Tuning Air Fuel Ratios

[gixslayer]

Ok so here's the debate!

Some people think that you should richen it up based on the air tempurature being low (high density) and some people think you should richen it up based on air tempurature being high (high tempurature).

So what does everyone think?

[KryptoSol]

A decent fuel management should allow you to tune 'fuel multipliers' for optimal fuels regardless of high/low temp, that way you are on target at all temps.


If your fuel management dosn't do that then just fudge it a lil fatter for cooler temps and seasonal changes.

[KryptoSol]

yes rrussell, IATs was the accronym i was looking for. By the way, what are you working on now-a-days?

[KryptoSol]

Wow, sounds like you have your hands full. I see why the civic had to go.

Well last friday i took it out and just kind of dialed in the 2 step. It was actually my first time doing 2nd gear burn outs and at first it was nerve racking but boy it sure heats up them DRs quick! nice and sticky. I'll be at high school drags this friday, it'll be 1st time ET since new tune and alky injection so i'm kind of excited to see if all the hard work pays off.

You going?

[Tokudai]

Cold air will be denser then hot air for the same given volume.

This is why all systems have IAT sensors to measure the air temperature so the ecu can add or take away fuel at the injectors. Based on the "ideal gas law".

The hotter the air the less time time the injectors will be open to get to the targeted A/F ratio. The colder the air temperature longer the injectors will be open to get to the target A/F ratio.



^Perfect explanation - I think of the MAP/MAF (density) signal as the parameters used for calculating the "base map", with IAT (and sometimes TPS and coolant temp depending on the ECU) used as trim factors to modify/adjust the base map.

[gixslayer]

Ok, the whole point of this post, was to prove that people on an internet forum CAN agree on something...Now if you all could only get the whole meet BBQ thing figured out...

[Kolat]

btw josh I was thinking, the problem may be that when your using the 750 map the bike changes the fuel ratios differently according to the temp than with a 600 map since the 750 will consume a larger volume of air.

T

[96gsx]

Ok so here's the debate!

Some people think that you should richen it up based on the air tempurature being low (high density) and some people think you should richen it up based on air tempurature being high (high tempurature).

So what does everyone think?


I would have to agree with both.??leaning the a/f's out with cooler air temps to provide higher gains (Assuming thermal efficiency of the turbo and intercooler where within their limits).??Cooler combustion temps always allow for higher timing and/or lower A/F's minpulation.??Higher intake/coolant temps do cause factory ecu to retard timing.??Same thing goes for having too cold of an intake/coolant temperatures.??In fact most EFI systems richen fuel up considerably as an anti-detonation precaution. Its a good practice if you have nothing else...??

[KryptoSol]

It all depends you know... i'm assuming that its for your bike, which i know jack about bikes, but its all gonna depend on the fuel mangement.

Comming from a Honda EFI "hacker" (or whatever you want to call it) background, earlier versions didn't have IAT and ECT corrections so we just either tuned for the season or tuned a little fat to deal with the cooler temps.

[gixslayer]

btw josh I was thinking, the problem may be that when your using the 750 map the bike changes the fuel ratios differently according to the temp than with a 600 map since the 750 will consume a larger volume of air.

T


hmm hard saying. the power commander only controls 4 out of 8 injectors.