can you utilize fuel trims and stay open loop?

[Kurtomac]

use your fuel trims to trim to commanded in the open loop table

but not command 14.6 all the time unless in PE

seems its just been the norm to set back to closed loop and turn on fuel trims after tuning

Any tips to get rid of bucking by anyway

I did the rafig on my Z06....tried high timing low timing still bucks bad in SD or SD/MAF both Open loop with no fuel trims and still get bucking from prob 1200 to 1800

I tried CL SD with fuel trims the other day and the bucking calmed down some


Your thoughts

[5.7ute]

use your fuel trims to trim to commanded in the open loop table

but not command 14.6 all the time unless in PE

seems its just been the norm to set back to closed loop and turn on fuel trims after tuning

Any tips to get rid of bucking by anyway

I did the rafig on my Z06....tried high timing low timing still bucks bad in SD or SD/MAF both Open loop with no fuel trims and still get bucking from prob 1200 to 1800

I tried CL SD with fuel trims the other day and the bucking calmed down some


Your thoughts

Why would you want to command 14.6 in PE?
Since a narrowband sensor is accurate only at stoich I cannot see it being set up to trim at a different commanded AFR. Sure, you can play with the switch points & get the resultant AFR richer or leaner than stoich, but I dont think the PCM will go into closed loop unless a stoich AFR is commanded.
(B3601 in the tune tool.)

[Kurtomac]

i said command 14.6 UNLESS in PE...I have my PE set up where i make the best dyno numbers and safe AFR

I didnt want commanded to to be 14.6 all the time like it is in closed loop (unless you were in PE...like i was saying) I have my PE table setup the way I like it...and I have my commanded in open loop setup where at 80 kpa it slopes down from 14.6 to 12.9 at 100-105kpa....I just like the smoother transition than 14.6 to commanded afr as Im leaning on the throttle

I thought my Fuel trims did a pretty good job of correcting the + or - 1/2 afr point and easier than adjusting constantly on my VE table...I figure do this...as like you say the narrow bands are good at stoich or close...so leave the fuel trim on...and at WOT/PE time....make it where if anything the Ftrims are negative so I know what the AFR will be....(i know you know but positive fuel trims stay when in OL WOT....but neg will go to zero and will run off of what your VE/....blahblablah down to IFR values to the point where we get the fueling) this way i know that Im controlling fueling and that Ftrims arent messing with WOT fueling...only curbing the small values that it is off driving around town.
Another game I could play would be mess with the TP % to get it to go PE at that 80kpa map reading and not bother with this post haha but I like the smoother transition witihout going straight to PE

[Kurtomac]

im not sure if I completely understand your last sentence...regarding the PCM going CL unless commanding stoich....I realize that using the fuel trims uses the front 02 inputs....can this not be done without the whole....closed loop temp enable....just using those to trim the fueling to whatever commanded is....not always trimming to stoich or in a lean WOT case leaving Fuel trims on to richen the mixture

[5.7ute]

but not command 14.6 all the time unless in PE



Sorry mate, I read it as a seperate sentence which gives another meaning.

Since the o2 sensors can only accurately measure stoich they cannot really trim to anything other than stoich. Hence the B3601 table lets the PCM know what AFR an EQ of 1.0 is incase you are using a different fuel.
I havent run closed loop for a long time but I am pretty sure closed loop will only enable when a stoich AFR is commanded. But I could be wrong.

[joecar]

Closed Loop uses closed loop feedback from the NBO2 sensors to trim to stoichiometric AFR (B3601 with some tweaking from the switch points table)...

i.e. when in CL the commanded and actual AFR's will be stoich.

[mr.prick]

You can use the NBO2's with the Open Loop Commanded Fuel Table
by setting {B4206} to enable.
See this thread for tuning with STFT's
A way to cheat and fix your strims/ltrims using Rtac Very quickly (http://forum.efilive.com/showthread.php?t=6318)

[Sid447]

....by setting {B4206} to enable.

B4206?

Where's that at? :)

........Keeping with the original idea of the thread. What effect would it have if e.g. the O2 switch points were changed to say 550Mv and you changed the values in CL Mode {B4107}. Has anyone messed with that (CL Mode) to any affect?

