E85 Continental Flex Fuel Sensor Info
 

This is blatantly stolen from an MR2 forum. Wanted it copied here in case the other link went down for some reason.

Affordable Flex Fuel Sensor - MR2 Owners Club Message Board

:likecat:

Does Vcc just get 12V? Does the MS3x FLEX input already have a pull-up?

MS3x Flex is ready to go, just hook up the signal wire.

ummmm, I thought it was 5V i'll double check.

Its 12v according to a few sources. Including some pictures above.

Just armchair but, wouldn't the clip on AN fittings work best with the longer tube unit? Or even the small one?

+1 :likecat: For post rip, good info all around :party:

AN clip on fittings shouldn't be used. There are reports of them leaking. Use the screw on ones.

Shorter tube ones are usually cheaper, at least mine was. The screw on one's fit fine on mine.

I have a couple threads on msextra about flex fuel and they are fuckin vague about the flex input. But they say it is good to go.

Here is the ms3x manual page for flex fuel.

MS3XV30_Hardware-1.4 page 35

I will take pics of my setup sans install tonight. I believe I linked the hardware elsewhere.

Derp, I assumed VCC = 5v. Off to fix my wiring :eggplant:

I did too lol. I'm guessing 5v would be fine, but there is some sort of internal regulator to drop 12v to 5v. Its probably more than a voltage divider because it accepts 9v to 18v.

The signal output is 0-5v which makes me think that the internal sensor actually uses 5v. But no way to confirm that without tearing into one.

I retract that last statement. The continental flex fuel sensor is an open collector sensor. So it will only output 0-5v if you have a 5v pullup. And uses a pullup to 5v in the megasquirt. I wish I still had mine out so I could test what value it uses because it is not specified in the schematics. It looks like the resistor value can actually change the characteristics of the signal.


https://www.miataturbo.net/attachmen...ine=1460579920

Here is some more info about how they actually measure ethanol content

Clemson Vehicular Electronics Laboratory: Flex Fuel Sensors

https://www.miataturbo.net/attachmen...ine=1460580584

I'm running 5v. Seems to be running fine.

Rumor is that the sensor flows about 500hp of fuel.

Thanks to Savington for a graph of the flow here:

https://www.miataturbo.net/attachmen...ine=1460580898

And if you are paranoid about having enough flow then jerry rig something like this

https://www.miataturbo.net/attachmen...ine=1460580898

While it seems like 5v should work. If you are doing a new install you should use 12v based on the specifications for the sensor.

Maybe @Joe Perez could clue us into why an open collector sensor spec'd for 12v could work of 5v. I need to go do real work instead of flex fuel sensor research.

Well, [utag] is clearly working. :D

Are we talking about the sensor you pictured in post #9? Because that sheet clearly shows that it'll accept any pullup voltage from 3.3 to 18v. And, in post #1, one of the images you posted (the one with the multimeter) clearly indicates to us that the sensor's output is variable in frequency, not voltage. This is pretty much the de-facto standard in fuel-composition sensors.

Open-collector outputs are really simple circuits, barely more intelligent than a mechanical relay. They're just using a transistor to provide a variable closure to ground. And in most modern applications, that closure is varied by pulsewidth modulation while operating the transistor in full-saturation intermittently, rather than in the linear region continuously.

So, within reason, they don't really care what the pullup voltage is.

Like, imagine that we're operating the output at a *really* low frequency, like 0.1 hz (one cycle every ten seconds.) And on the output, we have a light bulb pulled up to some voltage. It doesn't matter in the least what that voltage is (provided that it doesn't exceed the rating of the light bulb). If the output duty cycle is 50%, you'll be able to easy see "oh, the light is on for 5 seconds and then off for 5 seconds" regardless of whether it's a 12v lamp or a 120v lamp.

That's all that's happening with the sensor in real life, it's just a lot faster.

Not pullup voltage. VCC. Its spec'd for 9v-18v VCC, but Yanks is running fine of 5v.

Oh, I gotcha.

Dumb luck?

Internally, most microprocessor-based stuff is going to be internally regulated down to some relatively low voltage. 5, 3.3 and 1.8v are the most common I/O voltages for cheap micros.

I'm just gonna guess that this one is sufficiently robust that it can tolerate whatever drop below its internal Vcc is being caused by the voltage regulator when it receives a 5v supply. I'm sure the regulator isn't spec'd to work that low, but most components will work beyond their specs in both the positive and negative directions.

