Not seeing the gain I expected. :-( What's going on?? **solved**

[Kodename47]

.... Just take some fuel out the fuel map. If MAF scale is good, then don't use that to fix it. There's more than one way to do it

[solidONE]

Originally Posted by Tor

Thank you for your help. I didn't consider minute grip differences could be a factor, but that would make sense. But wouldn't wheel spin cause a lower reading? I mean we measure the time it take to accelerate a certain mass to a certain speed, and if it takes longer to get there it should show an overall lower reading? I understand it may locally bump the curve up where the spinning is taking place

I believe Vdyno measure how quickly RPM's build for a given gearing/weight to make it's calculations. Therefore, a spike in the RPM will be falsely calculated as an increase in power.

[Tor]

Originally Posted by Vin

I played around with some MAF scaling (generated by a friend) , the lean hump at 4 - 4.5k rpm was then resolved. However the rich dip at 3.5 - 4k rpm remained.

Yes it's difficult because it all happens between 3 and 3.4 volts when you only have 2 point on the curve to manipulate. I could try and richen up 3.4 a notch, but I am guessing it would create another problem.

Originally Posted by Kodename47

.... Just take some fuel out the fuel map. If MAF scale is good, then don't use that to fix it. There's more than one way to do it

You mean instead fix it in open loop fueling so that AFR becomes correct and AFR_Command has the tops and valleys instead?

Originally Posted by solidONE

I believe Vdyno measure how quickly RPM's build for a given gearing/weight to make it's calculations. Therefore, a spike in the RPM will be falsely calculated as an increase in power.

Yes, that's what I meant with locally more power. But once the wheels grip again I would assume the subsequent data would then be calculated as a decrease and looking over a bigger part of the graf RPM would build slower because time was wasted spinning the wheels?

[Wayno]

It doesn't necessarily mean it's running rich, just that there's more fuel blowing by the valves and past the O2 sensor, so may actually be lean. It's not even below 11.5. Unless making it leaner produces actual measurable power, leave it as is.

[Kodename47]

Originally Posted by Tor

You mean instead fix it in open loop fueling so that AFR becomes correct and AFR_Command has the tops and valleys instead?

Yes, in open loop you don't need commanded and actual AFR to match.

Originally Posted by Wayno

It doesn't necessarily mean it's running rich, just that there's more fuel blowing by the valves and past the O2 sensor, so may actually be lean. It's not even below 11.5. Unless making it leaner produces actual measurable power, leave it as is.

Reverse that logic Unburnt fuel isn't measured by the sensor, so it can't read richer than the burnt mixture. It can read leaner than the total fuel injected, but not the other way around. A more stable AFR is ideal, you want it to gradually richen up. For the sake of a quick tweak to the fuel map, it's an easy fix. Helps with EGTs etc, the timing curve I'd imagine is smooth so you don't want it too rich when the timing advance is less. You want them to almost be the reverse of each other.

[Tor]

I made a video of the drive when I was logging. The second of the 4 pulls is at 1:50 into the video with datazap overlay. As one can imagine from the rest of the video it's pretty difficult to find a flat level road here. The one in the video runs along a river, that's why I'm pretty sure it's level. There are a lot of roads here that looks level but has a lot of gradient, which becomes apparent when doing pulls in both directions.

[ame="https://www.youtube.com/watch?v=Hw0JiDWUpBc"]DIY tuning: Performance check... - YouTube[/ame]

Originally Posted by Kodename47

Yes, in open loop you don't need commanded and actual AFR to match.

Thanks for the explanation. It's good to know there are other options than messing with the MAF. Which I would rather not touch anymore except to richen up the top a bit if LTFT doesn't take care of that eventually (crap weather here again).

Reverse that logic Unburnt fuel isn't measured by the sensor, so it can't read richer than the burnt mixture. It can read leaner than the total fuel injected, but not the other way around.

