Yup that's the same sensor most of us are using. It's $67 on GMpartsdirect.com!

Beau

 

Love it, love it, love it.

Now we just need some Evo 9 support and I'm all over it.

In the mean time I would love if you could post an updated schematic, some labeled pictures, and complete parts list so I can make one of these signal converters for my self.

You guys are awesome, thanks and keep up the good work.

 

I played in LTSpice for the first time for a few hours yesterday (awesome program!) and found some interesting results. Evoredy, am I missing something in the circuit? It doesn't seem to be behaving consistently. Personally I like the idea of using a chip that actually is designed to accept a digital signal that looks for an edge instead of a 0v crossover point, when the original signal is just simply a 0-12v square wave.

Below is the circuit posted by AST using the LM2917-14 chip that I built. I must have zapped the chip because I got 0v out of it, so I'll be building the same 2917 circuit again on a solderless breadboard to see if I can get it to work correctly this time.





Beau

 

1. You are using an LM2907 model where I'm acutally using an LM2917-8 on the real setup and sim powered at 10.8V.

2. Your input has to emulate a 6V pulled up pulsed input JUST like the GM sensor. If you look at my schematic picture, the answer is there! You'll figure it out.

125hz (PULSE(0 6v 1ns 1ns 1ns .007 .008)) input simulated measured at out2:

 

Got my evoscan dialed in displaying what my e85 gauge is displaying..

 

The circuit AST posted seemed really stable but the big power-on delay to reach the proper output voltage is too large, I'm worried about a quick key-on and startup and not reading proper ethanol content in time to calculate accurate cranking fuel. I made some modifications to AST's circuit to improve response dramatically (~1s compared to ~9s) but still keep noise to a minimum. I'm really impressed with LTSpice, so far every time I've simulated a circuit, the actual circuit output voltage and response has matched absolutely perfectly.

I built the new circuit and I'm getting a maximum fluctuation on voltage of just 0.01-0.02v which is pretty solid. This thing should be on the car and testing this weekend!

Beau

 

Yeah for this purpose, the LM2917 is a great chip. Simple and accurate. We're only doing 50-150hz and the output of the GM sensor is already modulated perfectly by some internal IC inside it.

I am also liking the fact that I have documented what the chip and sensor read based on test fuels and a control. I have yet to see that for the other units, but hey, this is DIY time lol.

EDIT: I just mocked up the 2917-14 with my capacitances and resistances and........it performs the exact same lol. Whaddya expect?, it's the same chip. ^^^^can't wait to see some tuning results from the people that have this/ZT and the sensor mounted. I am interested in drivability with odd-mixture interpolation and how good the engine handles the numbers.

Edit: See attachments

 

The sensor is mounted in the return line correct? If so then you could just cycle the key a couple times after filling up which will get the newly mixed fuel to the sensor so it can interpolate the maps before you crank it up. just a thought

Also, how hard would it be to build a simple LED display that could display ethanol content using the output of evoredy's converter?

If I can make some kind of display for cheap I think I'll go ahead and order a sensor and build evoredy's converter so at least I can view my ethanol content.

 

I'm working on a simple cheap digital voltmeter tied to one of the pins. I'll test that out when it comes in. A small 3 digit 12v powered voltmeter is like 5 bucks shipped on ebay. I bought two lol.

As for the fueling issue, by the time the pump has primed the lines, the reading is good and it is up to the integrity of the fuel solution then. I takes about a half a second. LTspice's time seems on the modest side. It's pefectly fine though.

EDIT: if you notice I am missing letters once in a while, my keyboard sucks. MSI GT60 laptop keyboard FTL!

 

Just to double.check... ill be fine with 1/4W 5% Carbon Film Resistors and 100V Mylar Capacitors right?

I also could not find a normal LM317, I'm guessing the "LM317T - 1.5A Adj. Positive Regulator" will do the job?

And Futurelec.com didn't have the NTE962 so I guess ill have to make a trip to radioshack for that one.


About to place my order and we'll see how it goes when it all gets here.

 

1/4 W carbon is fine. Use tantalum and ceramic disc caps when possible. *But, as long as the spec of the cap is the same and the tolerance isn't something stupid high and they are not electrolytic, you should be fine. LM317T(TO-220 form factor for the regs) is fine. And yes, radioshack should have the NTE962 for the 6V pullup. Futurelec has a 5V regulator which should be fine too. The resistors come in 10 packs from futurlec. Remember, I used 2x220kohm resistors to get the 440kohm for R1. Buy a pdip-8 pin socket too. Soldering straight to chips sometimes burns them but you CAN get away with it. I'm gonna go spend more on my lunch now...

Edit: Don't forget to add an OPOAMP to the parts list and implement the latest schematic (in later thread).

 

Typically yes you'd want to place this in the return line. In OEM flex fuel cars, the sensor is installed in the feed line, but supposedly this sensor is rated to 200lph flow so it would be a restriction for most of us, and of course the return line will always have less fuel flow than the feed while the injectors are pulsing. For very high fuel flow setups, you might have to use a "Y" fitting and hope that enough fluid travels through the sensor for it to read properly. Side note: the sensor should be installed in a lower area of the plumbing so that fuel will tend to collect in the sensor. If the sensor goes dry, it will read too low of an ethanol content.

Also, the Evo/DSM vehicles do NOT prime the fuel pump on key-on so this wouldn't work. The fuel pump only runs during cranking or running, yet another reason why the sensor should be installed so the fuel doesn't drain out of it when the car sits.

Beau

 

what are the pros of using this patch over your already tuned rom ?

 

yes yes please Evo 9 support would welcome

 

The obvious one would be that it will automatically adjust fuel, timing, and boost for 91 or e85.