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THE Flex Fuel Thread

46K views 76 replies 25 participants last post by  Lotus 
#1 · (Edited)
Are you tired of the headaches when it comes to dealing with bouncing back and forth between pump gas and e85? Are you tired of dealing with ethanol blends with varying ethanol percent from pump to pump? Are you tired of draining your fuel tank to guarantee a switch between fuels results in an accurate "change" between pump gas and E85?

The wait is finally over for a solution to all those problems.

Some of you may be wondering what the big deal is about a LOT of owners of performance vehicles ( especially boosted applications) wanting to make the switch to E85. The are three main reasons to utilize E85 (85% ethanol and 15% gasoline):

1. The octane rating for E85 is approximately 107-110.
2. The evaporative cooling effect allows for increased ignition timing and/or increased compression ratio.
3. PRICE!!!! E85 is currently $1.99 per gallon. Even though you have to use approximately 30-35% more volume this is MUCH cheaper than other race fuels at $8.00+ per gallon.

Here's some official info and research on ethanol from MIT (while direct injection is discussed the properties of ethanol still apply for port injection)

http://mitei.mit.edu/system/files/2006-01-rp.pdf

Here's the products I have chosen to utilize for my Flex Fuel setup.

1. DPI Ethanol Flex Fuel sensor

This sensor comes from DPI brand new and also includes a new harness plug and pins to wire up the sensor.




2. 1200cc DPI Injectors

These injectors are compatible with all types of pump, race and ethanol fuels. Bigger injectors are a must on any K series on E85. I have maxed out stock 310cc injectors using 93 octane on a stock k24a1/k20a2 setup that was naturally aspirated.





3. Walbro 400LPH E85 model from DPI



(E85 400LPH on LEFT, Walbro 255 on right)



With increased fuel demand of around 35% an upgraded fuel pump is also a must. More importantly this pump is specifically designed to be ethanol compatible. Installing an ethanol approved pump is an absolute must. People have experimented with Walbro 255's, Walbro non E85 400 versions and many other fuel pumps. The bottom line is they all fail if not specifically approved for E85. Some Evo owners using the NON E85 Walbro 400 LPH had failures after a couples months, some a couple weeks and some even as short as a few days.

4. Fuel lines
•In tank: fuel lines here MUST be approved for ethanol SUBMERSION!!!! Using fuel line not rated for being exposed on the outside of the fuel line will lead to a loss in fuel pressure when the ethanol eventually breaks down the fuel line and creates a leak in your feed line to your rail and injectors. Here's the line I used that is ethanol approved ( I even know racers who are submersing this in 100% methanol without issues)



As you can see I also modified my OEM hanger and installed -6AN feed and return fittings



Fuel feed and return lines outside of tank

Aeroquip Startlite Hose
-ethanol compatible (inside line, submersion NOT approved)
-Kevlar outer layer is fire resistant, light weight and very durable





5. Fittings for flex fuel sensor






6. KPro4



The new KPro4 supports a flex fuel sensor. This sensor is integrated into the vehicle's fuel lines to read and provide a real time ethanol percent value of the fuel. Here's a quick video:

http://youtu.be/SYoV8U04zMw

Here's a screen shot from the current KManager Beta software



As you can see there are a TON of awesome features built in. The sensor can read from 0-100% ethanol. Let's talk about each feature

Fuel Compensation:
KPro4 will adjust fuel trim based off ethanol percent. This allows the proper volume of fuel to be delivered in order to operate at a desired A/F ratio. There are two different tables that allow you to setup different values for when the car is making a power pull (closed loop = richer A/F desired) and partial throttle (open loop= leaner A/F ok).

*An additional bonus of the KPro4 over the orginal KPro and KPro2 is the ability to send an aftermarket wideband signal into the ECU. This allows you to be able to datalog and see more precisely where lean/rich spots are in the map. The KPro4 accepts analog signals and also digital signals from some of the newer widebands.*

Ethanol ECT Compensation:
ECT is engine core temp and the OEM sensor used for this is the white plug you see on the side of the head. It measures the temp of the fluid (usually a coolant/water mix) circulating through the motor. This function allows the tuner to adjust the fuel trim based on that temperature.

Ethanol Cranking Compensation:
This function allows you to adjust the amount of fuel need to initially start the motor based on ethanol percent.

Ethanol Cranking ECT Compensation:
During cold weather, especially at and below 40 degrees F, a motor needs a SIGNIFICANT increase in fuel. In some cases as much as increase by a factor of 3! This feature allows you to adjust cold cranking fuel trim.

