Adjusting MAF with Open Loop Fuelling

[Tor]

4th attempt...

I think this time it looks pretty successful. Whether it's a good idea or not, I don't know. But it is indeed possible to steer AFR with OL fueling.


http://datazap.me/u/tor/tor-206-3-lo...zoom=9038-9141

But I got a feeling that this is just patching an underlying problem: That the standard OFT AVCS' are not correct for the Gruppe S header.

I am getting more and more tempted to get it dyno tuned if only there was someone here that would do it with BRZEdit and leave it unlocked so I could keep messing with it myself afterward. Alas, that's not going to happen.


I accidentally made a 4th gear pull. How do you do that by accident? Well, I was rolling on at 50-60 km/h as usual, and I somehow missed that it was in 4th. I did feel it going a bit faster than my usual 3rd gear pulls at the top, but I didn't look at the speedometer. So it wasn't until I got home and looked in the log that I was actually sure. That's how badass the car pulls now!

Topping out at 170 km/h it was good that this was of course done at a closed off test circuit.

But it revealed that there is a lot of work to do. Temperatures have risen, so my IAT is now 12-15 deg C instead of 5 degs, and the engine doesn't like that as far as timing goes:



http://datazap.me/u/tor/tor-206-3-lo...zoom=7558-7762

Somehow my otherwise predictable slight positive LTFT are now negative so that probably also counter productive. Could it be due to the load change at 3700 rpm? In any case, I am going to lower it back to where it was as there is no point in having it at 1.25.

Next test could be to revert it all completely and instead to lower exhaust AVCS a deg or two. Is there any effective way to adjust AVCS without a dyno?

[Tor]

...and of course, I had to throw that 4th gear pull into virtual dyno.

Correcting the dip/top didn't have any effect on the curve (but I finally have my 185 whp ).



50 to 170 km/h in 18.6 seconds without changing gears isn't all too bad me think.

[Kodename47]

Load limits will not have any impact on the load that is logged, you can set it to 0.5 everywhere and you'll get the true loads that are calculated from the MAF calculation in your logged parameter. What the load limits do are set the maximum look up values in the tables and in the fuel (load) calculation. This is worth noting especially in the fuel and timing tables.

If the OL fuel table values are the same for all the load columns, then lowering the load limit will make it run leaner. A rich spike can be countered by doing this. The opposite can be done by raising the limits, so long as the loads aren't lower than the set limit.

Don't forget that changing the MAF scale will change the engine load, this can have a knock on impact with the load limits etc.

You must also consider the delay between cylinder and sensor, when changing the correct load and RPM cells.

[Tor]

Originally Posted by Kodename47

Load limits will not have any impact on the load that is logged, you can set it to 0.5 everywhere and you'll get the true loads that are calculated from the MAF calculation in your logged parameter. What the load limits do are set the maximum look up values in the tables and in the fuel (load) calculation. This is worth noting especially in the fuel and timing tables.

If the OL fuel table values are the same for all the load columns, then lowering the load limit will make it run leaner. A rich spike can be countered by doing this. The opposite can be done by raising the limits, so long as the loads aren't lower than the set limit.

Don't forget that changing the MAF scale will change the engine load, this can have a knock on impact with the load limits etc.

You must also consider the delay between cylinder and sensor, when changing the correct load and RPM cells.

Thanks a lot, that really helped my understanding of load limits.

Since you are the one starting me on all this, what is you opinion about the corrections I did to OL?

I am going to undo the changes below 4000 rpm and instead try out this:

[freerunner]

To not get things more complicated than it needs to (for a novice like me at least):
It could be of benefit to shift the exhaust and intake cam symmetrically, e.g. if you reduce your exhaust retard value, add same value to intake advance. Then you don't change the duration of the overlap event.
Think of an old 2-valve engine with a single cam.
You're just trying to close the exhaust valves soon enough to prevent the loss of the charge where the lean spikes are.

[Kodename47]

@Tor if it's working, then it's working. I would try and avoid massive swings in the OL table and try and work out what's happening and why. What seems to be overlooked here is injection volumes/IPW. This gives a better idea of what is going into the cylinder, rather than relying on just the output The logged load gives a half decent idea of the torque curve and the VE. Therefore you should be expecting the fuel delivery to be similar shape.

Use VGI's tool in the WOT pulls section of the log view tab as it gives easy comparison. I just opened AFR, DI IPW, PI IPW and load on the same chart one pull (pull 7 of the log2_31 above). It gives you a good indication of the delays I mentioned and easy to see why the AFR output is doing what it's doing

[Tor]

Originally Posted by Kodename47

[MENTION=97309]I just opened AFR, DI IPW, PI IPW and load on the same chart one pull (pull 7 of the log2_31 above). It gives you a good indication of the delays I mentioned and easy to see why the AFR output is doing what it's doing

Thanks a lot again. I need a hint though as to why it's doing what it's doing, please.

I also opened pull 4 of log0006_9 where the OL fuelling was not corrected yet. It looks like this (delays not so prominen):

It's this log:
http://datazap.me/u/tor/tor-201-1-4-...?log=0&data=22

I also added AFR_Command to the selection of the pull you tried out:



So now I'm confused as to what I am looking for? If it's the delay, then it seems I caused it by changing OL?

