fuel calibration question

FreshDA9 · Post by **FreshDA9** » Thu Feb 19, 2009 10:42 pm

well im still learning tuning and my mentor asked me a question i couldn't answer he asked what do the numbers in the fuel tables represent i know the rpm and mbar but he is asking what do the "704, 450, etc". does it mean how many times the injector open or something totaly diffent? we are wanting to know what this number means i have searched all over and couldnt find my answer or i over looked it.

he also asked after tuning a vehicle when placing it back into closed loop does the narrowband sensor go off what you set in the cells or does it go back to stock setting of 14.7 and if it does how does the ecu tell it to go into open loop for your desired a/f. he has tuned Ford and LSX cars for about 10 years and he is wanting to know all of this and so do i. thank you for taking the time to read this.

Post by **Spunkster** » Fri Feb 20, 2009 10:12 am

The numbers have no specific meaning, they are just numbers and you cannot convert them into a meaningful value.

If you look at the closed loop tab, you can see how the settings work. You have to set the target voltage, at what map value it goes in and out of closed loop and set the min and max trims it will go to.

FreshDA9 · Post by **FreshDA9** » Fri Feb 20, 2009 5:54 pm

thank you!

Jaker · Post by **Jaker** » Wed Feb 25, 2009 11:19 am

They have no definitive value, but is it not correct that a cell value of 840 would inject pretty close to (accounting for opening and closing time) double the fuel of a 420 value? Right?

Post by **Spunkster** » Wed Feb 25, 2009 11:56 am

In some cases it might, in others it may not. It all depends on the fuel pressure, the injector dead time, the type of injector used...etc.

laziebun · Post by **laziebun** » Wed Feb 25, 2009 12:02 pm

I read somwhere that the number ment how many milla sec it stayed open.

FreshDA9 · Post by **FreshDA9** » Wed Feb 25, 2009 12:09 pm

i too thought i had read somewhere about milli sec. on another forum they said this. "The actual hex value of that entry in the .bin, converted to decimal, and multiplied by 4." but i know Smanager isnt a Bin file so i dont know if this would be the same but i guess similar.

Post by **Hondata** » Thu Feb 26, 2009 8:50 am

It is not an opening time in milliseconds. It is a linear fuel value which later gets converted to an opening time.

lowrider · Post by **lowrider** » Fri Feb 27, 2009 3:02 am

Hondata wrote:It is not an opening time in milliseconds. It is a linear fuel value which later gets converted to an opening time.

Is the mathematical formula available to calculate the actual opening times?

Because I find it really hard to know the correct duty cycle for the injectors by looking at the map values.
Even on the stock ITR B18 calibration included in the SManager software, there are duty cycles of over 100% and it just seems a little odd...

And from what I've experienced these fuel values have different meanings between a Crome and a S300 map.

Post by **Hondata** » Fri Feb 27, 2009 8:00 am

The simplified calculation is:
injector duration = fuel value + nitrous 1 fuel + nitrous 2 fuel + nitrous 3 fuel + launch control fuel + gear compensation fuel + overheating fuel + air pressure compensation + throttle tip in fuel + post start enrichment * air temperature compensation * water temperature compensation * closed loop compensation * injector size * overall fuel trim + injector minimum opening time
Yes, the stock ECU will drive the injectors to 100% at redline.