cant get fuel trims better than 8% less <=1200rpm

[bigassogre]

first. im a noob. so any help is greatly appreciated.

second truck is a 13 chevy 2500hd. 6.0l 4wd.

1200rpm and down i cant get my ltft any better than 6-8%. 1400-4000rpm ar in the 1-3% range for the most part.

the way im doing my tuning is basically logging ltft. drivin for 10 or so min after its warmed up. copying all the ltft cells. going to the virtual ve. pasting mutiply %. clicking the generate coefficient button. and writing. ive done it like 10-15x. and below 1200rpm i just dont like my fuel trims. only mods are a cold air intake, and an ls3 tb. any ideas? thanks in advance.

[schpenxel]

virtual VE isn't as exact as an old VE table was.. some "rounding" for lack of a better word happens when you hit calculate coefficients.

My opinion? Leave it alone and forget about it. It's not hurting anything. O2 sensors are doing what they were designed for, fueling is @ stoich because of them and getting LTFT's down to zero won't make a difference at all in how it drives in the end.

[bigassogre]

is there a table or some sort of enrichment adder or multiplier or somethin like that for fueling below 1200rpm? also, do u think it would help any to just manually multiply all the cells at 1200 and below by 10% or so? i guess it wont hurt to try it and see. i can always change it back. thanks for your help btw schpenxel

[schpenxel]

I'd try multiplying that section by 0.9 to reduce it by 10% and see what happens

I'm not a fan of the multiply by % thing most people do--it usually ends in a really rough VE table (which should be pretty smooth). I try to take trends that I'm seeing and apply them over larger sections of the VE/VVE tables

Also--you're probably already doing this, but make sure you're changing both the open and closed loop VVE tables. Only one of them is used on most vehicles, and it's not the one that opens by default.

[bigassogre]

i actually didnt know about the opened and closed loop vve at all. but if the pcm is having to add fuel wouldnt i have to multiply by 1.1 instead of 0.9?

[schpenxel]

You're right, I thought you said -8% originally but you said 8%

You need to change both open and closed loop tables in virtual VE editor... make them the same

There are separate tables for manifold switch open vs. manifold switch closed. Most cars don't use the one that HP Tuners opens by default.. so in that case changes would have no effect whatsoever. To be sure I've changed the right one I usually just make them both the same.

Change one, hit calculate coefficients, select the whole table, copy. Change to manifold switch open, paste the table you just copied, hit calculate again and you're done

VVVE.png

[mowton]

I will keep reiterating how important it is to set up filters when tuning on the street to preclude erroneous error data being used to correct your VE and MAF tables. Remember you can add/modify filters after you have logged to help isolate the good data from the bad. Carefully evaluate your logs in the trouble area's (using filters, View zoom data only etc) and look for consistencies and aberrations. Carson is right, there is a linear relationship between RPM and load. For a specific RPM, the trending (delta) will be consistent as the map increases or decreases. Look for these trends and hand smooth where need be. For the aberrations, figure out a filter which will help eliminate them. For the consistencies, figure out the scenario that they resulted from and try to replicate that in your logging plan. Keep you error corrections small and smooth rough transitions. A forum member once taught me to Mult % half, smooth (using the built in smoother and pick an area a little bigger than the area you corrected), Mult % half, smooth and reflash/log.

Also down that low, you might want to compare open loop WB readings to your closed loop Narrow band readings and see that they are the same....make sure you dont have an instrumentation issue. Also, make sure your injector data is accurate..you are starting to get into the area where offset and SPA will rear their ugly heads....

Be patient, visually evaluate/correct and keep you changes small and smooth. VE tuning is just not copy/paste sometimes. Also, just a clarification, the Open/Closed in the VVE toolset is for Manifold Switch where some setups use a 2 part, programmable plenum. If you don't have this feature than you need only update the Open table...but many do both (some even all 4) which is fine also.

Ed M

Update -- typed too slow, Carson already updated the open close reference.....:-)

[mowton]

Another thought that came to me is if this is an E38 setup 2008 and up, notice what GM did to the previous 16 LTFT zones (RPM/MAP Boundaries).....they cut it down to 2 and are using AF modes. So zone 1 is 0-31 and zone 2 is 31-64...no mre AF modes!!!! In my experience, this decreases the granularity down low for LTFT error collection and puts more burden on the STFT. I sometimes increase the granularity with smaller steps and it increase the number of zones thus settling down the SFTF.

Ed M

[bigassogre]

ok im definitely seeing some changes now that i started changing the vve switch open table. but i think i have something skewing my logging. im thinkin i may have dfco coming on.

[mowton]

Use this filter [6310] Fuel Trim Cell to filter out decel. Search Help for Fuel trim Cell and find the values pertaining to your specific setup. Accel pedal works good also.

Ed M

[schpenxel]

And keep in mind fuel trims will be a bit crazy for 10-15 mins after flashing usually.

[mowton]

And keep in mind fuel trims will be a bit crazy for 10-15 mins after flashing usually.

^^^^^^^^ Excellent point....don't collect data until IVT Parameter has stabilized

Ed M

[bigassogre]

im thinkin u guys hit the nail on the head with the 10-15min thing. ive been paying attention to that tonight. i didnt reallize it took so long to do whatever it is that its doin.ill try and figure out the 6310 filter. i hope one that oneday after i have been doin this a while ill be able to help people like u guys are helpin me. im 32yrs old. ase master tech. nissan master tech. gm certified. ford certified. i thought i was just goin to junp into this and be good at it. man was i wrong.

[schpenxel]

I think everyone that has a lot of experience working on cars thinks that at first. It's a whole new world though.

[cc-rider]

Have you been datalogging with your evap hose in the intake or removed? That's another thing that can throw off fueling at lower rpm.

[bigassogre]

i was making changes to the manifold switch closed table. i got everything within about 3% now. now im moving on to maf tuning. my intake tube is 1/2" larger in diameter than stock so now i need to figure out how to maf tune then i guess ill start on timing. thanks to everybody thats helping me so far. im trying to get this thing tuned in as close as possible now so that when i do the cam swap ill have a closer starting point and better understanding of whats goin on.

[mowton]

i was making changes to the manifold switch closed table. i got everything within about 3% now. now im moving on to maf tuning. my intake tube is 1/2" larger in diameter than stock so now i need to figure out how to maf tune then i guess ill start on timing. thanks to everybody thats helping me so far. im trying to get this thing tuned in as close as possible now so that when i do the cam swap ill have a closer starting point and better understanding of whats goin on.

Sounds good...love it when a plan comes together.....

Maf tuning is just like ve tuning. Log the same error parameter but this time set the column axis to the Hz values you will copy over from the Editor MAF table and select the MAF frequency Parameter you are logging. Take the error data and copy/paste special>mult like before.

Happy tuning

Ed M

[kennyspec]

Also when MAF tuning at WOT or when in PE I like to initially set the PE table to something fairly rich. About 11.0AFR (the table values would read about 1.336 14.7/11.0=1.336) Then once the MAF table is dialed in you can set the PE table to whatever you want and your AFR should follow. I find it is safer to start with the table rich and then lean it out once your MAF table is dialed in just incase you need to add a lot of fuel on the first WOT runs.

[Michael_D]

Zero out the afr spark adder too.....