I had to read this several times and my head is about to explode thinking about what unburnt fuel may do to an O2 reading. You say "it can read leaner" i.e it's actually richer, where Wayno say it "may actually be lean". If the O2 sensor just reads the oxygen ratio, isn't all what unburnt fuel can do just to dilute the remaining composition of the exhaust gasses? Which in terms would mean the sensor reads less oxygen (rich?) - In that the reading is rich and the actual combustion is leaner than the reading? Or where is the fallacy?

Arggg my head is slowly exploding in a lean, knock filled detonation! Got to think of something else quick!!




(Ahh, now I'm feeling better again. )

A more stable AFR is ideal, you want it to gradually richen up. For the sake of a quick tweak to the fuel map, it's an easy fix. Helps with EGTs etc, the timing curve I'd imagine is smooth so you don't want it too rich when the timing advance is less. You want them to almost be the reverse of each other.

As you can see the car hauls pretty good now. So on one hand, I am inclined to leave it as it is as Wayno suggests. On the other hand, I am curious by nature and yes, being a perfectionist, the bump bothers me. If I was to apply corrections to OL: Would this look in a reasonable order?





Markers at 3200, 3600, 4000 and 4400 rpm:
Log here...

[jvincent]

Originally Posted by Tor

Yes it's difficult because it all happens between 3 and 3.4 volts when you only have 2 point on the curve to manipulate. I could try and richen up 3.4 a notch, but I am guessing it would create another problem.

One of the things I did was completely change the MAF scale so that I have a lot more points in the critical region around 3V.

I don't have the numbers in front of me but my MAF scale tops out at 4.25 V since I am not boosted. I also changed the spacing of the voltage points down in the very low region where it is very linear. The end result is I have a more points to work with in the 2.5V to 3.5V region.

[Kodename47]

Same as the MAF, calculate the fueling error and multiply the commanded AFR as required. Need 5% less fuel, multiply the table value by 1.05.

Originally Posted by Tor

I had to read this several times and my head is about to explode thinking about what unburnt fuel may do to an O2 reading. You say "it can read leaner" i.e it's actually richer, where Wayno say it "may actually be lean". If the O2 sensor just reads the oxygen ratio, isn't all what unburnt fuel can do just to dilute the remaining composition of the exhaust gasses? Which in terms would mean the sensor reads less oxygen (rich?) - In that the reading is rich and the actual combustion is leaner than the reading? Or where is the fallacy?

The Lambda sensor is a gas sensor. Unless you were to literally flood the exhaust with fuel, unburnt fuel is not detected. Think about it like this, if you have a lot of cam overlap there can be air bypassing the cylinder and therefore the reading can be lean. But you can't have a reading that is richer than the mixture in the cylinder. Unburnt fuel reaching the exhaust will be almost always be when there is cam overlap and therefore a lean reading will occur.

[Tor]

Originally Posted by Kodename47

Same as the MAF, calculate the fueling error and multiply the commanded AFR as required. Need 5% less fuel, multiply the table value by 1.05.

I suppose if it is caused by the AVCS that I could adjust the whole rpm row where it's occurring, in all loads? I'm going to start out with the small change I showed above next time I flash and see that it doesn't mess anything up.

I am doing it just for fun and out of interest. I think if the timing doesn't make any problems when it get's warmer that I could just leave it as it is. The car runs great.

The Lambda sensor is a gas sensor. Unless you were to literally flood the exhaust with fuel, unburnt fuel is not detected. Think about it like this, if you have a lot of cam overlap there can be air bypassing the cylinder and therefore the reading can be lean. But you can't have a reading that is richer than the mixture in the cylinder. Unburnt fuel reaching the exhaust will be almost always be when there is cam overlap and therefore a lean reading will occur.

Not sure I understand that. If the fuel is not in the cylinder during combustion (because it bypassed the cylinder through the valve over lap). And the fuel in the exhaust is not being detected. Why would it read lean? Why wouldn't it read accurately? I mean the fuel is not there, and it's not being detected.

