V11 Engine Hot Rodding advice

[Pressureangle]

 

 

Forgot to mention...I was concerned about the low octane fuel that we use in Cali with the high-comp pistons.  Only time I have had an issue was at high altitude in the Sierra's in the summertime, it was around 95-100 degrees and 2-3k plus in elavation, some pre-detonation/pinging started to occur if I hit the throttle too hard.  Normal bay area weather has no effect even with our crap 91 octane fuel.

I've been thinking about this for a while before responding.

 

Elevation equals reduced cylinder pressure, no exceptions. So that cannot be the source of your ping.

 

I can say with certainty that the variability in pump gas out west was disconcerting and surprising. My 1100 Sport-i was sensitive to gas stops far more that it was to altitude. I never got pinging, but I did get noticeable weakness and a couple times generally unhappy low-throttle running. I don't believe for a second that either the octane number nor the alcohol listed on the pumps is a reliable indicator of what's going in the tank. Miles per gallon was the most noticeable difference, however. It varied between 45-ish in Georgia to 34-ish in New Mexico, though the performance aspect is not so apparent on those long flat fast stretches. NoCal and Washington State seemed the least consistent. 

Of course, none of this is scientific, only subjective- but over 10k miles one gets a good feel for what's going on.

So I'll suggest that your condition is a symptom of local fuel quality. The worst tank I had by far was somewhere South of Sacramento.

 

Not quite. Pre ignition or ping as well call it here is caused by hot spots in the combustion chamber that cause the fuel in isolated areas to, well pre ignite hence the sound you hear. Detonation is caused by the fuels inability to maintain its chemical stability during the ignition event and the oncoming flame front and then burns in an uncontrollable fashion combined with the spark ignited flame front and the two intersecting a lot more cylinder temp and pressure is created. A much worse scenario than ping. The reasons for both are many and varied.

But back to the original issue.Poor fuel can of course cause ping but the altitude can also play a roll if not be the actual cause. When you climb 3000 feet the pressure will drop 3/4 of a psi. (old aircraft engineers figure-1/4 psi per 1000 ft) Chuck may be able to confirm piloting and all. So thats about a 5% drop in atmospheric. The ecu of course leans out the mixture to compensate and of course you get a commensurate drop in power. 

Problem is your brain and right wrist dont necessarily accommodate this loss of power and unconsciously just apply more throttle to achieve the same performance. So what you end up with is the same load ( speed and resistance to climb the given rise) but with a leaner mixture and more throttle and if the temperature is also high more leaning.Result....increased combustion chamber temperature, hot spots and ping.

Your theory about elevation and cylinder pressure also only holds true for WOT or a given throttle position. But in the real world when we all ride the reduced atmospheric pressure is compensated for by opening the throttle more to maintain the performance we seek. Most of us even when we are "going for it" in the twisties are only using maybe 35-50% throttle. You'd be amazed how little time even a race bike spends at WOT.

Ciao

 

Throttle position isn't even in the equation here.

You need a given amount of cylinder pressure to do a given amount of work, and if you need to open the throttle farther to get that, it's irrelevant unless opening the throttle adds in more ignition timing, which is usually the opposite.

So your point about 'my theory' is problematic because you say it 'only holds true for WOT or a given throttle position' WTF even is there other than WOT or a given throttle position? Would you like to add acceleration enrichment to 'my theory' and explain how a richer mixture makes it ping? One might reasonably suggest that his ride at altitude was more aggressive than below, but I surmise that he rides pretty near sea level aggressively as well without the ping, or he wouldn't have bothered with the question eh? 

The point is that at one altitude higher than another, there is no point at which the cylinder pressure can be higher, at any given throttle opening, than at the lower altitude, so that cannot be the root of the problem. 

On to the next 'theory'.

[Lucky Phil]

 

 

 

Forgot to mention...I was concerned about the low octane fuel that we use in Cali with the high-comp pistons.  Only time I have had an issue was at high altitude in the Sierra's in the summertime, it was around 95-100 degrees and 2-3k plus in elavation, some pre-detonation/pinging started to occur if I hit the throttle too hard.  Normal bay area weather has no effect even with our crap 91 octane fuel.

I've been thinking about this for a while before responding.

 

Elevation equals reduced cylinder pressure, no exceptions. So that cannot be the source of your ping.

