Hondata

The reason im asking is becuase i tuned my 4b back in Feb to a steady 12.0-12.5 in boost. and i dynoed on sat and saw my a/f n boost went to like high 9's. So the weather made alot of change on my mas. is the only way around this to make maps for every season ?

anyone know the answer to this ?

29 VIEWS AND NO REPLIES? THANKS HONDATA

Perhaps if your question were more coherent, you'd get more answers. What do you mean by "i dynoed on sat and saw my a/f n boost went to like high 9's"? Are you complaining that your air-fuel ratio is off, that your boost dropped, or both? What kind of setup do you have?

The only effect weather has on air/fuel ratio is to alter the density of the air. In a speed-density system like Honda ECUs use, this basically means that the value read at the MAP sensor will change slightly, to which the ECU will respond by altering the amount of fuel. Warmer air is less dense, which will cause the MAP sensor reading to be slightly lower at a given RPM & throttle position, which will cause the ECU to inject slightly less fuel, thus maintaining the same A/F ratio it would have with cooler air. The intake air temperature sensor in the manifold and the atmospheric pressure sensor located in the ECU will also help make slight corrections in fuel delivery.

The bottom line is that changes in weather alone will not cause wild fluctuations in air-fuel ratio, and will not cause a 3 psi drop in boost (if in fact this is what you're complaining about). You will lose a little bit of power when the temperature is higher, because the air is sparser, but Hondata claims this value is roughly 1% per 5 deg. F increase in temperature, which is not terribly significant.

So no, you don't have to re-tune every season, provided that you don't make changes that would need additional tuning, and provided that it was tuned correctly to begin with.

Plenty of things can happen to a turbo'd engine in 3 months that would cause changes to air-fuel ratio and boost levels, besides weather. I would suggest looking at other components in your system.

nothing else has changed, the a/f we tuned was 12.2-12.5 in boost in Feb and now in June it is 9.8-10.0 in boost. the only thing that changed was the weather, i tuned on the same dyno, same map, same components, same compression and leak down reults, same psi of boost. ?
thats th eonly thing i can pin it on .

would open loop / closed loop make a difference in the case?

OK, now your problem is clearer - you're saying that your air-fuel ratio went from 12.x to 10.x as the weather got warmer, which means you're running significantly richer than you were before.

If you are running your ECU in closed loop operation (which you should be, unless you specifically turned it off) then the ECU is constantly monitoring your part throttle air-fuel ratio and adjusting the short term fuel trim as necessary to keep the mixture at a perfect 14.7:1. Over time, it adjusts the long term fuel trim (LTFT) to compensate for trends in the short term fuel trim.

So, for example, if your part throttle maps are tuned way too lean, then your ECU will have to add lots of fuel to bring the mixture to 14.7:1, which will cause your LTFT to be way positive. The LTFT is used even when you're running at WOT, so it can affect your A/F under boost. In extreme cases, the ECU can be adding 20-25% more fuel than your maps show, because of the LTFT. (Or even worse, if your part throttle maps are too rich, then your LTFT will be way lean - which will make things run lean under boost, which is very bad for one's engine.)

This is only one possible explanation for your problem. It's simple to verify - hook up datalogging to your ECU, and read the long term fuel trim while the car is running. If it's a significant positive percentage, then you might have found your problem. You can reset the long term fuel trim by resetting your ECU - pull all the plugs to it (or unhook the battery cables from your battery) and leave it for a few minutes, and it will reset your LTFT. Of course, if your part throttle maps are tuned wrong, it will eventually "learn" its way back to the old value.

thanks , these deff are things i will look into , orig we tuned the out of boost maps to mid 14's and in boost maps to mid to low 12's .
ill check a few more things out,
Thanks for the help