.8 or 1.0 Bar Wastegate Spring - Which to Install?
 

Well, I bought a 1 bar spring last month and an .8 bar spring off of Ebay that arrived today.
The moment of truth is here: which one to install. Currently there is a 1.2 bar spring installed by the PO :eek: I've never felt comfortable with it and really haven't driven my car very hard as a result.
Over on Rennlist there's a guy running a 1 bar spring with a stock WUR and fuel head. His posted dyno runs show a 11/1 AFR at WOT.
Still, I'm looking for opinions.
http://forums.pelicanparts.com/uploa...1192663556.jpg

Street driving 1.0 (unless you have some long straight aways), track driving 0.8.

Respectfully disagree.

1.2 bar spring - if you don't give a crap about longevity of the motor or are just interested in a quick rush. A mostly stock, air cooled turbo motor was not built for this boost and even more risky without some type of fuel management.

1.0 bar spring - only if you know what your AFR's are, and they are suitable for 1 bar of boost - track or road. Detonation and engine failure happens in a blink of an eye.

.8 bar spring - great all around spring and no bog mods needed to run this all day long.

I completely agree with Don concerning the boost springs.
What would bother me is that the PO had a 1.2bar spring in your car.

Yeah, it bothered me too but it was his 4th car and he only put 1000 miles on it in 3 years time. I think he was afraid of it.

OK, and how do you plan to >>lower<< the boost from 1.2 bar when running EBC and 1.2 bar spring? EBC cannot go lower from spring setting, it can only raise it.

I am running.....
 

a .9 bar spring on a Tial 46mm WG.....no issues, Euro fuel head, K27 7200, stock headers, and AFR's are great, no driveability issues either.......I was a little scared of the 1 bar spring, so I settled on .9......

.8 bar in my Tial. Often see .9 bar on my aftermarket boost gauge.

I will trade you a new 1.0 bar spring for the 1.2 bar. PM me.

Sandman,
that has me a little concerned, I want to run 1.0 bar with my Tial, B6 intercooler, headers with Borla and K27-7200. My AFR's are good with the 0.8 bar.(11.8 under full boost)

Is your aftermarket gauge a quality one and are you satisfied it is accurate?
On the dyno my 0.8 bar spring was not going over 0.8 although on my standard boost gauge, it regularly will show over 0.8 bar.
I have a 0.9 bar spring just in case.

Archie

I think that's actually a common occurrence with aftermarket headers. In fact I think you can order GHLs with a re-designed wastegate exhaust circuit (the pipe that runs from the headers that the actual wastgate attaches to) when running one of these "uber turbos" - something like a K27-HFS. I have experienced boost creep with both my B&Bs and now with my OBX headers.

If you look at the design of the waste gate attachment point to the exhaust system you will see the problem. On the stock 930 heat exchangers the W/G split is up steam of the turbo and branches off with a nice y joint. On the B&B headers the W/G attachment point is a T bend right at the base of the turbo mount.
It is always a good idea to check the A/F ratios and verify the pressure level when making a change in boost settings anyway so just stick your 1.0bar spring in and check everything, you may be just fine.

Update
 

I got my wastegate apart (thanks to advice from wcc) and it didn't contain a 1.2 bar spring :D It's in between the 1 bar and the .7 bar stock spring that I have. My guess is it's a .8 or .9 bar spring.
What a relief. It was the only way I'd know for sure.

That is stock for the 965.

Brian, what I've read was that .7 was stock for the 965.
Heights of respective springs;
1 bar - 7 15/16"
.8 bar (?) - 7 5/8"
.7 bar (stock) - 7 1/4"

0.7bar was stock for the 930. I don't recall the year but the boost was increased slightly along with the much larger C2T intercooler addition.

Edit - I looked it up in my manual. The 930/68 engine used in '89 put out 282HP while the M30/69 C2T for '91-'92 put out 320HP. No internal changes are listed for the 3.3L @7.0:1 engine so it stands to reason that the boost had to increase to jump 40HP.

Either way you're in good shape.

IIRC the gauge in a 964t does not read higher than 0.7bar even though the engines were boosted higher from the factory.

What does your factory boost display show?

Nathan, the display reads .7 bar.
Brian, 965's use the K 27 turbo. This is what might account for the higher HP.

I know for certain that some (if not all) models of 965 were boosted higher by the factory than what the gauge could read.

So what size spring do you guys suggest I run in my 86 930? I run headers, GHL exhaust not cat, K27s with larger intercooler. I plan on upgrading the wastegate and want to know what spring to have them install.