Supra Forums banner
1 - 11 of 11 Posts

· Banned
Joined
·
2,113 Posts
Discussion Starter · #1 ·
I recently built my fuel system around to use E-85 but I've been looking around and it seems like they have different percentages of ethanol from pump to pump and depending on the time of year (Winter blend/Spring/Summer). I would like to know if its possible to build some type of gauge using the GM Sensor found on flex fuel cars. Im pretty sure it just uses voltage as signals like any other sensor but has anyone done this?

I also know Zeitronix already sells a gauge but I'd rather not pay that price tag if I can build it myself for a lot cheaper.

Thanks

Im also going to be using HKS V-PRO
 

· Registered
Joined
·
7,851 Posts
I recently built my fuel system around to use E-85 but I've been looking around and it seems like they have different percentages of ethanol from pump to pump and depending on the time of year (Winter blend/Spring/Summer). I would like to know if its possible to build some type of gauge using the GM Sensor found on flex fuel cars. Im pretty sure it just uses voltage as signals like any other sensor but has anyone done this?

I also know Zeitronix already sells a gauge but I'd rather not pay that price tag if I can build it myself for a lot cheaper.

Thanks

Im also going to be using HKS V-PRO
Not happening,

the signal is not a voltage but a digital signal based on two parameters.

The Frequency of the signal and the DUTY cycle at the set frequency. (Pulse Width Modulation). That means you have to build a circuitry to read both those, compare to a look up table and then present the information. Unless you understand digital circuitry 100% better to pay Zietronix for what they are selling.
 

· 2JZA70
Joined
·
2,942 Posts
Not happening,

the signal is not a voltage but a digital signal based on two parameters.

The Frequency of the signal and the DUTY cycle at the set frequency. (Pulse Width Modulation). That means you have to build a circuitry to read both those, compare to a look up table and then present the information. Unless you understand digital circuitry 100% better to pay Zietronix for what they are selling.
Ive been toying with the idea of running e-85 as well. Do you think its something the Motec can handle? I have the M800
 

· Always Garaged
Joined
·
1,378 Posts
I am doing the same, but bought the Zeitronix. It should be done in 2 weeks. Like Figgie said, it's not worth it, just pay the 200 bucks for the readout. I would think someone would be a little harder pressed to pay the 600 for the damn GM FF sensor? Chris.
 

· Premium Member
Joined
·
2,919 Posts
Ive been toying with the idea of running e-85 as well. Do you think its something the Motec can handle? I have the M800
Motec can handle it incredibly well. Read below, describes the setup I did on a Viper a while back and have duplicated since on other cars.

Copied from a post I made elsewhere:

The car: Dodge Viper, twin turbo, 1000cc injectors, MoTeC M800 ECU, GM LS1 coils (x10), built engine, GM flex fuel sensor, GM boost control solenoid, and the usual host of upgrades you would expect from a car like this.

The MoTeC ECU allows a user definable 4th dimension to both the fuel and timing maps (the Z axis). Picture a typical fuel map, only now with up to 11 "layers" that are each a complete fuel map (rpm vs load). In our case I set the flex fuel sensor up to move the system on the "Z" axis, so as the ethanol content changes, it changes to different complete fuel maps automatically. The same happens with the timing maps. All seamless, all automatic based on input from the flex fuel sensor.

So first order of business was a pump gas tune, which ended up in the 700whp range with 10psi boost (very small turbos, instant spool). Wastegate springs were at 5psi, and due to traction issues I set the gear dependant boost up to be 5psi in 1st, 7psi in 2nd, 9psi in 3rd and 10psi in 4th+.

Now we proceeded to fill it with E85, and the flex fuel sensor data changes VERY fast. This of course tracks the system to a different "Z" axis fuel and timing "layer", and we proceeded to tune the car to 15psi of boost and 980whp (we were out of injector and fuel pump). Keep in mind the Motec is controlling the boost, and of course a tank of E85 does not solve our traction issues so this is how it was setup (all auto adjusted based on data from the flex fuel sensor). With the flex fuel sensor reporting back 85% ethanol, the boost targets become the following: 1st gear is 5psi, 2nd gear is 7psi, 3rd gear is 11psi and 4th gear is 15psi.

Now to add a special touch to the driveability, I tweaked the hot/cold start tables to include the incoming flex fuel data (to adjust start fueling based on ethanol content), acceleration enrichment values are trimmed based on ethanol content, etc.

Once the ground work was done, I then tuned a couple of blends to bring the two "ends" as it were together, in a seamless transition of 5 "Z" axis layers to go between pump fuel and E85 (and a couple out the far end in case we run into some strong Kentucky 'shine, given the home state of the car). The boost control shown above also does a linear transition between the two points illustrated above based on ethanol content. The fuel trims/start fueling/etc also have the same transistion tuned into them.

This is all done with one calibration file, no laptop is needed to switch things, it is all automated by the ECU. The car also has a keyed "valet" switch wired in, which allows 4 overall boost settings: minimum boost in all gears, 50% reduction in boost across the gears, 25% reduction in boost across the gears, and then maximum permitted by the control (see above values).

The Motec also can store 4 complete calibration files onboard, and it has a switch to select those on the fly but we have yet to find a use for the other three "slots".

If you made it this far, you must be a tuning nerd or just insanely bored. In either case, hopefully it was enlightening and it goes to show what makes a MoTeC ECU a good value in the long run. If you are running a simple setup, then the price can make you cry. But when you start making it work for its keep, it starts to show what good value it can really be. Now, mid 2009 the new series
MoTeC ECUs roll out, and make the above look like chump change. Stay tuned!
 

· Premium Member
Joined
·
2,919 Posts
I recently built my fuel system around to use E-85 but I've been looking around and it seems like they have different percentages of ethanol from pump to pump and depending on the time of year (Winter blend/Spring/Summer). I would like to know if its possible to build some type of gauge using the GM Sensor found on flex fuel cars. Im pretty sure it just uses voltage as signals like any other sensor but has anyone done this?

I also know Zeitronix already sells a gauge but I'd rather not pay that price tag if I can build it myself for a lot cheaper.

Thanks

Im also going to be using HKS V-PRO
The Zeitronix piece is nice, and if you don't like the price tag of it you really won't like what GM asks for the flex fuel sensor itself (which you also need).

The Zeitronix has a 0-5V output you could use for a simple fuel trim in your HKS.

Unless you don't value your time much, I doubt you will save money by attempting to build your own. But if you just like to do it for a challenge, well that is something different.
 

· Banned
Joined
·
2,113 Posts
Discussion Starter · #9 ·
I never really researched the price of the Zeitronix unit itself. But now that I see how complex it is than I'd rather buy it and the GM Sensor.

Thanks for the answers guys.

Seems like E85 is the way to go and Im happy I choose that route. I cant wait to get it all setup and running.
 

· Registered
Joined
·
7,851 Posts
Ive been toying with the idea of running e-85 as well. Do you think its something the Motec can handle? I have the M800
John Reed covered it. Basically what allows the MoTeC mx00 series Ecu to work correctly, 4D tables for fueling, ignition etc. :)
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top