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My Stelvio coughs on overrun and does not like idling!


LangleyMalc
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Well I finally got Guzzidiag to load and recognise the ports on the old Windows computer.  Then got hooked up and checked the TPS - it was at 4.6 deg.  Then checked all the screws on the throttle bodies and the ends of the linkages etc and all the painted ones were still painted and intact with the exception of the high speed adjust screw on the linkage on the left body and the two air bleeds.  After this I reset the TPS and it went to 4.8 and I cleared the learning parameters.

To make it easier to get at the left hand bleed screw, I took off the starter motor cover.  Needless to say one of the little dome head Allen screws socket stripped, so I had to use a stud removing socket to get it out, but after that no problem.  Must have been done up by Guy the Gorilla.

I then checked the air bleed screws with a view to shutting them.  Both were open to some degree, so I closed both.  That was tricker than it should be because of the location.   Then hooked up my ancient mercury powered Motion Pro vacuum gauges and after the first run, remembered to move the breather hose on the back of the

motion Pro to the open position; thus improving the stability and accuracy by a significant degree!  Ran the bike up to 3500-4000 rpm and held it there at a reasonably constant 3800 speed, with a G clamp on the throttle and then balanced off the mercury columns using the speed adjust screw.

Removed the G clamp and let the throttle snap back.  TPS was now 5.2  and then re-sett the TPS again (back to 4.8)and cleared the learning parameters. Finally, adjusted the slow running balance using the air screw on the right hand carb as it was higher.  On the tick-over part of this the mercury was bouncing about a bit, but both appeared to be level, or operating in the same range, so I called it a day. 

End result is that the tick over is around 1200 and not too lumpy.  (It got smoother once I took off the carb sticks and re-connected the vacuums.)  Cant tell about the over run as it was P-ssing down outside the garage so that will have to wait for another day.

All in all a successful mission and I now understand how the throttle bodies work and the logic behind the tunic sequence.

One question - If the stepper motor basically controls the slow running sequence via the computer, is it not possible that the pipework, or the stepper motor gets full of sh1t and so needs occasional cleaning?  (Not letting go of this one quite yet!)

Many thanks for the help and instruction Pete, - Anyway; I enjoyed it!

Malcolm.

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What exactly happens on the over-run? Is it backfiring? And what pipe are you running? If aftermarket, does it have a dB killer installed?

They will all tend to backfire a bit on the over-run. The stock mufffler tends to mask it pretty well and the sound of it becomes both more noticeable and more prevalent the more 'Open' the pipe.

It is one of the peculiarities of the Webber system that the ecu will keep delivering the idle fuel, that which is delivered at 4.8* throttle angle in the case of a Stelvio, at all engine speeds when the throttle is closed. Now while the crank is turning at idle speed the fuel delivered is just sufficient to keep the afr correct-ish so the engine will run and the mixture will ignite every second revolution as it should.

The problem occurs when the motor is spinning harder and therefore pumping harder. As the engine slows down the rapidly pumping pistons will greatly increase the manifold depression on the engine side of the butterflies so more aiir gets pushed past them. Now the ecu is delivering just enough fuel for the engine to idle but with this situation the mixture is incombustible lean. It won't ignite in the cylinder every revolution, it's simply too lean to do so and it gets pumped through the motor and expelled unburnt into the exhaust. Over a period of cycles of the engine harmonics and residual mixture left behind as end gas in the cylinder will periodically reach the point where the mixture will ignite and when this happens as soon as the hot, still burning, exhaust gasses are expelled into the exhaust they will ignite the previously expelled unburnt mixture causing the backfire. Harmonics play a big part in this and you will probably notice that the backfiring will occur at certain precise points as the engine is slowing down. That's why.

Most fuel systems nowadays get around this problem very easily. They simply stop all fuel delivery on a closed throttle until the engine slows down to a certain point. Phil has previously explained that it is very easy to do the same thing with the Webber system. You just yank the map out of the ecu, open it with Tunerpro and then reduce all the figures in the first two columns of the map to zeroes above the point where you want fuel delivery to recommence. Most people who do this opt for 2,500-2,700 rpm. It has the added advantages of slightly increasing engine braking, reducing fuel use as well as killing exhaust popping stone dead! If there is no fuel being delivered then there is nothing to burn. Nothing to burn and there is no backfiring! Simples!

Also if you are an easily entertained peasant like me it means that on hills like the one descending into Queanbeyan from Bungendore you can go down the hill in a high gear using engine braking to slow you down and playa game where you judge your slowing down so when the fuel cuts back in and causes the bike to give a little lurch as it does so it coincides with passing the 60kph speed limit sign on the edge of town!

Yeah. I'm a bear of very little brain....:lol:

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11 minutes ago, pete roper said:

What exactly happens on the over-run? Is it backfiring? And what pipe are you running? If aftermarket, does it have a dB killer installed?

They will all tend to backfire a bit on the over-run. The stock mufffler tends to mask it pretty well and the sound of it becomes both more noticeable and more prevalent the more 'Open' the pipe.

