Rev limiter limp mode? - MVAgusta.net
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post #1 of 19 (permalink) Old 02-04-2019, 01:44 PM Thread Starter
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Rev limiter limp mode?

Hi all I have recently rebuilt a MV F3 675 non abs engine.
bike has been on the dyno today but the bike seems to be in limp mode as it will only rev to 13800-14200rpm, the rev limiter is set to 15000 in the ecu.
The bike isn't showing any fault codes.

Any help much appreciated 😊
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post #2 of 19 (permalink) Old 02-04-2019, 02:12 PM
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Not sure that's a limp mode. Most limp modes would severely limit the RPM and or power not just 800 rpm or so.

A few questions.
1. What engine mode and settings are you using?
2. Was the power at 13000 rpm what you would expect or low?
3. Are you still running the exhaust valve?
4. How did you change the RPM, or did you send it away for a change?
5. Can you run a datalog (external or ECU)?

Cheers

Arron

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post #3 of 19 (permalink) Old 02-04-2019, 02:30 PM Thread Starter
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Quote:
Originally Posted by dansoarr View Post
Not sure that's a limp mode. Most limp modes would severely limit the RPM and or power not just 800 rpm or so.

A few questions.
1. What engine mode and settings are you using?
2. Was the power at 13000 rpm what you would expect or low?
3. Are you still running the exhaust valve?
4. How did you change the RPM, or did you send it away for a change?
5. Can you run a datalog (external or ECU)?

Cheers
1: sport
2:around 115bhp around 5hp lower than I would expect
3: no (long gone)
4: ecu flash by dyno tuner
5: unfortunately no

The only reason I'm thinking "limp mode" is because I know if you have an abs bike with an abs fault it runs a similar rev limit

Last edited by dudman; 02-04-2019 at 02:32 PM.
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post #4 of 19 (permalink) Old 02-04-2019, 03:08 PM
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If there's an abs fault you will get an error code, while the bike is running, not necessarily once you have turned the ignition off as the abs is a code that only displays if it's in active error and does not need to be stored.

When dynoing the ABS bikes you will get an ABS fault as the front wheel is not turning so I'm surprised that you say it limits the RPM on the F3. How would you tune it on the Dyno if it limits the rpm?

On the F4 an ABS error does not limit the RPM either on track or on the Dyno, same ECU and hardware but a different flash.

I'm assuming as it's a non abs engine you are running a non ABS ECU flash and the wiring etc is non ABS.

If you can't log the ECU, I'd ask the tuner to flash the rpm limit to 12000, check the flash and rev limit in each gear, then increment the flash and repeat.

Is the current rpm limit stable and the same in all gears or different in the higher gears?

Arron

----------------------------------------
2015 MV F4, ABS
ECU Mapped with ECUstudio
QS & Blipper working with ECUstudio

others
GSXR 1000
GSXR 750

Last edited by dansoarr; 02-04-2019 at 03:17 PM.
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post #5 of 19 (permalink) Old 02-04-2019, 03:11 PM
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It could also be an inaccurate tach.
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post #6 of 19 (permalink) Old 02-04-2019, 03:19 PM
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Quote:
Originally Posted by Mschwechter View Post
It could also be an inaccurate tach.
Most tach's are a little optimistic normally, but a possibility for sure.

Arron

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QS & Blipper working with ECUstudio

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post #7 of 19 (permalink) Old 02-05-2019, 03:46 AM Thread Starter
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Quote:
Originally Posted by Mschwechter View Post
It could also be an inaccurate tach.
Dash may be inaccurate but the bike has been on same dyno a number of times and has always behaved as I expected,

Another observation I've made over time is that the bike runs different maps when the clutch switch is bridged or not.

I'm hoping someone can give me a list of what sensors / swithches causes the bike to run a lower power / rpm limited map
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post #8 of 19 (permalink) Old 02-05-2019, 05:23 AM
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My advice don't mess with the clutch switch. If the ECU thinks the clutch is in, then the rev limiter for neutral will be used which is lower than for any gear. Typically we see issues when people fit aftermarket shorty levers that don't operate the switch correctly.

Most of the sensors will affect the ECU's decision on power, its a long list.

I suggest you list the modifications you have made from levers, loom, blipper, and the flash used. Then we might be able to suggest what is the most probable cause. Most decent ecu software for flashing, can see the sensor and error data in the ecu (request over the CAN bus), I'd be surprised if your flasher (forgive the term) cant see the data live, even if he cant record it.
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Arron

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2015 MV F4, ABS
ECU Mapped with ECUstudio
QS & Blipper working with ECUstudio

others
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post #9 of 19 (permalink) Old 02-05-2019, 01:23 PM Thread Starter
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Items disconnected 😣
-Side stand switch
-Exhaust servo motor
-Lamda sensor
-Clutch switch
-Front and rear brake switch
-Fan
-All lights

Auxiliary starter button fitted
Keyless ignition switch
Race ecu fitted
Replacement dash fitted (same part number)

I got the bike booked in at motocorsa on Friday to get it plugged into computer, otherwise I think I will take while to track the issue down, fingers crossed
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post #10 of 19 (permalink) Old 02-05-2019, 02:09 PM
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First thing is to check the clutch wiring. Have you bridged it or left it open circuit?

Arron

----------------------------------------
2015 MV F4, ABS
ECU Mapped with ECUstudio
QS & Blipper working with ECUstudio

others
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GSXR 750
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