Commanded Fuel when in open loop and PE modifier based on RPM

[Thumper]

Hi again
I have another noob question. I am finally getting cracking on with my autoVE. I have been set back by one duff sensor after another. I have intalled the new one and its now doing what it says on the tin....so to speak.

One thing that I need clearing up tho, is the PE modifier based on RPM and the OL commanded table.
How does the PE modifier affect the fuelling and why do you set it at 14.63 during the AutoVE process?
Does this mean that I should see 14.63 on my WB when PE mode is activated or should I see 12.95 as per the autoVE setting in the commanded OL table?

Hope you guys can help novice out here.

BTW, after reading all your posts on idle tuning, I have now waxed the idle. I even got the idle so smooth you cant hear the cam. I was a bit dissapointed so I tweaked around and got it sounding a bit meaner and still keeping a solid idle. This is addictive!!

Thanks for your help!!

[joecar]

Thumper,

During AutoVE you don't want transitions to/from PE to give you incorrect BEN values...
for example, if CFOL was 13.80 and PE was 12.80, when the transition CFOL->PE occurs, your commanded AFR jumps richer by 1.00, and the wideband being located about 24" from the combustion chamber would lag behind... your measured AFR would produce an incorrect BEN during that transition.

The PCM selects the richer of PE or CFOL... so you will see 12.95.

Cheers
Joe

[Thumper]

thanks Joecar, clears that up for me. Really enjoying the software now. The more I get a grasp on it, the more I enjoy it!!

[Redline Motorsports]

Don't forget that once you are done tuning the VE table and start to do PE, that you return the PE values back to "power enriched" air fuel ratio values. You should shoot for 12.7 in PE. Adjust your MAF to dial that in.

Howard

[SSpdDmon]

Another option - if you're planning on returning the car to closed loop operation - is to set it up to reflect how the car will be when you're done. In other words, above 130~150*F, I set the entire Comm. Fuel in OL table to stoich (14.63), adjust my PE enable settings to my liking (based on observed logs - kPa, RPM, TP%, etc.), and set my PE AFR's appropriate for tuning. While tuning, you can use the filters in your log to tune out PE, non-PE operation and the transition between the two (if AFR is less than x.xx, is greater than x.xx, or is changing more than x.xx per 500ms).

Personally, I like to tune based on how the end result will operate. Neither way is more right/wrong than the other though.

[hquick]

I thought I'd heard that people were leaving the PE enabled for AutoVE'ing?
Especially those FI'd???

[Redline Motorsports]

I thought I'd heard that people were leaving the PE enabled for AutoVE'ing?
Especially those FI'd???

Yeah but if command 12.0 in PE and hit PE conditions while trying to dial in cruise AFR of 14.7 you will dilute the readings. By locking out all PE you will ensure you will always be commanding stoich. This is why other adder tables are also zeroed out.

[SSpdDmon]

Yeah but if command 12.0 in PE and hit PE conditions while trying to dial in cruise AFR of 14.7 you will dilute the readings. By locking out all PE you will ensure you will always be commanding stoich. This is why other adder tables are also zeroed out.
Why would you want a 14.7:1 AFR anywhere where PE would normally be enabled? Those diluted readings you speak of should be filtered out IMO - not eliminated because you disable PE.

[BlackGMC]

I am confused, during the AutoVE process your logging the error inbetween commanded and actual... What does it matter if your in PE anyways??? Your still logging the difference between commanded and actual right?

[hquick]

I am confused, during the AutoVE process your logging the error inbetween commanded and actual... What does it matter if your in PE anyways??? Your still logging the difference between commanded and actual right?


That was my way of thinking....but maybe I'm wrong.

[redhardsupra]

yes, PE does not matter, cuz it's accounted for with commanded AFR. it's an old concept leftover from days of tuning with trims where commanded AFR was NOT accounted for. the problem is that it have proliferated into many writeups so it became a 'fact' regardless of how wrong it is.

[Thumper]

:cheers:Thanks for all the replies

[joecar]

PE is included in the commanded AFR...

The problem is when the PE differs widely from the CFOL, and the PCM transitions from CFOL to PE... (see my example AFR numbers above)... the wideband, being located some distance downstream, takes some finite time to react to the step change in AFR... during this transition the BEN will not be true.

It may or may not make any difference...

I do AutoVE with PE enabled... I set the last 2 columns in my CFOL equal to my PE... so there is no step transition.

$0.02...

[hquick]

That's pretty much how mine is setup Joe.

[VTC_WS6]

PE is included in the commanded AFR...

The problem is when the PE differs widely from the CFOL, and the PCM transitions from CFOL to PE... (see my example AFR numbers above)... the wideband, being located some distance downstream, takes some finite time to react to the step change in AFR... during this transition the BEN will not be true.

It may or may not make any difference...

I do AutoVE with PE enabled... I set the last 2 columns in my CFOL equal to my PE... so there is no step transition.

$0.02...


