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ECM and FI Tuning - Help, Tips & Tricks We invite members from across TriumphRat.net to post your questions, or share your expertise or experiences on TuneBoy, TuneECU and PowerCommander (etc).

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Old 11-22-2012, 09:58 AM   #1 (permalink)
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How does the return to idle works on Kehin anyway

This thread in intended for people that have a deep knowledge about the kehin (especially 1050 engine) algorithms and features.

On the 955i it became pretty clear for me as to how the return to idle is manage. You set a reference position for the stepper, and so after that whenever you live the throttle alone, the stepper goes in this position. After that the ECU adjusts the rpm using the idle table/O2 sensor. I assumed that for all the time the throttle is open, the stepper stay in this reference position. That is why adjusting the stepper influence the return to idle speed.

That's another story for the kehin/1050 business. The stepper actuate directly the throttle, so there is no way for the ECU to know whether you're cruising opening the throttle just a tad or if the throttle is only driven by the ISCV (stepper).

You can still play w/ the stepper adjustment and/or the tps voltages (0.75v...) but then there is a slight chance that the 0.5mm gap is not ok.

So I am wondering how the stepper react as soon as you open the throttle and how to tune the return to idle with such a little to leverage on the ECU behaviour.

Any clue about that mystery.

BTW I have fellow lister on Triumphall who is annoyed with a poor return to idle leading to stalling. In addition now that I have a GT better understand before the troubles.

Fred
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Old 11-22-2012, 03:25 PM   #2 (permalink)
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Quote:
Originally Posted by fredsprint View Post
I have fellow lister on Triumphall who is annoyed with a poor return to idle leading to stalling. In addition now that I have a GT better understand before the troubles.
If you are talking about a Sprint GT then the stalling issues have been discussed at length in the Sprint forum. I understand Triumph made some changes to correct this issue so a Sprint GT owner who experiences stalling when the bike returns to idle should take it to his Triumph dealer. Playing around with the ISC stepper will not correct the issue.

Read this thread for more information on Sprint GT Stalling on Return to Idle.
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Old 11-23-2012, 03:04 AM   #3 (permalink)
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Quote:
Originally Posted by champ87 View Post
If you are talking about a Sprint GT then the stalling issues have been discussed at length in the Sprint forum. I understand Triumph made some changes to correct this issue so a Sprint GT owner who experiences stalling when the bike returns to idle should take it to his Triumph dealer. Playing around with the ISC stepper will not correct the issue.

Read this thread for more information on Sprint GT Stalling on Return to Idle.
No I am not. This guy owns a Sprint ST 1050. My question was triggered by his problem but is not the reason of it. I just want to understand how the return to idle is managed on Kehin version and especially 1050cc.

BTW, yes I read the thread you mention before buying my gt and there is no attempt to understand how it works at all (unless I missed it).

Fred

Last edited by fredsprint; 11-23-2012 at 03:09 AM.
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Old 11-23-2012, 10:17 PM   #4 (permalink)
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Originally Posted by fredsprint View Post
I just want to understand how the return to idle is managed on Kehin version and especially 1050cc.
OK, you mentioned Sprint GT so I assumed you were trying to correct known stalling issues that appear to have been resolved by Triumph.

I don’t know if I can give you the detailed information you want but I’ll share what I know and maybe you’ll find some new information in there.

As you know the Keihin system on our 1050s uses a stepper motor that acts directly on the throttle cam to control starting, warm-up and idle. Keihin documentation also states that it controls “overrun correction”. This is related to your question but the documentation does not provide further explanation about what corrections it makes. The stepper motor can only control the throttle at small throttle openings. Its range will give a TPS reading of 0.60V when the stepper is closed to 0.75V when the stepper is fully open. Compare that to throttle position which reads 0.60V when fully closed up to more than 4V when fully open. My 1050 Sprint gives a TPS voltage of 4.1V when the grip is twisted to the max but this figure varies from one machine to another. It shouldn’t go higher that 5V since that’s the voltage sent to the TPS sensor.

When the ignition is off the idle stepper is closed. The control lever arm is not even touching the throttle cam. In this position the throttle return spring can close the throttles completely. When the ignition is turned on the ISC Stepper Motor moves the control lever arm to push against the roller on the throttle cam. This opens the throttles slightly for starting. Once the engine is started the stepper motor will move to maintain idle according to coolant temperature. As the engine warms the target idle speed is reduced. For my 1050 Sprint target idle speed is 1170 rpm at normal operating temperature. This is set in the engine management software but can be changed with TuneECU. The ECM compares actual engine speed with this target speed then signals the stepper to move to maintain target idle speed.

