930 Full Boost Issue?

[wcc]

Well I changed the boost sending unit a while ago so the gauge wasn't all over the place. Now it's consistently at .6 Bar. The car is completely stock. Wayne (Oh Haha) and I adjusted the throttle to make sure the car gets full throttle. So that isn't the issue. I thought the 930 came from the factory with .8 boost spring. So my questions are these:

What boost spring is OEM? .6 or .8 or something else?

Is the OEM wastegate adjustable?

Why aren't I getting full boost? Bad Wastegate?

[javadog]

The stock boost spec. is .6 to .7 bar. For a Euro car, it is .7 to.85 bar. The wastegate isn't adjustable, as delivered.

Even with a new sending unit, your gauge may still read incorrectly, as they weren't that accurate. I have fitted a Ruf gauge to one of my cars in place of the clock and it reads differently than the stock one in the tach. Your boost may, in fact, be fine.

You can always fit a different spring. It just takes a few minute to change.

JR

[Garen]

.6 bar according to the stock tach gauge? I'd be a bit skeptical of the accuracy of that gauge, even though you replaced the sending unit. Try a mechanical one, you might be getting the .8 that the car is supposed to get...

-Garen, (87 930, also in MI)

[wcc]

Yeah, according to the stock tach gauge I'm getting .6 Bar boost. It sounds like everything is fine then if the factory sent it out that way. Garen - is your 930 a USA or ROW?

So at .6 everything should be ok cause it's a USA version. I have some upgrades in the near future. Can I get away with a .8 spring with the rest of the car being factory without overboosting and ruining something?

[Miguel Antonett]

Mine, original with a K27 indicates .5-.6 during warm weather and .8 sharp during the cooling months - that's the way it has been for ever... I believe it is normal - it feels the same.

[Oh Haha]

Here's why we are where we are on this car.
I drove Bill's car today and it just didn't feel like it was getting the full turbo "kick". I drove an 89 Turbo last year that, when the Turbo spooled up, you could feel it in your stomach. It would set you into the seat dramatically. AFAIK, that car was stock except a B+B muffler.

It seems as if the wastegate is blowing off at less than .8.
It pulled a bit harder after the throttle adjustment but I think there is still more available. Bill is concerned about engine longevity and doesn't want to overboost.
Thanks,

[wcc]

Wayne sums it up pretty good. There's a TON of potential for this car.

I would like to add another couple of questions that just came to mind.

The turbo starts to spool up at around 3k rpm and isn't till about 4k rpm it's at full boost. Is that normal too? Or should it be at full boost at around 3k rpm?

[javadog]

The onset of full boost will vary with load, so it will be a different rpm in each gear. The higher the load and gear, the earlier you'll get full boost. You should be getting it before 4000 but a stock, US car won't see full boost at 3000.

You might want to take the top off the wastegate and make sure there isn't something amiss inside. To answer your earlier question, you can probably run a little higher boost, if you can get decent gas and the motor is healthy. .8 bar is fine with 25 degrees of timing and enough fuel. If all you can get is 91 octane, or if you are stuck with gas containing ethanol, I'd leave it alone.

You also want to make sure the advance/retard functions of the distributor are both working and you are getting the full advance and retard.

JR

[hobieboy]

Well, it could be the WG that is leaking boost. It could be your turbo is getting a little tired. It could be a leak in your intake track. etc.

The first thing IMHO is to determine the actual boost that you are getting. So use a mechanical gauge to measure that. The factory electronic gauge as everyone said is not that accurate.

I think stock, full boost comes around mid 3k so you are close.

You should also check your AFR if you want to make sure you are not running too lean to ensure longevity of the engine.

[Garen]

Originally posted by wcc
Yeah, according to the stock tach gauge I'm getting .6 Bar boost. It sounds like everything is fine then if the factory sent it out that way. Garen - is your 930 a USA or ROW?

So at .6 everything should be ok cause it's a USA version. I have some upgrades in the near future. Can I get away with a .8 spring with the rest of the car being factory without overboosting and ruining something?

Mine is a US model, and was first sold through a dealer in Chicago. I switched to a North Hollywood Speedometer boost guage (replaces clock), and it reads a solid .8 bar. I think the tach guage is a bit off and inconsistent on mine as well. My engine is totally stock, and only has a cat bypass and a modified stock muffler.

[VZ935]

Originally posted by Oh Haha
Here's why we are where we are on this car.
I drove Bill's car today and it just didn't feel like it was getting the full turbo "kick". I drove an 89 Turbo last year that, when the Turbo spooled up, you could feel it in your stomach. It would set you into the seat dramatically. AFAIK, that car was stock except a B+B muffler.

The muffler and the fact that the 89 has a 5 speed may be the difference you are feeling

[Oh Haha]

So there could be THAT much difference from 4 to 5 speeds?
It makes sense, I guess.

Lest you guys think Bill's car is a POS, it's not. It is a low mileage unmolested car. Well, unmolested until I opened my mouth. Sorry about that, Bill. Hmmmmm, that MagnaFlow sitting on your shelf might just have to get installed a bit earlier than we planned. Muwahahahahahahaha.

[wcc]

I always run Shell 93oct in the car. I was planning on having the WG rebuilt this winter so that's a good time to put in a .8 spring. Then I'll make sure the timing, advance/retard, and the air/fuel mix are all good.

Where do I get a mechanical boost gauge? I searched our host but it didn't show up or I missed it somehow.

Garen - Where in MI are you? If you aren't too far away, maybe you could give me a ride so I could feel the difference. That way I'd have something to compare mine to.

VZ935 - That's what I said cause I would think the '89 would be faster cause of the shorter gears.

[wcc]

Wayne - You jumped in there on me pretty quick this morning. Yeah, I think when the WG is out it's a good time to hook up that muffler.

The 930 is coming up on it's 60k mile service. Probably by the end of next year, but I may tackle lots of it this winter. Might as well do it when, should I dare say it?, snows........

[Garen]

I'm in Beverly Hills. Will you be attending any track events this year? I'll be doing the SEM event on 9/14, and also a DE run by POH on 9/9, both at Waterford. Where abouts are you located?

[Oh Haha]

I was thinking about this on the way in this morning. We should probably get your 85 back together before we start anything on the 930.
Maybe we should put the 930 eninge in the 85?

[wcc]

Garen - I live in Lansing. No I'm not planning on any track events this year. But, maybe we could get together at one of the PCA events coming up?

Wayne - That's probably a good idea. Lets button up one project before we start on another one. This is just research for the next project. I don't think that 930 engine would make it in the '85, but maybe a V8 450 HP crate motor?


EDIT: Where do I get a mechanical boost gauge?

[Oh Haha]

I don't think that 930 engine would make it in the '85, but maybe a V8 450 HP crate motor?


BITE YOU TONGUE,MAN!!!!!!!!!
Oh, the humanity.

[bkreigsr]

I bought my car at 83,000 miles with the orig wg. When I upgraded to full B&B, we found out that the orig wg had so much carbon build-up that the valve was never fully seating, and full boost was not being attained. I think that the DPO thought that boost was harmful to the motor (silly man) and never really boosted with any real conviction.
(Probably why the car looked so good cosmetically in the first place.)
Bill K

[Garen]

WCC, PM sent...