Standback can't make closed loop changes..

[cpolly69]

I see people say this all the time and I wonder where this information comes from?
Here's what I know from experience. When you plug in a pnp & sb on the MS3 your trims will go up and you will be adding fuel at idle and cruising speeds/rpms (even with all tables totally zeroed out on the tune that is loaded). It's almost a definite. This is because (from recently gained knowledge) the resistance to the sensors that the sb is tricking is increased ever so slightly because of the increase in the distance of the wires/electronics on the path from them to the ecu. If you just spend a little time driving around in closed loop with the bypass plug on, your trims will go down a little as the ecu learns. The won't go all the way down though. If you want them to you can add fuel by tricking voltages on the maf or tricking voltage on the fp sensor - Subtracting fuel by either by telling the ecu there is less air or telling it there is less fuel pressure then what there really is.
And, this works - you makes those changes and the trims go down and stay down.
Aren't trims closed loop calculations that are designed purely to maximize fuel economy?
So isn't what we are doing here closed loop changes??? I believe it is.
The bottom line to me is voltage manipulation is voltage manipulation - What difference does it make if you are in closed or open loop?
So to all the Cobb folks who always say SB can't make closed loop changes - Aren't you wrong? If I'm wrong, tell me how.....

[Lex]

closed loop refers to O2 feedback. If you modify the MAF voltage to adjust closed loop fueling, the trims will add/remove fuel to meet the 14.7 stoich AFR. If you adjusted so much it is outside the range of the trims you throw a CEL.

[gsrtype1]

im kinda D didint read the whole post but def sounds like an interesting topic!

[cpolly69]

Originally Posted by Lex closed loop refers to O2 feedback. If you modify the MAF voltage to adjust closed loop fueling, the trims will add/remove fuel to meet the 14.7 stoich AFR. If you adjusted so much it is outside the range of the trims you throw a CEL.

I understand the reference. I have recently learned that trims are being calculated via inputs from our narrowband, the fp sensor, and the maf, while cmd afr is coming more from the wideband, fp sensor, and maf. Hence why we have 2 sensors and the reason that if you put different parts on the car (like this pnp harness) you can have trims going bananas while stoich is being achieved at idle and cmd afr is still being achieved through various driving conditions. Hence, the more complex ecu/sensor setup in the MS3 that all the good ol port injected tuners out there do not get.

So each time I hear another tuner come along and say they already have tuned all these cars and have all this experience. I keep adding to the list of questions I have for them. Like -
How many o2s in the exhaust were on those cars?
How complex is your fuel pressure sensor, does it actually have integrated circuits inside it or it is simply volts in/ volts out.
I'm only learning, but I know what is working and what it not....

[CosmicArkie]

So, Lex and others, if you use the MAF Xfer, can you effectively adjust the trims for the PCM? I'm a complete rookie and just got a SB to play with. Be gentle.

J

[BoOdOg]

I'm just adding what happen with my car to this post. With no sb I would have very low ltft at idle +/-3 ltft. Add the sb drive 50 or 100 km and they would be +12. If I added the sb bypass within 20-30km my trims would go back to +/-3. I would then readd sb and it would go to +12 again after some driving. All easy driving no boost. Even with the +12 trims I would have near the 14.7 AFR at idle.

Changes to maf transfer in the sb gui and I was +/-1 after 200km. So I say your right and it can be adjusted to correct it. What you say now makes me understand why it changed when sb was connected. Thanks

[superskaterxes]

the SB makes changes for any RPM vs MAP/MAF/TPS. it doesent know if its in CL or OL but as long as your at x,y on the table its going to make a change.

[hnda etr]

Tricking vs. Reprogramming

Mmm

Hmmmm....

[Lex]

Originally Posted by CosmicArkie So, Lex and others, if you use the MAF Xfer, can you effectively adjust the trims for the PCM? I'm a complete rookie and just got a SB to play with. Be gentle. J

Trims just reflect how "accurate" your MAF table is compared to the actual mass air flow entering motor. The feedback is from the O2 sensor. So everytime you change the MAF table you are affecting what the ECU sees as MAF voltage and therefore impacting trims. Trims are most active during low load conditions, not WOT.

[subparpunk03]

There are other piggybacks on the market that make closed loop changes by changing the voltage output of the O2 sensor... the ecu sees 14.7 but reality is different and so you run richer.

When you change the things that the standback can control, the O2 sensor reports you running richer than intended so the ecu corrects via the trims.

When you change the o2 sensor itself, the ecu thinks you are hitting afr targets, but is actually running richer or leaner depending on how you set shit up. The second o2 sensor in our car might make this difficult to achieve because outside a certain threshold of error a cel is thrown.

So no, the standback cannot effectively make closed loop fueling changes because any of the sensors it can scale will be overridden by the o2 sensor providing the FEEDBACK part of the closed loop.

But yes, other piggybacks can make closed loop fueling changes, but only by altering the O2 sensor voltage. I don't think that will work on this car however. The feeback part of the closed loop fueling must be altered.

