Noise in flex fuel input on ms3x

[samh]

Hello I am usung Ms3 v3 mainboard and Ms3X. I am using flex fuel input on Ms3x board with a Ford flex fuel sensor. The problem is I keep getting random noise spikes and when it spike it can spike rich or lean, it can add or remove timing when it spikes. Has anyone else noticed behavior or been having this problem when using the flex fuel abilities of the MS. I am wonder what may be the cause of this? What can I possibly do to make things more stable. I would like to have the flex fuel capabilities the the MS provides. When I turn the flex fuel input off the problem goes away.

[S.Bretz]

I had BIG noise spike on my MS2 after I first installed a GM FFS. It tried rerunning all the wiring and twisting pairs and shielding.


...it ended up being ME. I was lazy on my intial install. The ground (voltage drain) on my TPS remained hooked up to the OEM PCM. I figured that the tps already had a ground and I didn't need to move it to the MS. WRONG. If you have any sensors that ground back to another module and you use them (IAT/TPS/MAT) you should probably ground the back to the MS...weither it be at the same ground point on the block, or, more perffablly, to the MS on one of the low current ground pins (like pin 1 or pin 2).


After many datalogs on of my trouble (it was very intermitten too, which made all the more PITA to find) i noticed that it happened only after very fast TPS changes. The spike was intermitten AND very fast, so sometimes the it would happen between the log events and not even be captured....it was a releif to finally gather the data needed to diagnose the issue.



If all of your grounds are good and go back to the MS, I suggest MANY datalogs of the occurance happening....The power thru them all and try to see what else is occuring in other fields at the same time that should NOT be happening.


Edit: some thought after a smoke and a brew; you mentioned that you are using a ford FFS. You might want to see what you can find on the operational perameters of that specific device as it may not operate the same as the GM counterpart. The GM sensor uses a fequency based signal to denote the ethonal content. 50hz at 100% petrol, 150hz at 100% ethanol and the frequency of of anthing inbetween is based on a value inbtween those to frequency on a linear scale. If the Ford sensor does not operate the same, that might explain the 'noise' you are experiencing.

[samh]

Thank you for your input I am looking in to all you have talked about. I find all of it useful. I will get back to you with feedback in a few days. You have given me a long laundry list.

[UnaClocker]

Still, it sounds like implementing some kind of sanity checking and or averaging on such a critical input might be a good idea.

[S.Bretz]

Yeah, that is still an option that would be nice. I was 200% for averaging before I found my issues years ago, but now it seems pretty stable. I still got some noise every now and then after I fixed my grounds. I had the original circuit hooked up as a direct siganl to the processor. When James found out how I ran it, he suggested a conditioning circuit. Since I implemeted that, it has been working without spike about 99.999999999% of the time. I still have seen some 'weird' issues in datalogs, but nothing during WOT or anything that has effected the power under WOT....when it was noisy, it felt like igntion break-up under high rpm and high load.

IDK if averagring would help much now...at least for me, but it would be nice to have peace of mind that it was there to throw out any 'reads' that fell way out of wack....maybe implent something that measured the last 10 sec mean, then threw out samples over 20% +/- the mean. When you change the comp, you can see it slowly change on the % when you crank it up and start to work the new fuel over the sensor. .....it doesn't change too fast. Large samplers reads should be easy to spot. The spikes I was getting where supernatural, IE: 300%.

[samh]

I have checked my grounds and do not beleive that to be an issue in this case. I can say I did not have this problem until I switched to Ms3 and used the inputs on the Ms3X card. Flex fuel worked fine on the Ms2. You may ask why I did not use the inputs I had built when the Ms2 was installed! The Ms2 was sequential and I had a spare board with no mods done to it I wanted to use with the Ms3. I have been looking for the specs on the Ford flex fuel sensor and have had no luck. I have been changing the frequency on both low and high and the spikes not as bad and happen less often. Also I have a few spare sensors and will swap this one to see if anything changes.

