Another wastegate spring question
 

Hi,
I posted yesterday that my wastegate ('77 930) is opening only at around 15 psi, and suspected I had a 1-Bar spring without knowing it.

Thanks to 5axis on this board, I found my wire diameter matches the wire diameter of a regular 0.8-bar spring (5mm).

Now, I'm wondering if it's possible that both the 1-bar and stock springs actually use the same diameter wire, but it's wound differently? Is diameter a valid way to tell which one I have?
Thanks,
Colin

Is your wastegate leaking at 15 psi?

No leaks through the diaphragm, if that's what you mean. The diaphragm is intact and holds the air.

The valve starts opening at 15psi - tested with three different gauges now. There is a fair amount of air slipping between the valve stem and its guide, but I have read that this is normal.

It's such a simple device, I can't figure out what the problem could be except the spring. Any ideas?

What do you mean it's normal? Where exactly is leaking normal? I thought mine was trash, but maybe not. I still dont see how any leaking could be ok. Hmmm

Dean (Blown) is a guy who knows his stuff about turbos. Take a look at this thread re:guide leaks:


I thought I had a bad membrane because I can blow and suck on my wastegate line. It turned out to be alot of clearance at the valve guide. I heard the wastegate valve needs a fair amount of clearence so not to worry. My wastegate works prefectly.
Oh yea I am a firm believer in 1 bar springs if that is what you choose :-)

http://forums.pelicanparts.com/porsche-911-technical-forum/75595-too-much-boost-930-then-engine-cuts-out.html?highlight=guide


So now I don't know if my guide leaking is the problem or not.

The diameter of the wire used in the spring influences the force produced by the spring and hence the opening pressure. The larger the wire, the more spring force it will generate; it is quite possible that the the OD of the springs remain the same between the .8 and 1.0 bar types but the wire size used increased. Jim

Thanks Jim,
I said "coil diameter" in my original post, but should have said "wire diameter" for clarity. I have a known measurement of 5mm for the 0.8 bar spring's wire diameter.

Now I'm hoping to find out if the 1 bar spring uses larger-diameter wire, or uses 5mm wire that is wound differently.
Colin

Ok, so the membrane in mine is also good(holds pressure with no leaks). However there are a few small corrosion holes in the body (where the actual valve is) from being mount horizontal for years with condensation inside. I dont see this as a real problem as I will be running a vent to atmosphere pipe anyway so vent is vent I guess to some extent. Hmmm I will have to retest my opening pressure. With a 1 bar spring should it actually be fully open at 14.5 psi or are there other acting forces with help the openeing of the valve? Sorry to highjack your thread but I think this will help us both.

So Len, you have a 1-bar spring right now and your wastegate is taken apart??

Any chance you could measure the wire's diameter and post it here? And maybe also count the number of coils in the spring?

Thanks!
Colin

Hey Colin,

Are you worried about running 15 PSI boost? I would try it out and see if you have a problem with detonation. When I compared the two springs the 1 bar was longer and stiffer. I didn't take any measurement so I don't know about wire dia.

It's out but not apart and yes it is a one bar unit. I am a little leary of cracking it open as I dont want to order new gaskets etc... About 2 years ago when I went to the 1 bar I put it in and immediatley hit overboost. This was one of those add a spring kits that went inside the original. Pitched that and bought an Andial 1 bar spring and have been happy ever since. However I tested it here at work and it did not open till 18 or so PSI, could be the gauge I guess. I think I will just put it back on as it worked fgine before I took it off. If I hit overboost I'll rebuild it . Sound like a plan?

Shoot. I've got a picture of mine taken apart (with a nice shot of the spring). Unfortunately, I won't be able to get to the picture until Monday...

Hi Colin, I have both a .8bar and 1 bar spring at home on the workbench. I'll take some measurements when I get home later for you, unless someone beats me to it.

Timothy

That would be really great, Timothy. That will let me get to the bottom of this question once and for all.

Dean, I am uncomfortable running 15psi because
1) It's 100 degrees here and I have no intercooler
2) We only have 91 octane available
3) I want some room to grow in a year when the car starts feeling slow :)

Thanks,
Colin

Does not the exhaust pressure help the wastegate open? Would this explain my reading when the gate opened? Can anyone say for sure if a 1 bar gate should open at 1 bar to the press line? Sounds like a stupid question but hey..

Colin, I get it. It is cold 50 degs here and rainy *****ty weather. I just got back from a parts run in the P-car and I scared myself a few times:D

Lenny,
The exhaust doesn't help to open the valve. The valve is opened by pressure in the intake path that is above the pressure rating of the spring.

Ok here's what I come up for measurements:

0.8 bar:
7.5" long
2.75" coil diameter
approx. 3/16" wire diameter

1bar:
7" long
2.75" coil diameter
approx. 7/32" wire diameter

I apologize for the measurements on the wire diameter. I forgot my calipers at work, so I did the best I could with my tape.

Hope this helps for you.

Timothy, thanks for the measurements. Unfortunately, I'm more confused than ever. 3/16" is 0.1875" (your 0.8bar spring) and 7/32" is 0.21875" (your 1.0bar spring).

Mine is 0.198" wire diameter - between the two measurements you give.

Mine is also 6 5/8" long - shorter than BOTH of your springs!

Is it possible that this spring is actually a 1.2bar spring, as sold by Performance (Automotion)? It sure acts like one - starts to open around 15, full opening at 16-17.

I just don't know what to do here. I would buy a stock spring, but I don't know if that will solve anything until I'm certain of what I have.

Colin

Colin.
I think I have a stock spring here. I will measure it tomorrow for an other data point

Sorry to add to the confusion!:confused: It's very possible that my measurements for the wire diameter are questionable. I used a tape measure that measures to 32nds, but I'm sure you can imagine how hard it is to measure wire diameter using a tape. I apologize for not getting better measurements. It's quite possible that my 3/16" measurement with a tape is close to your measured 0.198" wire diameter.

However, I know the .8bar spring was giving me .8bar boost when I was running it. The 1bar spring is a Weltmeister one I bought a while back but never used it, since I ended up going with a Tial wastegate instead.

So based on wire diameter, I would think you have a .8bar spring, but I can't really explain the sizable difference in lengths. In order to have a 1.2bar spring, I would think the wire diameter would have to be thicker than the 1bar spring. Do you know how many coils you have in the spring? I think I counted 7 turns on both.

Hopefully we'll get to the bottom of this.