I wouldn't do it if it were my car. Who knows if it'll start getting unreliable as it heats up, or as it ages, or even if it's operating outside of spec right now, with regard to the frequency vs. ethanol chart.

That was my guess. The sensor internally is probably on 3.3v or 5v, and as long as you are supplying above that it *might* work. Luckily it has.

That's a very conservative estimate, based on the published data I've seen. If you're running 400lph through the sensor (published maximum flow), that's ~6.67 liters per minute, or ~6,667cc/min, which is enough to max out four ID1300s at 90psi of differential pressure. That's way north of 500whp, even on E85, and that assumes you're feeding 100% of the fuel through the sensor, and that the sensor is in the feed line.

Hence the "rumor" comment. I agree that it is probably higher.

Been using this Conti sensor for a couple of years. Bought a long tube version with a harness pigtail for something like $75 shipped off of eBay. Works exactly as expected.

Fuel lines slip-fitted and hose-clamped in place over the tubes, sensor floatining in space between my regulator (on the firewall) and the OEM return line.

Update: Got mine wired in and working. Used 12v because thats what its spec'd for. Constant 8.1% ethanol on oregon summer gas. Fuel temp reading is pretty cool too.

What are the reasons for using AN lines as opposed to using a Dorman fuel line repair kit setup with factory style connections?

Nothing against AN... Just wondering.

Because I have AN line from FPR and rail. And eventually want to go full AN6.

Here is my install

Attachment 231979
Attachment 231980
Attachment 231981
Attachment 231982

What kind of fuel temps are you seeing over ambient?

Can't drive right now. No license.

Temps were reading ambient while idling.

Gotcha. Thanks for link in other thread, will be ordering stuff to add that sensor soon. Taking the miata on a 1200 mile trip in a couple months and won't have E85 all the way there, so will need flex fuel working.

Bringing back the discussion about 12v vs 5v supply. I just tested this with the sensor powered by a DC power supply, and fuel pump on 100% DC in test mode.

12v - 7.2% ethanol. Stays that way until about 5.8v. Drops to 6.5% ethanol. Below 5v it consistently drops ethanol percentage with voltage. I wouldn't use a 5v power supply, because it has no room for error. Using a 12v supply gives you lots of voltage fluctuation room without changing the signal.

Posting here instead of hijacking Sav's build thread, which currently has the best info I've seen about plumbing and fittings for a flex sensor.

I'm getting ready to install my flex sensor on my 99 and have been planning to do it exactly like Sav shows here. I bought the Dorman tool, connectors, and vinyl hose so that I can do it 100% OEM-style.

https://www.miataturbo.net/build-thr...9/#post1323441

I realized last night that, with this style fittings, I won't have a good way to disconnect a fuel line and empty the tank. I know these fittings are quick and easy to disconnect, but I don't want to subject the plastic Dorman fittings to that many connect/disconnect cycles during race weekends where I'll be using fuel load to set weight. I want to add a spec miata-style fuel sample port for easy tank draining.

I'm new to the EFI-style connectors, so I need some help getting the right combination of connectors without unnecessarily spending a shitload of money. I looked at some of the aluminum/AN stuff, but I think I can do it all with Dorman/Mcmaster stuff. I need to go from the 5/16 EFI hardline on the frame, to an NPT tee for the sample port, to the 3/8 EFI Flex sensor, and then back to the 5/16 EFI fuel rail.

I think this is my current plan, in order from frame rail hardline to fuel rail on engine:

Dorman 800-120 (is this the correct/best fitting to go from EFI quick connect -> rubber hose and hose clamp?)
5/16 EFI-rated rubber hose with Oetiker clamps
Mcmaster 5/16 hose barb to 3/8 male NPT fitting (entering tee)
Mcmaster 5799T23 3/8 NPT tee (5315K48 and 5315K31 for sample port- good reviews on spec miata forum)
Mcmaster 3/8 hose barb to 3/8 male NPT fitting (exiting tee)
3/8 EFI-rated rubber hose with Oetiker clamps
Dorman 800-121 (entering Flex sensor)
Dorman 800-091 (exiting Flex sensor)
Dorman 800-074 5/16 vinyl tubing
Dorman 800-080 or 800-081 on fuel rail

The two bold ones are the only ones I'm really unsure about, but I spelled everything out anyway in case someone else wants to duplicate this setup later. Any reasons why this setup will result in massive fiery death?

