Hondata

I've read the help file 20 times for this one. Although I think I understand what it is saying, I can't work out how to use the numbers to achieve a goal.

Let's say I want to add 14% post start fuel and I want it to last for 30 seconds so that it can help with heat soak until the closed loop comes online (which happens to be set to 30 seconds).

So to make the 14% last as close to the 30 seconds as possible what numbers would I put in the rate of decay?

The default that comes with the basemaps is: 11264, 640, 128, 8

It says the higher the number the faster the decay.

So if I set it to 8,8,8,8 would that be the most I could slow down the decay? I've noticed in the default values each seemed to want to be divisible by 8.

Second question it doesn't seem there is a precise way to see this trim in the graphs or am I missing something? ECT.c does not seem to include it. Only way I can work out to measure the duration achieved is by looking at the injector duty cycle changes. Is there another way?

I have been trying to figure this out for over ten years myself, still can't figure out the correlation. Anyone with info, please post

I played with it a bit yesterday. I did some tests using a higher % trim so easier to see on the AFR when it dropped off. Still pretty hard to figure out looking at the graphs when it stops and starts. I ran the tests at warm/op temp starts so there would be no ECT.c.

What I know so far:

The 4th column might as well always be 8, it's for a special circumstance (extreme heat soak, like well beyond normal) and is meant to be 8.

If you put 8 for all the values it pretty much never decays. Well it may eventually decay but I watched the ultra rich AFR longer than I was comfortable with (well more than 30 seconds).

If I put in 128 for the first 3 values then I get ~30 seconds.

If I put in 256 for the first 3 it's < 30 seconds by more than a few seconds.

If I put in 64 for the first 3 it's closer to 45 seconds before effects on the AFRs seems diminished.

If I put 96 for the first 3 it's > 30 seconds and < 45 seconds.

If you're trying to achieve 30 seconds of added fuel I think either 128 or 96 for all 3. Or maybe good to do 128 for the first value then 96 for the next 2.

I am also pretty sure at this point that the numbers do not matter relative to one another. The help file makes it sound like there is an interplay between the numbers like the ratio between them affects speed, but I think each number is standalone which makes it easy. This is just from my observation, be nice of Hondata could clear that up. Frankly I find there are a lot of "Magic Numbers" in the way Hondata works and I think these are no different. Instead of each value being a number of seconds I think each number is a standalone magic number that higher = shorter time, longer = longer time, 8 = infinite possibly, all with no tie from one cell to the next.

Keep in mind from the help file the first column is 50% worth of the decay, then the next 2 are 25% each. That's why I say maybe 128,96,96 that way since you're starting with presumably a high trim value the first 50% decays a little quicker to a more sensible value for the next 25% and the last 25% beyond that.

I've also found from looking at the logs that even if you specify closed loop to start at 30s it's not necessarily always >= 30 seconds. Seems more often a little ahead of schedule by up to 2 seconds, and that is from the moment I start the log (a moment before cranking) so if you start the timer after cranking then it's well less than 30s, maybe 25 or 26.

Take all this with a grain of salt, I'm hardly an expert.

Also, it might be best to stick to multiples of 8, can't be a coincidence that all the default values are. The "magic" math the ECU is doing may be a bitwise (binary) operation and that would like numbers like this. If that's the case I'd think multiples of 2 would also work but might have unexpected results.

IMPORTANT! Maybe not such a good idea to try my above suggestions, I just tried a cold start with it and the car misfired all over the place and barely started. I then removed the trim / set to 0% but left the decay values the same (all 128) and still misfiring for several tries. I set all the values back to default and it had a challenge starting probably coz flooded with fuel but got going back to normal. It appears the decay values may affect the tune even if trim is 0%.

Everything I did yesterday was fine on a hot start. But not so good on cold start.

thank you for the info. I'll have to do some more playing around with mine once the weather gets a bit warmer. E85 and 10-20*F temps don't get along well for cold start haha

Interesting that an administrator has not chimed in on this particular thread.

I tried playing with this when I had issues with hot restart/heat soak being excessively lean. I had the same issue where I was able to solve the problem when hot but then cold start was too rich.

I ended up “sort of” solving the hot restart issue by shortening the delay for closed loop down to 5 seconds (o2 should already be hot and it uses the ECT to go into closed loop when cold, so not much risk there since it won’t start correcting until above 129 coolant temp or whatever the default is).

I also adjusted the air temp compensation for low load to give it extra fuel when it is heat soaked from sitting. I set the temp range to no correction between 100-120 basically (again, only for low load/medium load table where closed loop is adjusting anyway) and then from 120-140 it gives it 1% for each degree of temp (so 0’s for the 100 and 120 cells then make the next cell 130-140 and set it to like 10 or 20 so it gives it like 1-2% per degree) depending on what kind of intake temps you’re seeing after sitting, I’m usually around 125-130 IAT on restart so I adjusted it so it adds like 5-10% which definitely helps and then closed loop kicks in earlier with the other change to start adjusting pretty much right away. It also cools off quickly once I’m moving and I never see temps above like 110 when I’m driving around so I don’t really have to worry about the correction being an issue unless I sit in traffic and even then if it gets above 120 it’s only adding a percent or two which the s trim will adjust for.

Anyway hope that helps maybe if you’re having hot restart problems with it going lean.

Got back to playing with this feature and tried setting to the same as Furble mentioned and had the same issues where the cold start was EXCESSIVELY rich and didn't want to run, even with only 4% in the 'Post Start Fuel Adjustment'.

It seems the values in the 'Post Start Fuel Rate of Decay' table definitely affect the AMOUNT of fuel being added as well as the length of time ... the help file makes it sound like this particular table is *only* the length of time that the post start fuel adjustment % is applied, but this is obviously wrong because changing those values affects the fueling even if the adjustment value is 0.

There is a note in the help file for the 'Post Start Fuel Adjustment': Changing the post start fuel adjustment will alter the amount of fuel and also the enrichment time period. This seems to apply to the 'Post Start Fuel Rate of Decay' table as well.

Wish we could just have a feature that was straightforward "add x amount of fuel for x amount of time" on hot restart only.