PC5 Good Info- RPM, TPS, Rev Limiter, Backshift, AFR readings

[NOS-PRO]

Here is some really good info on what's going on while the Powercommander V is recording using the POD.

The Pod allows you to record what's going on and now really starting to learn the PC5 I am understanding what the sled is doing and now many questions have been answered

Bear with me here.....

1) I found out by looking at this that the rev limiter (now this is my perception, I will explain soon) is really at 9,150 after the re-flash....according to the PCV anyway. The max recall on the gauge is different than the PCV readings, so what does one go by?

2) When the rev limiter hits it drops RPM because it is pulling fuel away, not just pulling spark away. You can see this on the AFR's.

3) This shows throttle position and is really cool! I can tell by the numbers what I am doing, part throttle, full throttle or slowing down/off throttle.

Here is a downloaded doc. of a wide open run from this past Sunday. I was full throttle coming down trail 8 by munising. The time is in seconds on the left column and records 3 x per second. My AFR's on a full pass should be around 12.8 and it's really good. My rpm's show perfect on this run but at 34 seconds, you see the rpm's go over 9,150 and hit the rev limiter. Look at the AFR reading! Under full throttle the rpm dropped 500 rpms. This confirms that fuel has been taken away and is the reason why I believe if you hit the rev limiter with a turbo setup, under boost you will be super lean. (Don't pay attention to the first 9.99 readings as this is the PCv learning everything upon start up)

Now take a look at throttle postion. When I am at 99.5 (or around there) i am full throttle. My PCv says 0% when I am idling and 100% when I am full throttle going down the trail.

This is how you want your clutching, climb up fast to 9,000 and stay there without hitting the rev limiter. This is where clutching can be a science because you need to have excellent take off and pull through the whole run. This was the COTC kit in my sled this weekend. Top mph was 108 on this run.

 

[NOS-PRO]

Here is another recording I did with the PCV and pod on Sunday.

This one I labeled as trail riding and shows corner to corner with some straights. This shows backshifting and how the clutching is working. This was on trail 7 just after you turn off of trail 8. (If anyone knows this trail it's twisty with hills. Shows how hard I am coming into these corners )

Same as above, watch the throttle position, RPM's and AFR's. I couldn't be happier with this setup.

 

[NOS-PRO]

Here is the last one from Sunday.

Can you tell me where the rev limiter kicked in? Look at the change in rpm's and the AFR readings.

 

[Srxspec]

Remember, its an O2 sensor. It reads oxygen content, not fuel content. So when spark is cut or fuel is cut (rev limiter activates) there's a ton of unburnt intake charge, so it will show lean regardless if its an 11.5 fuel charge or 12.8 fuel charge, it will instantly show lean, it's a "false reading" so to speak.

 

[Mtnviper]

Pretty cool, good info NOS-PRO!

Yes it is common to program ECM's to cut fuel a certain percentage along with spark at the rev limiter. Otherwise the "un-used" fuel would be pumped in to the exhaust system, which could cause a potential overheating condition or an explosion with in the exhaust system!
Also one gotcha to watch out for when using wide O2 systems, is ignition miss-fires can cause you to get a lean AFR reading due to the un-burned oxygen present in the exhaust system.

Edit: Allen is a faster at typing then I am! LOL
Bill

 

[cannondale27]

Remember, its an O2 sensor. It reads oxygen content, not fuel content. So when spark is cut or fuel is cut (rev limiter activates) there's a ton of unburnt intake charge, so it will show lean regardless if its an 11.5 fuel charge or 12.8 fuel charge, it will instantly show lean, it's a "false reading" so to speak.

Wouldnt what your saying be a WORSE situation then? Some of that leftover unburnt fuel should be helping keep AFR down but its not enough.

 

[TD Max]

One thing I will add for anybody running a Power Commander of any sorts is that to me it is absolutely critical to calibrate the device to the TPS on the sled. If you do not do this the cells may not line up properly especially if you have preloaded maps.

In my case the TPS was way off especially on low end.

 

[Srxspec]

Wouldnt what your saying be a WORSE situation then? Some of that leftover unburnt fuel should be helping keep AFR up but its not enough.

Any ignition cut or misfire will cause the O2 gauge to show lean, even though it's not actually lean.

 

[Srxspec]

The only thing Oxygen Sensors can measure is the partial pressure ratio of oxygen inside the pipe as compared to the outside air. Automotive computers use this info to adjust the mixture of the engine not as the only info however. Putting aside pump gas, as nobody knows what we got their, race gas can vary with the amount of oxygenates and the stoic values ranging from 14.0 to 15.3. The general accepted balanced is 14.7 pounds of air to 1 pound of fuel (this is what they call stoich). This affects what we are seeing on our meters. Another killer is misfires, this will give the indication of a lean condition as you are putting unburnt air and fuel in the pipe.

 

[TD Max]

OK Questions:

1) What does the idle and off idle look like when up to temp?

2) Can you adjust the resolution for TPS and AFR? TPS to whole numbers (skip all decimal) and AFR to one decimal for simplicity?

3) What can a guy do to get speed into the unit?

4) Is there a calibration procedure for the O2 sensor or is it just assumed accurate?

We have the makings of a pretty decent data logger here.

 

[Srxspec]

The other thing is the rev limiter actually starts to kick in at 9,000 rpm already. At that point, it starts what's known as a "soft" rev limiter. 9150 is the "hard" rev limiter where you will actually hear it audibly break up. At 9000 rpm, you can not hear or feel any change, but when on the dyno, my RPM graph begins to fluctuate as soon as you turn 9001 rpm. With a PCV and Ignition Module, we can set the rev limiter wherever we want and over ride the soft rev limiter, but still have the hard rev limiter.

 

[Srxspec]

OK Questions:

3) What can a guy do to get speed into the unit?

4) Is there a calibration procedure for the O2 sensor or is it just assumed accurate?

We have the makings of a pretty decent data logger here.

To #3, yes you can hook speed into it.

To #4, yes you can check to see if the O2 sensor is still in range.

 

[cannondale27]

Any ignition cut or misfire will cause the O2 gauge to show lean, even though it's not actually lean.

I agree with what you are saying that the unburnt O2 should show a lean spike but if they wouldnt cut the fuel it would not lean spike. The YFZ and Cannondales just cut ignition and there is no lean spike at rev limiter ever.

 

[cannondale27]

One thing I will add for anybody running a Power Commander of any sorts is that to me it is absolutely critical to calibrate the device to the TPS on the sled. If you do not do this the cells may not line up properly especially if you have preloaded maps.

In my case the TPS was way off especially on low end.

How far off was yours TD?

 

[cannondale27]

The other thing is the rev limiter actually starts to kick in at 9,000 rpm already. At that point, it starts what's known as a "soft" rev limiter. 9150 is the "hard" rev limiter where you will actually hear it audibly break up. At 9000 rpm, you can not hear or feel any change, but when on the dyno, my RPM graph begins to fluctuate as soon as you turn 9001 rpm. With a PCV and Ignition Module, we can set the rev limiter wherever we want and over ride the soft rev limiter, but still have the hard rev limiter.

Since reflash 9230rpm is where you feel and hear the hard revlimiter. Before flash 9150 is definitly where it was felt. On the gauge.