 

I can say with certainty that the variability in pump gas out west was disconcerting and surprising. My 1100 Sport-i was sensitive to gas stops far more that it was to altitude. I never got pinging, but I did get noticeable weakness and a couple times generally unhappy low-throttle running. I don't believe for a second that either the octane number nor the alcohol listed on the pumps is a reliable indicator of what's going in the tank. Miles per gallon was the most noticeable difference, however. It varied between 45-ish in Georgia to 34-ish in New Mexico, though the performance aspect is not so apparent on those long flat fast stretches. NoCal and Washington State seemed the least consistent. 

Of course, none of this is scientific, only subjective- but over 10k miles one gets a good feel for what's going on.

So I'll suggest that your condition is a symptom of local fuel quality. The worst tank I had by far was somewhere South of Sacramento.

 

Not quite. Pre ignition or ping as well call it here is caused by hot spots in the combustion chamber that cause the fuel in isolated areas to, well pre ignite hence the sound you hear. Detonation is caused by the fuels inability to maintain its chemical stability during the ignition event and the oncoming flame front and then burns in an uncontrollable fashion combined with the spark ignited flame front and the two intersecting a lot more cylinder temp and pressure is created. A much worse scenario than ping. The reasons for both are many and varied.

But back to the original issue.Poor fuel can of course cause ping but the altitude can also play a roll if not be the actual cause. When you climb 3000 feet the pressure will drop 3/4 of a psi. (old aircraft engineers figure-1/4 psi per 1000 ft) Chuck may be able to confirm piloting and all. So thats about a 5% drop in atmospheric. The ecu of course leans out the mixture to compensate and of course you get a commensurate drop in power. 

Problem is your brain and right wrist dont necessarily accommodate this loss of power and unconsciously just apply more throttle to achieve the same performance. So what you end up with is the same load ( speed and resistance to climb the given rise) but with a leaner mixture and more throttle and if the temperature is also high more leaning.Result....increased combustion chamber temperature, hot spots and ping.

Your theory about elevation and cylinder pressure also only holds true for WOT or a given throttle position. But in the real world when we all ride the reduced atmospheric pressure is compensated for by opening the throttle more to maintain the performance we seek. Most of us even when we are "going for it" in the twisties are only using maybe 35-50% throttle. You'd be amazed how little time even a race bike spends at WOT.

Ciao

 

Throttle position isn't even in the equation here.

You need a given amount of cylinder pressure to do a given amount of work, and if you need to open the throttle farther to get that, it's irrelevant unless opening the throttle adds in more ignition timing, which is usually the opposite.

So your point about 'my theory' is problematic because you say it 'only holds true for WOT or a given throttle position' WTF even is there other than WOT or a given throttle position? Would you like to add acceleration enrichment to 'my theory' and explain how a richer mixture makes it ping? One might reasonably suggest that his ride at altitude was more aggressive than below, but I surmise that he rides pretty near sea level aggressively as well without the ping, or he wouldn't have bothered with the question eh? 

The point is that at one altitude higher than another, there is no point at which the cylinder pressure can be higher, at any given throttle opening, than at the lower altitude, so that cannot be the root of the problem. 

On to the next 'theory'.

 

Maybe what I omitted was at a given static throttle position". So without getting into a major pointless debate here clearly throttle position is a factor. Here's the OP's quote " pre-detonation/pinging started to occur if I hit the throttle too hard. So the variable is altitude and and temperature as he normally has no issues at sea level even on the crap 91 fuel he has in the bay area and has no issue riding up a mountain and NOT hitting the throttle too hard. 

​So assuming he has the same crap fuel as normal its all about the altitude and temperature and the controllable variability is the right wrist which is governing the combustion pressure and temperature. 

 

Ciao 

[GuzziMoto]

Sorry, I have to agree that it was likely an issue with crap gas and not altitude that caused the issue.

Unless you are saying that the increase elevation caused his motor to overheat I don't see how the increase in elevation would cause the detonation. My direct experience with riding / driving at higher elevations, along with the basic premise that increased elevation results in reduced cylinder pressures on non-forced induction motors, says that the elevation did not cause the detonation.

[LowRyter]

more elevation = less oxygen = lean mixture = detonation

 

Then consider steep grades and more strain on the engine.  

 

Having said that, I have no idea why the gasoline octane content is lower in the Rockies.  So I could be wrong.

[Chuck]

 

more elevation = less oxygen = lean mixture = detonation

Nice try, no cigar. More elevation means richer mixture. In your normally aspirated airplane, you have to keep leaning the mixture as you climb.

[GuzziMoto]

Yeah, sorry but Chuck is right. If you have less oxygen and the same amount of fuel you would have a richer mixture, not leaner. But, since the V11 is fuel injected and it has a air pressure sensor it should reduce the fuel to match the decrease in air density (which is where the less oxygen thing comes from) and so the fuel mixture should stay roughly the same. I say roughly because the FI on the wife's V11 is not very sophisticated and it is only guessing on how much fuel to remove.

