Found out a tidbit of information that is probably of use to those of you running fuel computers.

If you cut the air temperature sensor signal coming from the MAS so that the ECU gets no signal it will automatically throw a CEL and go into limp mode.

So reading that you say well why the hell would I want to do that? The reason is that the ECU functions more or less the same at that point except that it dumps in extra fuel just in case there is more air going in then it think probably is there. So that means the mixtures are nice and rich.

Since the fuel computers seem to be only effective at leaning out the system this is obviously a good thing. So by just cutting a wire you can get the extra fuel you need to then tune with. It also prevents the computer from going into closed loop control, and therefore will not try to correct your adjustments.

If this doesn't work... obviously it's not that hard to rewire one wire!

DO NOT try this unless you have an AFR meter to verify that you have indeed gone rich before making your adjustments.

Later!

Steve

 

You know, Steve you keep impressing me. Have you had a chance to try this out or is this still speculation for the time being? The theory is definitely a sound one.

For those tuning, be sure to leave a margin of error for significant temperature changes. If it were hot and damp one day and dry and cold the next day you could probably run into major problems.

 

It's something I/we are going to try on my brothers MP3... but they just had a baby on the 30th (my first nephew!) and working on the car isn't a high priority right now obviously.

One problem that we had encountered is that we got his MPI piggyback all tuned in and running great. And then a little bit later it was lean and we were like WTF!? Found out later that the computer keeps adapting and ruining your settings. You have to keep doing it until the computer maxes out or so forth... essentially the cycle of retuning and things going back lean should wear out after about 3 weeks of on and off tuning. Well someone with a tuned Protege discovered that cutting the temp wire gave them that limp mode and the rich conditions. And that the computer never corrected out the tunes once they got the car dialed in.

I've spent enough time working on Jeremy's MP3 to see it is set up pretty similar to our Lancers... and we seem to run into similar ECU problems...

So long story short.. things are still a bit of speculation for Lancer's but it has been put into practice by some Mazda owners.

I don't think the environmental temp changes will have a massive impact, but you will definitely want to keep in mind the weather, and probably have a few maps to handle different sorts of conditions...

You know.. the rainy day map, the hotter than hell outside map, the blistering cold and drier than a witches tit map, the everything is beautiful today map.. etc

 

When you live in a temperate area like around here (where it can be anywhere from sub zero in the winter to 90+ in the summer) it would definitely be a good idea to do multiple maps, keeping temp in mind. The barometric pressure sensor should still handle the whole humidity thing in theory though....

 

very interesting... So what your saying is that if someone was to cut the air temp sensor signal... that basically your car will run super rich.. and therefor allow you to tune the afc to its desired positions because it will be like +50% or whatever. I think as soon as some snow gets off the road I am going to try this...

 

would one of those ebay resistors work here?

3 weeks to dial in is kind of a hassle, but if it works, it works. let's not get too desperate to get this to work. the fact that you can make it work at this point is still pretty significant.

 

Incredibly Significant

 

^definately in your case. i'd wish someone would try raising pressure with an fpr or upgrade to larger injectors on a NA app.

 

3 weeks is if you DON'T cut the wire... the ECU is in closed loop then and can end up screwing your settings progressively. Have you noticed any fade of your settings thus far? I know my brother and I certainly saw it with his car. With this cut you should be able to do this once and be golden.

I agree with Andrew on the maps for sure. The question is going to be whether or not 10-20 degrees (morning to mid afternoon) will be a problem. Some piggybacks do have a temp correction factor that you can apply... So you may be able to run the temp sensor to the piggyback and NOT to the ECU and then you'll have the best of both worlds...

I may do the FPR and injectors this summer... depends on cost and getting a piggyback... my concern is that I want a true wideband for accuracy sake.. you just can't trust a narrowband.. and that's a good 350 with sensor and meter. Which is a lot to me at this point.. but who knows.

 

word.

when i wasn't tinkering with my MAS, i had no fade in settings. set it and forget it. lately i've been trying different things so maps are always changing. definate tune will come (to LO settings) next week when i get my scan tool as i'll be able to monitor stft and adjust accordingly.

would welding a bung at the collector on a rpw header cause an inaccurate reading because of how far from the head it is? i thought i'd just ask. i've been thinking that if i do get a wbo2 that that is where i'd place it. forget about integrating it with my current ecu as i wanted to before.

changing maps everyday isn't really a problem to some people. some 3G eclipse guys have to play with a potentiometer everyday to get a good rpm reading on their safc.

 

I don't think that putting the wide O2 at the top of the collector would be too bad. I don't think the gases would cool off too much so the temp won't be a big factor, and obviously with no cat the O2 levels themselves aren't actually going to change.

I don't think it'd be a problem, but I'm trying to figure out which way the bias would go if it was too far down... but that would be the thing to watch for.

Later,

Steve

 

what wire do i cut (color)

 

Good question... Andrew or anybody got that color?

I haven't gotten a tech manual yet so I have no wiring diagrams or anything yet... so I'm SOL.. and I haven't had a need to do this yet.. but next year .

Someone here should know for sure.

 

i was a bit frustrated reading too many resistor chip install requests.

-rhyzin

https://www.evolutionm.net/forums/sh...ht=iat+harness

 

I'm not too big on cutting any MAF wires. Modern ecus are so complicated since they always check and balance all of its sensors. I doesn't take much for it to trip a CEL.