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Old 08-16-2006, 08:07 PM   #1
xolosis
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Default Injectors - Short Term and Long Term Fuel Trims

The UTEC guys have answered this questions for scaling Deatchwerks 740cc injectors with UTEC. Now I can edit the stock ECU I wish scale the injectors there.

The car is a 2004 Forester XT 2.5L and apparently has 550cc injectors. The stock ECU Injector Scaling map is scaled to 503.93 (shouldn't this be nearer to 550?). After the injectors go in can I simply punch in 740 to get me close? Or is it more like 693.93 (550-503.93=46.07, hence 740-46.07=693.93).

Also when logging in EcuExplorer is what parameters represent ST and LT fuel trims. Is it ST=Air Fuel Learning and LT= Air Fuel Correction. As you know I'll need to ODB-II log this to close to 0 as possible.

Cheers!
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Old 08-17-2006, 12:52 AM   #2
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Download the newest version of enginuity with the latest def file. This has been fixed so that it represents the actual injector size more closely. From what i read the conversion that was used was a little off. (ie stock wrx is 440cc injectors, but the rom said 380).
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Old 08-17-2006, 09:42 AM   #3
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Already have the latest version 0.3.2 beta and definitions file UPDATE ver 1.73 08-07-06 for Enginuity 0.3.1b. Injector Flow Scaling still reads 503.93 and have you notice if you look at a 06WRX/STi or 06XT the injectors are scaled to 550.67 within Enginuity.

Strange...
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Old 08-17-2006, 10:55 AM   #4
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The conversion is just to get you somewhat close. You still need to tune from there. There is no conversion that will exactly match the advertised flow rates for all OEM and non-OEM injectors. The formula was recently changed to get it closer, but this does not affect the underlying value on the ecu, just helps the user better visualize what's going on. The conversion formula could be made to read anything - 10000000000 cc and it would not affect the value stored on the ecu.
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Old 08-17-2006, 07:30 PM   #5
xolosis
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So what you're saying is 503.93 is interpreted by the ECU as 550 at the moment? So to get me close with scaling the 740cc I should input 740 and monitor my ST LT fuel trims.

Can some confirm that which the parameters are the fuel trim values.

ST=Air Fuel Correction


LT=Air Fuel Learning
Or the other way around?

Cheers!

EDIT: Corrected ST LT above.

Last edited by xolosis; 08-17-2006 at 11:38 PM.
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Old 08-17-2006, 07:55 PM   #6
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ST=A/F correction LT=A/F learning

Yes, punch in 740 and go from there. Nothing has changed on the ecu. The conversion formula that displays what you see has changed and hopefully will get people closer to where they need to be.

So, let's say someone has already scaled their injectors before the update. After the update, they would see the value displayed change but the underlying value on the ecu would be exactly the same, so they wouldn't need to touch the value at all.
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Old 08-17-2006, 11:38 PM   #7
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Clear as mud. Many thanks!
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Old 08-18-2006, 10:06 AM   #8
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Ok, maybe i can help.
The ECU has a value stored for the injector flow rate. That is converted to a user value via an inverse equation; something like 2450000/ECU=display. EcuTek picked a number that was semi-close years ago. Cobb then used the same number in ST/PT to make things easier for tuners to migrate. The open stuff started using the same number, but it was later decided to change it to a better number, ~2700000, that allows one to put in the actual flow rate and be very close. The constant number is completely arbitrary, and only exists for the user's convenience. That 2700000 number looks to have some basis in terms of figuring out fuel flow rates, though. It also works well with known flow rate injectors.
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Old 08-18-2006, 10:35 AM   #9
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The OEM injectors on a 2004 FXT are 500cc side feed. The OEM injectors on a 2006 FXT are 550cc top feed.

I'd start with 740 as the injector scale. Turn off UTEC fueling and drive around for a few days. Log A/F Learning #1. It's value is a percentage. If it's positive, decrease the injector scale by that percentage. If it's negative increase injector scale by that percentage. Repeat.

Let us know here what scale value you settle on.

Last edited by Jon [in CT]; 11-21-2006 at 04:50 PM.
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Old 08-19-2006, 04:19 AM   #10
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gregsachs thanks for that technical info and its clear.

Jon I've been told over many years that 2004XT's are 550cc side feeds which look to be incorrect. After viewing my ECU Rom and saw 503.93 then that comfirmed my suspicious.

Also does UTEC control fuel even if you have the map switch on 0-Stock mode? Do I have to go into the parameters and disable things?

Anyway I'll do as you say and let you know what I end up with. Thanks!
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Old 09-01-2006, 02:26 PM   #11
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Quote:
Originally Posted by xolosis View Post
Also does UTEC control fuel even if you have the map switch on 0-Stock mode? Do I have to go into the parameters and disable things?
no it does not, and no you will not have to go into the parameters.
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Old 09-04-2006, 08:58 AM   #12
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My stock STI injectors were ~500cc.

http://www.bescaredracing.com/sti/fu...r/DSC05985.JPG
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Old 09-09-2006, 11:52 PM   #13
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Quote:
Originally Posted by Jon [in CT] View Post
I'd start with 740 as the injector scale. Turn off UTEC fueling and drive around for a few days. Log A/F Learning #1. It's value is a percentage. If it's positive, increase the injector scale by that percentage. If it's negative decrease injector scale by that percentage. Repeat.

Let us know here what scale value you settle on.
Further to this will I need to do anything with A/F Correction and Injector Latency? I believe I won't need to ajust Latency since the DeatschWerks are modified OEM STi units. However if I were running Sards the deadtimes/latency will need to be rescaled!
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Old 11-20-2006, 04:21 PM   #14
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Quote:
Originally Posted by WolfPlayer View Post
My stock STI injectors were ~500cc.

http://www.bescaredracing.com/sti/fu...r/DSC05985.JPG

I'm confused. Do the 2005 flow less than the 2004 US STi injectors?

