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Can't get MFI Idle right
Guys,
My winter project comes to an end (pulled engine, cleaned the lot, repaired leaks, set valves, cleaned throttle valves, new injectors, plugs, pertronix, etc etc) it's time to hit the road again. One issue, can't get the idle right while following CMA to the letter. So revving, 3000rpm synchronization, timing at 1000 rpm all no problem). Still the idle is far too low (no matter what I do to the bypass screws) and far too lean. My Dayton AFR meter shows at idle somewhere between 18,5-19,5 AFR. I know this is far to lean. Before pulling my engine it was somewhere in the low 12... I haven't touched the MFI pump yet (calibrated by Mark Jung). At 1000rpm (bit of hand throttle) the engine makes a popping noise at the intakes. Revving from that point generates nice flames at the air intakes :-( AFR at 2000 RPM is fine. Do I have to adjust the richness with the MFI pump because I have new injectors? Any suggestions how to proceed? THANKS, Ed
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72 911E Targa (fun car) BMW 535i Xdrive (work car) Volvo XC90 Ocean Race (family car) VW T2 Riviera Camper van |
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04-21-2013, 04:16 AM
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The main enrichment screw behind the allen bolt will lean or richen the mixture through out the range, turn it out two clicks, and check a/f. The one through the fan changes idle and up to somewhere around 2500 rpm so I have read, not sure about that. If it's popping at idle through the stacks then it's lean or you have leaks in the intake. What changed via engine drop?
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72 911 Although it is done at the moment, it will never be finished. |
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04-21-2013, 05:06 AM
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Thanks, I'm sure there is no leakage in the intake. Just changes all the seals as well. Must be the MFI setting. I adjusted the pump from calibration because before I pulled the engine, the setting was far too rich. No the setting is far to lean....
Ed
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72 911E Targa (fun car) BMW 535i Xdrive (work car) Volvo XC90 Ocean Race (family car) VW T2 Riviera Camper van |
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04-21-2013, 06:51 AM
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Remember, these cars like to run rich, so richer is better in regards to mfi, gives great throttle response.
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72 911 Although it is done at the moment, it will never be finished. |
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04-21-2013, 07:00 AM
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Join Date: Jun 2003
Location: Camarillo, Ca.
Posts: 2,418
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If you cannot achieve a flow meter measurement of around 4 kg/hr with the mixture screws turned out approx. 2 turns from bottom it can very well be worn throttle plate/bushings.
The pics below are a set for a 73RS I recently rebuilt with new throttle plates, bushings, as well as the original DOW coating.    
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Aaron.  F.S. 1965 Solex engine w carbs/cleanerBurnham Performance https://www.instagram.com/burnhamperformance/ |
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04-21-2013, 08:13 AM
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Aaron...looking at those throttle assemblies gives me more pleasure than watching a beautiful woman walking...wait...what?...Ummm..where was I?....LOL
Bob
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Bob Hutson |
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04-21-2013, 09:18 AM
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Kermit
Tobluforu
Harley
