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Leaning out under boost

I am just finishing my 930 and I am noticing under boost lack of power when I really get on it. I installed a lean rich gauge and it shows a lean situation under hard driving. My fuel distributor is new as well as all injectors. Is it possible the injectors I install are to small volume wise ? Is there a fuel pressure gauge I could install on my dash to see if thats the problem ? I also have new acumulator,fuel filter.
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1986 blk 930
2000 expedition
2000 bmw 3 series convertable
1996 Silverton 312 sedan bridge
Old 11-14-2006, 12:36 PM
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Are you running a stock fuel injection system, or is it a european system?

If it is the standard US system, You can try richjening the mixture slightly at idle and see if the situation improves.

You may also have to adjust the fuel pressure at the distributor - you do this by adding shims to the regulator. (The large nut on the side of the distributor)

AFJ
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Old 11-14-2006, 01:17 PM
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Are you using a good wide band or a low cost narrow band O2 sensor?

The wide band will really give you best results as will a dyno session.

Ditch the narrow band if you have it IMHO.

Last edited by A930Rocket; 11-14-2006 at 03:50 PM..
Old 11-14-2006, 03:47 PM
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stock fuel u.s system wide band 3 wire 02 sensor.
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1986 blk 930
2000 expedition
2000 bmw 3 series convertable
1996 Silverton 312 sedan bridge
Old 11-14-2006, 04:48 PM
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OK. That takes care of that.

You can get a fuel pressure gauge from Pelican, but it's not something yuo want run into the passenger compartment. It's for testing the fuel press at various stages hot and cold.

You might be running out of fuel? The stock injectors are one size fits all. You can get a modded fuel head from Imagine Auto that flows more fuel.
Old 11-14-2006, 04:54 PM
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Perhaps get your car on a dyno to see what the A/F's are doing under load... sounds to me like a fuel starvation issue

Have you changed boost spring/level at all?
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Old 11-15-2006, 07:39 PM
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no it's stock. I believe that it is starving. I wonder if I should adjust the fuel distributor pressure .
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1986 blk 930
2000 expedition
2000 bmw 3 series convertable
1996 Silverton 312 sedan bridge
Old 11-16-2006, 02:36 AM
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What are your AFR numbers?
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Old 11-16-2006, 05:25 AM
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FWIW, after I finished my engine, I wasn't able to harness all of the power until I invested in a CIS gauge set for testing my cold/warm/enrichment WUR fuel pressures.

My condition was overly rich and the car just wouldn't rev past 5,500 before chocking on gas. I had the Imagine Auto fuel head, but no amount of adjusting at the fuel metering plate would lean it out. Thus I made my WUR adjustable and the engine just came to life!!! Revs to my limit of 6,500 effortlessly!

http://forums.rennlist.com/rennforums/showthread.php?t=297546
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 11-16-2006, 05:32 AM
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Per the factory manual, there is a static test you can conduct to determine sufficient fuel delivery. First, be careful. I recommend doing this test on a completely cold engine in a well ventilated area, like outdoors. Disconnect the return line from the fuel distributor and attach a hose that can be placed in a graduated container. Switch the key on and prepare to measuse the deliver by time, Disconnect the plug from the top center of the distributor and the pumps will begin delivery. Reconnect the plug to stop the pumps after the test. Your system should be capable of delivering 1500cc per minute. I measured a 15 second delivery and multiplied by four. (I have a short attention span) An engine will only create as much power as the fuel available to convert.
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Old 11-16-2006, 06:14 PM
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