O2 Feedback-SMEC

[MopàrBCN]

Hi,

is there an easy way to switch on and off O2 Feedback in the SMEC Cals?

I would love to try something out but haven't got my car running, therefor no chance to trial and error.

Info apreciated!

Thanks!

[Anonymous_User]

Well, kind of... push throttle to floor = no O2 feedback. Lift right foot = O2 feedback.

Probably not what your looking for

[ShelGame]

I've never tried this, so I don't know if it will work. But, you could try to set MAPDEC_NoCellUpdateAndO2CNTRHeldBelowThisMap to a high value. I think this will essentially force the O2 control to work the same as if you were at full throttle.

If you look at the S60 cal, it has this value set to 0xfe or oxff. So, I think this is the one to use to disable O2 feedback.

I assume you want to do this so you can tune your part throttle fuel? I think that's probably the best way to do it. If you disable the O2 feedback (and the adaptives) then you can see what effect your fuel tables actually have in part throttle. When you're done, set that value back to stock (0x0d) and you should be good to go.

[GLHNSLHT2]

Rob is there a place to get the address' for the O2 kick and the above table in your old T1 based cals?

[ShelGame]

The primary ramp values start at 0c845a ; the first 2 values are the RPM boundaries ; the 2nd 2 bytes are the MAP boundaries (I have the MAP boundaries ID'd in the old cals) ; the kick cells start at 0x845e and go thru 0x8470 ; the limit cells start at 0x8472 and go thru 0x8484.

For each cell, the first byte is the 'rich' value, the 2nd is the 'lean'. if the O2 sensor is reading lean, then the 'rich' kicks are used and vice versa.

Here's what Geoff wrote about how these cells work:

; *****************************************
;      O2 Controller Ramp Calibration
; *****************************************
; How it works:
;   The O2 sensor is monitored but ONLY for "rich/lean". Even though
;   the O2 sensor value is from 0 to 15, the only thing that counts
;   for this system is whether it is "rich" or "lean". A change from one
;   to the other is a "toggle". The system constantly toggles between
;   rich and lean so that the overall average is around stoichiometric.
;
; Background information (from the net:)
;     An "ideal" fuel/air mixture in which both the fuel and the oxygen in the air are
;     completely consumed is called the "stoichiometric" mixture. The stoichiometric mixture
;     is usually specified as the ratio of the mass of air to the mass of a particular fuel.
;     For example, if a fuel required 10 kg of air to precisely burn 1 kg of the fuel (that is,
;     all the fuel burned and there was no oxygen left in the air afterwards) then the
;     stoichiometric ratio for that fuel would be 10:1.
;
;     Chevron give the stoichiometric ratio of air mass to fuel mass for gasoline as 14.7:1,
;     but don't specify the composition of this hypothetical gasoline.
;
;     From http://www.faqs;.org/faqs/autos/gasoline-faq/part2/ comes the following table
;     of typical stoichiometric air-fuel ratios:
;
;	     Fuel   | Stoichiometric air-fuel ratio
;	 -----------+------------------------------
;	   methanol | 6.4
;	    ethanol | 9.0
;	       MTBE | 11.7
;	 ETBE, TAME | 12.1
;	   gasoline | 14.6
;
;     An oxygenated gasoline with 89% gasoline and 11% MTBE would then have a stoichiometric
;     ratio of 14.281 (note that this would require a Wide Band O2 sensor to adjust, since the
;     O2 sensor in our cars is designed for gasoline only, and is a very narrow range. In case
;     you were wondering, this is one reason some people are interested in Wide Band O2 sensors.)
;
; *****************************************
; This system divides a range of RPMs and MAP readings into "cells". The number of
; "kicks", or increases/decreases in fuel required to toggle the O2 reading, is different
; for each of these cells. This allows some fairly powerful flexibility in tuning. The
; only time you might want to adjust these values is for different injector flow rates,
; or to speed or slow the adjustment being performed.
; *****************************************
; Note to tuners: DO NOT AIM FOR STOICHIOMETRY! Although it might be fine for idle or
; low speed operation, at higher RPMs and under boost you DEFINITELY want a RICH mixture.
; This is because stoichiometric combustion generates the most heat. No current engine
; would survive very long with the temperatures this would generate, hot enough to melt
; the engine.
; *****************************************
; Each cell has a kick value. This is the amount of change applied to the running fuel
; every eleven millisec until a rich/lean toggle occurs. The net result is the
; familiar rich/lean flashing that your O2 sensor gauge shows you.
; *****************************************
;
; (one kick per 11ms)
; Fudge factor: if an O2 toggle occurs before the primary ramp
; finishes, then the "first" step in the new direction is limited
; to the accumulated steps before the toggle.
;
;		Cells:
;
; HIRPM  +-----+-----+-----+
;	 |  2  |  5  |	8  |
; RPM#2  +-----+-----+-----+
;	 |  1  |  4  |	7  |
; RPM#1  +-----+-----+-----+
;	 |  0  |  3  |	6  |	    Idle Cell: 9
;	 +-----+-----+-----+
;	  Map#1 MAP#2 HIMAP

The kicks are calculated by the following :
Say you want a 5% kick -> (1.05 * 512) - 512 = 25.6 (dec) = 0x19 (hex)
So, each bit is ~ 0.2%.

If you want to make P/T run leaner, then simply increase the lean kicks and/or decrease the rich kicks. Keeping in mind of course how much percentage change each 'kick' is worth.

Also, you may want to adjust the 'limit' cells if you are making a large change to the kicks. The limit cells are how many kicks can be added before the adaptive cells get updated.

