Cylinder Fuel Trim

s300 and SManager software questions & answers
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2x0
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Joined: Sat Feb 04, 2017 6:51 pm

Cylinder Fuel Trim

Post by 2x0 » Fri Jun 29, 2018 3:40 am

When I took ownership of my car, it had the cylinder fuel trim settings as follows:

Cylinder #1 - 0%
Cylinder #2 - 2%
Cylinder #3 - 2%
Cylinder #4 - 0%

My instincts were to leave the settings alone as much as possible as they should have been input by the previous tuner. However now I am questioning the methodology, or whether this could have been a result of a corrupted calibration.

Under what circumstances should these cylinder trims be used? I would think only when reading individual AFR or EGT from each cylinder, which I know was not done when the car was tuned.

I had the injectors cleaned, and found that there was initially a 2% difference between flow rates in two of them. It is now 1.4%. So I could assume this is why they set it up this way, and they had the lower flowing injectors in cylinders #2 and #3. But still is this a correct way to use these trims, or should it just be tuned using the average AFR from all cylinders and call it good?

I am thinking about zeroing out the cylinder trims and adding 1% to overall trim to average it out, and see if it helps get a smoother running engine. Currently I have a weird engine vibration at certain RPMs and loads and am wondering whether this could be the cause. But I also do not want to damage anything by having one cylinder running leaner than the others.

Thanks
'91 CRX, B18c1, T3/T4, 17psi on e85, FIC 1000cc's, S300 V3 P28

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Spunkster
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Re: Cylinder Fuel Trim

Post by Spunkster » Fri Jun 29, 2018 9:55 am

You can always try it and see how it reacts.

2x0
Posts: 87
Joined: Sat Feb 04, 2017 6:51 pm

Re: Cylinder Fuel Trim

Post by 2x0 » Mon Jul 02, 2018 9:37 am

I tried it. Didn't really notice any difference in the vibration, must be unrelated.

But back to my question, is it proper practice to adjust cylinder trims to try and match the injectors, or should the trims be left at 0%?
'91 CRX, B18c1, T3/T4, 17psi on e85, FIC 1000cc's, S300 V3 P28

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Spunkster
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Re: Cylinder Fuel Trim

Post by Spunkster » Mon Jul 02, 2018 10:19 am

That really all depends. You should discuss this with your tuner. This is something normally used in custom builds making a lot of power.

2x0
Posts: 87
Joined: Sat Feb 04, 2017 6:51 pm

Re: Cylinder Fuel Trim

Post by 2x0 » Mon Jul 02, 2018 12:48 pm

Alrighty. It runs just fine with them at 0% so I will leave it like that for now. When I go for a dyno tune I will have my injector data sheet handy and discuss with the tuner.

Thanks,
'91 CRX, B18c1, T3/T4, 17psi on e85, FIC 1000cc's, S300 V3 P28

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