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Title: AFR graph/curve Post by: Manford on February 12, 2018, 07:46:21 AM Can someone show me an ideal AFR curve/drop off over a WOT run?
I know its meant to start at 14.7 and taper, but how quick and to what? Title: Re: AFR graph/curve Post by: nyet on February 12, 2018, 01:21:52 PM Depends on octane, boost, and compression ratio.
Worst case (91 oct, stock compression) you should see below 12 by peak boost. Title: Re: AFR graph/curve Post by: Manford on February 12, 2018, 01:25:35 PM Stock aum, uk fuel 97ron,I’m down to 11 by 5k. Will post afr curve I have, currently has a big drop after 4k
Sent from my iPhone using Tapatalk Title: Re: AFR graph/curve Post by: nyet on February 12, 2018, 01:37:13 PM Stock aum, uk fuel 97ron,I’m down to 11 by 5k. Will post afr curve I have, currently has a big drop after 4k Sent from my iPhone using Tapatalk anything richer than 11.5 is probably pointless (and might actually raise egts significantly from excess fuel burning in the exhaust stream) Best bet is to start at 11.7/11.8 and only add fuel if you need to pull a lot of timing to prevent knock or regularly see very high IATs YMMV, this is for stage 3 2.7t on US 91oct R/M running 22+ PSI A stable (flat) AFR during WOT pull post peak boost usually gets me the best results. Title: Re: AFR graph/curve Post by: nyet on February 12, 2018, 01:40:21 PM Stock aum Just saw this. If you aren't running significant boost, 12 is more than enough fuel. Title: Re: AFR graph/curve Post by: Manford on February 12, 2018, 01:53:16 PM Am I aiming for 11.7/8 flat across the wot run or still tapering to something lower?
Sent from my iPhone using Tapatalk Title: Re: AFR graph/curve Post by: nyet on February 12, 2018, 01:55:26 PM Am I aiming for 11.7/8 flat across the wot run or still tapering to something lower? Sent from my iPhone using Tapatalk anywhere around 11.8/12.0 is fine. flat is fine. If you aren't seeing significant knock and your timing looks good, you can go a bit leaner even. Only way to know for sure if your timing/fueling tradeoff is good is on a dyno. Title: Re: AFR graph/curve Post by: adam- on February 12, 2018, 02:23:03 PM Stock aum, uk fuel 97ron,I’m down to 11 by 5k. Will post afr curve I have, currently has a big drop after 4k 97? I thought BP was 98, Shell is 99? Big drop? Did you put this big drop in - or was it a file you found? Title: Re: AFR graph/curve Post by: Manford on February 12, 2018, 02:32:21 PM I stand corrected, BP Ultimate @98 Its a tweaked map from my car, taking info from others, but I realised this morning I was being a k**b and adjusting the timing in the wrong direction so my knock was getting worse not better. If im aiming for 11.8/12 I think its more my early afr is high and then drops to what im aiming for. Title: Re: AFR graph/curve Post by: nyet on February 12, 2018, 02:53:08 PM Yes, that is far too late.
Title: Re: AFR graph/curve Post by: Manford on February 12, 2018, 03:03:07 PM Don't understand? too late? I need to drop my early AFR? Title: Re: AFR graph/curve Post by: NBR on February 12, 2018, 03:24:42 PM Yeah like nyet said earlier, your AFR should drop to between 11.7 and 12.0 when you hit peak boost. Looking at your engine load graph, you're around 13.9 when your boost peaks
Title: Re: AFR graph/curve Post by: prj on February 14, 2018, 05:20:44 AM anything richer than 11.5 is probably pointless (and might actually raise egts significantly from excess fuel burning in the exhaust stream) This is not how gasoline engines work. |