Here's an example of a piggyback that can do this, the MAP ecu:
http://www.urdusa.com/product_info.p..._id=1260518555

[cpolly69]

As to the maf xfer table - Think of that table as nothing more then a wide range adjustment tool vs the big maf table (primary or secondary) as a fine adjustment tool. You can do the adjustments on the big maf table and dial in exactly the rpm range (prob 800 to about 4k) and the voltage ranges needed (prob .5v to 3.3v) where u want to put some negative numbers if your fuel trims are high. Or if you used the maf xfer you would be just doing the same thing across all rpm ranges on the voltages you selected.
The maf xfer table is really best for weather changes. Ideally you develop your tune in the summer or winter (for those of us who live in changing climates), then when the climate changes you add or subtract fuel across all rpm ranges to keep things safe. You also may not want that fuel addition or subtraction in the higher wot throttles that you need to fix the trims.

When thinking about correcting trims, some of the articles I've read would suggest that newer ecus (like ours) may actually occasionally do a sort of ping or test some times where it goes min to max voltage to a sensor in order to keep things calibrated. I don't know if this is true for the mzr, but if it is a good way to combat this would be to use the big maf table and just put your changes across the entire voltage range from idle to 4k rpm.

[cpolly69]

Originally Posted by subparpunk03 There are other piggybacks on the market that make closed loop changes by changing the voltage output of the O2 sensor... the ecu sees 14.7 but reality is different and so you run richer. When you change the things that the standback can control, the O2 sensor reports you running richer than intended so the ecu corrects via the trims. When you change the o2 sensor itself, the ecu thinks you are hitting afr targets, but is actually running richer or leaner depending on how you set shit up. The second o2 sensor in our car might make this difficult to achieve because outside a certain threshold of error a cel is thrown. So no, the standback cannot effectively make closed loop fueling changes because any of the sensors it can scale will be overridden by the o2 sensor providing the FEEDBACK part of the closed loop. But yes, other piggybacks can make closed loop fueling changes, but only by altering the O2 sensor voltage. I don't think that will work on this car however. The feeback part of the closed loop fueling must be altered. Here's an example of a piggyback that can do this, the MAP ecu: Underdog Racing Development

I don't understand how I can make these changes on the maf table and the trims go down then. I know this method works form experience and so does changing things in the fuel pressure table (neg numbers to add, pos to take away).
We have already learned that this ecu is taking these pieces of information and putting them into many tables (mostly load tables) that other less complex ecus don't do. So maybe this ecu with it's 2 o2 inputs is doing something different allowing this to work....

[bykeryder4life]

in my experience, the only closed loop changes that can be made successfully on the SB are with the maf xfer to adjust fuel trims. cpolly You CAN make changes in the closed loop section of the maf table but when you do that the ecu learns those changes over time and eventually trims them out and you end up back where you started...

[SilverDemon]

I have never made any adjustments to the Xfer tables, only to the MAF tables. Some of the adjs. were made in the lower voltages and lower RPM's (cruising closed loop) to help with the LTFT's, and the ECU never "learned" the way back around those adjustments. Both LTFT's and SFT's were damn near zero. I ran that tune for 6 - 7000 miles. So, I am not sure if I totally understand how the SB is making these adjustments, but I do know it works.

[cpolly69]

What about the fact the Cobb guys are openly discussing that this ecu actually shifts the point at which it transitions from closed to open loop?
ECU Load cap shattered!
This shows that the information being taken is being factored into more complicated load tables before the decisions are actually made.
Some of our sensors actually have integrated circuits on them, they aren't just simple volts in/out.
Also why would CPE even make the tables with the lower, out of open loop areas if the changes you can make there didn't stay? Why not just make the table with 4krpm & up - and higher voltage ranges that can only be achieved at wot??
I think this ecu/sensor setup is more complicated and it allows single sided changes of input to the ecu to make real differences and I think CPE figured this out a long time ago.
Hell it's had the ability to crank up the fuel pressure since it's conception, they just knew that if you did you would run into all these barriers in these load tables I'm talking about. But they are doing this with only a single sided input change on the fuel pressure sensor. So if it works for the fuel? Why can't it work on the air? It seems like everyone is making the assumption that the maf/ 2 o2 setup works the same way it works on old obd1 cars.

[subparpunk03]

Originally Posted by SilverDemon Some of the adjs. were made in the lower voltages and lower RPM's (cruising closed loop) to help with the LTFT's, and the ECU never "learned" the way back around those adjustments.

No of course not. You are helping the ecu get closer to its target.

The fuel trims are there to make the ecu try and hit its desired AFR. When you adjust ANY of the maf tables, the ecu will say "oh, more air coming in, i should inject more fuel" and all of a sudden ,you are closer to your target, thus, trims go down. You are using the standback here to "trick" the ecu into doing what its already trying to do.

The problem is lets say you wanted to idle at 13.5 afr instead of 14.7. This is a hypothetical situation to illustrate my point, so don't get caught up in whether you would or would not want to do that. So you bump your MAF tables up so the ecu thinks more air is coming in than really is, so it injects more fuel. For a while you run your desired 13.5 afr, then slowly the ecu realizes this, and adjusts via the trims to pull fuel so you will eventually go back to 14.7 afr.