It is one of the peculiarities of the Webber system that the ecu will keep delivering the idle fuel, that which is delivered at 4.8* throttle angle in the case of a Stelvio, at all engine speeds when the throttle is closed. Now while the crank is turning at idle speed the fuel delivered is just sufficient to keep the afr correct-ish so the engine will run and the mixture will ignite every second revolution as it should.

The problem occurs when the motor is spinning harder and therefore pumping harder. As the engine slows down the rapidly pumping pistons will greatly increase the manifold depression on the engine side of the butterflies so more aiir gets pushed past them. Now the ecu is delivering just enough fuel for the engine to idle but with this situation the mixture is incombustible lean. It won't ignite in the cylinder every revolution, it's simply too lean to do so and it gets pumped through the motor and expelled unburnt into the exhaust. Over a period of cycles of the engine harmonics and residual mixture left behind as end gas in the cylinder will periodically reach the point where the mixture will ignite and when this happens as soon as the hot, still burning, exhaust gasses are expelled into the exhaust they will ignite the previously expelled unburnt mixture causing the backfire. Harmonics play a big part in this and you will probably notice that the backfiring will occur at certain precise points as the engine is slowing down. That's why.

Most fuel systems nowadays get around this problem very easily. They simply stop all fuel delivery on a closed throttle until the engine slows down to a certain point. Phil has previously explained that it is very easy to do the same thing with the Webber system. You just yank the map out of the ecu, open it with Tunerpro and then reduce all the figures in the first two columns of the map to zeroes above the point where you want fuel delivery to recommence. Most people who do this opt for 2,500-2,700 rpm. It has the added advantages of slightly increasing engine braking, reducing fuel use as well as killing exhaust popping stone dead! If there is no fuel being delivered then there is nothing to burn. Nothing to burn and there is no backfiring! Simples!

Also if you are an easily entertained peasant like me it means that on hills like the one defending into Queanbeyan from Bungendore you can go down the hill in a high gear using engine braking to slow you down and playa game where you judge your slowing down so when the fuel cuts back in and causes the bike to give a little lurch as it does so it coincides with passing the 60kph speed limit sign on the edge of town!

Yeah. I'm a bear of very little brain....:lol:

The problem with the fuel cutoff on the closed throttle above a designated rpm is I've found that systems that do this don't respond sharply to a quick flick of the throttle on downshifts in that area which I find annoying. The RE does it and the K100's I owned were the same as was a K75 I rode.

You can add some fuel in the RPM affected on closed throttle to stop it as does upping the CO setting as well which isn't necessarily ideal but gets it done.

Ciao 

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Cut-in on mine is at 2,700. I haven't noticed any problems but that could simply be me.
 

Mark's maps generally have the fuel edited out to that point unless specifically requested otherwise. I don't think he has many requests for its reinstatement.

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6 minutes ago, pete roper said:

Cut-in on mine is at 2,700. I haven't noticed any problems but that could simply be me.
 

Mark's maps generally have the fuel edited out to that point unless specifically requested otherwise. I don't think he has many requests for its reinstatement.

Yea that might work. The RE is 2,000 and I think the BM's were around 1800 or so and you mostly downshift above those RPM's so thats when you get the hickup which I find aggravating. Means you need to roll the throttle on the downshifts.

Ciao

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Ok, Pete is witness to all of this, basically I had Beetle map Mk1 installed to a stock standard Bellagio.

And life was good, better fuel consumption, slightly more power and no popping on over run but - that only applies on a country run where your engine is thoroughly warmed up and you are surfing the mid range.

The bike was remapped in winter, combine that with a destroked 1200 that suffers massive barrel finnage suitable for that larger motor and you get an extremely cold blooded bike that takes minimum of 3 minutes to warm up or it stalls regardless of the fast idle collar setting.

My thoughts were that that the AFR was too dry and cold at off idle settings, and here Mark modified the map to include very slightly more fuel across the map - and it worked.

Downside, very slight popping on over run but FAR better manners in city cycle where speed bumps and slow roundabouts would easily cause a flame out.

To sum up, I am sure that Mark got the map right from square one but the gross amount of finnage and overcooling defeated that from the start.

One fault had to be reintroduced to counteract another.

If I ever have cause to remove the barrels then I would be sorely tempted to grind back the fins somewhat.

Chris.

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43 minutes ago, Chris Wilson said:

Ok, Pete is witness to all of this, basically I had Beetle map Mk1 installed to a stock standard Bellagio.

And life was good, better fuel consumption, slightly more power and no popping on over run but - that only applies on a country run where your engine is thoroughly warmed up and you are surfing the mid range.

The bike was remapped in winter, combine that with a destroked 1200 that suffers massive barrel finnage suitable for that larger motor and you get an extremely cold blooded bike that takes minimum of 3 minutes to warm up or it stalls regardless of the fast idle collar setting.

My thoughts were that that the AFR was too dry and cold at off idle settings, and here Mark modified the map to include very slightly more fuel across the map - and it worked.

Downside, very slight popping on over run but FAR better manners in city cycle where speed bumps and slow roundabouts would easily cause a flame out.

To sum up, I am sure that Mark got the map right from square one but the gross amount of finnage and overcooling defeated that from the start.

