slickfx3

So if it is working right, isn't changing the MAF tables futile?

please explain...

I installed a wideband and at cruise it is at 13.2 they say a bigger cam need richer true?

Orr89RocZ

iTrader: (20)

Its suppose to adjust fuel alittle to keep motor around "stoich" air fuel of 14.7 or so. Basically O2 sensors feed data to the ecm, and from that you get BLM/INT parameters. 128/128 BLM/INT is suppose to be spot on 14.7 air fuel. If you dip above or below those 128/128 values, you go rich or lean of 14.7 air fuel ratio.

So as long as you adjust MAF tables to achieve BLM's of 128 or close to it, the ECM will be happy and shouldnt be changing the fuel delivery.
Thats generally how it works.

And a bigger cam doesnt necessarily need more fuel to run. I've run as lean at 16 to 1 just fine for short periods of time when first starting the tune on my old 383, but then made a few minor adjustments to the MAF to bring air fuel back to the mid 14's and the motor was happy with that.

So I would say you are slightly rich and you could try to lean it out some.

slickfx3

thanks reread your post...I get it the MAF table trumps the ECM in guiding towards stoich

slickfx3

Okay, I tried to play with the MAF tables and all it did was made the car run like crap, all the time the Wideband showed no changes, and the BLM gets pegged in the RED,....


so I know.... I don't know what I am doing, but at least most of the knocks (spark Table) are gone and I can finally redline the car....

Orr89RocZ

iTrader: (20)

Try disabling closed loop and just tune open for awhile. closed loop enable temp, set it to something very high for now to work open loop only.
Work the air fuel ratios to near 14.7 for the cruise stuff. MAF tables and some of the open loop AFR % change tables will help with this. You should clearly see changes in MAF settings effecting the wideband output.

Try that and see if the car runs/feels better. Once you get there, try the closed loop operation again to see what the BLM's and wideband readings do. Report back.

I ran open loop on my car with no problems and enjoyed it. It was easy to do and I never went back to closed loop. I had run closed loop for awhile but had problems with idle due to cam size/overlap. Couldnt not get BLM's to match 128 at idle no matter what O2 settings I used. I just ignored the BLMs for idle and trusted my plugs and wideband. Motor was happy so I was happy and we both ignored the electronics.

slickfx3

That is actually my first concern, the ECM "correcting" the tuner's changes back to stoich; so what you are saying with your post is your ECM was not able to achieve 128 BLM at idle due to the CAM, although theoretically, it "is" responsible to center the AFR at any given scenario. So you suspect it was not doing it's job? and you "circumvented" the "loop".

Will cams always be the culprit?

My question is why is this not "standard procedure" for all tuners; to disable close loop, since the close loop "Negates" changes. UNLESS it is a case by case basis whereby some situations the close loop will "accept" the changes. Is this why I have to go back to close loop to monitor effectiveness?

Another thing is I called my wide-band gauge sellers, as to why in their instructions, states "calibrate" they say do not claibrate the "controller against the instructions, as this is done and only required if I change fuels, as in alcohol or something like that.

Is it possible the gauge is not calibrated properly?

lastly, for now, how is emissions affected by open loop only operation?

Orr89RocZ

iTrader: (20)

I'm not sure what you are seeing in your tune, but changes to the MAF will change the air fuel ratio, and the ecm will TRY to pull it back in the direction that gets it to stoich. BUT I do not believe its capable of making the entire change. Say your cruising at 12 to 1 air fuel, and the ecm trys to correct. I do not think it has the ability to swing the air fuel back to 14.7 to 1. Thats a lot of change. Changing the MAF tables or scalars or even the battery voltage pulsewidth offsets should swing air fuel rato and thus you will see your BLMs go more towards stoich if your shooting for stoich on your wideband.