On the other hand, wouldn't some of the fuel burn in the runners before reaching the sensor? If that was the case (don't know if that is possible), it could read richer than the combustion taking place in the cylinders?

[Tor]

Originally Posted by jvincent

One of the things I did was completely change the MAF scale so that I have a lot more points in the critical region around 3V.

I don't have the numbers in front of me but my MAF scale tops out at 4.25 V since I am not boosted. I also changed the spacing of the voltage points down in the very low region where it is very linear. The end result is I have a more points to work with in the 2.5V to 3.5V region.

Still, it would need to be scaled to a weird shape (in my case at least) so I'm not sure that would help. I think Kodename47's solution is more elegant as it keeps the MAF scale linear (or exponential or whatever the correct mathematical terms is for smooth ).

[jvincent]

Perhaps.

I managed to get my AFR / commanded AFR pretty close and flat with my last round of load limit and MAF changes but then it got cold up here so I can do any more changes unti it get warm again.

[Kodename47]

Originally Posted by Tor

I suppose if it is caused by the AVCS that I could adjust the whole rpm row where it's occurring, in all loads? I'm going to start out with the small change I showed above next time I flash and see that it doesn't mess anything up.

I would just do it in the load regions you're seeing in that pull and then taper it in the table if it's vastly different. Don't go changing the whole row with a blanket change. Don't forget that you can give yourself more accuracy where you want it by changing axis etc. There's a fair bit of redundancy is the stock fuel map

Originally Posted by Tor

Not sure I understand that. If the fuel is not in the cylinder during combustion (because it bypassed the cylinder through the valve over lap). And the fuel in the exhaust is not being detected. Why would it read lean? Why wouldn't it read accurately? I mean the fuel is not there, and it's not being detected.

On the other hand, wouldn't some of the fuel burn in the runners before reaching the sensor? If that was the case (don't know if that is possible), it could read richer than the combustion taking place in the cylinders?

What I meant was that if there is unburnt fuel in the exhaust, it's likely that it's in air that has gone right through the cylinder without being part of the combustion cycle. This unused air will make the O2 sensor read leaner as there will be a higher ratio of oxygen gas.

If the ignition event is retarded enough that it continues to burn as it exits the valve, then this will still be converted to gases and read more normally. This is more common, but your solution here is less fuel or more advanced ignition timing as this is bad in every way as it causes high EGTs, can damage valves, creates more emissions and usually makes less power.

Originally Posted by Tor

I think Kodename47's solution is more elegant as it keeps the MAF scale linear (or exponential or whatever the correct mathematical terms is for smooth ).

86Inches on Romraider has just released a spreadsheet that gives a perfect exponential curve, I have yet to flash the result but a well respected user says that it makes the car smoother..... will feed back and post my version of the tool if it works.

[freerunner]

Originally Posted by Kodename47

86Inches on Romraider has just released a spreadsheet that gives a perfect exponential curve, I have yet to flash the result but a well respected user says that it makes the car smoother..... will feed back and post my version of the tool if it works.

Interesting. I'm in.

[Nah]

Avcs doesn't effect AFR. I tried addressing the rich dip with avcs. No bueno. The rich dip is due to an incorrect load calculation. So that leaves MAF and Load Limits. Right at 50-60 g/s on the MAF scale take away a % or two. If that doesn't work Perhaps raise your load limits a tad. Around 1.12. Uhhhh, if you're not gaining power up top it's Becuase your VE is off. Which is due to AVCS... But before you do that fix your FLKC. The ECU will just run richer and not as smooth.

Back to avcs, start by adding/removing 5 degrees to the intake cam and 5 for the exhaust. cam. Log a WOT pull. Compare where you gained power and where you lost. That'll give you an idea where to start.

Also I actually prefer shivs injection ratios with port injection restored at 5000 rpms. Keeps AFR's flatter in that 3-4K region and allows me to run more timing and intake advance in that area for better performance.