)

leave the 5 psi spring in it and use the boost controller to up the boost and see if it makes a difference.

SPRAYED 01

iTrader: (22)

Lastls1i was hoping you would chime in. Im running tr6s gapped at .032,and new msd wires. The coils seem to be working fine. The motor sound fine when it looses boost. It sounds completely normal just at 0lbs so its really slow. The a/f is not okay,when i loose boost it goes very lean. Ive stayed into it for about 2 secs after the boost falls off and it will go off the charts lean on my wideband. I have tried putting the 5lb spring in with a controller with the same results.

Brady

iTrader: (3)

It should go fat first if it loses boost (air flow into the motor). it may be running out of fuel? What's the fuel system consist of?

I really have zero experience w/turbo LSX, but I've had a twin turbo LT1 and a single thumper turbo SBC in my '96 Z28... Your problem intrigues me.

SPRAYED 01

iTrader: (22)

The fuel system is seiman 60lbs injectors,97-98 vette rails with the evap line as a return and a boost referenced 1:1 regulator. Running off a racetronix plug and play. The fuel pressure looks great when it makes boost, it will go up to about 70psi. I dont suspect the fuel system not being enough but maybe being shut off for some crazy reason.

Brady

iTrader: (3)

MAF?