Open loop vs closed loop on 2013

[Orange monster]

So I was reading a thread started by Rabtech earlier and noticed he said the 2013 does not enter open loop until 8000 RPMs. So if I understand this correctly the computer is going to make adjustments to hit the target A/F ratio at anything under 8000 rpms under normal throttle. For anything over 8000 rpms and any rpm with heavy throttle input the computer refers to the pre defined map to get fuel values. Is this correct and does anyone know what the target A/F ratio is for closed loop mode?

 

[billrob71]

Im unsure on the spyders but in cars the o2 sensors in cars keep the computer in rich mode (open loop) until the car starts to warm up and then goes closed loop to lean out. Mainly to help with warm up.

At 8000 rpm the engine needs more fuel so computer may be compensating for how lean they are saying the 13's run by richening the mixture.

 

[Sny]

Im unsure on the spyders but in cars the o2 sensors in cars keep the computer in rich mode (open loop) until the car starts to warm up and then goes closed loop to lean out. Mainly to help with warm up.

At 8000 rpm the engine needs more fuel so computer may be compensating for how lean they are saying the 13's run by richening the mixture.

More or less correct.

When any fuel injected motor starts up, the temp reads low and they automatically richen the fuel a bit so it won't stall out. This only lasts a little while and it starts to lean it out to build up the temps to normal operating temperature.

The ECM/ECU reads the throttle position and engine RPM and if it is within the closed loop range it consults a fuel map using these values plus corrective values for intake temp and MAP (manifold absolute pressure) and comes up with an injector pulse value to apply fuel to match the amount of combustible oxygen in the cylinder which is about to fire. It then reads the O2 sensor to get an idea of how much unspent oxygen left the cylinder(s) and uses that to adjust the pulse width up or down accordingly.

Outside of the closed loop range, it switches to an open loop map where it basically ignores the O2 sensor but still applies everything else it knows to come up with the injector pulse width. It is normal for this map to be very rich to protect the motor from detonation, extreme EGT's or other lean condition damage.

These maps from the factory tend to be pretty boring, as boring is safe. It is not unusual for factory vehicles to run lean in closed loop especially in today's world of fuel economy and emissions regulations. Lean isn't always bad, but extremely lean can be very bad.

From the condition of several rear plugs, it appears that some (if not all?) of the 13's run very lean lean in closed loop. This could mean one of the input values is wrong, such as a bad MAP sensor, or intake temp sensor... or it could mean the closed loop map itself is overly lean.

I'm guessing it's some kind of vicious cycle. They run a little lean. This makes them hot. Hot fuel tanks have less dense fuel. Less dense fuel makes them run even more lean. This makes them run even more hot. Heat damages components. Sensors fail, wiring doesn't carry signal right, O2 sensors read wrong... This leads to more lean conditions and heat. Ultimately they start having serious heat issues, don't want to start after heat soak... don't want to idle right... won't stay running... overheat and limp mode on the highway...

A power commander or other fuel modifier can be used to modify the injector pulse width for more fuel while lying to the ECM about the O2 readings.

Another think you stumbled on is that you can trick input temperature sensors into thinking it's cold out, which will make the ECM provide more fuel thinking there's a more dense charge on the way.

To answer the rest of your question, I don't know the default target AFR for closed loop on the 991 motor. I do know it was 14.7 on the 990 (according to what dynojet said, who knows if that's right) which had much less focus on emissions. The open loop area went to 13.2 which is overly rich but "safe". I'm going to guess the 991 is not far off from that in it's target AFR's, but it does not appear to be achieving them.

 

[rabtech]

I had a 2002 hayabusa that I leaned out just a little bit to much. I rode it all day and I will say that it was probably the strongest it has ever been. I never had an issue that day. I came home that afternoon and parked it. The next day I went out to ride and it wouldn't start. It would crank over and would just pop and backfire. I pulled the sparkplugs and none of them had any tips on them. I am going to assume that while the engine was hot it was sparking from the sides of the plugs to the center. After it cooled off it didn't have enough spark to crank. I richend up the mixture and put in a new set of Bosch quad fire plugs and all was well again. I was lucky. Lean can melt an engine pretty fast. Also another reason against "seat of the pants" engine adjustments.

Sent from my Galaxy S3. I may have made a spelling error or may have some grammer issues. My fingers are way to big to type on this tiny screen!

 

[Bob Denman]

(Old Two-Stroke tuner here...)
They always run best right before...

Thanks for the information on open, versus closed loop operatiion. :thumbup:
It actually made sense to me!
(I'm not getting smarter; am I? :shocked

 

[safecracker]

Great explanation.

 

[Flanker]

I had a 2002 hayabusa that I leaned out just a little bit to much. I rode it all day and I will say that it was probably the strongest it has ever been. I never had an issue that day. I came home that afternoon and parked it. The next day I went out to ride and it wouldn't start. It would crank over and would just pop and backfire. I pulled the sparkplugs and none of them had any tips on them. I am going to assume that while the engine was hot it was sparking from the sides of the plugs to the center. After it cooled off it didn't have enough spark to crank. I richend up the mixture and put in a new set of Bosch quad fire plugs and all was well again. I was lucky. Lean can melt an engine pretty fast. Also another reason against "seat of the pants" engine adjustments.

Wow! That is lean! Quite a few years ago, a friend had a Kawasaki KZ650. He bought and installed a supercharger kit for it; he'd been unsure whether he should throw in forged pistons or not, but had been told by a couple of "performance mechanics" the stock cast pistons would be fine if he kept the boost down to 10 PSI or less. Once the parts were installed; he engaged in a couple weeks of seat of the pants R & D, swapping all three jets multiple times, and pulling numerous plug checks for color. While testing his latest set of main jets at about 110MPH one day; he told me the engine made a really loud "whuffing" sound; followed immediately by the sensation he had peed himself, and the bike fish tailing violently. He said he thought it was a miracle he was able to pull over OK, as the rear end was sliding allover the place at all speeds. He told me he was coated with oil from the waste down, and the back half of the bike was completely oiled, including the rear tire! Anyway.................between the 10 PSI he was running on the charger, the stock forged pistons, and likely jetting that had been consistently way too lean for the two weeks of R & D........................on tear down; he discovered he'd blown the crowns out of 3 out of 4 of his pistons! When the crowns went, the 10 PSI had explosively pressurized the crankcase and fired all 4 quarts of oil out the overflow hose...................oiling himself and the back of the bike! He kept one of the three destroyed pistons on the shelf in his garage as a reminder to himself. The piston crown had a quarter size hole through it, surrounded by a crater that looked like a high pressure sand blaster had been directed on it until it had chewed through the aluminum (probably between 3/8" and a 1/2" thick). Too lean can be bad.

 

[jcthorne]

The piston crown had a quarter size hole through it, surrounded by a crater that looked like a high pressure sand blaster had been directed on it until it had chewed through the aluminum (probably between 3/8" and a 1/2" thick). Too lean can be bad.

Just an FYI, forged pistons melt just as easily as cast or hypereutectic ones. The forged are stronger and can withstand more force ie less likely to break but that would not have helped in this case. Lean is mean and melts things quick. And yes, this is from first hand experience.....

 

[Sny]

I had a 2002 hayabusa that I leaned out just a little bit to much. I rode it all day and I will say that it was probably the strongest it has ever been.
Also another reason against "seat of the pants" engine adjustments.

Two very good points.

Max power is found towards the lean end at high throttle/high rpm operation. This is why tuners have to play it so dangerously close to the point where it goes foomp and lets out the magic smoke.