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The mkiv Supra Owners Club

AFR 11s at idle - 264 cams stock ecu


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Hi guys,

After a head refresh I've put in some BC 264 cams. Car is stock ecu and stock fuel for now. OEM narrowband is in place. It's a jspec, so it's MAP.

Like expected the first start was a bit rough and stalled a few times. After a while the car started running a lot better, however my idle is around 11-13 AFR. Even at 5-10mins at idle.

Is the stock ecu able to relearn the fuel trim to the proper AFR with aftermarket cams?

Maybe I should drive a few miles to see how it is adjusting?

What AFR's are you seeing with aftermarket cams and stock ecu?

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No, the ECU cant relearn. Bigger cams dont draw as much vacuum as stock cams, less air flow means more fuel, Ive been through it myself. Adjustable cam gears help to a degree but you'll need to time them up with the cam card if you havent done already

You'll need an after market device to trim the fuel back

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Thank you.

What would be the best short term solution to this? Put in an afpr to lower the fuel pressure?

I would like to upgrade the fuel system and ecu to standalone later this year.

I just need to get it through emissions for now.

Thanks again.

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  • 2 months later...

A little update. After speaking to several tuners with plenty of Supra experience , I decided to follow my initial AFPR route.

I have adjusted the AFPR to Toyota OEM spec. The AFR is good at idle, cruising and WOT. No issues at all. Lambda is also where it should be. Fresh MOT as well 🙂


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