Dorman catalog:
http://www.dormanproducts.com/catalo...Disconnect.pdf

Seems like a lot of fittings, and a lot of NPT. As you mentioned, you could reduce the count quite a bit by spending a bit on some of the nice two-piece all-metal EFI/AN adapters.

If you do it the NPT way, here is a thread sealant that I found that is meant for E85 fuel systems:

Gasoila® E-Seal Thread Sealant - Pipe Thread Sealants - Products

Gasoila is good stuff. If you've ever had permatex sealant flake and lose sealing properties over time, it doesn't do that.

The only way I've found to completely remove NPT from the system is with Aeromotive 17119 (edit: it's still NPT) but it's $140 and only 1/8" outlet, so draining the tank would be way too slow. It also doesn't use the 2-piece threaded EFI clip like the Russell fittings. I could piece together a complete AN setup with Russell and Aeromotive parts, but the number of threaded connections would still be the same... I'd just be swapping NPT for AN. I have no problems with NPT fittings as long as the correct sealant is used. The miatacage.com and the 5xRacing spec miata fuel sample ports both have NPT connections and work fine.

Yeah, but you could get down to one 1/8NPT connection (just the port) pretty easily.

Nothing wrong with NPT per se, just a little more of a pain than angled seat seals.

This issue has probably already been discussed here in someone's billion page build thread, but...

So I'm switching everything to nickel plated brass, since stainless fittings are either super expensive or cast and ugly. Updated list:

Dorman 800-120 (is this the correct/best fitting to go from EFI quick connect -> rubber hose and hose clamp?)
5/16 EFI-rated rubber hose with Oetiker clamps
Jegs 555-16020 nickel plated brass 5/16 hose barb to 3/8 male NPT fitting (entering tee)
Mcmaster 9151K43 nickel plated brass 3/8 NPT tee (5317K88 and 5315K13 for fuel sample port- good reviews on spec miata forum)
Jegs 555-16021 nickel plated brass 3/8 hose barb to 3/8 male NPT fitting (exiting tee)
3/8 EFI-rated rubber hose with Oetiker clamps
Dorman 800-121 (entering Flex sensor)
Dorman 800-091 (exiting Flex sensor)
Dorman 800-074 5/16 vinyl tubing
Dorman 800-080 or 800-081 on fuel rail

I'm still slightly unsure about the 800-120 and 800-121. Everything I've read says they're what I need, but the push-loc end looks very different from all the plastic connectors for vinyl hose.

https://static.summitracing.com/glob...-120_DH_ml.jpg

vs.

https://images-na.ssl-images-amazon....nL._SX300_.jpg

I hate NPT. Its leaked on me twice now in the fuel system.

I cranked the fucker down as hard as I could. And then some. Stopped leaking

Looks like I was heavily overthinking this. I'm still relatively new to NBs and I didn't realize that it's generally considered safe and acceptable to put rubber hose and hose clamps on the plastic OEM/Dorman fittings. That means I don't need an intermediary adapter tee to jump from the Dorman 5/16 metal connector on the frame to the Dorman 3/8 metal connector on the Flex sensor. The bonus of all this searching is that I found a much nicer racing-oriented fuel quick disconnect with machined-in hose barb, which means I don't have to add a single threaded joint to the fuel circuit.

Dorman 800-081 5/16" Steel to 5/16"(8mm) nylon elbow adapter (on frame tube)
Gates Barricade 5/16 fuel injection hose and Oetiker clamps
Earl's 782405ERL 5/16 hose barb tee
Gates Barricade 5/16 fuel injection hose and Oetiker clamps
Dorman 800-091 3/8" Steel to 5/16"(8mm) nylon elbow adapter (on flex sensor)

Then a Jiffy-tite 22505 routed to a convenient location for the drain port. $19 from Summit vs. $60 for the appropriate stainless NPT QD from Mcmaster.
http://www.jegs.com/images/photos/500/517/517-22506.jpg

And then $50 for a 21505 socket and 22505A plug on the drain hose, that way I can plug the ends of the drain hose together and keep dirt out of the line while it's in storage.

Sorry for the thread drift/ newb questions. Hopefully this will be helpful to someone else in the future.

I just ordered 13577429 (the small one). Going to see if it works like proven larger ones.

It does. I have it on my car. Our gas seems to be around 8% ethanol.

I plan on getting a drum of E98 soon to play with mixes and see what works best for me. You tuned for ethanol yet?

