Megasquirt MS1 - Another tuning help request post..

[bodumatau]

Fatboy ...... I was getting the same 5V AFR table that you pointed out in this post before and emailed TunerStudio to try and figure it out.......

doing this I have learnt a few things.....

1. DONT ASK THEM MORE THAN ONE QUESTION PER EMAIL.......they only answer the last one

2. they don't really know why this happens

3. they have no idea how to fix it

4. they recommend wide band but not sure how to stop the program giving you a AFR voltage table

5. they say the voltage table is because of narrowband

so, if you are as confused as me about the information above then good...... I won't feel so alone.....

still trying to get more info out of them, maybe my simple language one question emails will finally get through to them.......on a level they can answer.

one thing they did write to me was that the narrow band sensor voltage range should be between 0-1V, sent me a chart and all, very mathematical, but then why does the program spit out 1-5V? how can that be if the program has the right math formulas?

[Fatboy]

Bodumatau,

Thanks for that update! Please keep them coming, and don't give up.

That made me chuckle.... in a "going mad" sort of way. "Bump"..

There is a lot of useful information in the last few posts on this thread that I need to digest and implement. Unfortunately, I reached SWMBO's "are you tampering with that car again?" threshold, so for the past few days, its been parked in the weeds while I do garden / house projects.

[FridgeFreezer]

If TS is causing you guys issues, you could always fall back on MegaTune, it's not as modern but it does the job and may help you spot what's going on just by dint of presenting it differently.

I always find when you get so far down the rabbit hole with things like this it's best to stop, go back to the absolute basics and make sure it all works as expected with the setup you had before you started fiddling. Then change one thing at a time and make sure it still does what you expect after each change.

[bodumatau]

Megatune refused to work with me...... haven't been brave enough to try it again..... was so grateful that TS was working and that I could get my truck running..... might be time to try again.

[bodumatau]

right, FATBOY, this is what TS got back to me with once I figured out how to ask the question:

0-5V Table range vs 0-1V Sensor output range:

The EGO ADC circuit is able to read voltages between 0 and 5 volts, but most narrow band sensors only work in 0 to 1 volt range.

Why the generator fills NB/Voltage AFR table with 5s:

All the values generated by the tool have values between 12 and 17 (AFR). When go to save these values into a AFR table that uses Voltage the bin values are limited to 5V as that is the maximum voltage that the circuit can read. Since all the generated values are greater than 5 you will end up with a table filled with 5.0V.

Why the engine runs terribly (Rich) with the table at all 5V

When the ECU scales a 5V value to the 0-1V output range of most sensors It will cause the engine to run pig rich.

Bottom line: Our AFR table generator was designed for use with Wideband Sensors only. You need to come up with your own values. We recommend you start with 0.45-0.5V for the entire table, tune VE to match those readings. This is the only range where the narrowband is accurate. Once that is dialed in then you scale the areas you want richer(0.7-0.83V) and leaner(0.3-0.2V)

SOOOO.... let me know if you can make that AFR table work if you change your settings to WIDEBAND, (they shows me a screenshot of the initial setup where you choose whether wide or narrow band, might be worth starting a new project, reading off your ECU and putting in wideband from the get go, let me know if you get anywhere

as for me, have changed to the "correct" voltage range, buggered if I can feel any difference , but I will keep on trying.

[FridgeFreezer]

OK, that seems to have solved the mystery, but you need to understand why what you are NOW trying to do can't work:

The narrowband sensor acts like a switch, not a linear sensor:

If the mixture is EXACTLY 14.7:1 then the voltage will be 0.45v

The voltage drops below 0.45v when the mixture is leaner than 14.7:1

The voltage rises above 0.45v when the mixture is richer than 14.7:1

There is NO relationship between ANY other voltage and ANY fuel mixture with a narrowband, you cannot say "0.7v is 12:1" or anything like that as it will vary with temperature etc. etc. and will NEVER be the same twice.

From your target AFR/voltage map it looks like you may have your target voltages the wrong way round, you want to be RICHER at the top of the table, not leaner!

[bodumatau]

and what do you pros do FF? most of you on wideband?

how much of a mission is it to change to wideband?

[FridgeFreezer]

I've never run a wideband on any of my megasquirts. I also mostly use Megatune not TS. Also, I suck at tuning so mostly get it close enough then lose interest the regular EGO correction sorts things out when you're cruising along anyway so MPG doesn't suffer too badly if you've landed somewhere within its adjustment range.

There's a few options;

As someone said earlier, you can tune the old fashioned way by feel.

You can use Megatune's auto-tune to get the map close (but NOT the idle or high-load/rpm areas), then dial the rest in by eye around it (see option 1) keeping an eye on the O2 reading, basically try to avoid going lean at high load/rpm.

You can datalog & use MSTweak3000 (more old technology) to calculate the fuel table tweaks to hit target AFR's. It will get the idle zone wrong, but you can eyeball that.

Widebands need a controller (usually come as a kit) & you need to understand the setup, many of them need some sort of calibration and you need to change settings in MS + TS to tell it it's got a wideband and make sure everything's reading right. On a physical level, widebands screw in the same hole & need 12v & ground, no show-stoppers that side of things.

[bodumatau]

From your target AFR/voltage map it looks like you may have your target voltages the wrong way round, you want to be RICHER at the top of the table, not leaner!

Ahem....., yes... Well.....I was aahhmm.... just testing if you were awake FF

carp....was another one of my brain farts

So now doing it correctly........