Construct was 100% right as per his research and knowledge. The people that are successful with this circuit that do not have an OPAMP most probably have adjusted the scaling for the FF sensor input in the ROM to account for the halved resolution.

I or others can't see any specific defects unless you post a picture and parts list, but if you add the LM741 between the output of the circuit and ECU wired like in the diagram I just posted (that's an updated one BTW), it will solve the impedance issues/as long as there are no major issues with your circuit build.

An 8-pin LM741 pin-out:

 

Ok, I misunderstood your previous post. Was thinking the 741 was a part of the original circuit. I will try this and see.

Looking at Futurlec's site I see a 741CH and a 741CN. Does it matter which I choose? Looking quickly through the data sheets the difference may just be packaging?

And thank again for your input.

 

NP. Yes, it's the packaging. the CN variant is the 8-pin DIP.

 

well, this thread certainly went south LOL.

hopefully someone will post a new one.

 

The issues being experienced by me are actually nothing to do with the patch, just the home made frequency to digital converter.

It will just take someone to buy a Zeitronix ECA and implement the patch and pretty soon guys will be jumping all over this. It seems like people don't realize that you don't have to build the box yourself to implement the patch.

 

I have ordered the LM741. I will provide an update once I put it in and test it.

 

Okay, I got the LM741. I bought the version that resembles a mini water tower. There are no pin numbers, but it has a little tab on it that locates pin # 8. What I need to know now is how the other pins are referenced from this one. Are the pin numbers determined when looking at it from the top or from the bottom (pin side). I assume it is the top side but want to be sure.

 

The marked pin of a package is always viewed from the top with the pins facing down in my 4 years of experience in electronics, but just to make sure we can compare the figure 1 package to the figure 3. They wouldn't draw one package from the bottom and one from the top in the same diagram.

As you can see below in comparison with the link, pin 1 is marked, and read on the top left


I hope this makes sense.

 

Ok, thanks for your confirmation.

 

I've been wanting to do this for years, but never found any tuners in CA that do this. It seems this is still the case and everyone on flex-fuel setups self tunes them?

 

You can also get a remote e-tune if no one locally tunes with flex fuel

 

Thanks to everyone for the help. I wired in the op amp and it works as intended, problem solved. The voltage in equals voltage out. I wont be able to drive the car for a while yet so I wont be able to report back as to my experiences with the patch itself.

Thanks again.

 

Good to hear. Keep us posted when you get a chance to play with it some more.

 

After many many months I finally started my car with the converter circuit and ethanol content sensor connected. I put a couple gallons of pump fuel in the tank to start with. I measured this with my ethanol tester beforehand and found it to be E07. This showed as E06.9 with the voltage to ethanol percent scaling I used in Evoscan. Threw a half gallon of E98 into the tank and got E22 registered which is roughly correct for the amount I added to the original pump gas. I intend to drain a little bit and check it in the tester also but haven't done so yet.

At this point I am not making use of the free fuel patch rom, just logging ethanol content. The 02 feedback is adjusting for the additional ethanol currently. What I found though is that the ethanol content reported fluctuates a little bit, jumping down to 17% momentarily and back up to 22%. I'm wondering if this is corresponding to changes in my battery voltage (it fluctuates somewhat) or if this is to be expected.

I will update further when I actually implement the patch. At the rate i am going it might be several more months.

 

Glad to hear you're getting somewhere with this. I currently run the Innovate content gauge and it does fluctuate a bit but not as much as you mentioned. On initial start it usually reads a certain percentage then moves anywhere from 1-3%.

Now my gauge is able to output a 0-5v signal would this help? What's the converter circuit for? I'll go back and read tomorrow but maybe you can summarize what's been going on or point me to key posts.