One fault had to be reintroduced to counteract another.

If I ever have cause to remove the barrels then I would be sorely tempted to grind back the fins somewhat.

Chris.

He could have tried playing with the engine temp trim which you can adjust as a % for each temp break point so richen it up when it's cold. Also there's the option of the start enrichment map which enriches the fuel delivery for 4000 engine revolutions which is around 3 min running until it gets some temp into it. These parameters make a massive difference to cold start and running as I found out when I used the V11 2 valve engine temp break points and warm up trim initially on my Centauro engine. With the much larger and completely different 4 valve head design the engine temp trim % and break points were totally wrong for the Centy engine and it was nearly impossible to start and ran poorly until up to around normal engine operating temp. At or around normal engine temp it ran very well but starting and cold were really bad.

Ciao    

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Having read all the comments above (at least twice), I would comment as follows:

The bike is stock, with a colostomy bag and standard exhaust.  It does have a washable air filter - I did listen to Peter's comments on that; in my defence it came with it and this is BC and despite the four months of absolutely dry weather for the summer this year, most of the time it rains here!  However, I will replace with a paper filter next time I am in the dealer - assuming he doesn't suck his teeth and say "Not a lot of call for that.  We'll have to order it in".  In that case it will be at least 8 weeks and by that time it will be Christmas and we will be worrying about frost and snow.

Since the latest check of the valves, (all within 1 thou of 4 & 6,) plus the reset of the throttle bodies, it now idles quite nicely at 1200.  On a point of information it always did idle well on cold start up, but once the engine was warm it would then start to bumble a bit and could stall on tick over.  Not any more.

The popping on overrun was worse with the original map and mostly went away with the Beetle map.  I tend to blip the throttle on downshifts and use engine braking alot. So while it still pops a bit, based on Pete's latest dissertation above, it apears that this is now a "Feature."  So not a problem as long as I know what is causing it and I think now I do.  It was just my Cali 1400 did not do it! (different engine and different map I presume.)

Either way - I will now leave the bike alone and ride it for a while - weather permitting - knowing that I have the fuelling as near to right as you can get it, without resorting to re-mapping.  Quite frankly, the bike is still capable of a lot more than me and as such, apart from the weight of it and even worse the weight of the Cali, I think it is a fine bike and I am very fond of it and its associated "Features".

The next job is putting back together the V11 that my daughter dropped!  Nothing major, but lots of bits of unobtainium.

Thanks again for all the help and a very interesting discussion and learning experience.

Malcolm

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53 minutes ago, Lucky Phil said:

He could have tried playing with the engine temp trim which you can adjust as a % for each temp break point so richen it up when it's cold. Also there's the option of the start enrichment map which enriches the fuel delivery for 4000 engine revolutions which is around 3 min running until it gets some temp into it. These parameters make a massive difference to cold start and running as I found out when I used the V11 2 valve engine temp break points and warm up trim initially on my Centauro engine. With the much larger and completely different 4 valve head design the engine temp trim % and break points were totally wrong for the Centy engine and it was nearly impossible to start and ran poorly until up to around normal engine operating temp. At or around normal engine temp it ran very well but starting and cold were really bad.

Ciao    

Hi Phil, I believe that the slight fuel increase was very easy to do and had maximum effect at low speed and minimal at high.

As mentioned, this bike is extremely tolerant to heat and I have ridden along Parramatta Road in summer with the dash reading 52C and it was fine - the rider not so much.

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42 minutes ago, pete roper said:

Phil, believe me. Mark knows exactly what he's doing and knows the W5AM inside out.

I know Pete, I wasn't doubting his methodology just offering alternative thoughts. I spoke to Mark before I transposed the .bin file from a 16M to the 15M asking for his thoughts on the logic of my plan and he surprisingly said, sure that should work, be fairly simple. I say surprisingly because others with very capable knowledge about these things weren't supportive of the plan at all. The rest is history and good old "Aussie Logic" won out.  

Ciao

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5 hours ago, Chris Wilson said:

Hi Phil, I believe that the slight fuel increase was very easy to do and had maximum effect at low speed and minimal at high.

As mentioned, this bike is extremely tolerant to heat and I have ridden along Parramatta Road in summer with the dash reading 52C and it was fine - the rider not so much.

Chris, the dash reading is simply ambient temp, it's sensor lives up by the dash and doesn't have any feed into the ecu. The ambient air temp sensor is in the airbox and the engine temperature sensor is in the back of the RH head.

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1 hour ago, pete roper said:

Chris, the dash reading is simply ambient temp, it's sensor lives up by the dash and doesn't have any feed into the ecu. The ambient air temp sensor is in the airbox and the engine temperature sensor is in the back of the RH head.

Yep, I agree.

The point was that at 52c in the blazing sun on a summer's day surrounded by diesel trucks and stopped in traffic with no air flow over the engine, I was almost passing out.

And the engine ran faultlessly.

If it was my old K75 BMW it would have boiled it's fuel easily and burnt my thigh when the fan cut in .

As you might say, I part my buttocks at your water cooling.

Chris.

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