Flex fuel sensor reading inconsistent

Clos.95 · 01-27-2021, 06:58 PM

I’m back for another noob question
So I’ve been tuned on E85 for around 2 years now, and I’ll admit my first tuner was probably the worse tuner I could’ve gone too, I’m tuned by someone a lot better now. Anyways i never replaced the flex fuel sensor that my first tuner installed. He made it himself, it’s non branded, I now have HP tuners and datalog everything and have seen my Ethanol content read E75 while idling and during some pulls reads E78 and some E80 all in the same tank of gas, just different pulls done a few minutes after each other. Is that normal or do I have a bad/crappy sensor?

MatthewAMEL · 01-27-2021, 10:11 PM

I'm shocked you have E readings that high from pump E85.

When I use 100% E85, I usually sit around E67 here in Florida.

What do you mean when you say 'non-branded'? Pretty much everyone uses the GM FlexFuel sensor. Do you know how he tapped power for the sensor? You might want to check the pin is secure.

Clos.95 · 01-27-2021, 11:12 PM

Quote:

Originally Posted by MatthewAMEL

I'm shocked you have E readings that high from pump E85.

When I use 100% E85, I usually sit around E67 here in Florida.

What do you mean when you say 'non-branded'? Pretty much everyone uses the GM FlexFuel sensor. Do you know how he tapped power for the sensor? You might want to check the pin is secure.

Non branded as in it’s not a DSX or lethal garage, or SMG or EFI kit
We have pretty good E here in Cali.
He tapped into the fuse box for power, and it’s pinned properly since I have readings. Just wondering if it’s normal for the readings to vary so much from idling to full throttle

Umbriel · 01-28-2021, 10:19 AM

Mine jumps around a little like that also and it is an SMG kit. It doesn't jump by huge numbers but sometimes it will read 78 sometimes 74 sometimes 72. Sometimes it will flicker back and forth between like 73 and 74 and then settle. I think it is just the way the fuel is, I could be wrong but I have never worried about it and I am making 901 rwhp on it.

KingLT1 · 01-28-2021, 10:09 PM

When he says non-branded, likely just means GM sensor with diy parts to make the rest of the kit.

Not uncommon in some parts of the country to see upwards of E80. My local E85 pump is normally E78 summer, E66 winter.

I never see more then 1% fluctuation in readings from my SMG flex sensor kit after filling up and the fuel mixes/settles in. Normally takes around 5 miles or so of driving. If you are seeing consistent fluctuations of 5% or more then I would check connections.

Clos.95 · 01-29-2021, 03:41 AM

Quote:

Originally Posted by KingLT1

When he says non-branded, likely just means GM sensor with diy parts to make the rest of the kit.

Not uncommon in some parts of the country to see upwards of E80. My local E85 pump is normally E78 summer, E66 winter.

I never see more then 1% fluctuation in readings from my SMG flex sensor kit after filling up and the fuel mixes/settles in. Normally takes around 5 miles or so of driving. If you are seeing consistent fluctuations of 5% or more then I would check connections.

Yeah it’s a home made kit that my old tuner made, since then I’ve been tuned 2 more times once by a big local tuner and now Brett, non of them have said anything yet, but I have noticed how much the reading changes from Idle to full throttle. To me 75% at idle and 80% at full throttle seems a little odd. I also have seen that on some pulls it’ll be E77 some E78 and one as high as E80.4 and timing changes a bit Lower content E77 I’ll see 26.5 degrees and at E80 I’ll see 28. If this is not normal I wouldn’t doubt that my old tuner made a crap kit, and I’ll replace it with a Pray kit

Clos.95 · 01-30-2021, 10:32 PM

So after hooking up HP tuners to my buddies car, I think I know the issue.
We pump at the same station and have been for the last few months.
His SMG kit reads E80 at idle while my bootleg home made sensor reads E75 at idle.
His under light load 1,500-2000 rpm in park sees E80-E81 max consistently
While mine doing the same never stays constant it keeps moving back between E75-78. We should both have E80-E81
I’m gonna swap over to either a Pray kit or SMG
Now I wonder since the wiring is done correctly, if I can just swap the sensors and leave the current wire plugged into the correct pin.

01-27-2021, 06:58 PM	#1
Clos.95 Drives: Black 1SS Join Date: Dec 2018 Location: Los Angeles Posts: 103	Flex fuel sensor reading inconsistent I’m back for another noob question So I’ve been tuned on E85 for around 2 years now, and I’ll admit my first tuner was probably the worse tuner I could’ve gone too, I’m tuned by someone a lot better now. Anyways i never replaced the flex fuel sensor that my first tuner installed. He made it himself, it’s non branded, I now have HP tuners and datalog everything and have seen my Ethanol content read E75 while idling and during some pulls reads E78 and some E80 all in the same tank of gas, just different pulls done a few minutes after each other. Is that normal or do I have a bad/crappy sensor?

01-27-2021, 10:11 PM	#2
MatthewAMEL Drives: 2023 CT5 Blackwing Join Date: Sep 2016 Location: Orlando Posts: 1,618	I'm shocked you have E readings that high from pump E85. When I use 100% E85, I usually sit around E67 here in Florida. What do you mean when you say 'non-branded'? Pretty much everyone uses the GM FlexFuel sensor. Do you know how he tapped power for the sensor? You might want to check the pin is secure. __________________ 2017 HBM SS 1LE Sold 2023 Wave Metallic CT5-V Blackwing M6

01-28-2021, 10:09 PM	#5
KingLT1 Drives: 2016 1SS NFG A8 Join Date: Aug 2017 Location: 46804 Posts: 6,800	When he says non-branded, likely just means GM sensor with diy parts to make the rest of the kit. Not uncommon in some parts of the country to see upwards of E80. My local E85 pump is normally E78 summer, E66 winter. I never see more then 1% fluctuation in readings from my SMG flex sensor kit after filling up and the fuel mixes/settles in. Normally takes around 5 miles or so of driving. If you are seeing consistent fluctuations of 5% or more then I would check connections. __________________ 2016 NFG 1SS A8 Options-2SS Leather/NPP Perf. mods-Whipple 2.9/Fuel System/Flex Fuel/103mm TB/Rotofab Big Gulp/Cat Deletes/Corsa NPP Per. times- 10.5 @ 137 w/ 1.8 60ft Full weight on 20's 1200DA

01-28-2021, 10:19 AM	#4
Umbriel Drives: 2016 Camaro SS Join Date: Sep 2018 Location: Bartlett, TN Posts: 1,121	Mine jumps around a little like that also and it is an SMG kit. It doesn't jump by huge numbers but sometimes it will read 78 sometimes 74 sometimes 72. Sometimes it will flicker back and forth between like 73 and 74 and then settle. I think it is just the way the fuel is, I could be wrong but I have never worried about it and I am making 901 rwhp on it.

01-30-2021, 10:32 PM	#7
Clos.95 Drives: Black 1SS Join Date: Dec 2018 Location: Los Angeles Posts: 103	So after hooking up HP tuners to my buddies car, I think I know the issue. We pump at the same station and have been for the last few months. His SMG kit reads E80 at idle while my bootleg home made sensor reads E75 at idle. His under light load 1,500-2000 rpm in park sees E80-E81 max consistently While mine doing the same never stays constant it keeps moving back between E75-78. We should both have E80-E81 I’m gonna swap over to either a Pray kit or SMG Now I wonder since the wiring is done correctly, if I can just swap the sensors and leave the current wire plugged into the correct pin.

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