OK, so that describes normal operation but what happens when you open or close the throttle? Well, I don’t have any official information so I can only give you my thoughts. If you twist the throttle slightly for a small increase in rpm then I would guess the stepper will close slightly trying to reduce the engine speed. Of course this has no effect because the throttle cables are holding the throttles open. I think the stepper will stay in that position until you release the throttle grip and the rpm reduces back to idle speed. Then the stepper will move again to maintain idle. There is another possibility – maybe when throttle opening goes above a certain value or the rpm goes above a certain speed the ECM tells the stepper to move to a “normal” idle position ready for when the throttle is closed. I have not watched the stepper in that situation to see which of these happens but my guess is the first situation applies.

If your friend is having trouble with poor return to idle and stalling then the first thing I would check is throttle balance. If he's done that already then obviously he should check TPS and ISC Stepper Adjustment. If the readings are correct then the stalling is caused by something else and trying to fix it by adjusting the stepper away from the correct settings could result in poor starting.
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Last edited by champ87; 11-23-2012 at 10:52 PM.
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Old 11-24-2012, 09:29 AM   #5 (permalink)
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Thanks for taking some time to answer. I made the same guess in fact. I am not too much in the mood of removing the tanks just to find out. But i'll look at it whenever I'll have the occasion to remove the tank.

Obviously the stepper adjustment has been made. He is heading to replacing the TPS. Don't know if it's done or not. I also suggested some extra play in some parts around the throttle body.

Keep you posted about the outcome. Currently the guy is forced to maintain the idle "manually" at 1200 unless it stalls.

Fred
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Old 11-24-2012, 12:36 PM   #6 (permalink)
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On my Speed ​​Triple 1050 05/06, I also had the problem of dying at idle.
After all attempts to resolve the problem of the settings, it's ultimately been a faulty map sensor.

The error could not be measured, I changed this sensor only on the supposition, because he has come as the last source of error in question.

BR, Tom
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Old 11-24-2012, 05:07 PM   #7 (permalink)
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Guys,

Just had some news about the outcome: Turns out the balancing screws were too tight letting too few air getting in. The ref position on cyl 1 was 1 turn. The guy put 1/2 turn more and started from that to balance cyl 2 and 3. And here we go.

This problem was suspected (by me) but as the tuning was performed by the dealer mechanic, the guy didn't dare to think the balancing was wrong.

This outcome is very important on the way to a better understanding of the 1050 management. This would have not happen w/ the IACV of sagem. But I alway suspected that this reference is very important even fot the 955.

Fred
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Old 11-25-2012, 05:57 AM   #8 (permalink)
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Thank you for your feedback, a very interesting information.

BR, Tom
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Old 11-26-2012, 04:41 AM   #9 (permalink)
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Originally Posted by Tom_Hamburg View Post
Thank you for your feedback, a very interesting information.

BR, Tom
I think so. I even think it could be a way to tune the return to idle.

Fred
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Old 12-04-2012, 12:43 AM   #10 (permalink)
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Hi Champ,

Thanks again for posting all the good info. I am learning a lot. I've got an 09 st and been chasing a "low idle speed issue" since almost day 1. In my quest to find the root cause i've found issues (cracked boot between air box & throttle body, loose clamp on throttle body, ect..) that i thought would explain the low idle issue but although not as severe (not stalling anymore) the issue remain. Before putting the bike in the shed for the winter, i plugged tune ECU to verify some stuff;

1) As you stated, the TPS is reading of 0.60V when the stepper is closed to 0.75V when the stepper is fully open.
2) The throttle position reads 0.60V when fully closed and 4,19V when fully open.
3) When the ignition is off, the idle stepper motor's control lever arm is touching the throttle cam. This is contrary to what you are stating...Maybe that could explain my issue. What do you think ?
4) I've also noted that before starting the bike, the coolant temp was showing 3 Deg C while the air intake temp was showing 10 Deg C. The bike was cold soaked since a week and the ambiant temp was indeed around 3 - 4 Deg C. So there was a split of 7 Deg C. I would have expected both temps should be within a 2 -3 deg C. Not sure if 7 Deg is too much. What do you think ?
5) Swapped both press sensors (same PN), issue remain
6) Isolated the coal canistor and its tubing, issue remain.
7) Throttle are balanced, checked.
8) New spark plugs & air filter. Issue remain.
9) MAP sensor tubing checked OK.
10) Tried "ethanol free" gaz, issue remain.
11) Remapped the ECU at the dealer shortly before the winter. Don't know if it will make a difference. We'll see next spring...

I am running out of ideas...Any ideas / hints are more than welcome.

Thanks
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