Injector scaling and latecy for different injectors. - Page 2

Ludikraut · Jun 30, 2006, 08:52 AM

Quote:

Originally Posted by DCSilvrEvo

Sorry but whats STFT?

STFT = Short Term Fuel Trim
LTFT = Long Term Fuel Trim

l8r)

evo 8 ya · Jun 30, 2006, 09:07 AM

Quote:

Originally Posted by DCSilvrEvo

Im havin a little problem of crusing @ 70mph my A/F's will drop to 11s sometimes 10's when I give it like 30% fuel. I have 780s and fuel scaled to 585 i guess I need to go up. Only prob is the car idles rough. 18-19 on A/F. Do I need to try setting the voltage up or down?

edit....... can't belive I said that

razorlab · Jun 30, 2006, 01:56 PM

Quote:

Originally Posted by evo 8 ya

damn I would just get a E-Flash from Al to be safe.

Al unfortunatly does not change the injector compensation or scaling.

razorlab · Jun 30, 2006, 01:57 PM

Quote:

Originally Posted by DCSilvrEvo

Sorry but whats STFT?

Im havin a little problem of crusing @ 70mph my A/F's will drop to 11s sometimes 10's when I give it like 30% fuel. I have 780s and fuel scaled to 585 i guess I need to go up. Only prob is the car idles rough. 18-19 on A/F. Do I need to try setting the voltage up or down?

585 seems a little low for 780s.

gunzo · Jul 1, 2006, 07:18 AM

Quote:

Im havin a little problem of crusing @ 70mph my A/F's will drop to 11s sometimes 10's when I give it like 30% fuel. I have 780s and fuel scaled to 585 i guess I need to go up. Only prob is the car idles rough. 18-19 on A/F. Do I need to try setting the voltage up or down?

Mind if you post your map ?? suspect your fuel tables may be messed up at or around low load regions ..

dryad001 · Jul 1, 2006, 10:18 AM

Quote:

Originally Posted by DCSilvrEvo

Sorry but whats STFT?

Im havin a little problem of crusing @ 70mph my A/F's will drop to 11s sometimes 10's when I give it like 30% fuel. I have 780s and fuel scaled to 585 i guess I need to go up. Only prob is the car idles rough. 18-19 on A/F. Do I need to try setting the voltage up or down?

I've been having the same problems. The cause of the rough idle is the front 02 sensor is most likely bad.

MalibuJack · Jul 1, 2006, 01:53 PM

Quote:

Originally Posted by DCSilvrEvo

Sorry but whats STFT?

Im havin a little problem of crusing @ 70mph my A/F's will drop to 11s sometimes 10's when I give it like 30% fuel. I have 780s and fuel scaled to 585 i guess I need to go up. Only prob is the car idles rough. 18-19 on A/F. Do I need to try setting the voltage up or down?

I'm not sure of the mods on your car, but you will have to adjust the injector scaling a bit more.. Probably have to set it closer to 660-700 or so..

There will be some other adjustments you can make too.. but basically when you drop out of closed loop fueling, the ECU maps are still running rich..

Once you have the injectors scaled, look at your fuel trims, if their more than +25% you can adjust the scaling a little more until your closer to +/- 10%

Then you have to watch your fuel trims at idle, and cruising.. This is where your Injector Latency Voltage comes in.. If the trims at cruise are okay, then you adjust the lower voltage readings (below 13 volts) to increase the amount of fuel at idle slightly

Now, once your trims are within +/- 10% you can then make fine adjustments, but your open loop maps will be "Fairly close" but you have to watch it carefully not to go too lean, but you now have enough adjustment room to tune the car specific to its needs.. But at this point, when you transition to open loop, it should initially tip in a bit leaner, then stabilize a bit richer, but then the open loop maps get tuned.. Again, be careful since you don't want to let it go very lean, or be too lean at higher boost.. If it is, add fuel to the map, or adjust your injector scaling slightly (make the number a little lower) until its somewhere you want to work.

