-25% Fuel trim on decel and start up

FlashPro questions & answers specific to the 2006-2009 (US, UK, Asia) S2000
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Piv
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-25% Fuel trim on decel and start up

Post by Piv » Tue Sep 23, 2014 4:41 am

Hello, we had that issue for a while now and the latest update hasn't changed anything.

When you start the car up, the ECU is doing a -25% short trim compensation before working alright, then on deceleration it will do the same thing making the car stalls

Any reasons or way to fix the issue ?

I tried on both 1.9.1 and 1.9.3beta
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Short trim issue.fpdl
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Spunkster
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Re: -25% Fuel trim on decel and start up

Post by Spunkster » Tue Sep 23, 2014 9:26 am

Post the calibration and also list everything that has been done with this vehicle.

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Hondata
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Re: -25% Fuel trim on decel and start up

Post by Hondata » Tue Sep 23, 2014 12:32 pm

The -25% trim is a 'learned fuel value' which is like a short term trim, except it is used after the injectors first re-start.

The value going to -25% indicates that the short term trim is pulling a lot of fuel. You fuel tables need a lot of tuning, or it could be that the o2 sensor is failing.
Hondata

Piv
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Re: -25% Fuel trim on decel and start up

Post by Piv » Mon Feb 09, 2015 6:54 am

Spunkster wrote:Post the calibration and also list everything that has been done with this vehicle.
The car has a Rotrex C38 81 kit and the usual breathing mods, the O2 sensor seems to work correctly on normal driving and the tuning is good.

While I do understand the indications of a lot of fuel removed by going -25% I know the car isn't running that rich

I would expect the corrections to behave like this before the O2 has warm up enough to work, same goes on deceleration when compensation should be 0%. I tried to get the window of correction narrower but that didn't works too.
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Short trim issue2.fpdl
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Dyno Final C38.fpcal
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Spunkster
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Re: -25% Fuel trim on decel and start up

Post by Spunkster » Mon Feb 09, 2015 11:24 am

Are you tuning this yourself, or was this tuned by a shop on the dyno?

Piv
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Re: -25% Fuel trim on decel and start up

Post by Piv » Mon Feb 09, 2015 2:25 pm

It was tuned by another shop and brought to me for a tweak, done on a Dynodynamics but the issue became present when the customer updated the firmware on its flashpro a year or so ago before I saw the car for the first time.

Piv
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Re: -25% Fuel trim on decel and start up

Post by Piv » Sat Feb 21, 2015 2:48 am

Hello guys,

Any ideas you would suggest?

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Spunkster
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Re: -25% Fuel trim on decel and start up

Post by Spunkster » Mon Feb 23, 2015 10:39 am

It sounds like it just needs better tuning so that it is not maxing out the trim at startup. You might try starting with a factory calibration and then tune from there instead. Sometimes it takes less time to start over than to try to fix a poorly tuned calibration.

Piv
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Re: -25% Fuel trim on decel and start up

Post by Piv » Thu Jun 04, 2015 3:32 am

For people having the same issues, it ended up being a faulty sensor, replaced it and it fixed the problem :)

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Re: -25% Fuel trim on decel and start up

Post by Hondata » Sun Jun 14, 2015 4:14 pm

Thanks for posting the resolution.
Hondata

andrew87890
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Re: -25% Fuel trim on decel and start up

Post by andrew87890 » Sat Aug 15, 2015 11:31 am

what sensor?

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