At idle, a cam with alot of overlap will have a self EGR effect and fresh air will get into the exhaust stream. That air is sensed by the o2 sensor and the ecm will try to make changes at idle. Thus the blm's and INT are different from 128 when you have near 14.7 to 1 air fuel. It can and does happen.
There are offsets in the bin for o2 milisec voltages. You can tweak these to compensate for the extra air but that may throw off the restof your readings for cruise and medium throttle. So I ignore BLMs at idle and just shoot for 128 during cruise rpms since cam overlap effects are reduced due to more rpms.


Closed loop is only suppose to make changes due to different air conditions. MAF will sense different amounts of air in different weather conditions, so will the IAT and coolant temp sensors. They all have input on fueling in closed loop. If your MAF tables are calibrated correctly, you should be seeing blm's near the 128 mark when your wideband reads near 14.7 to 1 or so. In the ball park of 14-15 to 1 would be acceptable. (assuming wideband is calibrated correctly as well)

Closed loop is not going to negate your changes...if it did then how did they tune the cars in the first place? They had to start somewhere. The cars are tuned in open loop at first because on first startup the motor is not ready for closed loop operation. It runs until it warms up and then gets to closed loop. Open loop should be pretty close to stoich as well at idle, or somewhere in that happy range of 14-15.5 to 1 or so. General range for idle and cruise. Closed loop then takes over to monitor changes in air conditions from temperature and pressure (barometer) Colder air is more dense, with more o2 so the MAF would pick up more air flow and adjust fueling to get the air fuel back to stoich.

If your making changes and not seeing blm's/int's near 128 when your wideband reads differently, there are some other things goin on that are causing a problem. I've read many threads on blms not matching widebands and i'm not sure why except for maybe the o2 settings in the bin are not correct anymore for the modifications to the car. Thats why I went open loop only for ease of tuning. Even tho my car ran fine on closed loop after it got hot, I liked the ease of just tuning MAF/LV8/RPM vs wideband o2.

Give the engine what it wants and if its happy, I normally dont worry about what the electronics say. Carb cars ran fine for years by tuning with spark plugs and track times. Its no different with EFI.

I dont think emissions will be effected but that depends on if the AIR EGR and charcoal cansister are tied into closed loop operation. I dont think they are, but I never looked into that.

slickfx3

Thanks I have to pick out every word and I'm an starting to understand your insight...will work on it

slickfx3

Okay I get what you are saying, those little, words like happy, we, generally, etc, packs a big punch, off of close loop at the moment, unfortunately, my Autoprom wants to not work mid-emulation, I don't really or can't figure it out right now, so I an burning and re-burning chips galore.

used an old MAF table #1 and it cruises at 16.5 and I think the DFCO on decel makes it go way lean to 20 is this correct when I let off the pedal?, I bumped the table up 1.25%, I messed with smaller, but it was wasting time, and I think ( drove it around the block one tonight) It will idle and cruise at 14.8, anyhow, need to drive it more, flooring it, well almost flooring it( too many cops around here lately) the "feed" of richness seem linear with no crazy spikes, this is what I am looking for correct?.

darn thing has a stock Corvette MAF 3-6 #2 has been upped though, I don't see MAF 3 and beyond could be optimized given the TPS has to move so much just to engage the tables, Thoughts?

In reality, will just changing the injector size (UP) on the bin do most of the air fuel work? just a thought.

did my driving the 40 miles at 16.5 burn my valves?

Orr89RocZ

iTrader: (20)

Thats normal. You can disable the DFCO if you wanted but I dont see anything wrong with going dead lean with throttle off as long as the car isnt stalling out. Dont need fuel on deceleration. My turbo car uses DFCO but my 383 didnt really seem to lean out when I left off the throttle with stock settings. No big deal.

You can have a smooth fuel delivery so that the "richness" comes on in a linear fashion. A cruise light throttle to pedal MASH WOT run will need acceleration enrichment which is just fuel pump shot, so the air fuel will jump quickly from cruise 14.8 or so to whatever you are shooting for at WOT (say 12.8 to 1)

I like to gradually become richer with load increase. As I get nearer to WOT I want it to be abit more rich. Heavy throttle but not all the way into it, I'd like to see mid 13's to 1 air fuel so by the time I get into WOT is close to 12.8 or so. Needs less of a pump shot then. Do not know if there is any advantage to that but thats the way I did it.

