E85 idle question - occasional surge at a stop - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

brillo · 07-30-2017, 02:09 PM

I'm running the Motoeast flexfuel kit on an otherwise stock motor (stock intake/exhaust etc....).

occationally at a stop, my idle (with the A/C on) will bounce upwards from 850ish to 1,000rpm. It doesn't seem to fall down below 800 but you can see the surge upwards on the tach (and my Scanguage). I wouldn't call it rough as its something you see more than you feel (given its not dipping down).

I'm told this is basically normal, is this the injectors cycling to push more fuel due to the e85? My idle didn't do this on my regular 93 tune.

Love the kit and tune, otherwise everything is rock solid and I'm very happy with the power (193whp).

Just curious others experiences, not a deal breaker, just want to make sure I'm not missing something.

steve99 · 07-30-2017, 11:20 PM

Pretty normal with a\c compressor cutting in\out to have small idle variation

churchx · 07-31-2017, 04:51 AM

If AC is switched OFF, can AC compressor still impact readings/logs? (thinking of how to make most consistent results/lessen variables)

brillo · 07-31-2017, 09:37 AM

I've tried shutting off the A/C and I occasionally still get the surge. I totally get that the A/C compressor and general idle characteristics mean idle is going to flux 100 rpm or so. Those kinda rpm fluctuations don't even register on the car's tach, but I can see them on my scan gauge.

Jumping up 150 rpm or so seems a little more unusual, which is why I was wondering if maybe I'm seeing something related to the injectors needing to push more fuel at idle on e85 than normal and that is resulting in the surge (could the port injectors be kicking in?).

Its not something I feel as the rpms never fall as part of the process to a level where the idle gets rough.

smg1138 · 07-31-2017, 10:03 AM

Mine does this a little when the AC is running. Doesn't seem to happen with the AC off though.

07-30-2017, 02:09 PM	#1
brillo Senior Member Join Date: Nov 2011 Drives: 2013 Firestorm FR-S Location: Houston Posts: 506 Thanks: 18 Thanked 77 Times in 64 Posts Mentioned: 10 Post(s) Tagged: 0 Thread(s)	E85 idle question - occasional surge at a stop I'm running the Motoeast flexfuel kit on an otherwise stock motor (stock intake/exhaust etc....). occationally at a stop, my idle (with the A/C on) will bounce upwards from 850ish to 1,000rpm. It doesn't seem to fall down below 800 but you can see the surge upwards on the tach (and my Scanguage). I wouldn't call it rough as its something you see more than you feel (given its not dipping down). I'm told this is basically normal, is this the injectors cycling to push more fuel due to the e85? My idle didn't do this on my regular 93 tune. Love the kit and tune, otherwise everything is rock solid and I'm very happy with the power (193whp). Just curious others experiences, not a deal breaker, just want to make sure I'm not missing something. __________________ 2013 Firestorm FR-S, MTX, build date 1/13.

07-31-2017, 09:37 AM	#4
brillo Senior Member Join Date: Nov 2011 Drives: 2013 Firestorm FR-S Location: Houston Posts: 506 Thanks: 18 Thanked 77 Times in 64 Posts Mentioned: 10 Post(s) Tagged: 0 Thread(s)	I've tried shutting off the A/C and I occasionally still get the surge. I totally get that the A/C compressor and general idle characteristics mean idle is going to flux 100 rpm or so. Those kinda rpm fluctuations don't even register on the car's tach, but I can see them on my scan gauge. Jumping up 150 rpm or so seems a little more unusual, which is why I was wondering if maybe I'm seeing something related to the injectors needing to push more fuel at idle on e85 than normal and that is resulting in the surge (could the port injectors be kicking in?). Its not something I feel as the rpms never fall as part of the process to a level where the idle gets rough. __________________ 2013 Firestorm FR-S, MTX, build date 1/13.

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07-30-2017, 11:20 PM	#2
steve99 Banned Join Date: Dec 2013 Drives: FT86 Location: Australia Posts: 7,996 Thanks: 1,035 Thanked 4,997 Times in 2,985 Posts Mentioned: 598 Post(s) Tagged: 2 Thread(s)	Pretty normal with a\c compressor cutting in\out to have small idle variation

07-31-2017, 04:51 AM	#3
churchx Senior Member Join Date: Mar 2015 Drives: 2014 GT86 Location: Latvia, Riga Posts: 4,336 Thanks: 698 Thanked 2,091 Times in 1,437 Posts Mentioned: 53 Post(s) Tagged: 1 Thread(s)	If AC is switched OFF, can AC compressor still impact readings/logs? (thinking of how to make most consistent results/lessen variables)

07-31-2017, 10:03 AM	#5
smg1138 Senior Member Join Date: Jan 2014 Drives: 2013 Raven FR-S Location: Nashville Posts: 775 Thanks: 968 Thanked 213 Times in 136 Posts Mentioned: 3 Post(s) Tagged: 2 Thread(s)	Mine does this a little when the AC is running. Doesn't seem to happen with the AC off though.

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