Look at this link from MZM (the flow test was done by RC eng. at 43psi)
http://mzmperformance.com/Merchant2/...ecs550flow.jpg
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Old 11-20-2006, 05:03 PM   #15
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Quote:
Originally Posted by Jon [in CT] View Post
I'd start with 740 as the injector scale. Turn off UTEC fueling and drive around for a few days. Log A/F Learning #1. It's value is a percentage. If it's positive, increase the injector scale by that percentage. If it's negative decrease injector scale by that percentage. Repeat.
That's totally backwards, dude. If its positive, the car is adding extra fuel to get the closed-loop AFR to lambda=1.000 You have to decrease the injector flow scaling by the same percentage to trick the ECU into adding that extra fuel right off the bat when the fuel trims are still at zero.

If the flow scaling is set to 740 and your fuel trim at idle says +13%, change your flow scaling to 740/1.13

. . . and I've never had to repeat. You don't have to get it exactly right, that's what A/F learning is for. Its better to have it set too low so it starts out rich and leans itself out instead of the other way around.
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Old 11-21-2006, 07:15 AM   #16
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well the injector scale always had head room from
the factory. this way if you went static you still had
40~50cc of fuel left.

Ecutek, showed pinks to flow 500, when we know they flow ~540 to 550.
sti yellow side feed to flow 498, when we know they flow ~540 to 550.
wrx dk blu top feed to flow 500, when we know they flow ~540 to 550.

so you can see the trend and summize.

back to st / lt fuel trim.
maf scale table in ecutek, to check st
activate the table trace the cursor, double check
with deltadash for the percentage and adjust.
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Old 11-21-2006, 07:34 AM   #17
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Quote:
Originally Posted by Tea cups View Post
ST=A/F correction LT=A/F learning

Yes, punch in 740 and go from there. Nothing has changed on the ecu. The conversion formula that displays what you see has changed and hopefully will get people closer to where they need to be.

So, let's say someone has already scaled their injectors before the update. After the update, they would see the value displayed change but the underlying value on the ecu would be exactly the same, so they wouldn't need to touch the value at all.
As far as LT goes,its the rear O2 sensor that affects this right?How important is it to use the rear O2?And what other factors affect LT?
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Old 11-21-2006, 09:01 AM   #18
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Originally Posted by dumdum View Post
As far as LT goes,its the rear O2 sensor that affects this right?How important is it to use the rear O2?And what other factors affect LT?
the rear o2 is only used to adjust long term fuel learning #3.

it is not important to use the rear o2. this trim should always be very small if your front o2 and maf sensors are in working order.

LT is populated via the ST trims taken as an average.
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Old 11-21-2006, 01:41 PM   #19
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So can you just remove the whole thing,CEL fix through Enginuity and be done with it?
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Old 11-21-2006, 03:34 PM   #20
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yes, that's what i've done.
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Old 11-21-2006, 04:50 PM   #21
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Quote:
Originally Posted by w_o_t_boy View Post
That's totally backwards, dude. If its positive, the car is adding extra fuel to get the closed-loop AFR to lambda=1.000 You have to decrease the injector flow scaling by the same percentage to trick the ECU into adding that extra fuel right off the bat when the fuel trims are still at zero.

If the flow scaling is set to 740 and your fuel trim at idle says +13%, change your flow scaling to 740/1.13

. . . and I've never had to repeat. You don't have to get it exactly right, that's what A/F learning is for. Its better to have it set too low so it starts out rich and leans itself out instead of the other way around.
You're right, so I'll correct my original post to avoid future confusion.
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Old 11-21-2006, 05:17 PM   #22
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Quote:
Originally Posted by jaxscuby View Post
well the injector scale always had head room from
the factory. this way if you went static you still had
40~50cc of fuel left.

Ecutek, showed pinks to flow 500, when we know they flow ~540 to 550.
sti yellow side feed to flow 498, when we know they flow ~540 to 550.
wrx dk blu top feed to flow 500, when we know they flow ~540 to 550.

so you can see the trend and summize.

back to st / lt fuel trim.
maf scale table in ecutek, to check st
activate the table trace the cursor, double check
with deltadash for the percentage and adjust.
The injector scale from the factory tells the ECU how long it must inject fuel to match one gram of air intake to achieve a stoichiometric A/F ratio. If you know your fuel's specific density and stoichiometric A/F ratio, then you can convert that time scale factor to a cc/min flow. It appears to me that the factory engineers used reasonable estimates for those two unknowns. I have no idea how EcuTeK arrived at the conversion factor they use for the injector scale.

There's no reason to change MAF scaling when the only physical change is new injectors.
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Old 11-22-2006, 01:36 AM   #23
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So can you just remove the whole thing,CEL fix through Enginuity and be done with it?
Elaborate
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Old 11-22-2006, 10:51 AM   #24
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Quote:
Originally Posted by Smoby View Post
Elaborate
With the ECU editing software you can disable the CEL's.
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Old 11-22-2006, 02:10 PM   #25
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Quote:
Originally Posted by jaxscuby View Post
sti yellow side feed to flow 498, when we know they flow ~540 to 550.
This is absolutely not true. I worked with Christian from Cobb to nail down what the stock STI yellow side-feed injectors flow. They do not flow 540-550 cc's. This is now easily explainable and I reported on it awhile ago.

http://forums.nasioc.com/forums/show...0&postcount=72

In the ECU the yellow side-feed injectors are rated at ~500cc. When you view the blue top-feeds they are ~550cc.

t
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