Assuming you set CFOL so that the highest columns read what your PE AFR would be tuned for (say 12.95 AFR just an example number), and you dial in the VE table that way, what would the difference be when you later activate PE and set it to command the same AFR? Theoretically by disabling PE, you're ensuring the VE table is acurate without any outside influence so that you're starting with as accurate a fueling model as possible.. is this correct?

If so I guess it wouldn't really matter whether or not you have PE enabled during tuning since ultimatley the commanded fuel would be the same number dialed in while tuning.

I love this stuff :cheers:

[joecar]

PE and CFOL set the AFR... VE sets the airmass.

The problem occurs when CFOL transitions to PE and the AFR is significantly different between the two... the actual AFR always lags a little behind (it's measured further downstream from where the VE is applied) so your BEN will be slightly inaccurate for some number of tenths of a second.

[SSpdDmon]

PE and CFOL set the AFR... VE sets the airmass.

The problem occurs when CFOL transitions to PE and the AFR is significantly different between the two... the actual AFR always lags a little behind (it's measured further downstream from where the VE is applied) so your BEN will be slightly inaccurate for some number of tenths of a second.
Which is why you filter out transitions. :D

Like I've always maintained - if you plan on going back to closed loop, you should tune based on how that system works. In order to do that, you set the CFOL table to stoich for all kPa just below operating temps (i.e. ~150*F and up). Then, use your PE as it was intended to be used. If you're not getting enough fuel soon enough, you'll need to adjust the PE enable based on your TP%.

In closed loop, this is how the car operates. If you're not at the right TP%, you'll be commanding stoich even if the MAP is reading 90+kPa. Now is the time to get that ironed out.

[Chevy366]

Which is why you filter out transitions. :D



Which is why it is the same as without PE , hence "filter out" to remove .
I say do PE at Stioch , no need for filtering , not really setting AFR just airmass with VE .

[WeathermanShawn]

SSpdDmon:

Not my thread, but relevant to the poster's original question.

Could you elaborate further on your method of CFOL vs PE TPS% enable?

I believe I understand what you are getting at. You don't want to be at stoich when you are at higher kPa's. Sounds like you have a different twist on how to do this.

Got any more details that you can share?

Thanks.

..WeathermanShawn..

[SSpdDmon]

As I mentioned above, those who are tuning in open loop and have plans to return to closed loop should simulate how the car is going to perform in the end. In order to do that, you simulate closed loop by commanding a stoich AFR for all kPa’s in the CFOL table near operating temps. Any time PE is not active, you’re commanding stoich (just like the car does from the factory). Once PE kicks on, it overrides the stoich AFR and commands the richer AFR (like the car does from the factory). IMO, tuning this way is a more accurate simulation to how the car will perform when it’s returned to CL.

What I was getting at was…as you’re tuning, you should be paying attention to how much throttle it takes for you to hit higher MAP kPa’s. This will help you set the PE Enable vs. TP% table to avoid placing the motor under a heavy load while still commanding a stoich mixture. Down low (less than 2K RPMs), it may not be as vital. At those levels, you can probably get away with a leaner mixture. But, once the engine starts making power, you’re going to want to richen the AFR up at the right time (i.e. by 85~90kPa). The stock enable table is rather high for my tastes – especially when you’re dealing with an engine that has had some upgrades (cam, headers, etc.) – and it may end up putting you in a part throttle hole that commands stoich with too heavy of a load on the engine.

If it were my car, I’d want PE to kick in by 90kPa at any RPM. Then, I’d probably set the PE AFRs so that they start out a little lean (13.5:1 or so down low), have them progressively richen up to 12.8:1 by 2800~3200RPM, and then ride that 12.8 out to the top. Mix that AFR with about 27* of timing @ WOT from 2800RPM on up for most any cam swapped LS1 and you’ve got a great starting point for making some nice numbers. :D

[WeathermanShawn]

O.K I am pretty sure I got it now.

Your main point is to be aware of what TPS% relates to a certain kPa and to be in PE mode during those heavier loads/higher rpm.

Got it.

I'll start mapping TPS% against kPa. For now, I have followed your advice and enabled throttle openings for PE to 20%.

I'm at altitude and 83-85kPa is max out here.

Thanks for the explanation. To the original poster, thank you for letting me add a question.

..WeathermanShawn..

[SSpdDmon]

O.K I am pretty sure I got it now.

Your main point is to be aware of what TPS% relates to a certain kPa and to be in PE mode during those heavier loads/higher rpm.

Got it.

I'll start mapping TPS% against kPa. For now, I have followed your advice and enabled throttle openings for PE to 20%.

I'm at altitude and 83-85kPa is max out here.

Thanks for the explanation. To the original poster, thank you for letting me add a question.

..WeathermanShawn..
Wow - only 85kPa? That must be fun.

[Thumper]

Thanks for the explanation. To the original poster, thank you for letting me add a question.

..WeathermanShawn..

Hey so long as I can learn a thing or two from it, add as many as you want.

[WeathermanShawn]

Yes, up here in the 'High Country' 60kPa equates to ~20% throttle, 100% throttle ~85kPa.