There is also a secondary ramp starting at 0x8492. It has the same structure as the primary ramp. I am not yet sure on the conditions that force it to switch between the primary and secondary ramps.

[turbovanman²]

Damn, lol, why do they have to make it so complicated,

[ShelGame]

OK, looks like the secondary ramps only come into play if the O2 sensor is stuck rich or lean for too long. Too long being a second or two I think.

[MopàrBCN]

I've never tried this, so I don't know if it will work. But, you could try to set MAPDEC_NoCellUpdateAndO2CNTRHeldBelowThisMap to a high value. I think this will essentially force the O2 control to work the same as if you were at full throttle.

If you look at the S60 cal, it has this value set to 0xfe or oxff. So, I think this is the one to use to disable O2 feedback.

I assume you want to do this so you can tune your part throttle fuel? I think that's probably the best way to do it. If you disable the O2 feedback (and the adaptives) then you can see what effect your fuel tables actually have in part throttle. When you're done, set that value back to stock (0x0d) and you should be good to go.

Hi, THANKS, yes, you got it :-)!!

[GLHNSLHT2]

I'm just as lost as simon.

[MopàrBCN]

Hi,

look:

Tuning fuel for wide open throttle is fairly easy even if you haven't got a Wideband, because O2 Feedback is not used to control fuel. Instead the computer looks up preprogrammed table values tu give you the fuel you need.

Why is this easy?

Because meanwhile the Computer is not trying to dynamically adjust fuel, the O2 Sensor reading is constant. Even with a narrowband you can get your fuel quite reliably to where you would like it.

In Part Throttle the game changes.

While you have base fuel tables you can tweak, whatever you do, O2 Feedback will try to fight it.

Thus, if you have a Narrowband it is impossible to read if you are lean or rich. More importantly you don't really know, what is responsible for where you are: Your Fuel Setting or the Correcting algorithms the computer uses.

However, it is quite important to have the base fuel tables right - as well in part throttle, because only then you can take advantage from the Pumping Efficency Table to tweak the global picture of your tune.

To get to this, one thought of mine was, if I could disable O2 Feedback, I should be able to get a good baseline for all fueling conditions, I.E. Part Throttle and Full Throttle. Once set so that they are related well proportionally I can re-engage O2 Feedback, and then, knowing where Part Throttle fuel realy is, I can foresee/judge the effect, tuning the kick cells

[MopàrBCN]

Well, kind of... push throttle to floor = no O2 feedback. Lift right foot = O2 feedback.

Probably not what your looking for

So you mean, with my throttle pedal I would have kind of a "On/Off" Switch an switch modes whenever I want to.... it's not a bad thought

[GLHNSLHT2]

I know what you mean about tuning and wanting to turn off the O2 feedback to tune the idle/PT tables and it would be nice. But when Rob starts talking about kick cells and min/max/square root this and that blah blah blah I get lost fast. I can drag the line around to do with what I want. But once you get into the code and how it works I'm like a deer in headlights. I just don't get it having it explained to me over the internet. for the most part and I don't have someone local that will walk me through the programming/HEX side of things. I also probably don't have the programs on my computer to be able to look at that stuff anyways.

[turbovanman²]

I know what you mean about tuning and wanting to turn off the O2 feedback to tune the idle/PT tables and it would be nice. But when Rob starts talking about kick cells and min/max/square root this and that blah blah blah I get lost fast. I can drag the line around to do with what I want. But once you get into the code and how it works I'm like a deer in headlights. I just don't get it having it explained to me over the internet. for the most part and I don't have someone local that will walk me through the programming/HEX side of things. I also probably don't have the programs on my computer to be able to look at that stuff anyways.

In the same boat.

I have a Hex editor loaded so I can see that part, google has plenty, and apparently you can alter it in Dcal but I haven't figured that part out either.

[ShelGame]

Well, I labelled all of the O2 kicks and limits in the template files for T-SMEC - with the original address. So, you could load up one of the 2.5 cal templates and read what all of the cells are and what thier addreses are.

I wish I could make it easier, sorry.

Geoff was planning to add a ramp editor the CHeM2, but never did...

[turbovanman²]

How do you turn off the ox sensor?

I've had some good chats with some guys and the reason our/anyone's MPG sucks is the need to cycle the ox sensor to light off the cat, this waste's fuel.

I want to put my system in open loop and tune it accordingly.

[ShelGame]

How do you turn off the ox sensor?

I've had some good chats with some guys and the reason our/anyone's MPG sucks is the need to cycle the ox sensor to light off the cat, this waste's fuel.

I want to put my system in open loop and tune it accordingly.

Post #3, this thread...

[turbovanman²]

Post #3, this thread...

Crap, I'd thought I'd seen it but didn't go up that far,

What is the file name for it? the one you list or?

[risen]

Damn, lol, why do they have to make it so complicated,

Because that's the way of the TD ECU . Although, I thought the O2 code was as straightforward as something that complex could be. But, there's plenty of other things that are more complex than they need to be. The fueling and timing code/tables come to mind along with the boost goal calculation.

[puppet]

Wouldn't it be something if you could load MS code on our chip and tune with that?

[ShelGame]

Because that's the way of the TD ECU . Although, I thought the O2 code was as straightforward as something that complex could be. But, there's plenty of other things that are more complex than they need to be. The fueling and timing code/tables come to mind along with the boost goal calculation.

Actually, I think the boost goal calculation is as simple as it gets in our code. Though, you're right about the spark and fue lstuff - especially the adaptives...