Ignition Compensation:
Finally we get to discuss making power!!!!! This function allows a person to setup up increases in timing based on ethanol percent. Increasing timing is what is going to make horsepower and there's two main reasons why increases are possible and both reduce the likelihood of detonation (aka "knock".) The first is the increase in octane rating ( approx 107 if we have to label e85 with an octane rating and in reality you can't calculate an octane number for alcohols like other fuels using the same math) and the other is the awesome evaporative cooling effect. Go from pump gas to e85 and timing adjustments are made automatically (after your setup has been tuned of course.) Both naturally aspirated setups and all forms of forced induction can benefit from this. Until now I have been describing closed loop functions but open loop has a separate timing adjustment table as well.

Boost Compensation:
Turbo guys here you go! There might possibly be some instances where a supercharged setup would use this function but mainly I see this mostly relevant to turbo setups. If you are at the limit of detonation at a certain boost level on pump gas then switching to E85 can allow you to run more boost because of the cooling effects and increased knock resistance. You can enter values into this table that will automatically turn up the boost (boost solenoid required) based on the ethanol percent.

When you combine all of the above mentioned features it really makes utilizing E85 an option for all types of setups from mildly stock naturally aspirated cars to a dedicated all motor drag car and especially any and all forced induction setups. A flex fuel system does all of the following:

-eliminates the need for multiple maps having to constantly being loaded

-allows a person to mix/top off tank with any combination of volumes and/or ethanol content

-provides protection in the event a person fills up with what they think is E85 but is really a winter blend of E70 ( only 70% ethanol). Filling up with winter blends puts a motor at risk of detonation when a true E85 map/tune is loaded in the ECU due to fuel trim and timing values not being accurate.
-allows a car to start up immediately every time no matter what the ethanol percent is or what the current TEMPERATURE is.

Now let's get everyone on Flex Fuel setups :cool:

Please feel free to chime in and discuss :up:
 
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#6 ·
More pics and info to come :up:
Great info. I plan to utilize flex fuel with kro4 in my new street driven 14.5:1 motor. Looking forward to this.

Question: does it matter where in the feed line the content sensor is placed?
Awesome! Your new setup is a perfect candidate for a flex fuel setup.

It doesn't matter where the sensor is placed. In the feed line is ideal, however it can be installed on the return side. I will most likely be installing in the return to prevent a "bottle neck" in my feed. Only boosted setups close to maxing out the limitation of a -6AN line or cars with -8AN and larger are pretty much forced to install on the return side.

Great info! :up:
Thanks, you should get your car on E85 with a Flex Fuel setup :wink:
 
#4 ·
Great info. I plan to utilize flex fuel with kro4 in my new street driven 14.5:1 motor. Looking forward to this.

Question: does it matter where in the feed line the content sensor is placed?
 
#8 ·
some good info in here :up: i'll be switching to flex fuel next winter so there will probably be tons of info in here by then.
 
#10 ·
I'm going to throw a little wrench into plans here.

I have found that depending on placement, the ethanol content sensor will drop reading on higher power cars if placed close to the regulator on the return line when the fuel system is being taxed (usually on higher-power cars).

I, along with another tuner, have requested access to the sensor's filtering speed read by the ECU to alleviate this, or to have the ethanol content locked above a certain load or engine speed.

This shouldn't be a problem for the guys using this on a feed line (on returnless setups), or those with HUGELY overkill fuel pump combinations.

Also, one should note that even with this sensor working, do not expect it to make cold starts on 85% ethanol fuel instant in temperatures below 45deg or so. The flashpoint of pure ethanol is 55degF, so increased cranking time should be expected the colder the temperatures are.
 
#11 ·
I'm going to throw a little wrench into plans here.

I have found that depending on placement, the ethanol content sensor will drop reading on higher power cars if placed close to the regulator on the return line when the fuel system is being taxed (usually on higher-power cars)...
I'm unclear when you said that there'll be problems if the sensor is "placed near the regulator." How can placement matter when flow anywhere downstream of the fuel rail is equal?

Your post is the second one I've seen about this, and AEM confirmed that it's an issue with users of their Infinity ECU (it uses the same type of GM sensor). At the moment I have mine in the return line, but am wondering if I should move it to the supply side... I modified mine with a low-restriction bypass, where only a percentage of fuel actually goes through the sensor.

Sort of depends if I get everything else done in time...

 
#12 · (Edited)
part numbers

Russell 644123 -6AN Male to 3/8" SAE Quick EFI Adapter Fitting
- I used this item on both sides of the E85 sensor
Flex Fuel Sensor Fit For 2012 CADILLAC SRX 13577379 1219900737
- Sensor purchased
CONN-75811 GM Delphi / Packard - 3-Way GT 150 Plug kit for Fuel Sensor Applications
- Plug to go into the e85 sensor
 
#16 ·
Yes and no. I agree that under full throttle it'll be fine, that most of the fuel is being consumed by the engine and not returning to the tank.