Thanks for the CFOL tip (stoich). As many times as I used that table, it was not until now I totally realized that values of AFR (richer) are not referenced unless you are in PE mode.

Makes me reconsider my VE computations. It is all based on the 'stock' CFOL settings which richen AFR as kPa's increase. But, if running closed-loop and not in PE, then it's 14.63.

On a side note SSpdDmon, successfully utilized your hotly debated IFR tuning method for us 'closed-loopers'. Worked like a charm. Trims went from +10% to 0 to -5. And this was after I calibrated the MAF, so there was not much room to go there.

And it took all of about 10-15 minutes.

Thanks.

..WeathermanShawn..

[SSpdDmon]

Yes, up here in the 'High Country' 60kPa equates to ~20% throttle, 100% throttle ~85kPa.

Thanks for the CFOL tip (stoich). As many times as I used that table, it was not until now I totally realized that values of AFR (richer) are not referenced unless you are in PE mode.

Makes me reconsider my VE computations. It is all based on the 'stock' CFOL settings which richen AFR as kPa's increase. But, if running closed-loop and not in PE, then it's 14.63.

On a side note SSpdDmon, successfully utilized your hotly debated IFR tuning method for us 'closed-loopers'. Worked like a charm. Trims went from +10% to 0 to -5. And this was after I calibrated the MAF, so there was not much room to go there.

And it took all of about 10-15 minutes.

Thanks.

..WeathermanShawn..
Eh....skinnin' cats....you know how it goes. http://motownmuscle.com/forums/images/smilies/lol.gif

[Dopey]

Sorry if its a stupid quesion, but what if you were to flip the coin and have PE constantly enabled and set all PE values to say 12.8 AFR? That way there is 0 transitions, even between different points on the map!

[WeathermanShawn]

Someone else may have to clarify if this is a practical solution.

If you were to successfully enable a PE of 12.8 (constantly?), that would be a pretty rich AFR for everyday driving.

Fuel economy, plugs, etc., might suffer.

I get your point, but perhaps PE is best served as a 'semi open-loop' tool.

Better to just set your PE TPS% to enable sooner when your engine is under load.

..WeathermanShawn..

[joecar]

For tuning: set CFOL and PE as SSpdDmon said.

For driving: set CFOL suitably for cruising and PE for power enrichment with suitable enable (i.e. when you mash the throttle).

[SSpdDmon]

For tuning: set CFOL and PE as SSpdDmon said.

For driving: set CFOL suitably for cruising and PE for power enrichment with suitable enable (i.e. when you mash the throttle).
:D ...

[Kurtomac]

if youre not at 100% TP is PE still gonna get activated?...or is it just based on the RPM B-0120 is set at

[redhardsupra]

what's a CFOL?

[WeathermanShawn]

Yes, it can be enabled for any TPS %.

The table you need to look at is B3616.

For instance I have mine set to enable from 15-20% 1600 rpm's up. In my case it has really helped push in a little more fuel when under load.

I am running closed-loop with MAF. Ran flawlessly this week on a run at elevations near 12,000 feet. For me I am essentially using the PE function as a 'semi-open loop', and after 2-3 months of learning and effort I am very pleased with my tune.

Hope it works out well for you.

..WeathermanShawn..

[redhardsupra]

Shawn, if you're running that high up, your airmass is a lot smaller than in normal conditions. Your effective compression is much smaller than it would be at sea level, so you could probably get away with a much more aggressive settings for PE activation, as it takes a lot more effort for your car to hit the compressions where you'd need the enriched mixture. same goes for timing, but that's automatically covered since the timing table is on a airmass axis.

[WeathermanShawn]

Marcin, thanks for the tip.

I will definitely do some testing at various loads and elevations over the next few months.

Scientifically I understand what you are saying about altitude and compression. My sea-level CR is ~11.0:1, but even at this higher elevation I have had to constantly fight that inevitable pinging and occasional knock.

This was the first tune I put over 300 miles on and beat the ping!

Again thanks for the tip.

..WeathermanShawn..

[redhardsupra]

hm, you might be confusing a ping coming from too much timing per compression, with a ping that happens from high load as a result of going up hills, which happens a lot at altitude, unless you're at some huge plateau.

i spent few weeks trying to pinpoint a cause of ping in this supercharged cts-v once, and it turned out that the owner was just lazy and thought driving up a hill in 5th gear with a 4000+lb car is OK. hills don't show up in logs, to me it just pinged at random. this is why dynos and steady flow conditions are golden.

[WeathermanShawn]

Agree.

Down shifting cures many a problem. It is easy to 'lug' up hills if you don't figure out it is time to down shift.

Fixed it though.

Yes, the dyno is a good controlled way to figure out many a problem. Terrain and elevation has its own unique challenges.

Talk to you later.

..WeathermanShawn..

[joecar]

Yes, one is pre-ignition, the other detonation, they work differently but have similar results.

[joecar]

Marcin, CFOL == OLFA (the table).