Wastegate abnormalities! Or not?

lendaddy · 06-23-2003, 09:43 AM

With the new K27-7200 my old wastegate seems to be getting overpowered for lack of a better word. I am running late euro exhaust with the stock gate w/1 bar spring(gate with 1 bar spring was fine before turbo and exhaust upgrade) Anyway with my straight pipe off the gate I can hear when it opens and it is opening at like .5 bar, but it is also over boosting, hitting the overboost protection!?! These two things seem to contedrict but hey what do I know. Anyone have some input here? Thanks

beepbeep · 06-23-2003, 09:50 AM

That probably means following things:

1. Wastegate exhaust valve is rusted/leaking
2. Membrane is shot

Dissasemble and check both...and get rid of that pesky 1-bar spring...sell it to some Flintstone instead ;-)

lendaddy · 06-23-2003, 09:58 AM

The diaphram is fine. I can blow in the vent tube and it holds pressure perfectly. Why would it be opening early and still overboosting?

Also I will be going to a tial unit with a .7 or so spring and EBC. Can you recommend a certain model of Tial gate?

beepbeep · 06-23-2003, 10:11 AM

It's not so critical which wastegate you use as long as it's bigger than 35mm in diameter. If membrane holds pressure and it still leaks then i think that piston is stuck or it gets stuck in it's opening movement.

Check also that all hoses are OK, that vent hose breathes freely and that intercooler-hose isn't pinched. Tial is also good and lighter to boot.

0.7-spring and bleed-orifice or EBC is good way of controling boost. 1-bar spring is bad...

hobieboy · 06-23-2003, 10:13 AM

If it starts to open @ .5 bar, I think its pretty normal.
If it overboost, is it by a lot ? Did your boost pressure switch kicked in?

I'm using a Profec B EBC. In normal street driving, everything is very normal. On the track going uphill on a long straight, I find that my boost would go up by maybe .1/.2 bar. Haven't had time to fully diagnose it, but I suspect it might be because of the narrow sized pipe from the exhaust to the wastegate. Not enough volume to vent all the un-needed exhaust fast enough?

lendaddy · 06-23-2003, 10:22 AM

Well, the kicker is that it doesn't overboost according to my gauge(which seemed very accurate before) in other words it is hitting the overboost protection at an indicated lower boost level than I ran all the time before with no issues. Perhaps I need an accurate guage with a telltale to mount back there to see. Hmmm

dean · 06-23-2003, 03:36 PM

If I were you I would test the wastegate off the car with an accurate gauge. Then I would test the overboost sw off the car. The sw could be weak and closing prematurely. My new sw closes at 18 psi. My old one at 14psi.

Amac · Amac's Garage

If your going to a Tial wastegate, a 40mm for up to 500hp.
I run a 46m, good to 700hp.
You can order them with any size spring, but you might
look into some kind of boost controll.
I like manual boost controll, but not everyone wants to
dance with Devil.

tsuter · 06-24-2003, 10:27 AM

Tial Co with a Slowboyracing.com manual boost controller. The MBC actually seems to smooth up the opening of the wastegate. You can even get pretty Tial Co colors.

lendaddy · 06-24-2003, 10:28 AM

What is the deal with the flanges on the Tial units? Do we use their adaptors or what? Do you even need adaptors? Thanks

beepbeep · 06-24-2003, 10:39 AM

Quote:

Originally posted by lendaddy
What is the deal with the flanges on the Tial units? Do we use their adaptors or what? Do you even need adaptors? Thanks

Yeah, they have oval flange so you need to fabricate adapter or weld new flange...unfortunately.

They are much cheaper than stock 930 wastegates though.

lendaddy · 06-24-2003, 10:43 AM

Actually they have square flanges on the 40mm and greater units. Just wondering about adaptors. Why do they offer adptors for $40, how could they possibly know what I need them "adapted" to?

tsuter · 06-24-2003, 10:48 AM

Seems like there is always a bit of welding to do. Oh well!

lendaddy · 06-24-2003, 11:14 AM

I think I get it now, They sell me adaptors to weld onto my exhaust system, not adaptors to allow the gate to bolt to my existing setup. Makes sense. Does anyone know the bolt circle that comes stock on the Tial 40mm units? Like the one in the pic I posted above?

beepbeep · 06-24-2003, 11:19 AM

Quote:

Originally posted by lendaddy
Actually they have square flanges on the 40mm and greater units. Just wondering about adaptors. Why do they offer adptors for $40, how could they possibly know what I need them "adapted" to?

Hmm...i didn't know they had those with 4-bolt flange too. It looks very stock-ish and might be just a bolt-on, actually.

Take off your OEM w/g and measure the flange, it might fit...

Btw, do you have open wastegate pipe on your current setup?

lendaddy · 06-24-2003, 11:27 AM

Yes have an open pipe, sounds great! I can measure mine but I need to know what the Tial units are.

Emission · Emission's Garage

I would check the diaphram again. Mine had a slight tear (nearly invisible) and the car would overboost. PIA.

On a related subject, I have a "Wastegate Dump Pipe" for sale. 100% stainless steel - barely used, in perfect condition. PM or E-mail me.

lendaddy · 06-24-2003, 11:31 AM

Diaphram is fine, I think I have too much blowby on the stem. It is pretty corroded in there. I just modified my original "to the muffler" pipe for the dump and am pretty happy with it. Thanks anyway though.