When you make corrections to lower fuel trims via the maf xfer or just the maf table, you are doing this to compensate for other things, but you are attempting to get the ecu to run how it WANTS to run. When YOU want the ecu to run richer than it wants to run in closed loop, thats when it fights you.

Originally Posted by cpolly69 So if it works for the fuel? Why can't it work on the air? It seems like everyone is making the assumption that the maf/ 2 o2 setup works the same way it works on old obd1 cars.

Because it doesn't work for the fuel... you add fuel pressure in closed loop, the ecu will run less duty cycle on the injectors to achieve its fuel targets. You trick the ecu into thinking it sees more air in order to get it to injecto more fuel, it eventually corrects because it reads the O2 sensor.

[cpolly69]

If trims are the real time calculation of cmd afr, then how can trims be wacko and cmd afr & actual afr be fine - via the stock sensor & an after market one i have?
Also, lets say that what you are saying about fuel pressure is true, since the ecu can decide to change shift to open loop based on load when ever - the fuel pressure still works great for flooring it. I guess the same principal can apply for fueling changes via the maf too, but I still think something else is going on.

[subparpunk03]

Originally Posted by cpolly69 If trims are the real time calculation of cmd afr, then how can trims be wacko and cmd afr & actual afr be fine - via the stock sensor & an after market one i have?

Can you elaborate a bit on what you mean by trims are wacko?

Trims are a percentage adjustment the ecu makes in order to hit its fuel targets. LTFT of 11% means "Inject 11% more fuel than baseline configuration calls for"

So if your trims are 11%, 15%, or whatever, its the ecu saying "inject more fuel in order to hit target afr. Does that make sense?

[fjames]

cpolly, I'm going to restate what I think you're saying and if I'm wrong just ignore me. If I'm right, maybe I can help.

Example scenario:

1. You show a consistent LTFT of +10

2. You add fuel by MAF manipulation and your LTFT is now +3

3. You interpret this as having made a CL change with the SB.

If the above is accurate (but simplified) then I think you're technically right, but fundamentally wrong. What you've done is make a change that the ecu compensates for in CL. It just happens that the compensation is a good thing. You didn't increase any fuel in the equation, you just stopped the ecu from adding it as a trim because you added it first.

[SilverDemon]

fjames, that is a very good explanation, and, to me it makes good sense. I think what cpolly is getting at is the blanket statement that is always said about piggybacks "you can't tune in CL". subpar said that you cannot change the target AFR in closed loop, I agree with that statement, but the trims can be manipulated so the ECU is not always adjusting for the mods on the car.

[cpolly69]

Thanks fjames
That was a good explaination. I think I understand now. The adjustments on the sb are not really making a cl change it basically just pushing things in the right direction. I've kinda had another thought in the middle of this at the same time. I think most of the port injection tuners are used to the ecu switching from cl to ol at a set point. Where as this ecu can swith when ever, depending on load conditions. I think this the real reason the standback works so well. Because it's changes do apply in ol. If you take a look at that thread loosh wrote on sb tuning, he's got a beautiful datalog at the beginning, and you can kind of see where things are crazy below 3100 rpm or so and then after that they get perfect. I would say that's the point where he floored it, the ecu switched based on the high load, and his changes took over at that low rpm.
Thanks for the feedback guys.


Sent from my iPhone using Tapatalk

[bykeryder4life]

nows when I wish laloosh was around still, he'd be able to tell us all about this shit. fuckin guy was a SB guru! I read his really old shit here and on 247..he was way ahead of the curve on this car

[cpolly69]

So after some testing and tuning with SilverDemon today - I believe SB can make closed loop changes to fuel pressure just fine (according to Lou at CPE as well) - It's the fact that (just like Subpar said) that the ecu is making decisions on info from maf & wb/nb and the sb is only intercepting the maf that does not allow it to makes cl changes in fueling that way -but
If your trims are up, you can toss some neg numbers in fp table and they will go down and stay down...
SB FTW

[djuosnteisn]

Didn't read every post, but most of them.... and it's as simple as this:

SB cannot change the closed loop afr targets of the ecu...


but it can definitely be used to calibrate an intake to hit the stock closed loop targets (stoich).

In fact, i'm 99% sure you can even calibrate a "big maf" without even getting the flash. 3.25" maf housing is roughly 75% increase, and the SB maf xfer table allows for 80% change IIRC.

And as stated, fuel rail pressure changes are also an alternative method for calibrating the intake, not just the maf xfer table or maf 30x30 table.

[SilverDemon]

Correct!! To me, there is no need to change the target AFR in closed loop. Let the cars ECU logic decide what the car needs to do when you are driving like a normal person..........LOL!! I did go out yesterday and adjust the fuel pressure tables to get the LTFT back into check, I was running about -8.2 in the LTFT's and -2.3 in the STFT's. After about 60 miles of driving and adjusting I finally got the STFT's to 0 and the LTFT's to -3. I am satisfied with the results and will probably leave them alone.