[mr.prick]

B4206 is in the Fbody OS.
I changed the O2 switch points to 500.0 across the board
and that really helped keep LTFTS in line after OL VE changes.
Didn't mess with CL Mode.

[Kurtomac]

so i cant do this on my 2002 vette OS? sounds like Mr. Prick is doing what I want to do

Utilizing Strims and Ltrims to trim fueling commanded by his open loop table

I just didnt want to command 14.6 all the time and wanted the smoother transition from 14.6 to my desired PE AFR...my OL commanded fuel table is kind of simulated CL anyways....14.6 most of the table then at 75kpa i think i slope down to 12.9 at 90kpa and 12.9 from 90 to 105....then I have my PE enable so it will select the richer of the 2 commanded AFR's for my desired WOT fueling...IE fatter at peak tq then leaning out toward redline

Im not tuning with narrowbands, I use a LC1 with on of TA quickness's fancy serial cables on my V2

So can I do what I want without per say "reenabling closed loop fueling"

[Kurtomac]

btw checked out that link mr. prick posted....good stuff..I may give it a try next week but like they were saying use that method to tune 15-80kpa in the VE table and use the wideband for 80 and above

[dfe1]

Don't know if this will get you where you want to go since I'm not sure of you level of OCDness, but if you switch to a custom operating system, you can run "semi-closed loop". If you're not familiar with this, it uses short term trims to maintain stoich when commanded AFR is 14.63/14.68, and runs open loop whenever a non-stoich AFR is commanded. I run this on my 01 C5 and haven't had any issues.

I suppose if you really wanted to get creative, you could set stoich to 15:1 (or whatever) and run closed loop at that ratio and open loop everwhere else. Narrow-band sensors aren't accurate only at stoich, their accuracy is relative to reference voltage. Narrow band O2 sensors are actually switching devices, not absolute measurement devices. In essence, they're designed to switch upon crossing a voltage threshold. In theory, you could set up a system to run closed loop at virtually any AFR (obviously within limits) by altering the reference voltage. I don't have all necessary electrical data/knowledge to give you a voltage-versus-AFR reference, but I'm sure someone on this forum can.

[Kurtomac]

ive been going nuts today....got tired of messing with it for a while and hopped back on that horse a month or two ago and then spent a good portion of today messing with it....trying to get rid of some bucking and surging im getting on my HCI C5Z06 with a 236 238 cam in it....bucking drives me crazy at 1200 to 1800ish
tried all sorts of different timing values....i just redid my shit and put all airflow tables regarding TC and TF stock to see what that does and inputed .0157 in the B4349 table and had to reRAF....my shit is wanting wayyyy more air than any other tune ive seen....anybody have a clue there....per the raf process/STIT...my car wants like 17.6 grams in the desired air table

[dfe1]

Let me guess, the bucking only occurs at air flows of .20 grams per cylinder or less??????

[Kurtomac]

yes..light load, decel just off idle...IE 1200ish to 1800-1900ish

[Kurtomac]

is the Cos3 for me? Cos5 is for FI applications correct?

[joecar]

You can use COS5 anywhere you can use COS3 (you can COS5 with FI or without).

[dfe1]

A fairly common misconception is that the Custom Operating Systems are for use only with forced induction, extremely long duration cams, speed density only and the like. In fact, they'll work fine with a completely stock engine operating Mass Air and closed loop. The COSs simply provide options not available in a stock OS. Those options may not offer the same tuning advantages with a stock engine, that they do with a modified one, but that's because stock and lightly modified engines don't have the "special needs" of highly modified or forced induction engines.

[joecar]

Yes, I use COS5 on my stock motor (only mod is LT's) with/without MAF and/or CL (as the mood strikes me).

[Chevy366]

(as the mood strikes me).
Dang tell Mood to quit striking you . ;-)
I to ran a stock motor for couple of years with COS3 OLSD , loved the way it ran .
Now that I put a Small Cam and LTs , I am running MAF just because I am lazy and don't want to tune COS3 just yet (wanted to try LC) .
When I did my VE on stock motor though , the LC-1's resolution was so close to stock they almost looked the same , there were small differences that helped .