No. I don't have a built engine. No need to right now.

https://cimg3.ibsrv.net/gimg/www.mia...6a9b7f1035.jpg

https://cimg4.ibsrv.net/gimg/www.mia...de0b7fc839.jpg


Used the charcoal mount by bending the tabs in. I would NOT recommend the small sensor. It is a pain to mount. I would use the medium or large if I did it again. Used Dorman 3/8 steel to 5/16 barb 90s. They are meant for nylon so I added fuel clamps to the barbs just in case. Hopefully I don't burn to death. I used the stock return line and used a brake line bender to adjust the stock return line. Waiting on my pigtail and wire from amazon to get it running.



*Pigtail arrived. It is not working. Of course my soldering iron and my voltmeter both died. All I have is a test light and crimp fittings. Tried to use the o2 wire. When it did not work ran a temp jumper signal outside of the car to the edu and still nope. Best I can do for now. Going to have to wait for new voltmeter from amazon to figure it out.

I stumbled across this video and wondered if anyone had any other information on flex sensors and false ethanol content readings due to water contamination. It looks like he's using a run of the mill large Conti sensor that is popular among most tuning platforms.

That was a pretty ridiculous amount of water he added. 10%? 5%? Thats like a gallon of water in your fuel tank.

At the end he also claims that mixing in gasoline and e85 is just as detonation proof as the "pure" e85.

I'll take that as deviation is otherwise negligible considering the volume percent of condensation found in tank at any given time, unless someone maliciously added water.

Were you able to get the small sensor to work? I am wondering if this small sensor uses the same settings as the larger sensors. Other than the issues mounting the sensor, did the sensor work correctly?

One quoted picture = one dead kitten

With regards to water in E85 I wonder how this affects the tune? Water injection can be damn effective at reducing detonation so I can't see problems with timing. Higher % of ethanol means increased injector duty cycle so realistically it's probably a wash at concentrations most are likely to see.

On the other hand I was surprised to see my catch can accumulate as much water as it did. Makes me wonder how much water was in the last batch of E85.

Are you thinking the extra water in your catch can is from the water in the e85 you put in the tank? I think the chemical reaction of the fuel burning is making far more water than whatever is actually in the fuel.

I found some documentation from AEM for their Flex Fuel Sensor and it looks to be the small sensor referenced above. According to page 4 of their instructions, the frequencies look the same as what I have seen listed for the large and medium sensors. I am running E85 currently without the flex fuel sensor as a test. I made it to the station (Known to have consistent E85 at around 80-85% by some people who actually have functional flex fuel sensors) on fumes and filled the tank with E85. I went in to the settings and increased the required fuel by 35%, then waited for the wideband to show the AFR's leaning out as it went from 93 to E85. I then started doing some autotuning to refine the fuel map. I will do some more tuning today and tomorrrow morning and am scheduled to put the car on the dyno tomorrow afternoon. If I see some decent gains with E85 (I define decent as more than 5% increase in power) I am going to pick up the smaller sensor and install it.

AEM Documentation referenced above:
http://aemelectronics.com/files/inst...nsor%20Kit.pdf

Small one did not work for me. Fucker was dead on arrival. Which was fun because I doubted my wiring and went through a bunch of drama checking everything not thinking it could be bad from the factory.

Anyone tried the ones from China? I see a few on ebay at $30.
I am suspect but sometimes it's all of Chinese origin and really just comes down to how much you pay at the end..

No personal experience yet, but I recently had the same thought and research showed it wasn't worth gambling on the cheap chinese sensors.

Sadly I'm hearing and feeling that logic about a lot of things lately :/ At the end of the day its all probably coming from the same factory

Resurrecting this, farpolemiddle how is the 5/16 fuel hose doing with the clamps on the quick connect nylon barbs? Debating on doing this same setup with my flex sensor. Or doing the Quick connect to AN metal fittings...

good thread

-1 cat, no sad, ordered sensor on ebay and saved over half my money, someones mad

I sure hope you got a proper one and didn't get some china knockoff like some on ebay

It's the same continental flex sensor sold by all the vendors here, same name / model

yes. Just like the ebay walbro fuel pumps that have exact same name/model/stamp on them but are junk and many people got scammed with
also like ebay ID1000's which look identical except the logo is a sticker and not laser etched.

there are many fakes out there is what I'm saying. they all look the same

shit - didn't know that, hope mines good.

How do you recognise a fake from an original?
I sent an email to continental but no answer.
I bought one on ebay, paid import tax (product came from USA), sold as genuine sensor, but there was no GM label or part number.
https://www.ebay.fr/itm/New-Genuine-...53.m2749.l2649
Any thoughts?
cheers