injector offset vs overal fuel trim.

jerseydevil · Post by **jerseydevil** » Sat Sep 04, 2010 10:26 am

When people talk about adjusting offset at idle to get 14.7 are they refering to the injector offset or the overall fuel trim. I had been doing this using the injector cal tool, which says on the very bottom adjust offset at idle and has two large buttons + and -. When these are clicked though it actually changes the over all fuel trim. It's a little misleading. I found in the hardware panel another injector section, which here has both of these fields, injector offset in FV (fuel values? what is does that mean exactly?) and below it is overall fuel trim in a percentage. So which of these two values are the the one that should be adjusted at idle to achieve the 14.7 at idle? The hardware panel also says offset effects injector latency? Are we talking altering when the injector fires as opposed to how much it fires?

Almighty-Si · Post by **Almighty-Si** » Mon Sep 06, 2010 9:15 am

I asked this question a couple of times and didn't get an answer. Hopefully you have better luck.

Post by **Bugermass** » Mon Sep 06, 2010 12:49 pm

yeah, the buttons where changed to affect overall trim a few rom versions back. I personally don't use overall trim, I use FV. The buttons need to be changed back.

jerseydevil · Post by **jerseydevil** » Mon Sep 06, 2010 1:15 pm

Thanks for the reply. Perhaps this has been part of my headache where i was using the wrong feature set. If you wouldn't mind, and if you know, could you clarify what the FV injector offest actually does? I think I understand fuel trim, where it simply adds a percentage ontop of the final value effecting the entire fuel map. What exactly does FV do and what is 1 fuel value? Does FV in this instance mean raw fuel, the numbers you see in the tables?

Almighty-Si · Post by **Almighty-Si** » Mon Sep 06, 2010 3:33 pm

Yea, pretty certain it just adds the number you put in there to the raw values in the table.

dbsharp · Post by **dbsharp** » Mon Sep 06, 2010 8:43 pm

I heard someone on here mention waves in the fuel table if the offset was wrong. I have noticed that I do have some waviness in my fuel tables, I thought this was just due the cam's efficiency vs rpm; afrs are nice and happy though. I was thinking about adjusting the FV and seeing what effect it has.

jerseydevil · Post by **jerseydevil** » Mon Sep 06, 2010 10:32 pm

So do they essentially do the same thing? One adds raw fuel values to the tables, and one seems to act like a mulitpier on the end. Would seem the overall result is the same? We must be missign something that creates a need for two fields doing the same job.

Post by **Bugermass** » Wed Sep 08, 2010 9:06 pm

they are added/multiplied at different points in teh fuel calc. Just us FV...

shogun · Post by **shogun** » Thu Jan 13, 2011 4:25 am

I'd like to be sure to well understand \"injector offset\" features. According to the \"help guide\", it's linked to \"injector latency\". Is injector offset related to the speed of injector reaction between injection duty cycle variations (which indirectly will affect the A/FR)? In this hypothesis the offset would be the \"time lag\" betwwen the injector voltage variation and its effective change in fuel injection, so the \"'injector offset\" would be the way to compensate the difference anticipating (or retarding) the injector voltage change. May be it's just a stupid idea

, I really just want to understand. I've noticed an enrichiment between very heavy tps variation in a short while, may be due to injectors speed reaction ( my tps tip in fuel correction is set to 0%).

TopMountGSR · Post by **TopMountGSR** » Thu Jan 13, 2011 7:36 pm

I actually use both, I bring them both up at the same time and do what I can to make them both equal. So if I run a 12 fuel trim, I run a 12 offset. I found that this prevents high fuel trims and the fuel curves end result is very smooth. A long time ago I found that odd offsets can cause weird fuel curves. Anytime I see it wanting a weird fuel curve, I play with the offset and it'll change what fuel curve its wanting. I look at the offsets as a larger rough fuel trim and and the fuel trims to be a smooth fine fuel trim. Try it a few different ways and see what works best for you and leads your map into a smooth graph.