Megasquirt rich idle

[lteone]

i tried posting this in the tuning section but im a newbie

have my eclipse running MSnS fuel only... i cant get it to idle above 10:1 on my lm1. If i advance the timing as far as it will allow it will idle at about 10.5:1.

im running 660cc injectors, stock cams and stock displacement running prez's dsm file. I have pulled the ve down untill the idle gets very eratic. Also tried incresing VE but that didnt help. I have good compression and pulled each plug wire one at a time and all cylinders seam to be fireing.


Any ideas suggestions would be helpfull

 

[zippyshoe]

I'm not too familiar with Megasquirt's tuning capabilities, coming more from a DSMLink background, but you may want to confirm that your fuel compensation value is at about -32% and, if these are Denso 660's, that your deadtime is set to roughly 180usec. Adjusting these two values allows you to get your fuel trims close to 0%. You may also want to make sure that your injectors are indeed 660's. If you can log your front O2 voltage, when idling, this voltage should cycle between roughly 0 volt and 1 volt. If it remains at roughly 1 volt, then this would confirm that you are running rich. If you can log your long-term fuel trims, ideally these will be close to 0%. If they are large negative values, then this would also confirm that you are running rich. Hope this helps.

 

[mobythevan]

If you are decreasing VE enough to get an erratic idle and the wideband is not changing, that sounds weird to me. Are you sure the LM1 is set up correctly? Unless you are saying that if you change AFR to be leaner than 10.5:1 then your idle is erratic.

I think I am just mis-reading your post. My setup with MSnS idles great with 850cc injectors at about 11:1, I can't really lean out the idle any more unless I switch to hi-res code which I haven't had time to do. If I try to lean it out right now so it shows like 13:1 at idle then it misses here and there, so I just put it back richer at idle.

 

[lteone]

im decreasing my ve untill the injector pulse width is too short and not opeing fully thus giving me a erratic idle. its possable the my wideband is hosed up, but the plugs are look very rich-black

i have some other ideas im going to try tonight ill update tomarrow.

 

[lteone]

I'm not too familiar with Megasquirt's tuning capabilities, coming more from a DSMLink background, but you may want to confirm that your fuel compensation value is at about -32% and, if these are Denso 660's, that your deadtime is set to roughly 180usec. Adjusting these two values allows you to get your fuel trims close to 0%. You may also want to make sure that your injectors are indeed 660's. If you can log your front O2 voltage, when idling, this voltage should cycle between roughly 0 volt and 1 volt. If it remains at roughly 1 volt, then this would confirm that you are running rich. If you can log your long-term fuel trims, ideally these will be close to 0%. If they are large negative values, then this would also confirm that you are running rich. Hope this helps.

completlely diffrent languges and terminolgy.. but thanks for the help.

 

[donmagicjuan]

I know it's not in your profile, but you aren't by chance running an aftermarket fuel pump with the stock fuel pressure regulator, are you? Also, what is the shortest IPW you are getting before the idle turns erratic?

 

[lteone]

I know it's not in your profile, but you aren't by chance running an aftermarket fuel pump with the stock fuel pressure regulator, are you? Also, what is the shortest IPW you are getting before the idle turns erratic?

Yes walbro 255 wth a stock fuel pressure shortest IPW is about 1.4ms

 

[donmagicjuan]

Well, there's your problem. The stock regulator gets overrun at idle, resulting in very high pressures in your fuel rail. Even with the shortest possible pulse width, the injectors will shoot in too much fuel for you to get a stoich AFR. I guess you know what you need to do now...

 

[lteone]

hmm... ok thanks for the help

 

[donmagicjuan]

No problem. Just make sure you update your profile as well.

 

[zippyshoe]

completlely diffrent languges and terminolgy.. but thanks for the help.

Sorry I couldn't be of more help. I did some quick web research on Megasquirt and also found it to use a very different injector tuning approach compared with DSMLink. Best of luck resolving your problem.

 

[lteone]

thanks for all the help.. figured out a seprate issue last night a pinched vaccume line to the map sensor caused it to run very rich..

Scott

 

[donmagicjuan]

Just for my own edification, is that a MAP sensor for your Megasquirt or the stock one on the top of the intake manifold?

 

[brute]

You can use the stock one if you're running up to 21 psi. More than that, you'll need an after market 3-bar or even a 4-bar.

 

[lteone]

Just for my own edification, is that a MAP sensor for your Megasquirt or the stock one on the top of the intake manifold?

the one for the Megasquirt... its located inside th box.

 

[donmagicjuan]

Cool, thanks.