[S.Bretz]

Are all your sensors for the MS grounded back to the MS ground?



SO by changiing the low/high freq settings, the spikes have become less prevalent? If so that suggests to me (in my twisted thought process) that its a component compatibility issue and not a wiring issue.

[UnaClocker]

Odd that you needed special circuitry, the FFV input on the MS3x doesn't have any special circuitry, just a pullup, if that.

[samh]

Hello I replaced the sensor and I still have the problem. This is the circuit diagram I used when I had the Ms2 http://www.msextra.com/forums/viewtopic ... 53&start=0. It worked fine when I built this circuit used with Ms2 and when I changed to the Ms3 and used the input on thevMs3x card I get random spikes. Looks like I will have to build this circuit and switch back to the main board to get things stable again.

[jsmcortina]

I would strongly advice that you do not use the circuit you linked in the Megamanual. It is dangerous and offers no protection to the CPU in case of unexpected voltages from the sensor.

James

[samh]

The one I used is the second diagram! I tried the first diagram and it did not work!

[jsmcortina]

I only see one diagram?

James

[samh]

Ok lets see if this works. this is the diagram I used.

quote="jsmcortina"]Well, Megamanual or not, that's a really dangerous circuit and I urge you to change it as soon as possible.

Try the following.


James

PS. The images you linked to earlier didn't work due to the Referr and other access bans that some of the other Megasquirt sites implement.[/quote]

[S.Bretz]

Ahhh, yes. That old thread. That is the circuit I use now and have been using since Jame suggested it. It has help tremdously. IDK why the original manual diagram was drawn up with no protection, but it should be fix asap if it hasn't already. Thre original diagram has caused me many hours of greif.

I think something similar to that circuit exsists on the MS3xs card, but I cannot confirm since I do not have and have not used a 3x card.


Edit:
here is the link to ms3 ff. It does state at the bottom of the page that the circuit in the manual is unsafe as there is no protection.... http://www.msextra.com/doc/ms3/flexfuel.html#wiring


....it would be nice if that diagram above was inserted on that page and some thing simple like: If you choose to construct your own circuit and use on of the inputs that is NOT on the MS3x card.....then it should look like this. That would save people the headache.

[samh]

Ahhh, yes. That old thread. That is the circuit I use now and have been using since Jame suggested it. It has help tremdously. IDK why the original manual diagram was drawn up with no protection, but it should be fix asap if it hasn't already. Thre original diagram has caused me many hours of greif.

I think something similar to that circuit exsists on the MS3xs card, but I cannot confirm since I do not have and have not used a 3x card.


Edit:
here is the link to ms3 ff. It does state at the bottom of the page that the circuit in the manual is unsafe as there is no protection.... http://www.msextra.com/doc/ms3/flexfuel.html#wiring


....it would be nice if that diagram above was inserted on that page and some thing simple like: If you choose to construct your own circuit and use on of the inputs that is NOT on the MS3x card.....then it should look like this. That would save people the headache.

I agree with you on the above

[samh]

Someone please tell me why the Flex fuel input on the Ms3x card does not work so well? I changed to the circuit I built on the main board and made adjustments in the correct fields it now works like a charm!

[jsmcortina]

Did you include the 0.01u capacitor in your circuit? That isn't included in the stock MS3 circuit.

James

[samh]

Did you include the 0.01u capacitor in your circuit? That isn't included in the stock MS3 circuit.

James

Yes I did. I followed your wiring diagram and it works very well.

[samh]

I will add the cap. to the flex fuel input on the Ms3x card and let you know how that works shortly.

[samh]

Did you include the 0.01u capacitor in your circuit? That isn't included in the stock MS3 circuit.

James

Yes I had a Ms3 install I just finished added the Cap. to the Ms3x flex fuel input and no noise at all so far works great! I put the cap in the 37 pin connector between the ground pin and the flex fuel pin.