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Help: Bank 1 Trims high (120%) at idle when "cold" only

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#1
someone

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Has anyone experience this issue before? I recently built the motor and installed an A10 kit, triple pump fuel system, 1700x injectors, etc. I also replaced both o2 sensors about a month ago when the car was built. I know is not a tune issue because trims are dead on spot while cruising and at WOT. Issue started about  a week ago and only happens at Idle.

 

Symptoms:

1. Only happens in the mornings, before going to work.

2. Bank 1 trims slowly rise to 120% at idle. Bank 2 is ok.

3. If I rev the car a bit, trims settle to close to 100%, but then bank 2 begins to slowly rise to 120% again.

4. I drive the car to work, and by the time I get there everything is perfect. Both bank trims are ok at idle.

 

This repeats every single day. Any ideas what it could be?

 

My best guess are:

1. Bad injector that does not respond well when car is below operating temps

2. Exhaust leak before the o2 sensor

3. Loose o2 sensor

4. Very very bad luck and got a bad sensor from CourtesyNissan =(

 

Any help will be greatly appreciated.



#2
someone

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Video: https://www.amazon.c...uxAST5QvEVD6mLC

#3
Doug@WGP

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I love when people automatically assume it's not a tune issue ;)

Doug Ross
Owner of Weapons Grade Performance
-Northeast/Pacific Northwest Shops where we ONLY work on GT-Rs
-Owner/Builder of the 1st Ever Home Garage GT-R Drivetrain Removal
Cobb Protuner / EcuTek Tuner
-All Wheel Drive Mustang Dyno in House
doug@weaponsgradeperformance.com
Our Online Store
East Coast Location 226 N. Plains Industrial Rd, Wallingford CT 06492 203-668-4765


#4
haul s

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I love when people automatically assume it's not a tune issue ;)


So assuming it is a tune issue, what should OP look at given the symptoms he posted and the stable & correct trims while cruising or WOT once at operating temperature?

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#5
Doug@WGP

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He should look at his injector pulsewidth and final AFR vs target on that bank. If the injector is pulsing at or near the minimum it will operate at, you'll get an idle misfire and it'll trim lean.

Doug Ross
Owner of Weapons Grade Performance
-Northeast/Pacific Northwest Shops where we ONLY work on GT-Rs
-Owner/Builder of the 1st Ever Home Garage GT-R Drivetrain Removal
Cobb Protuner / EcuTek Tuner
-All Wheel Drive Mustang Dyno in House
doug@weaponsgradeperformance.com
Our Online Store
East Coast Location 226 N. Plains Industrial Rd, Wallingford CT 06492 203-668-4765


#6
someone

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I've check pulsewidth of all banks and they are all dead even. Throttle angle on both TB are the same. Again, nothing that would indicate a tune issue since one bank works perfect, the other don't. All compensations tables disabled. All bank-based tables the same.



#7
someone

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I tested different target AF at idle. This is what happened:

 

1. AF target set to 13. Same issue. Car idles perfectly, but bank 1 trims go to 120%, bank 2 remains 100%. Note that the car does meet target AF on both banks, is just that trims get messed.

2. AF target set to 13.5. Car idles well (not as good as when set to 13 a/f). Issue goes away. Bank 1 stays between 100%-105% at idle, so as Bank 2.

3. AF target set to 14. Car begins to idle somewhat unacceptable. Idle bounces constantly. Probably fixable with the ISC tables. I might spend some time here later.

 

I do notice Bank 1 "reacting" slower than Bank 2 at idle. Under throttle both behave the same. Any ideas?


Edited by someone, 02 September 2017 - 03:40 PM.


#8
Doug@WGP

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If idle set at 13.5 and trims on both banks react normally then the issue is likely tune related. You're tuning the car yourself?

Doug Ross
Owner of Weapons Grade Performance
-Northeast/Pacific Northwest Shops where we ONLY work on GT-Rs
-Owner/Builder of the 1st Ever Home Garage GT-R Drivetrain Removal
Cobb Protuner / EcuTek Tuner
-All Wheel Drive Mustang Dyno in House
doug@weaponsgradeperformance.com
Our Online Store
East Coast Location 226 N. Plains Industrial Rd, Wallingford CT 06492 203-668-4765


#9
someone

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Yes.

