jmb614

Glad I caught this before heading out to the track Friday...

Forrest Gump 9

Is it a little lean?

clkwork

Looks like it went lean, but you were running pretty rich before that.

GT-ER

Oh wow...I don't mind the A/F ratio touching 12's ( like 12.0 or 12.1 ) but 12.9@5,500rpm really sucks.

What are you logging the A/F ratio with?

urbamworm

You have that backwards, the higher the number means more parts air, less fuel aka leaner. At the end when it says 11.4 it went richer.

jmb614

I'm logging RPM, TPS, Boost, and AFR with a Zeitronix ZT2 connected to a Dashdaq. The other signals are from the OBD2 connected to the Dashdaq. Sooner or later I will pick up another ZT3 for the other bank.

Forrest Gump 9

And all this time you complain about your car being too rich.

GT-ER

Nice...

what injectors are your running?

jmb614

I know, right? Black exhaust tips do not equal rich

TTM 550cc

chiromikey

and what tune?

jmb614

The car was tuned in 85F heat, ambient temp on that pull shown in the log was 57F. Isn't it natural for the car to lean out considering the colder, denser air?

Evolved8

EC

jmb614

In my opinion I don't think it matters whose tune is on the car, point being I am glad I am data-logging. I figured the car would lean out in colder temps, and sure enough it has. Luckily I caught it, had I not, who knows what would've happened.

FASN8N

Please educate me, the car had an a/f ratio that was around 12.5 until you closed the throttle and then it leaned out... This is normal, I don't see the issue?

jmb614

It got richer as the throttle was closed.

FASN8N

If it got richer wouldn't you have a lower numerical value? a/f of 10 is pig rich and 14+ is lean right?

The green line spiked way up indicating lean right?

urbamworm

Like I said before, a lower number means RICHER not LEANER. You want the car to be tuned in the upper 11s for ideal forced induction tuning for making power and also being safe. Tuning LEANER making the car run in the 12s air fuel will make more peak power but the closer you get to 13 or going over 13 toward 14 the more risk you are taking of detonation under boost. Not saying that an a/f of 13 will cause detonation because it is possible to run a tune that lean. His car was running slightly lean in the mid 12s and the got rich at the very end when the throttle closed.

Think of it as 10=stupid rich, 14=stupid lean, 12=perfect. Going over 12 will give more peak hp but less midrange around peak tq, going below 12 will do the opposite.

And to the OP, the car should not go lean because the weather is cool out. The tune has a target air/fuel based on different parameters like load, boost, iat, etc and also the point of having an oxygen sensor is to sense the amount of air/fuel in the exhaust to signal the ecu to make corrections to hit the target a/f if it is straying from what the ecu is programmed to request from the map.

jmb614

But under throttle isn't the system running in an open loop mode?

urbamworm

The car should run in open loop when it is first started and warming up and then go to closed loop unless for some reason this Bosch Motronic works differently than others I am used to. It doesn't make sense to run in open loop though because that is not as safe and even more so because this car doesn't have a mass air flow sensor to read airflow and use a table to reference for fuel based on the airflow from the maf. It would be more likely for a car with a narrowband o2 sensor not to use closed loop since the o2 isn't accurate like a wideband o2 for adjusting fueling but like I said this car doesn't have a maf so I don't know how it would work using open loop since it doesn't know airflow or an accurate air/fuel reading to run from.

Maybe someone that is 100% sure how it works in this car can say but I personally don't see how it could run open loop from what I said above especially being a forced induction car where a proper air/fuel would be more critical.

GT-ER

It will go open loop due to the fact that it's a narrowband sensor...narrowband sensors cannot read A/F ratio's that aren't in the 14's properly so it'll be useless to keep them active. The car may not have a maf but it does have a MAP sensor, a TPS and an IAT sensor which is all it really needs to calculate how much fuel to feed it. Stand alone systems work this way and they are great.

MAF systems were introduced due to emissions and the fact that it helps to save fuel by being more precise...but for making safe power they are pretty useless thus why stand alone systems rarely ( if ever ) use MAF sensors.

The big issue here is just his tune, nothing more.

jmb614

Do you think it's just a matter of changing the pulse-width of the injectors?

urbamworm

I understand what you are saying but a standalone computer has to be retuned for different weather if being tuned open loop and only referencing a preprogrammed fuel table with no adjustment on the fly ever possible. I couldn't imagine an oem ecu would work like this without a maf since it has to run in a wide variety of climates and elevations. I understand how it could reference boost with the map sensor to adjust fueling based on load, rpm and the present manifold pressure but how does it account for different air density to not run rich or lean? I guess some how they take intake air temp readings and go by cool air is dense and hot air isn't but that still leaves the elevation part. Do you know how they would account for that with the present sensors?

chiromikey

i think it's more natural for the car to lean out because you can't reproduce ram air...(or even produce the available amount of air) on the dyno that our cars get on the street.

jmb614

That's what I was thinking as well, that it would need to be re-tuned dependent upon climate conditions. If that is the case, it would be nice to have several files available to choose from and flash the car with the appropriate file depending upon conditions.

chiromikey

i don't either and what i meant was, is it a canned tune or a custom tune on the dyno (or doubtful, on the street)...?