Fuelling problems on over run and after.

[Norzilla]

I have come up on a new fuelling problem on my Aprilia v-twin.

The symptoms are as follows;

Directly after hard acceleration on the over run, the engine starts to misfire baldy and it takes 15-30 secs of managing the throttle with the clutch in to keep the engine alive, after which the engine comes back to life and continues to run normally.

This misfire is only induced after hard acceleration and not medium or moderate accel and the following rpm overrun.

I have played with fuel cut setting ranging from 0 - 50 - 100% and there seems to be no difference. I thought maybe it was the a low fuel condition where fuel moved away from pump causing it to run dry, so I filled the tank and retried the test and the same condition presented so it was not a fuel starve issue.

Any ideas?

[grippo]

The two things I would ask are:
(1) is it losing synch or is trigger +/- changing. If the tolerances are forgiving enough so that you lose teeth, but the ecu thinks its still on track, this could cause misfiring.

(2) are you using X-Tau and is the decel factor too high under the conditions you are encountering so that its doing bad things with the fuel, that is the pulsewidth is too long or short ?

[Norzilla]

CurrentTune.msq

this is the msq with the misfire on overrun

(30.27 KiB) Downloaded 167 times

Hi Grippo,

I am not using Tau X.

I have attached the msq that I have been using on code V3.760. above.

I have just loaded the latest code v3.780 and with the virtually identical MSQ ( below )the bike will not start.

[grippo]

From your datalogs in your other thread it looks like you are having problems with the vr signal. You also have a very high pulse tolerance in cranking (150%). The engine seems to run fine at 500 rpm as long as you don't blip the throttle. Is 500 rpm the cranking speed or the idle speed ? If its the cranking speed then its either not sparking or sparking at the wrong time because the rpm isn't going up. If its the idle speed, will it run at that speed by itself for as long as you want ? Is the timing correct ? then try very very slowly giving it some throttle to see if the rpm goes up and again see if the timing remains correct.

[Norzilla]

I have the bike running better now from a tuning perspective , there seem to be many setting that are different or don't translate straight across from v3.760 to 3.780 which I have now solved.

However, Grippo is right in that for some reason the system is losing tach sync and the tach count is resetting.

See latest MSQ and a couple of datalogs. You can see the tachcount reset in the datalogs

Are you sure that it is the VR and maybe not the Cam sensor that is causing the problems as the Cam sensor is the one that creates the sync?

What could be the problem with the signal and what should I attempt to do to fix the problem?

NB: Looking at the datalogs that is no rpm or tach count recorded while cranking and the ECU does not show that status as cranking when it is actually cranking to start the engine..... Any Ideas? Could this be linked to the Tach sync / tach count resets? or is it settings related?

[grippo]

Are you sure that it is the VR and maybe not the Cam sensor that is causing the problems as the Cam sensor is the one that creates the sync?

>>>>>> Once you are running full synch (green indicator on the bottom of screen says sequential) you could pull out the cam sensor wire and nothing would change. Even without a cam sensor, but set in the sequential mode you are using, the engine will not lose sync - it will just run in wasted mode(blk & whte indicator at bottom says wasted) and keep looking for a cam sync. The trigger +/- shows you are mostly missing crank teeth.


What could be the problem with the signal and what should I attempt to do to fix the problem?

>>>>> What is different between when it was running well and not - is the problem the hard decel ? There is no difference in this area between 3.76 and 3.78 code. If I get a chance in the next day or two I will try running your setup with 3.78 code and see what I get on the bench.

[Norzilla]

Hi..

From memory the things that did not translate across with the code upgrade were the cam tooth in 3.76 was tooth 1 and in 3.78 it is 34.
The setting for the temp sensors were dropped out
The Required fuel was dropped out and reset at the default settings for a 350 ci V8
For some reason when I put the req fuel back in at the 5.4 with the 61ci , 2twin cyl, that I had for my original maps , the pulse width that it translated to was much greater than with the 3.76 version which was very strange. I am now using req fuel of 8 and have adjusted my maps as I know the PW at idle was 2ms so i reverse engineered the maps again from that point.

The losing teeth seems to be an issue that has only arisen in the last few months, before that there was no issue and I have not changed any of the hardware config since I set it up.

I have another VR pickup which I think was one I shaved a mm or 2 off the boss to get it closer to the teeth for a stronger signal, but it was not needed when I first set the bike up using the 2500ohm resistor. Would it be worth trying this sensor? or is it better to increase the resistor in the VR wire instead? What else can I try ?

Thanks

[grippo]

Ok I finally got to test your latest msq and it works fine on the bench.That doesn't mean it will work fine on your engine but that should be a tuning matter, and of course resolving the vr sensor problem.

As I understand you had the bike running with 3.760 code with no problems, then had an over run fueling problem ?

Was this problem always there or was it something that popped up in a scenario you had never encountered before ?

Since it misfired, that is telling me it may have been caused by the vr sensor losing sync. Switching to 3.780 code is a separate problem which I don't understand, because there were only some internal logic changes in the code, but these have been well tested and I haven't heard of any problems there. But I also don't think it will solve your overrun problem, so I would go back to 3.760 and try another sensor and datalog any problems with that.

[Norzilla]

Hi Grippo,

I want to focus on the VR sensor issue first before reverting back to the older code.

What should I try in order to resolve the sensor problem?

The losing tach sync and the over run problem first occurred when I loaded 3.760 and had the issues with the auto tune dumping all the tables when in flash mode, so I switch to ram only and manually saved the autoune files when I go back to the workshop. The engine did not lose sync prior to the 3.760 code upload.

Thanks
John


ps I am already using the sensor that had been move closed to the trigger wheel, so maybe there is something else I can do the condition the signal from the VR sensor or should I try swapping it out for a new one first?

[mfro]

ps I am already using the sensor that had been move closed to the trigger wheel, so maybe there is something else I can do the condition the signal...

When getting out of sync at high RPM, it's usually better to do the other way round: move the sensor further away from the wheel. It's most likely seeing teeth that aren't there. If that's not enough to tame it, you'll need to experiment with resistors or other conditioning means. Results seem to be very different depending on individual setup. I've put a 100kΩ resistor into my pickup circuit which works reliable up to >130000 rpm when adjusted to about 30 kΩ, for example.