Hondata

Is there anyway to have the primary wideband o2 sensor adjust to a user specified value instead of the regular 14.7?

I'd rather not run in Open Loop all the time :)

cranny wrote:lol.

What's so funny, douche?

Of course I could tune part throttle to say, 15.5:1

but part throttle A/F is always changing for me when I am open loop, I can tune part throttle one day, and then a week later while closed loop, my o2 sensor is taking out 6, 8, 10 percent of fuel according to short term fuel trim at times..

If the ecu is changing fuel that much when in closed loop, then sounds like you still need to work on your fuel maps.

How long are you driving/logging when you drive to do part throttle? I use to just drive up the street to a shopping center and back. Maybe 15miles or so round trip, but a lot of it was the same driving style and I didn't get good coverage over all of the cells/points on the map.

Lately I've been taking a different route. Takes about 30miles/45 minutes of driving. A good chunk of back road, side road, highway, street driving and I literally fill up the entire table with a/f values.

The new route gives me a very good dataset to use for adjusting fuel. Good enough that my long term fuel trim is usually -1%.

Now, to make sure I don't make any bad assumptions. You *are* locking the cam angle when you do part throttle tuning right?

Have you taken time to determine your gear compensation as well?

kommon_sense wrote:If the ecu is changing fuel that much when in closed loop, then sounds like you still need to work on your fuel maps.

How long are you driving/logging when you drive to do part throttle? I use to just drive up the street to a shopping center and back. Maybe 15miles or so round trip, but a lot of it was the same driving style and I didn't get good coverage over all of the cells/points on the map.

Lately I've been taking a different route. Takes about 30miles/45 minutes of driving. A good chunk of back road, side road, highway, street driving and I literally fill up the entire table with a/f values.

The new route gives me a very good dataset to use for adjusting fuel. Good enough that my long term fuel trim is usually -1%.

Now, to make sure I don't make any bad assumptions. You *are* locking the cam angle when you do part throttle tuning right?

Have you taken time to determine your gear compensation as well?

No, I am tuned for part throttle. I just want to run leaner, instead of the common 14.7 without keeping my car in open loop all the time.

The only thing that concerns me is, for a week straight, I'll have perfect 14.7 all the time, very minimal short term corrections, then the next day, I could see +-5, +-9, etc

and it bothers me, but then again, I have not locked the cam angles, I didn't feel it was needed, but thinking about it, its a good idea.

My gear compensation is set up as well.

My part throttle trips usually only last for about 10 minutes, I know I am not covering the entire map but I didn't really feel it was necessary and that it wasn't a threat to my gas mileage

Not hitting all of the areas on the map for part throttle tuning should not hurt your fuel economy. You mostly need to focus on the section you hit when driving. However if you do not tune all areas then it *will* affect your short term and long term trim. During normal driving, you hit all areas of the map and if they aren't tuned, they will impact your short term.

As for trying to run lean when cruising for fuel economy, I haven't found a way yet aside from running in open loop.

For tuning part throttle, I found the easiest way was to lock in the cam angles one at a time, run the computer in closed loop all across the map, then go for a drive and try to run for at least several seconds through all the major portions of the fuel map.

Then go back and set up a graph to look at AFR, TPS, and short term fuel trim (STFT). When you get to a portion of the graph that is a 'steady state', see what the STFT settles at, then + or - about that much fuel in that region of the graph. Seemed like running closed loop kept the engine running smooth and the STFT shows you what you need to adjust the fuel.

I've been trying to save gas and working on the 'cruise leaner' issue, too. Kpro Nitrous control would be an excellent way to do this - just use a negative number for the fuel, and set all the parameters for when it should kick in. Unfortunately, Nitrous 'fights' with closed loop...nitrous tries to add or subtract fuel according to it's program and closed loop tries to keep the AFR at 14.7:1 until it bumps up against the STFT limits. This doesn't work well for drivability!

My second best solution was to set the closed loop max MAP to about 37kpa - this lets the car idle in closed loop and keeps most part-throttle cruising in open loop. I then pulled out fuel from the 30 and 40 cams around 1750-3000 rpm and 40-80kpa. This was good for about +3mpg.

The most complicated, but also best solution I can think of would be to build a small, isolated voltage source, then use one of the nitrous controls in Kpro to apply this voltage to the O2 sensor as an offset. Under certain light throttle cruising - as defined by the nitrous parameters - the O2 sensor could be made to think the engine is running rich using the applied voltage offset, the ECU would then pull out a bit of fuel to get it back to what it thinks is 14.7:1, but would actually be your 15.5:1 or what ever was dialed in. But at least you would be actively controlling the AFR in closed loop.

magnEsium wrote:The only thing that concerns me is, for a week straight, I'll have perfect 14.7 all the time, very minimal short term corrections, then the next day, I could see +-5, +-9, etc

I have found that humidity affects the a/f, so I don't bother tuning when it is really dry or really humid. If it isn't humidity, it must be your temp or gear comp tables that need adjusting.