Injector latency changes

***Majin*** · 04-09-2007, 08:55 PM

once you have scaled the injectors, tuned the timing, boost, MAF voltages and everything else for proper air fuel ratios, in which way will they be effected by changing the injector latencies?

sti752 · 04-10-2007, 09:32 AM

It will throw it all off. You should tune your latencies and injector scalar on a stock MAF to get any kind of good results. If your latency is too great for your injector then you will run richer than intended and vice versa for the opposite case.

sti752 · 04-10-2007, 09:33 AM

Oh, and Cobb has some pretty good data for most injectors (scalar and latency).

***Majin*** · 04-10-2007, 09:34 AM

thanks sti752 - i have been on their forums today and found a ton of good stuff...

WolfPlayer · 04-10-2007, 10:24 AM

Quote:

Originally Posted by sti752

It will throw it all off. You should tune your latencies and injector scalar on a stock MAF to get any kind of good results. If your latency is too great for your injector then you will run richer than intended and vice versa for the opposite case.

Ding ding. Bingo

t

***Majin*** · 04-10-2007, 10:35 AM

i have the stock latency values for the JECS 720 - but scaled them correctly (3731)... i have to get the latency values in now...

then i'll have to re-do everything else, correct Wolfie?

WolfPlayer · 04-10-2007, 11:17 AM

Quote:

Originally Posted by Majin

i have the stock latency values for the JECS 720 - but scaled them correctly (3731)... i have to get the latency values in now...

then i'll have to re-do everything else, correct Wolfie?

Majin,

Use what Cobb published for the Latency and Scalar for the JECS injectors. Daemon and myself helped Cobb with regard to those values. They work. Once you input those values, then move on and tune your MAF curve. Long story short, you want the AFR on the wideband to match the AFR that is in your Primary Fueling. This will require that you tweak your MAF curve in order to make that happen.

t

***Majin*** · 04-10-2007, 11:22 AM

Wolf,

i have that info with me now, and will exactly do that. you are very helpful (as usual).

i will keep you posted [with some logs].

daemon · 04-11-2007, 06:20 AM

Just as an on-topic, off-topic post for those wondering how/why changing latencies effects AFR...

The latency basically says how soon the injector can start to spray after the ECU tells it to. So if you tell the ECU the injectors are slower (by increasing the latency value), the ECU will say to itself, "self, my injectors take a little while to turn on, so I better turn them on before I actually need them to". So what happens if the injectors are actually faster than you tell the ECU they are? The ECU still turns them on earlier, but they actually start injecting fuel sooner too (because they are faster at turning on, e.g. lower latency). Since they are on earlier then expected, more fuel is sprayed than expected. Therefore you run richer.

***Majin*** · 04-11-2007, 06:22 AM

thank you daemon - that is pretty clear...

***Majin*** · 04-11-2007, 06:27 AM

it seems that the latency changes (and exact injector scale you and Wolf helped Cobb with) work perfectly... i think, however, that i may have fouled out my plugs.

i ran the car with the incorrect latency and injector scale for about 4 days, and was throwing misfire codes in all cylinders (mainly 1, 3, and 4).

now that the car is running smoother, this morning i threw the same misfire codes on my way to work, so i cleared them out and got to work with no problem.

i think a new set of plugs are in order now, and that i have to mess with the WGDCs now since i have the Perrin EBCS.

Wolf has a nice post in here (among others) that will hopefully get my boost to come down from 25+ PSI to 19 PSI.

R4ND0M_AX3 · 04-11-2007, 12:36 PM

I'm going through this right now with PE850's I have everything pretty close.

I started with Cobbs latest set of numbers. That got me in the ballpark. I've been doing about 1-1/2 hours of datalogging per day for the last week. Then about 2-4 hours of excel manipulation. (2007 has some nice new functions that I'm using like AVERAGIFS and more advanced conditional formating for gradiated cell coloring)
I was gonna start a new thread illustrating what I've had to go through to get this far.

Back to the topic,
I'm thinking about disabling the alternator for a few minutes (remove belt) to get some better data near the 12V area. Is this a bad idea?

***Majin*** · 04-14-2007, 03:06 PM

update: after entering in the values for the latencies and injector scare for the JECS 720s, the car runs much better, i have successfully calibrated the intake (with lots of help from jays05 - thanks Jay!

) as well.

i only have one issue that really bothers me now - when i start the car up and it's cold (roughly 50° F lately), the car idles low and shakes until it warms up a bit. before it's warmed up, it throws misfire codes (my cylinders 1 & 3 typically throw 2 misfire codes these times).

any guess as to what i have done wrong (or haven't totally done right)?

R4ND0M_AX3 · 04-14-2007, 04:17 PM

Have you watched the trims during warmup to see if they are ok?

***Majin*** · 04-14-2007, 04:40 PM

R4ND0M - i just got back inside from checking them out with the wide band, and the car was in the 11s!

i thinned them out again so they were around 14.7:1 again and it sounds much better... i am currently waiting for the car to get cold again, and will be re-checking them.

there is a voltage though that is not really touched until i am on the gas, so i should leave that bigger jump alone, correct?

cliff notes: you were right.