In every other situation though, depending on the fuel pump, there could be a fair bit of pressure drop across the sensor. I'm pretty sure that pressure drop gets added to the fuel pressure regulator, such that "43 psi" indicated on the gauge may well be 50 psi at the injectors.
 
#19 ·
Pressure drop across the sender is really irrelevant. The sender should be after your regulator, in which case again, it wont affect your rail pressure. The sender will not provide more resistance than the regulator which is already holding rail pressure at ~45psi.

Anyway, do as you prefer, just trying to help
 
#20 ·
Agreed. I only like the russell style fittings which have the screw in locks, the other ones which just clip in dont seem sturdy enough to me. That said, they wont take any real pressure so shouldnt be a concern and I think this picture shows a good setup using the screw in style fittings.

The tubes on the sensors are very tough, I would prefer to flare and use tube nuts/sleeves, but they are pretty hard to flare unless you have a good stainless tube flare tool.
 
#18 ·
Ethanols octane rating has been revised fyi. E85 is around 95-96 octane, especially based on the fact that the base 15% gasoline they mix it with is 85 octane. The evaporative fuel properties provide nearly all the benefit, not the actual octane rating.

http://en.wikipedia.org/wiki/Octane_rating

Check out the AKI rating for e85 and ethanol on there. Now that's NOT to say it doesn't perform similarly to high octane race fuels because it does.
 
#25 · (Edited)
I've done the conversion but am using an AEM Infinity ECU. The tuner handled the gas tune and go it to idle okay, then we turned to E85. He took care of the power end of things but we ran out of time before really dialing in the E85 idle.

In my free time I've been trying to teach myself how to tune the idle and it's kicking my ass. So many variables, some closed loop, some temperature dependant, some time dependant, all mixed together such that it's hard to tell what's causing the irregular idle, surging, and stalls. The tuner thinks that my 1650 cc injectors are too large to sustain a smooth idle, that E85 is pooling behind the intake valves because there isn't enough heat to vaporize it at idle. I don't know enough to argue with him, as he's tuned a lot of cars - but very few or even none on the Infinity. The ECU is so new that there are few tuners who really know it, so for now we're all left to figure it out on our own.
 
#26 ·
Just bought kpro4 for this feature mostly... Also the wideband integration which is pretty neat.

Running in my return line about 1ft from my fpr, everything wired up properly according to the kpro help file using their recommend GM sensor.

Readings are all over place, even on just pump fuel my ethanol % readings move from 0 up to 90%!!! Thankfully I haven't enabled the flex fuel option, as this would royally mess with the tune, but it's no good.

Just can't seem to get it reading right, not sure if it's a kpro problem, or a issue with the sensor itself:(

Anyone else getting whacked readings or am I the isolated case?
 
#27 ·
The flex fuel sensor is open-collector, meaning that you won't get a signal unless the output is connected to something that lightly pulls the output up to +5 or +12V. The point being that you should double check that it's being run to the correct input pin. Also, double check that the sensor is wired correctly... many of the online instructions seem to have it wrong (backwards). Then of course there's also the possibility that the sensor is bad - a scope would tell you what's going on, but most people don't have access to one.
 
#29 ·
My first post in this thread outlined a concern with high-power systems using the return line as the reference point for the ethanol content sensor, with the regulator dropping off return line fuel flow at high demands.

Hondata has made a change to the latest version of KManager to add filtering speed and maximum engine speed parameters to the FlexFuel features, which should alleviate any problems with content reading dropping mid-pull.

Just thought I would update!
 
#30 · (Edited)
Another thing to keep in mind when mounting the ethanol sensor is to make sure it can't become a high point in the system. If that happens it can trap an air bubble inside and regardless of fuel, it'll always read near zero ethanol. I was able to mount the sensor down low and she self-purges better than an anorexic supermodel.
 
#32 ·
Does anyone know if KManager will let me input negative values in for fuel and ignition compensation? I'm already tuned for E85 which is what I plan to mostly run. The main reason I will be adding a flex fuel sensor is to adjust for differences in E85 blends. If I can subtract fuel and ignition from my existing E85 tune that would be more optimal than re-tuning on 91 and figuring out comp % values from there.
 
#34 ·
Hondata said explicitly not to enter negative values, but I have now used negative values for fuel on a few cars with zero problems.

As far as ignition timing goes, just remove timing from the tables and add it in with positive values on the ethanol compensation.
 
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