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08-16-2006, 08:07 PM | #1 |
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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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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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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... |
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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08-17-2006, 07:30 PM | #5 |
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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. |
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. |
08-17-2006, 11:38 PM | #7 |
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Clear as mud. Many thanks!
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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. |
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. |
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! |
09-01-2006, 02:26 PM | #11 |
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09-04-2006, 08:58 AM | #12 |
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09-09-2006, 11:52 PM | #13 | |
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Quote:
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11-20-2006, 04:21 PM | #14 | |
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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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11-20-2006, 05:03 PM | #15 | |
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Quote:
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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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. |
11-21-2006, 07:34 AM | #17 | |
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Quote:
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11-21-2006, 09:01 AM | #18 | |
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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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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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11-21-2006, 03:34 PM | #20 |
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yes, that's what i've done.
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11-21-2006, 04:50 PM | #21 | |
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11-21-2006, 05:17 PM | #22 | |
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There's no reason to change MAF scaling when the only physical change is new injectors. |
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11-22-2006, 01:36 AM | #23 |
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11-22-2006, 10:51 AM | #24 |
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11-22-2006, 02:10 PM | #25 | |
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Quote:
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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