Well, bank 2 is always within trims. Bank 1 is the one that "benefit" from the tune change.

Could it be posible that an injector is behaving "different" than the others on a specific pulsewidth?

#10
someone

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I will post a video soon. Maybe you can spot something that I can't. I switch between 3 maps where the only difference is the target AF at idle.
Video starts with the 12.98a/f target map. Bank 1 trim is already at 120%.

Later I switch to a 13.15 a/f target map. Trims go down from 120% to 110% on bank 1. Bank 2 remains unaffected.

Then i switch to the third map which target is 13.35a/f. Bank 1 trims go to 100%, bank 2 remains unaffected.

BTW thanks for helping!

#11
someone

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Here is the link to the new video: https://www.amazon.c...RnujCQy25cSCNqe

 

Pay attention to the A/F Ratio CMD to identify when I switch maps.



#12
someone

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Notice how both Bank pulsewidths are about .55, latency 1.0x, but then Pulsewidth bank 1 is 1.7 and Pulsewidth bank 2 is 1.6.

As I change maps to the map that eliminates the behavior, the pulsewidth in both bank get even.

Is there anything that could affect pulswidth in just one bank?

#13
someone

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Well I gave up on this. I've tried everything to my knowledge. Tweaked the ISC tables to get car idle with the minimum feedback corrections. Enabled Differential Pressure compensation to keep trims on target even when pressure changes (on mornings pressure is about 2-3psi higher than base, when fuel gets hot it goes down 5-7psi below base). I'm also using 3D Injector latency to compensate latency on fuel pressure changes. I have tried with and without these compensations and results are the same. Also tried with Injector Dynamics recommended Minimum Injector Pulsewidth (COBB) of .1, all the way thru .55 (this last one gets me a 13.5 a/f even if target is 14.7). I feel I'm trying to "tune away" an issue.

  

Car idles somewhat "ok" @ 14.7. RPMS do not bounce much, however I get a lot of rattle/pops when target AF is 14.7, but Bank 1 issue goes away. If I set target AF to 13.5, car idles perfect, but then Bank 1 trims go to hell.

 

How come I can do a 14.7 AF, and keep trims somewhat "on target", but when I set target to 13.5 AF, only Bank 1 goes "lean" (120% trim). Any ideas what could be wrong?

 

Here is the latest video: https://www.amazon.c...wmneyLMelCmgmFJ



#14
Doug@WGP

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Curious as to where you got the data to populate the 3D latency and differential fuel pressure tables...?

 

Also... are your throttle bodies stock?  if so you shouldn't have to mess with any of the ISC tables... Is this your first attempt to tune a GTR?


Doug Ross
Owner of Weapons Grade Performance
-Northeast/Pacific Northwest Shops where we ONLY work on GT-Rs
-Owner/Builder of the 1st Ever Home Garage GT-R Drivetrain Removal
Cobb Protuner / EcuTek Tuner
-All Wheel Drive Mustang Dyno in House
doug@weaponsgradeperformance.com
Our Online Store
East Coast Location 226 N. Plains Industrial Rd, Wallingford CT 06492 203-668-4765


#15
someone

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3D latency got it from Injector Dynamics support. Differential Fuel Compensation tables from experimentation. Tuned my VE table part throttle Area using log data from areas were Diff Fuel Pressure Error was within -.5% and .5%. Then adjusted compensation percentages on diff pressure error boundaries (in my case 5% and -10%). I have no issues with trims on part throttle. Its just idle, in Bank 1, and target AF below 14.

TB are not stock. I have the old AMS 63mm ported bodies. I already scaled the Opening Area to Throttle Angle x-axis as suggested by Cobb.

I've been tuning my GTR since I bought it (about 2 years now).


Edited by someone, 11 September 2017 - 05:15 AM.





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