04-09-2007, 08:55 PM	#1
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,790 Join Date: Apr 2004 Trader Rating: (2)	Injector latency changes once you have scaled the injectors, tuned the timing, boost, MAF voltages and everything else for proper air fuel ratios, in which way will they be effected by changing the injector latencies? This ad is not endorsed by this member. Please register or login to hide this ad.

04-14-2007, 04:40 PM	#15
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,790 Join Date: Apr 2004 Trader Rating: (2)	R4ND0M - i just got back inside from checking them out with the wide band, and the car was in the 11s! i thinned them out again so they were around 14.7:1 again and it sounds much better... i am currently waiting for the car to get cold again, and will be re-checking them. there is a voltage though that is not really touched until i am on the gas, so i should leave that bigger jump alone, correct? cliff notes: you were right. This ad is not endorsed by this member. Please register or login to hide this ad.

04-10-2007, 09:32 AM	#2
sti752 Senior STI Driver Car: 05 Subaru WRX STi Fav Mod: Exige Location: Starkvegas, MS Posts: 379 Join Date: Jul 2005 Trader Rating: (6)	It will throw it all off. You should tune your latencies and injector scalar on a stock MAF to get any kind of good results. If your latency is too great for your injector then you will run richer than intended and vice versa for the opposite case.

04-10-2007, 09:33 AM	#3
sti752 Senior STI Driver Car: 05 Subaru WRX STi Fav Mod: Exige Location: Starkvegas, MS Posts: 379 Join Date: Jul 2005 Trader Rating: (6)	Oh, and Cobb has some pretty good data for most injectors (scalar and latency).

04-10-2007, 09:34 AM	#4
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,790 Join Date: Apr 2004 Trader Rating: (2)	thanks sti752 - i have been on their forums today and found a ton of good stuff...

04-10-2007, 10:35 AM	#6
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,790 Join Date: Apr 2004 Trader Rating: (2)	i have the stock latency values for the JECS 720 - but scaled them correctly (3731)... i have to get the latency values in now... then i'll have to re-do everything else, correct Wolfie?

04-10-2007, 11:22 AM	#8
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,790 Join Date: Apr 2004 Trader Rating: (2)	Wolf, i have that info with me now, and will exactly do that. you are very helpful (as usual). i will keep you posted [with some logs].

04-11-2007, 06:20 AM	#9
daemon Professional STI Racer Car: 2004 STi Location: Florida Posts: 827 Join Date: Feb 2004 Trader Rating: (0)	Just as an on-topic, off-topic post for those wondering how/why changing latencies effects AFR... The latency basically says how soon the injector can start to spray after the ECU tells it to. So if you tell the ECU the injectors are slower (by increasing the latency value), the ECU will say to itself, "self, my injectors take a little while to turn on, so I better turn them on before I actually need them to". So what happens if the injectors are actually faster than you tell the ECU they are? The ECU still turns them on earlier, but they actually start injecting fuel sooner too (because they are faster at turning on, e.g. lower latency). Since they are on earlier then expected, more fuel is sprayed than expected. Therefore you run richer.

04-11-2007, 06:22 AM	#10
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,790 Join Date: Apr 2004 Trader Rating: (2)	thank you daemon - that is pretty clear...

04-11-2007, 06:27 AM	#11
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,790 Join Date: Apr 2004 Trader Rating: (2)	it seems that the latency changes (and exact injector scale you and Wolf helped Cobb with) work perfectly... i think, however, that i may have fouled out my plugs. i ran the car with the incorrect latency and injector scale for about 4 days, and was throwing misfire codes in all cylinders (mainly 1, 3, and 4). now that the car is running smoother, this morning i threw the same misfire codes on my way to work, so i cleared them out and got to work with no problem. i think a new set of plugs are in order now, and that i have to mess with the WGDCs now since i have the Perrin EBCS. Wolf has a nice post in here (among others) that will hopefully get my boost to come down from 25+ PSI to 19 PSI.

04-11-2007, 12:36 PM	#12
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	I'm going through this right now with PE850's I have everything pretty close. I started with Cobbs latest set of numbers. That got me in the ballpark. I've been doing about 1-1/2 hours of datalogging per day for the last week. Then about 2-4 hours of excel manipulation. (2007 has some nice new functions that I'm using like AVERAGIFS and more advanced conditional formating for gradiated cell coloring) I was gonna start a new thread illustrating what I've had to go through to get this far. Back to the topic, I'm thinking about disabling the alternator for a few minutes (remove belt) to get some better data near the 12V area. Is this a bad idea?

04-14-2007, 03:06 PM	#13
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,790 Join Date: Apr 2004 Trader Rating: (2)	update: after entering in the values for the latencies and injector scare for the JECS 720s, the car runs much better, i have successfully calibrated the intake (with lots of help from jays05 - thanks Jay! ) as well. i only have one issue that really bothers me now - when i start the car up and it's cold (roughly 50° F lately), the car idles low and shakes until it warms up a bit. before it's warmed up, it throws misfire codes (my cylinders 1 & 3 typically throw 2 misfire codes these times). any guess as to what i have done wrong (or haven't totally done right)?

04-14-2007, 04:17 PM	#14
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	Have you watched the trims during warmup to see if they are ok?