Fuel tuner questions & thoughts..

[FordFasteRR]

I've heard some people talk about how the stock ecm and trim the duty cycle of the sonata injectors during idle and part throttle without any additional help...


that means that the ecm reads an overly rich condition and then trims the injector pulse on its own...

This is the problem... ... if I installed a fuel tuner, and say.. turn it down - 10% at idle... the ecm will read a lean condition and then increase the duty cycle accordingly by +10% to reach the air fuel ratio that it was programmed for, my changes were basically cancelled out...

My point is that the modified fuel curve that i am trying to get is quickly changed by the ecm.. what is the point of trying to tune the stock injectors? The ecm will quickly adapt and run at stock air fuel levels...

Obviously my question has nothing to do with installing bigger injectors and tuning them down... the ecm will not compensate for their size at WOT which is a great reason to use a fuel tuner.. the ecm only reads the map sensor input to trim fuel at WOT so it is very useful in this sense.. however part throttle and other tuning points like cruise and idle are basically auto-configured by the ecm so its pointless to bother with all of these settings on an NA car...

I just got the SS fuel tuner... not the ARC1... I just got their all out fancy fully programmable 3d tuner with built in map sensor... I dont know if i'm going to install it just yet.. but if i decide to go higher with boost then I might try it out :) for now, the arc1 does the job just fine and it will be a great help with tuning with the sonata injectors (if i get them) when I want to add more boost without re-programming the UNICHIP since that is a real pain in the arse.

:)

[Statik]

I'd guess that what the fuel tuner will be doing is telling the ecu that its over-rich and the ECU will probably drop its signal to compensate (Just shooting in the dark here) thats what any piggyback system does anyway... confuse the S#!T out of the ECU so that it does whatever the tuner software says.

[FordFasteRR]

I'd guess that what the fuel tuner will be doing is telling the ecu that its over-rich .....

I dont think you have this straight...

The fuel tuner usually tells the ecm that there is less LOAD on the map sensor.. that is why the ecm trims the injector pulse ...Dudring low load condities.. ie.. less than 80% TPS signal.. like part throttle and cruise .. the ecm continuosly trims fuel based on o2 + map readings to keep the emissions people happy... In this condition, a fuel tuner has little or no effect since the ecm will override the map readings based on o2 sensor input...


however if you are at WOT the ecm in our cars ignores the o2 sensor and reads from a static fuel map + the real map sensor... that is why the fuel tuner works best at WOT and the ecm does not adjust based on o2 readings...

[azwildfire]

at WOT the ECU goes off the long term fuel trim and the internal map.

btw i know on my 04 86.9% throttle is when it kicks into WOT conditions :P

and you are right Ford, the ECU will learn adjust and put the fuel ratio where it wants it at all settings that are NOT WOT

even with larger injectors, all you have to do is get CLOSE and the ECU will fix the rest.

Hey Ford,

I have been doing some experimenting over the last few weeks with my SAFC and i think i have a way to set it up so your ECU doesnt over learn it

how the ECU learns the settings is by adjusting your long term fuel ratio... and thus adjusts the fuel maping via this number at WOT

however... i set my SAFC so i run 4% lean *i run off %'s because i use an OBD-II logger to tune* so i run 4% lean at idle and up to 2k rpms i am between 4-8% lean on LOW THrottle... so during normal driving and idleing the computer shifts the LRFT to add more fuel... and thus when you are driving it hard and it shifts the LRFT to lean out the fuel mixture, when you go back to idle it starts tuning down the LRFT

this is what works on my car and has for the last week now so i feel confident in the logic.

also if you run a colder plug, running a little on the lean side helps keep the colder plug in self cleaning temps, and at those low rpm's you are not in danger of knock esp under LOW throttle settings

just my thoughts and experiments

[FordFasteRR]

......

however... i set my SAFC so i run 4% lean *i run off %'s because i use an OBD-II logger to tune* so i run 4% lean at idle and up to 2k rpms i am between 4-8% lean on LOW THrottle... so during normal driving and idleing the computer shifts the LRFT to add more fuel... and thus when you are driving it hard and it shifts the LRFT to lean out the fuel mixture, when you go back to idle it starts tuning down the LRFT

.....

I got everything you said up until LRFT ,, does that stand for long term fuel trim ?

So you leaned it out at low throttle by 4%.. and how does this make a difference on WOT conditions ?

if you set it at -4% across the board, then ecu will see -4% and compensate, when you hit WOT, it will revert to the stored fuel maps and still see -4% and trim a little fuel out ...

how does this trick the ecu any different than what I explained earlier ?

Also, why do you want to run constantly leaner ? as if that is what could be happening... the ecm will just compensate for your low throttle map changes on the fly...

[ppwazzup]

Build yourself a TPS fooler that will make your ECU run in open loop constantly. It will make the ECU ignore the o2 sensor for triming fuel and just use the fuel map. I have a schematic somewhere. I will look for it if you are interested.

Matt

[slow 2K2GT]

Yeah lets see it man, our ECUs are pretty tricky and tend to pose problems with tuning.

[ppwazzup]

Keep in mind that this is for a boosted aplication, however I am sure that with the minds here it can be made to work with NA cars.

Oh, and the digikey list on the site is the parts list for http://www.digikey.com/

This should allow you to have full control over the fuel tuning of your ECU with a piggy back fuel tuner.

http://custom-kia.com/site-picts/elantraxd/TPS_tricker.JPG

Matt

[tharptroy]

the ECU is "trained" to constantly try and achieve 2.35v (I think) which represents a AFR of 14.7:1

if you have a 4 wire O2 that can will output 2.35v at 13.5:1 or any other AFR, then the ECU could still be happy while you get the AFR you want at low or part throttle conditions.

experimenting with different O2 sensors might actually be a potential solution for the rear O2 sensor when running no cats.

its hard to know how to properly trick the ECU unless there is a manual detailing specifically how it works, and what it will do if "insert something here" is done to the system.

but the ECU is definetely not smart enough to outwit an O2 sensor that puts out the "right" voltage for the "wrong" AFR

Thats the only non-screwy solution I can think of

[ppwazzup]

Are you saying to hook up a wire that has a constant 2.35 volts to the signal wire for the o2 harness, that way the ecu will see a constant 14.7:1 afr? I am tired so I might be reading that wrong LOL.

Matt