[Tor]

@freerunner thanks. My thought was actually just to smooth out the phasing in of the overlap, so it doesn't onset so abrupt.

Maybe I just plain and simple just straight over copy the OTS standard UEL AVCS instead. What I am running now is pretty much the OFT/OFH AVCS.

If I do change anything, I will be sure to study the ratio they are changed between the OFH and UEL tables. Thanks for the hint.

[aagun]

what is the secret on avcs? this is high technology knoledge on engine operation . on ur map there are 44° of overlap duration at uncontrollable area 4K rpm. that's mean in FA20 that the intake and exhaust cams opened 2mm at same time. in that error will push the air from intake to exhaust Directly without burn it . that air is full charge of fuel . (thats why it coz jumping afr to rich at that dip)
this is first reason .
2nd season there is low exhaust back pressure on aftermarket headers .
the 3rd is timing advance . it makes intake vacuum
4rd is where is the top of overlap

[Tor]

Originally Posted by aagun

what is the secret on avcs? this is high technology knoledge on engine operation . on ur map there are 44° of overlap duration at uncontrollable area 4K rpm. that's mean in FA20 that the intake and exhaust cams opened 2mm at same time. in that error will push the air from intake to exhaust Directly without burn it . that air is full charge of fuel . (thats why it coz jumping afr to rich at that dip)
this is first reason .
2nd season there is low exhaust back pressure on aftermarket headers .
the 3rd is timing advance . it makes intake vacuum
4rd is where is the top of overlap

How can I calculate the overlap from the two tables? And wouldn't it be on purpose that the intake and exhaust valves are open at the same time to help scavanging?

[Kodename47]

Originally Posted by Tor

Thanks a lot again. I need a hint though as to why it's doing what it's doing, please.

I also opened pull 4 of log0006_9 where the OL fuelling was not corrected yet. It looks like this (delays not so prominent).

It's this log:
http://datazap.me/u/tor/tor-201-1-4-...?log=0&data=22

I also added AFR_Command to the selection of the pull you tried out:

So now I'm confused as to what I am looking for? If it's the delay, then it seems I caused it by changing OL?

Are these done in the same gear? Obviously the delays change if the ramp is different speeds? The delay isn't the cause, my point was more of the case that you may need to change lower cells than the point of issue, so if the log is showing an issue at 4k you may be better adjusting those of 3.6-3.8k etc. Same with load if it's sweeping through cells quickly.

As for some help, have in mind this: If the fuel quantity remains the same but the AFR output goes rich, then the cylinder is getting less oxygen. If it goes lean, it's getting more oxygen but not all of this may be remaining in the cylinder depending on the overlap so may get a "false lean". There may be instances where EGR can mess with AFR readings, but this won't be the case on WOT so can be discarded. If you add fuel but it stays "lean" then there is a good chance that the intake charge is passing through the cylinder. What I've been trying to suggest is that you want the in cylinder AFR curve to be smooth and not swinging rich to lean. You want to repeat tests in the same gear etc but even then the AVCS can vary so you get differences pull to pull. So you want to look at changes of fuel quantity, the AVCS activity and the output AFR to get a good idea of what's going on. It's also why I treat the OL fuel table as just a fuel additive, because I'd much rather have my fuel delivery how I want it than needing my O2 sensor reading matching the AFR tables.

Originally Posted by aagun

on ur map there are 44° of overlap duration at uncontrollable area 4K rpm. that's mean in FA20 that the intake and exhaust cams opened 2mm at same time. in that error will push the air from intake to exhaust Directly without burn it . that air is full charge of fuel . (thats why it coz jumping afr to rich at that dip)

This could explain why it goes lean after the rich dip, not why it reads rich. The sensor won't see the fuel in the exhaust. It's also highly unlikely at low RPM that there is enough vacuum to pull the charge straight through the cylinder, this is where the load logs will be of some use. Those logs show a dip in VE where these fluctuations are happening so it's not a sudden vacuum. Also, most of the fuel is provided by the DI. There is a much lower possibility (almost impossible?) of this being blown through the exhaust valves.

Originally Posted by Tor

How can I calculate the overlap from the two tables? And wouldn't it be on purpose that the intake and exhaust valves are open at the same time to help scavanging?

My AVCS tool

There's a formula in there you can add to your logs if you want to get the overlap into the log tools.

[aagun]

my tool for overlap calculation
CAM LUMPY TOOL

[Tor]

Thanks both of you, I will check out those tool.

I did make one more test, with little success.

This time I tried the OTS stg 2 AVCS:

It looks like this:


Vs. OTS/OFH AVCS:




I think this has been enough testing for me. I will revert to the OFH AVCS and just correct the lean bit above 4k with OL and live with the dip and leave it alone. All the pulls with the heavy correction to OL shows the delay no matter which gear. So I suppose the conclusion of this could be: For smaller corrections OL is okay, for bigger ones it can potentially mess things up?

P.s. I might try smoothing the exhaust valve below 3600 as shown previously as a last test.

[Kodename47]

Originally Posted by aagun

my tool for overlap calculation
CAM LUMPY TOOL

I believe many of these calculations were wrong, you had both cam settings the wrong way round. Intake is advanced and exhaust is retarded by values in the table. Nice idea though, so I have re-worked it. I'll have it up later,