930 engine set up recommendations

[millhaus]

Need some advice on my new rebuild.

Just rebuilt my 1980 930 3.3 engine.

- SC profile cams
- K27-7200 turbo
- 1 bar spring
- Stock IC
- Stock CIS with Euro fuel dist.

Car is not running and pulling GREAT! Like new.

However, when it boosts it wants to keep going. I can hear the wastegate dump on short shifts but when I pull to redline, the boost gage (stock) is pinned at 1 bar and it feels like i am hitting the boost pressure limit. Feels like the fuel is intermittently cutting off due to too much boost. (approx 4000-5000 rpm)

Assuming my stock wastegate is working properly, should I be running 1 bar boost with this set up or go back to the stock 0.8 bar spring?

My thinking is that it is pulling so hard now with these SC cams that I don't need to run that much boost. Plus with the stock IC, I don't want to have issues in the summer. I think I'll switch back to the 0.8 bar spring. Agree, disagree?

Any advice or opinions appreciated.

[cole930]

Millhaus,

My opinion would be issues with the wastegate if it is not opening at 1 bar. Also with the stock IC I think you need to put the .8 spring back in until you
upgrade the IC. Typically the general consensus is the overboost switch trips at around 1.1 or 1.2. What you described sounds like the switch is tripping and the wastegate should have opened before then. I would pull the wastegate off and check it and then reinstall the .8 bar spring and try things again.

Cole

[A930Rocket]

I would back off the redline as well. It'll make your engine last a lot longer.

Just my .02

[pkracer21j]

I wouldn't rev over 6k unless you've checked your AFR's on a dyno or wideband... most hot rodded 930's run out of fuel above 6k. I have the shattered rings for evidence. lol

[911st]

If you are saying your boost keeps building with acceleration?

And you hear the boost pressure escaping with shifts?

It sounds like you wast gate mikght be sticking and your compressor bypass is working as it should.

Is your over boost switch stock and conected?

Are you boosting enough to triger it and kill the motor (apx 1.2 bar I think)?

A little over boost is expected.


More importantly, it is not recomended to run 1 bar with a stock intercooler.

[RarlyL8]

Stupid question; is your waste gate boost pressure line plugged into the intercooler?
Forgetting to attach the hose or having it pull off is an easy mistake to make. If your overboost switch is activating you will know it. That "windshield in face" abrupt power cut is unmistakable.
This overboost switch can also be activated by boost spikes. Do you have headers?
With the 7200 and SC cams you don't need to shift past 6200rpm as the power is falling off at that point.
Yes with 1bar it is prudent to use a larger than stock intercooler, especially in the summer.

[millhaus]

RarelyL8,

I forgot to mention the headers on my set up.

I am not getting a winshield in the face but a slight stuttering hesitation if I stay on the throttle.

I've had the IC on and off quite a bit so I'll check the wastegate hoses to make sure they are all secured. Sounds like possibly a fault wastegate. I'll change the spring back to the 0.8 Bar and see if there is a difference.

I am in Michigan so my driving days are just about finished for this year. I'll swap out the spring and if the 0.8 is good, I'll upgrade to a Tial next year for better engine insurance. Th IC has to wait unless I can find a good deal. Too many kids to feed!

Thanks