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Old 07-30-2016, 09:09 PM   #1
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Default flex fuel sensor location

So my flex fuel sensor came in. Where abouts are you guys putting it, from what i read it has to be on a return line? is this true, if so why? i was thinking about on the passenger side where all the fuel lines are, but those are supply lines. some pictures would be nice if anyone can get some.

this is a 01 miata
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Old 07-30-2016, 10:01 PM   #2
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Above the fuel filter.

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Old 07-31-2016, 02:31 AM   #3
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Can go on the return or feed line.
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Old 07-31-2016, 03:37 AM   #4
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If you are still returnless, you want it as close as possible to the fuel rail in the feed line. I have mine mounted to the shock tower brace.
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Old 07-31-2016, 02:37 PM   #5
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Originally Posted by nitrodann View Post
Above the fuel filter.

Dann
I worry a bit that there's enough fuel between the filter and the engine that you could end up running severely rich or lean for a bit as the maps would adjust prior to fuel actually entering the engine.

On the other hand, the tiny Continental sensor is rather hard to put anywhere in the engine bay without it looking cludgy. Mine is just floating in space right now :(


Not a great pic, but if you look closely behind the squaretop you'll see where mine is floating here
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Old 07-31-2016, 05:09 PM   #6
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I worry a bit that there's enough fuel between the filter and the engine that you could end up running severely rich or lean for a bit as the maps would adjust prior to fuel actually entering the engine.
This. It takes way longer than you might expect to clear the OEM NB feed line at idle. Like, 90 seconds after pumping 12+ gallons of E85 or gas into the tank for a full switch-over. If you have the sensor next to the fuel filter, you're relying on closed-loop idle corrections to compensate for the fueling difference for those 90 seconds. I certainly don't send cars out into the world with EGO authority of ~35%, which is what it would take to compensate for the difference between an 80% blend and a ~15% blend during changeover.

Here's where mine is:

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Old 07-31-2016, 05:27 PM   #7
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This. It takes way longer than you might expect to clear the OEM NB feed line at idle. Like, 90 seconds after pumping 12+ gallons of E85 or gas into the tank for a full switch-over. If you have the sensor next to the fuel filter, you're relying on closed-loop idle corrections to compensate for the fueling difference for those 90 seconds. I certainly don't send cars out into the world with EGO authority of ~35%, which is what it would take to compensate for the difference between an 80% blend and a ~15% blend during changeover.

Here's where mine is:

Custom bracket? Looks nice.
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Old 08-01-2016, 01:39 AM   #8
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Just a piece of aluminum angle trimmed/drilled to fit, yeah. I used Dorman's vinyl fuel line tool to build OEM-style lines for it.
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Old 08-01-2016, 01:57 PM   #9
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90seconds is probably on the shorter side. Pumping the tank out on an NB at dyno and putting E85 in the tank, it took probably 5mins of idling to get the sensor read 70% (it was a 80% blend). So yes, it does take a very long time!

By the way, which sensor is that? Do you know of any that could have AN fittings fitted to them?

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Originally Posted by Savington View Post
This. It takes way longer than you might expect to clear the OEM NB feed line at idle. Like, 90 seconds after pumping 12+ gallons of E85 or gas into the tank for a full switch-over. If you have the sensor next to the fuel filter, you're relying on closed-loop idle corrections to compensate for the fueling difference for those 90 seconds. I certainly don't send cars out into the world with EGO authority of ~35%, which is what it would take to compensate for the difference between an 80% blend and a ~15% blend during changeover.

Here's where mine is:

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Old 08-01-2016, 02:09 PM   #10
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This sensor: Continental Flex Fuel Sensor

The sensor ends are 3/8" fuel injection fittings, so you can find lots of adapters to jump to -6AN if that's what your fuel system is plumbed with.
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Old 08-01-2016, 02:19 PM   #11
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Quote:
Originally Posted by Savington View Post
This sensor: Continental Flex Fuel Sensor

The sensor ends are 3/8" fuel injection fittings, so you can find lots of adapters to jump to -6AN if that's what your fuel system is plumbed with.
Something like this: https://www.summitracing.com/parts/e...IDphoCzHXw_wcB
?
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Old 08-01-2016, 02:23 PM   #12
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Yes
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Old 08-01-2016, 02:29 PM   #13
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The price of the combined parts necessary lead me to second guess my desire to go with AN lines. I am thinking of just going with stock appearing lines (dorman kit). The only question in my case would be how to add a fuel pressure sensor and where.
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Old 08-01-2016, 02:50 PM   #14
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The price of the combined parts necessary lead me to second guess my desire to go with AN lines. I am thinking of just going with stock appearing lines (dorman kit). The only question in my case would be how to add a fuel pressure sensor and where.
I have one of these sitting on my desk:
Russell 640730 | Buy Russell Specialty SAE Quick-Connect EFI Adapter Fittings at JEGS
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Old 08-01-2016, 05:27 PM   #15
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Quote:
Originally Posted by Savington View Post
This sensor: Continental Flex Fuel Sensor

The sensor ends are 3/8" fuel injection fittings, so you can find lots of adapters to jump to -6AN if that's what your fuel system is plumbed with.
How do you go from the 5/16" feed line to 3/8" sensor line? Just inquisitive.

EDIT: With the Dorman connectors that you call out on your website to be used with the sensor.

Last edited by DNMakinson; 08-01-2016 at 05:30 PM. Reason: Answered my own question.
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Old 08-01-2016, 05:54 PM   #16
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Originally Posted by DNMakinson View Post
EDIT: With the Dorman connectors that you call out on your website to be used with the sensor.
Yep From site: "This item includes the Continential sensor and wiring pigtail. You will need fuel injection adapters to install the sensor. Use Dorman 800-085 (straight) or 800-091 (90deg) adapters."
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Old 08-02-2016, 06:20 AM   #17
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I put all my fuel stuff over on the RHS of the engine bay away from everything hot and up out of the way. I'm running an inline Earls Performance filter which feeds into the FPR and the return runs through to the Flex sensor then back to the tank. I like running the filter in an accessible spot as I've changed it a few times now to make sure no crud gets to the injectors. The e85 does seam to free up a bit of debris from my old tank. I find on my system the sensor will pick up any changes to the e85 content fuel as it's hitting the engine, which is normally whilst it's cranking.



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Old 08-02-2016, 09:33 AM   #18
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I can't imagine that puny little radiator is very effective. I'd like to see some data behind that.
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Old 08-02-2016, 12:39 PM   #19
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Quote:
Originally Posted by DNMakinson View Post
How do you go from the 5/16" feed line to 3/8" sensor line? Just inquisitive.

EDIT: With the Dorman connectors that you call out on your website to be used with the sensor.
Ive got connectors that are quick connect to barb (so you can just clamp a hose on)makes going from 3/8 to 5/16 easy. I think i ve 20 bucks in parts for it. Not going to look pretty, but that not my goal.
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Old 08-02-2016, 12:46 PM   #20
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I can't imagine that puny little radiator is very effective. I'd like to see some data behind that.
It doesn't overheat... not even on very hot days. I've run it like that for a couple of years now with zero issues. No thermostat, diy coolant reroute, oil cooler and ebay Honda radiator.

Now back to flex sensors. Has anyone got the fuel temp to work? The e85 composition is a frequency whist the temp is voltage... or something like that.
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