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Ronnie's.930 Ronnie's.930 is offline
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Join Date: Nov 2007
Location: Rockwall, Texas
Posts: 8,765
I've never heard of anyone hearing "air box pop" on a 930, regardless of the lean or richness of the mixture, and don't think it is possible. In order for popping to be audible in the airbox, sound from ignition that takes places in the intake manifold, or while an intake valve is still partially open (that's what causes intake pops), would have to travel backwards through the intercooler, turbo compressor (and all associated plumbing before and after it), and finally through the K-Jet air metering assembly (the airbox is fastened on top of that). You must be hearing something else.

I also wonder what you are calling a "back fire", as those are also very rare for these turbo engines - would have to be quite a large/loud ignition taking place in the headers to be heard through the turbine portion of the turbo. Are you hearing some popping and crackling when you close the throttle? If so, that is normal as the K-Jetronic/CIS fuel system dumps a lot of wasted fuel when the throttle is closed and that excess fuel lights (sort of) in the exhaust system and turbine, producing crackling. A backfire is a loud, sudden, boom sound.

If you think you have timing and/or mixture issues you need to verify that on your end with a timing light and an air-to-fuel, exhaust meter as trying to determine that based on noises that the car is making is just guess work and won't help much.

Last edited by Ronnie's.930; 04-01-2014 at 11:03 PM..
Old 04-01-2014, 10:30 PM
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