Now, if you run forced induction it all changes. Forced induction will maintain combustion pressures (within the limits of the system) so at altitude your octane requirement is not diminished.

[czakky]

The v11 has an air pressure sensor?

[GuzziMoto]

The v11 has an air pressure sensor?

Ours does, a barometric pressure sensor that is under the seat as I recall.

[68C]

Yes, it is inside the IAW15M ECU, that is why the case is not sealed and so vulnerable to getting wet.

[MartyNZ]

 

more elevation = less oxygen = lean mixture = detonation

Nice try, no cigar. More elevation means richer mixture. In your normally aspirated airplane, you have to keep leaning the mixture as you climb.

Chuck is right again.

Scud asked a similar question here:

https://www.v11lemans.com/forums/index.php?showtopic=19977

 

Yeah, sorry but Chuck is right. If you have less oxygen and the same amount of fuel you would have a richer mixture, not leaner. But, since the V11 is fuel injected and it has a air pressure sensor it should reduce the fuel to match the decrease in air density (which is where the less oxygen thing comes from) and so the fuel mixture should stay roughly the same. I say roughly because the FI on the wife's V11 is not very sophisticated and it is only guessing on how much fuel to remove.

Now, if you run forced induction it all changes. Forced induction will maintain combustion pressures (within the limits of the system) so at altitude your octane requirement is not diminished.

GuzziMoto is right too. The V11 ECU auto corrects the mixture as altitude changes.

 

The v11 has an air pressure sensor?

Yes, that little black button on the top corner of the ECU.

[LowRyter]

 

 

more elevation = less oxygen = lean mixture = detonation

Nice try, no cigar. More elevation means richer mixture. In your normally aspirated airplane, you have to keep leaning the mixture as you climb.

 

 

 

doooooh !

 

(it was early when I wrote that and I was contemplating taking off the bodywork on the Duc,  I was totally distracted and not myself) (the dog ate my homework too)

[GuzziMoto]

 

 

 

more elevation = less oxygen = lean mixture = detonation

Nice try, no cigar. More elevation means richer mixture. In your normally aspirated airplane, you have to keep leaning the mixture as you climb.

 

 

 

doooooh !

 

(it was early when I wrote that and I was contemplating taking off the bodywork on the Duc,  I was totally distracted and not myself) (the dog ate my homework too)

 

Ducati bodywork will do that to you.

I am lucky, the only street Ducati I have to deal with nowadays is the wife's 1100 Monster.

But I have had my share over the years.

[Kuni0]

Ok, so a bit of an update to the thread.

I talked with Mike Rich about porting and polishing the heads, but unfortunately the turnaround time is too long for my goals. Instead I'll have a friend who's a master motorcycle mechanic and experienced hot-rodder to do the porting. 

I've dropped in a Megacycle 620x9 cam (along with new tappets) and a roper plate. I have the new clutch/ intermediate plates, springs and will be keeping the stock flywheel. At this point, I have everything I need engine wise besides the porting, and just need to go through it and make sure everything is torqued down and replace the engine consumables (rings, gaskets, valve stem seals) 

I also took this opportunity to take off the Ohlins and get them serviced (JpH suspension) and will go back to him for further adjustment when everything is back together. 

r3datom9,

I'm more then willing to trade bikes when everything is back together and explore what riding the north bay has to offer. It'll be interesting to compare the bikes once all is said and done.

[swooshdave]

Will you have before and after dyno results to compare?

[Lucky Phil]

6 hours ago, Kuni0 said:

Ok, so a bit of an update to the thread.

I talked with Mike Rich about porting and polishing the heads, but unfortunately the turnaround time is too long for my goals. Instead I'll have a friend who's a master motorcycle mechanic and experienced hot-rodder to do the porting. 

I've dropped in a Megacycle 620x9 cam (along with new tappets) and a roper plate. I have the new clutch/ intermediate plates, springs and will be keeping the stock flywheel. At this point, I have everything I need engine wise besides the porting, and just need to go through it and make sure everything is torqued down and replace the engine consumables (rings, gaskets, valve stem seals) 

I also took this opportunity to take off the Ohlins and get them serviced (JpH suspension) and will go back to him for further adjustment when everything is back together. 

r3datom9,

I'm more then willing to trade bikes when everything is back together and explore what riding the north bay has to offer. It'll be interesting to compare the bikes once all is said and done.

Dont worry too much about the valve stem seals.

 

Ciao