I have tryed individual cylinder fuel trim with poor resaults. My BLM's were closer together but the car ran like crap.

 

I imagine this is possible if you are taking/adding fuel from/to the wrong cylinders, but on the right side of the engine. The BLMs will end up correct for the side, but one or more cylinders will be off. That is why you'd need a thermometer on each cylinder exit to be sure.

FWIW, my car feels much better in addition to having close BLMs, by modifying the trim tables. So it can/does work.

WS6, I suggest starting with the tables even at 1 for all cylinders; then tune the trims to match the side that is closest to 128. But like the previous poster said, it can end up just guessing without proper temperature readings.

 

I got a chance to play with ve master over the last week a little, prelim test shows it brought my blms closer together as well as made them 127 which was the target, this was done in maf mode only. Throttle response and cold start and running were also much much improved.

This weekend i will try and even out some of the individual trims a bit. My plan is to remove a little fuel from some cylinders and add a little to others keeping about the same % difference as factory. just closer together, and then noting the results. I will only do very minor changes.

I will also note that by changing the blm cell boundaries along with ve master i picked up 3mpg this week. Basicly i just looked at my logs and adjusted it so my "resolution" was a little better and i was using more cells therefore making my long term fuel trims were more effective. The factory blm boundaries just dont really work that well for a cammed car with different gears.

 

That's great. I actually forgot to tell you about the cell boundaries. Too much to remember I guess. But changing the MAP boundaries is a must to maximize cell usage as our vacuum levels are so different.

As for VE master... I chose 124... a few points less than 128, just to make sure all my BLM's were less than 128 for WOT tuning.

If you BLM's are so close, and the car is running so well... why are you adjusting the individual fuel trims. I'd like to learn more about how you are going to validate if you tune is improved or not. Maybe there is something to learn here.

 

Far as i know it doesnt try to do too much until you cross 130 just like when you're at 124. Also to be clear my right blm is 125 constantly and my left blm is 127, they never move more than maybe 1 number now. Also in theory your open loop mode when you cold start the car runs purely off your ve tables, and yours are rich by about 5% if your blms are 124 but i understand your logic in doing so. I would have done the same but i dont ever get it to add fuel so i'll leave it where it is.

My strategy is more to bring the fuel flow closer together in the individual fuel trims, but keep the same patern as the factory did. the right side is apparently always running rich compared to the left as it always pulls fuel, it also has a couple of numbers i think are crazy as far as cyl fuel trims. Basicly the fuel trims and short term stuff is just an average of what every cylinder on a bank is doing so obviously some are running rich on the left and lean on the right on AVERAGE. I am building another lt1 at the moment for a different app, i will put dyno headers on it and the 8 channel wbO2 setup we have at work and then do the fuel trims on the engine dyno when i get the chance. I would do this in my car but i'm not drilling and welding and all that fun business on a set of coated headers already in the car. When i switch headers for some stainless ones next year i'll do in car testing on my engine if i dont swap for a boosted setup before then.

As for why i'm still working at it when it so close, i just cant leave well enough alone, thats why i couldnt stay with just a mail order tune also. I mean by that line of thought why not just tell it the injectors are smaller than they are so your blms stay between 108 and 128 and you're done tuning? or are you? "good enough" isnt really is it?

The next project after that though is pe idle just to see if i can get that a little better although right now it doesnt actually stink that much.

I also have something else to share in the way of smoothing idles, the overspeed and underspeed spark tables imo need to be zeroed within about 75 or 100 rpms of your actual target idle, i had a bit of a surging problem with my car when i first started messing with it and it was because the over and underspeed tables were advancing and retarding my timing at idle about +-4 deg and making it surge and jump all over the place, the pcm was chasing its tail trying to hold an idle. I also backed the timing down to 25 or 26 degrees from where it was set at about 28 and the motor got alot less "nervous"

Just a little food for thought and discussion, keep talkin guys i'm learning alot, i appreciate all of your experiences and input.

 

I'd love to hear how things turn out when... it'd be interesting to see how much better the car runs... and even if you can get a little more power out of it. I wonder if there is a way of just wrapping each header with a temp sensor... and checking the temp of the actual metal versus actually drilling into it. You would not really be able to measure the exhaust temp correctly, but you COULD measure the variability between each cylinder. Then you can place 1 or 2 bungs in the Y-pipe to get an average temp for that bank... so that once you smooth out each cylinder, you can use the average temp to tune.

I wonder how something like that could be rigged up. The nice thing is that you could use it for any car... not just the LT1, for more effective tuning.

I tried playing around with the over/underspeed spark. I removed it completely, and also tried removing it for small idle fluctuations... and interesting enough... my idle got WORSE as it couldn't compensate as quickly. I think with a lumpy cam... allowing the computer to adjust timing is necessary to keep it as smooth as possible.

To minimize how much "work" the computer needs to do, I actually found that when I trying to determine my closed TPS timing, I'd set a specific timing... and then would watch how the computer adjusted it on it's own. If it tried to always adjust it up... I would reprogram it at a higher spark advance. If it seemed to drop more than go up, I tuned down. Once I got to the point where the over and underspeed fluctuations were about equal... I knew I was close to the "sweet spot" for the car. I also used my MAP levels as well as general driving in Drive and Park at different temperatures to fine tune it even more. I do change it once in a while... in the middle of the summer versus in the spring/fall, and this year when cruising Woodward where the car would idle for hours in stop/go traffic, I'd remove a little timing as the car stayed cooler that way.