Trim values

Nistune topics related specifically to the 6303 cpu

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Torque
Posts: 626
Joined: Wed Jun 16, 2010 10:08 am

Trim values

Postby Torque » Thu Apr 06, 2017 6:20 am

I noticed that my short term and long term trims are really all over the place under driving conditions.
(even where O2 sensing is disabled)

They seem to be low OK at idle so I'm starting to wonder why they change so much.

Short term:
short term.JPG
short term.JPG (66.82 KiB) Viewed 987 times


short term max.JPG
short term max.JPG (62.63 KiB) Viewed 987 times

Matt
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Re: Trim values

Postby Matt » Thu Apr 06, 2017 7:16 am

The ST/LT fuel trims in Nissan ECUs appear only to be accurate when the vehicle is in cruise conditions (for some vehicles and Z32 ECU is one of these)

For Z32 ECU I notice that the trim values do NOT report closed loop trims when the vehicle is at idle or going from the point of acceleration for example. What they seem to report is the amount of acceleration and temperature enrichment only

Once the vehicle is at cruise (say light load, 2000rpm) then it will at that point properly report the fuel trims

It seems to be a quirk with the output of the Nissan consult data from the ECU rather than something in Nistune. The only thing I was thinking we could do software wise is not report the O2 trims for those particular ECUs at idle so it doesn't throw people off during tuning

Torque
Posts: 626
Joined: Wed Jun 16, 2010 10:08 am

Re: Trim values

Postby Torque » Thu Apr 06, 2017 8:03 pm

Also from my experience the Z32 does not report any O2 sensor voltage oscillation until you're in gear and hold a certain rpm.

Maybe that's connected to the trim behaviour as well.

If I compare the area where trim takes place with my O2 sensing areaI feel that it is not an exact match either ..

short term max.JPG
short term max.JPG (62.63 KiB) Viewed 980 times

o2.JPG
o2.JPG (178.67 KiB) Viewed 980 times

Torque
Posts: 626
Joined: Wed Jun 16, 2010 10:08 am

Re: Trim values

Postby Torque » Thu Apr 06, 2017 9:36 pm

On that note ..

When mapping the car what procedure do you recommend to not have the trims interfere ?

Thanks

Matt
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Posts: 8038
Joined: Sun Jan 29, 2006 1:45 am
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Re: Trim values

Postby Matt » Fri Apr 07, 2017 8:37 am

When you have the K constant in the correct spot, the trims (on cruise) should be close to 0%

That way they will not work against you in the closed loop area

Yes I have noticed this also where the trims are adjusted even outside the closed loop area. So it appears you cannot restrict adjustments to a particular area. I believe there are RPM/TP parameters (to be discovered) which are used to determine where the limits of this area are

This is why when you move K constant around, and it moves where TP cursor traces, it can affect the closed loop area of the maps


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