I recently used some scalings I found on the boards to scale my PTE 780cc injectors and while I probably shouldn't be complaining about this, I've noticed that all 3 of my LTFT's on BOTH evoscan and mitsulogger are being logged as perfect. In Evoscan they are all showing up as 100 during cruise and idle and 0 on mitsulogger during cruise and idle as well. I've done multiple logs to make sure and each time they check out fine. Even when I rip on it and go WOT, my AFR's are perfect I mean I believe it gets .2 richer towards redline but stays around 11.1 instead of the 11.2/11.3 I was tuned for.

I've conducted a boost leak and found nothing and also recently had my injectors cleaned/flow tested and they were/are perfect.

Is this odd or should I not be complaining?

 

meaning your tune is actually really good

 

It is possible to get that magic number where the injector scale and latency values will be real close to perfect.. Most of the time it takes trial and error, occasionally you can hit on it pretty quickly.

So yes, its definitely possible, and highly likely with enough work.

The problem is when weather conditions, or engine load (A/C and other accessories) changes, the fuel trims will shift.. Same with the condition of your plugs and whatnot.. So expect that they won't always be "Perfect" but your at an advantage, because it now means that the 14.7 in your fuel maps, or other AFR reading, should be fairly close to what your car is actually reading..

When I tune, the first things I do before I tune for performance:

1: log car, make sure everything works right..
2: Run car in open loop and scale injectors until I get values that I'm expecting
3: return car to closed loop to verify the fuel trims are good.
4: Adjust idle, RPM settings, fuel cut, etc...
5: Run car with *ALL* accessories that generate load, A/C, Defogger, Radio and check fuel trims, make adjustments accordingly.
6: Drive the car in traffic, do all of those things that cause "Idle dip" to make sure it doesn't stall as its nearly impossible to eliminate the dip with the stock MAF

Once the car is drivable, feels good, and runs well overall at low boost with safe fueling and timing.. I **THEN** start tuning for power.

Not something that can get done on a 1 hour dyno tune.. But at least if you can get that far, you've made it easier to later on get a dyno tune and get a good drivable car and good power. Or just do it yourself..

 

There are a couple of threads over the last week that outline issues with the fuel trims not changing as expected. If all 3 trims are perfect, I'd say there is a problem. Even on an excellently tuned vehicle, the trims should still wander 1% - 2% at the least.

 

What potential problems could there be?

 

We honestly don't know ... but it seems to be linked to a CEL relating to the O2 sensors.

 

Your trims should be changing. For a sanity check, look at your STFT. If that isn't moving either, then there definitely is a problem. If that is moving and is averaging (bouncing around) something other than 0, then your LTFTs should eventually change.

If they aren't, then either the conditions aren't being met to change them or something else is wrong.

 

Well the STFT bounces around all the time. Maybe a log longer then 10 minutes must be done then.

I recently replaced my primary o2 sensor, I imagine it can't be that. My car has never seen race gas either and there is no CEL.

 

perfect NO.. tuned really good YES

 

I had the same problem with an Evo 9 that I just finished tuning. I posted a thread about the problem. The STFT move around, but the LTFT do not budge no matter what I did. I tried Evoscan/Mistulogger and it did not change.

We even changed the front O2 sensor and that did not change things.

I eventually tuned the car w/o triggering the trims. Nothing bad happened.

The car had the ECU disconnected for 6 months before we tuned it. We were told that this will cause the trims not to get triggered. We are told that after a fair bit of driving the trims will trigger again.

 

Try changing the scaling slightly and see if it strays from perfect. Simple enough of a test.

 

that makes perfect sense.....i knew about these problems but always forgot about them until after the POWER TUNE.........need to make sticky notes...LOL

 

Yeah, I do sometimes get this weird idle dip, not sure what it's from though.

For example, when I start the car in the morning and put it into reverse to pull out of the garage, the rpms will fall down to the 700ish range and afr's will go full lean but after a few seconds it will come back to normal and idle rock solid. Is this occurring because of the fuel trims?

I'll try and see if changing my fuel trims does anything. I'm almost tempted not to because at WOT my afr's are solid and they're solid at cruise and idle (aside from the little blip I get when the car is in neutral and at idle).

 

That sounds in line with what I've seen. A guy's car that I tuned had cut his o2 harness installing his exhaust because he couldnt get the o2 sensor out of the cat while it was on the car. So then he drove it without the rear o2 for a while and then eventually put the rear o2 back in. That car's fuel trims were stuck for a while, interstingly enough I think it maybe ran open loop all the time and it ran really good. I was pretty early at tuning and was very jealous about his rock solid fuel trims, and went searching for why my car didnt have solid fuel trims.

 

It's hunting or trying to calibrate. It will go full lean and then full rich and then get control.