At this point, you should have STFT's that hover around 0%-5%, and LTFT's that are within 10%... You can adjust your idle speed slightly, and timing at idle to help the quality of your idle after you get to this point.

The result will be a drivable car, with a roughly stock-ish fuel table.. Then you go tune the car like you normally would...

STFT = Short Term Fuel trims..
LTFT = Long Term Fuel trim..

Any additional closed loop adjustment would be in the fuel table, in closed loop fuel control, when you alter those settings in the fuel table, your just altering what would happen if your car had to run in open loop at idle and part throttle.. Obviously not useful unless you have a problem, but once you have those numbers close, the fuel trims are now closer to optimum and don't adjust as much.. Its not a huge deal if its not perfect, it just makes cold starting and driving the car (before the O2 sensor warms up) a little easier and less prone to poor drivability in those conditions, don't forget to check it a few times through the year as climate changes so you can get the best drivability.

chmodlf · Jul 1, 2006, 02:22 PM

^ Nice post.

justchil · Jul 3, 2006, 01:27 PM

I'm having a hard time understand what you mean by getting your STFT and LTFT's within X%.

Is this the reading 99.84% and 149.76%? I've got 780's scaled to 720(713). I've yet to get a 100% smooth idle although it does idle pretty well about 75% of the time. The other 25% of the time it either gets real rich or real lean and barley stays alive around 500rpm.

Also my ISCV and idle stepper tables have been altered some per recommendation of noogles.

justchil · Jul 3, 2006, 01:29 PM

Also I have not ruled out my front o2 sensor being on the fritz although the car did idle perfect with my custom dynoflash (didnt use scaling). I do get the P0171 fairly often.

razorlab · Jul 4, 2006, 01:08 PM

Quote:

Originally Posted by justchil

I'm having a hard time understand what you mean by getting your STFT and LTFT's within X%.

You have to log the STFT and LTFT via OBD2 with a pocketlogger or such.

The STFT should fall within -/+ 5 and the LTFT should be close as well.

STFT is what the ECU is doing right now to get as close to stoich (14.7:1) as possible, adding or subtracting fuel over the base fuel map to reach that target.

LTFT is a stored value that the ECU has learned to do to reach that target. It takes longer to show changes.

You are probably getting the P0171 code because you are maxed out on the STFT either way.

justchil · Jul 8, 2006, 03:21 PM

I think it's on the lean side :\

I'm going to try bumping the scale down like 5% and see what happens. Right now I'm running Precision Injectors 780cc.. I set the value to 720 which shows 713.

gunzo · Jul 8, 2006, 08:03 PM

when you change the scaling for injector.. its better to rescale the latency too..

take a look at the scaling for the stock jdm evo and you will notice the difference between the usdm and jdm injectors though I strongly believe its the same injectors we are using.. and even the latency is off..

justchil · Jul 9, 2006, 01:16 AM

Just for kicks 780cc injectors would be roughly 39.28% larger than stock. I keep re-reading all this stuff.. the more I'm understand it

So what do I need to get to monitor STFT? Maybe evoscan will do this eventually but I've got less than a week to have her ready for the dyno

Quote:

Originally Posted by MalibuJack

Then you have to watch your fuel trims at idle, and cruising.. This is where your Injector Latency Voltage comes in.. If the trims at cruise are okay, then you adjust the lower voltage readings (below 13 volts) to increase the amount of fuel at idle slightly

To increase the amount of fuel at idle slightly you would increase or decrease the latency? I would assume the latency would be decreased below 14 volts in this case.

MalibuJack · Jul 9, 2006, 08:48 AM

Yes, around 13 volts.. below 12v if you go below 1000rpm..

I think if you increase the value, you compensate MORE for latency so it adds more fuel essentially.. I may have it backwards since its been a few weeks since I tried this.