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E85 Questions

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sinned4g63

Proven Member
320
86
May 1, 2017
Pasadena, Maryland
Bought a built GSX with a 2.3 6bolt stroker and trying to do some prep before having it retuned, first thing is an oil change (going to go with Valvoline VR1). Then I need to verify if the car has flex fuel and drain the tank to add some fresh fuel. It for sure has E85 in it now but when I asked the last owner if it had flex he said "it should" but didn't sound %100 sure as he hasn't driven the car in some time. That being said I'm going to assume the fuel in the tank is old as well but if it isn't on flex then I'm looking at about $160 a tank to fill up using 5 gallon can of E85 and I'd rather just drive 20 minutes to the nearest pump and pay around $3 a gallon but it's seldom true 85.

So, checking under the hood I didn't see much that would look like a flex fuel sensor. I suppose it could be somewhere near the backseat closer to the tank but I would have to get back into the car and verify that. Otherwise it looks like I might be able to find out through link by looking into the log values or ethanol sensor settings. I would assume that if the setting is enabled for the ethanol sensor and the min/max octane @ (x) ethanol% are set then it would stand to say the car is setup for flex fuel. Want to know what is safe to put back in basically.. Then after I've drained the tank and have fresh fuel ready is there anything like an additive I should run through the system or would that be necessary? Thanks in advance.
 
If you can't find the sensor or see that the tune is setup for flex-fuel then it almost certainly doesn't have a flex-fuel sensor. I've never heard of somewhere putting their sensor anywhere besides the engine bay on DSM but you never know. I'd for sure drain the tank and run some gasoline for half a tank. Send out the injectors for cleaning and install your flex-fuel sensor.
 
If you can't find the sensor or see that the tune is setup for flex-fuel then it almost certainly doesn't have a flex-fuel sensor. I've never heard of somewhere putting their sensor anywhere besides the engine bay on DSM but you never know. I'd for sure drain the tank and run some gasoline for half a tank. Send out the injectors for cleaning and install your flex-fuel sensor.
I honestly looked for maybe 10min if that, the line runs under the JMF intake mani and it's a bit hard to see where it routes or if there is a sensor further down the line. I think it might be easier to verify through the tune but I'll look harder when I'm at the car next. When you say run gasoline do you mean 93 pump or fresh e85? I suppose that would depend on the tune setup but I would assume pump if those settings check out. Also he did happen to give a fresh set of injectors with the car so I can just slap those in thankfully.
 
Look for the checkbox in the extrapolate feature. If it is checked, it has a sensor to tell how much alcohol is in your fuel. That is how it changes fuel and timing maps. Also, the FF sensor is USUALLY mounted in the return fuel line, so look for it there. :thumb:
 
Look for the checkbox in the extrapolate feature. If it is checked, it has a sensor to tell how much alcohol is in your fuel. That is how it changes fuel and timing maps. Also, the FF sensor is USUALLY mounted in the return fuel line, so look for it there. :thumb:
Thanks! I'll look a bit better while I'm doing the oil change, maybe it's tucked away where I can see it easier from underneath. I'll be hooked up to link to drain the tank as well, you're saying if that box is checked then it should have a sensor?
 
Yes.
It will look very much like THIS.
 
I could not find a sensor anywhere on the return line and looking into the fuel tank access hatch saw very little. I looked into the tune through link and it looks like nothing is checked in the ethanol sensor section leading me to believe it is only e85 at the moment. Where would this "extrapolate" feature be?

Link I've been researching with: http://www.ecmtuning.com/wiki/ethanolsupport
 
It is in "Aux Maps" :)

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Technically, you can run E85 and not have a sensor, the tune just has to be for only E85 or it will be running rich on gasoline with an E85 tune, as you have to scale up the injectors to give about 30% more fuel on E, so "maybe" it is on E.
Can you post a log of the car running? We can examine it and probably tell by looking at the injector size and the global fuel setting.
 
I'll have to get one after work or this weekend but I'm %99 positive it's on E85 right now. It smells like it and so does the oil, injectors are also 2200cc. I'll get back to you on the log.
 
The smell of E85 is very noticeable so the car is BURNING E85 but is it tuned for it? I have separate tunes for E or gas on one of my cars and just swap tunes for either one but my Blue 92 is setup as a Flex Fuel car and I can put whatever in it and it will run using the correct fuel and timing maps using the extrapolate function.
On E85 with those injectors, your Global Fuel setting should be around -67ish. Look at what it is set at. If it is much higher (-70-80) it is on gasoline or the tune is funky.
 
Well it was last tuned in Colorado 6000 feet above sea level in 2018 so I plan on having it retuned anyways, I assume it'll need it. At that time I believe it was on E85. I'll still verify those settings because I'd like to know all I can anyways but I'd like to set the car up for flex fuel before bringing it to the tuner and having him do it that way.
 
For plug and play status, you can use THIS from ECMtuning if it isn't already set up that way and you need a GM Flex Fuel sensor like THIS along with the pigtail and since you said the car was on SD, it may already have a harness and just needs sensors. :thumb:
 
I know you didn't find the flex fuel sensor but for anyone who needs locate it, it's on the return side. So check the hose after the fpr or the rail. It will not be located anywhere else, like under the back seat since you have to run the wire to the MAF connector plus it's much easier to install on the firewall before it goes into the hard return line. You can also look at the MAF connector and follow the two wires to the sensor. If you don't see two wire coming out of the connector, it doesn't have it (for ECMlink anyways).

1g
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2g
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For plug and play status, you can use THIS from ECMtuning if it isn't already set up that way and you need a GM Flex Fuel sensor like THIS along with the pigtail and since you said the car was on SD, it may already have a harness and just needs sensors. :thumb:
So the kit I have is actually this one with the bigger sensor bolted to the firewall. Would the sensor install still be the same?
 
I know you didn't find the flex fuel sensor but for anyone who needs locate it, it's on the return side. So check the hose after the fpr or the rail. It will not be located anywhere else, like under the back seat since you have to run the wire to the MAF connector plus it's much easier to install on the firewall before it goes into the hard return line. You can also look at the MAF connector and follow the two wires to the sensor. If you don't see two wire coming out of the connector, it doesn't have it (for ECMlink anyways).

1g
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2g
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That's a good idea, probably would have been easier then blindly feeling around what should be the fuel return line. LOL
 
That’s speed density kit and does not come with flex fuel sensor. Here’s a list of sensors


and the cable

I know it just has a different pig tail then what comes with the kit he linked so I wanted to see if install would be the same, I imagine it would. This is all new to me and a bit overwhelming because there so much for me to learn both in terms of this in particular and the car in whole.
 
I understand but you'll get the hang of it. So the big sensor bolted to the firewall is likely your MAP (manifold absolute pressure) sensor, don't get that confused with MDP (manifold differential pressure) sensor. Are you asking how to install flex fuel sensor? The two wires for the flex fuel sensor plug into the speed density cable, and the last wire to chassis ground.
 
I understand but you'll get the hang of it. So the big sensor bolted to the firewall is likely your MAP (manifold absolute pressure) sensor, don't get that confused with MDP (manifold differential pressure) sensor. Are you asking how to install flex fuel sensor? The two wires for the flex fuel sensor plug into the speed density cable, and the last wire to chassis ground.
Essentially, I was just wondering if the sensor wiring would differ between the kit they linked and the one I have on the car, they linked the Mitsu style where as I have the GM style on mine. I'm probably overthinking it like usual.
 
This is my flex fuel sensor. Email ecmlink with a picture of your sensor or look it up on link’s wiki I posted with the list of sensors.

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