I would say 80% of your driving will be in table 1 and 2. There will be alittle bit in table 3 but you start to get into heavier throttle to get into table 3. In the 2000-2500 rpm range with 1/4 throttle to 1/2 throttle, you will see you are in table 3. LV8's in the 130-150 range. With a different stall converter you may see table 3 more often since rpms will be higher with given throttle input due to slip.

You can easily get into table 4 if you go 1/2-3/4 throttle and over 2500 rpm or so. Even as low as 2000 if you really load the motor up with a mild to stock stall speed converter.

But depending on the settings, you may be going into PE mode there anyway so you can tune air fuel ratios by using PE % enrichment vs RPM to dial in those spots. I try to use that only for WOT runs when the MAF gets maxed out however. Usually after 4500 rpm on a hot setup. My car however had a bunch of PE adder in the 3200-4400 range before the MAF was actually maxed. It is easier to tune this way than fussing with hitting table 4-6 MAF cells. I did this tuning on the dyno. We watched wideband vs rpm and made changes to PE vs the rpms to dial in WOT tune.


IF you can hit the high MAF table cells in table 3-6, then by all means feel free to try tuning them. I found it much easier to tune MAF table 1 for idle and table 2 for most of my part throttle ranges and really just left table 3-6 alone. PE % enrichment was used for WOT tuning and my motor was ready to race within a few chip burns.


No they should be fine. Thats abit lean but not horrible. Especially if just doing mild throttle runs. My 383 did full pulls at WOT with over 17 to 1 air fuel before finally getting PE mode to bring it back to mid high 12's. I ran mid 14's to 1 around peak torque for a month before I dyno tuned it and saw I was that lean in the midrange. No damage.

slickfx3

Okay too lazy to hook it all up.. so I just went by the wideband...

I upped top half of maf 1 and the bottom 3/4 of maf 2, +10% and cruised at 12.5, that wasn't it; whoa,

back to the computer, I brought it back down, OK so the idle and cruise is a little leaner than before, hey I forgot where they were, I could read the old chip but the heck with it, cruise 14.8 -15 close enuff.

I did at that time hit maf 3 with a 10% increase, not thinking the whole time my foot was in it that much, but I was wrong,( you helped) it did the trick, on a cruise I can gingerly and I mean granny, press the pedal and it stays at 14.7 all the time gaining speed faster than the flow of traffic and when I look down at the speedo, I am breaking laws on the street.

punch it hard and it pegs at 12.4 and stays until I let up, through down shifts and everything, frankly it goes no lower than 15.4, unless I hit DFCO and it will see the 16.2.

I know I didn't get every little spot, so the question is....

how do you know the engine is "happy"?

and...

The pwr enrichment vs. rpm has negative numbers in it, is there an explanation?

-7.82
-7.82
-7.82
-7.82
-7.82
-7.82
-7.82
-7.82
-0.00
6.25
6.25
6.25
6.25
6.25
6.25
11.72
11.72

slickfx3

anyone are to chime in?

The pwr enrichment vs. rpm has negative numbers in it, is there an explanation?

-7.82
-7.82
-7.82
-7.82
-7.82
-7.82
-7.82
-7.82
-0.00
6.25
6.25
6.25
6.25
6.25
6.25
11.72

tequilaboy

With the standard PE vs coolant temperature settings for warm coolant (22.66%) and stoich of 14.73, 0% rpm PE will result in a target AFR of 12.0.

Positive PE vs rpm values will shift the target AFR richer than 12.0, negative PE vs rpm values will shift it leaner than 12.0, hence the need for signed values.

slickfx3

Thanks, I am currently only in open loop, I suppose this relationship is applicable to both open and close loop?

Orr89RocZ

iTrader: (20)

Yeah even in closed loop, when PE mode engages it looks up those values from that table. Negative is pulling fuel. Chances are you may need to add alot more for your motor once the MAF cant handle it anymore.