V11 Engine Hot Rodding advice

[Pressureangle]

Thanks guys! See, now that was worth it - I’m sure from the number of readers there’ll be many cogs spinning & awhirrin’ around with these thotfull gems.

 

I cannot quite remember where I read this, I think maybe on a Thumper forum but I’ll try & paraphrase what some old hand opined his recommendation to “economically” do to ports - which I retained in my head because it was a ‘best bang for buck porting tip’ I’d heard put forward succinctly.

 

It went something along lines of - if you find someone experienced with porting heads - but hasn’t previously worked on heads like yours before now, just ask him to do his favourite angled valve job, clean up & pocket port only - I seem to recall it was suggested to even excessively hog out on the pocket AND then lay down epoxy for raised flat floors & D shaping the SSR.

 

It wasn’t the nth degree in porting advice but always produced improvement across all & sundry heads .

 

...care to add your thots?

Two points are paramount, and ultimately far more important than max-lift flow numbers.

First, Low-lift flow. The intake valve spends all but a short period of time at less than max lift, and the closer it is to the seat, the more slowly it moves. So 10CFM between .050" and .150" lift is far more productive than 10CFM at max lift.  

Secondly, port velocity. The higher the velocity, the more air can pass a given opening in a given period of time. To maximize velocity, the port has to be the ... uh ... 'correct' cross section and taper to match the curtain area of the intake valve ('curtain area' is the area open between valve and seat at a given lift). Your port guy who suggests a good valve job is right on the money; getting the curtain velocity up by shaping the valve head and seat can find big gains even without port changes. 

Where the Guzzi port fails, is that it's already large, to make up for the water-pipe shape; velocity produces inertia, and if velocity gets too high for a short turn, the air separates from the floor and gets turbulent, can't make the turn and kills ultimate volume. The ports on my LMIV are raised, floor filled, and tapered from carb to valve. (Not discussed is venturi effect from the smaller throat to larger valve opening).

 

So a perfect port would simply be a velocity stack with a given taper (I don't know that perfect number) without a valve in it. Modern engines come as close to this as physically possible. Then, RPM, camshaft duration and overlap, compression, and exhaust scavenging all have an effect on intake timing and velocity as well. 

 

It's complicated.

[swooshdave]

Just about every engine faces the same issue, having to put the valve somewhere in the port. At some point in a traditional valve train that valve is going to bisect the port. Given that working on the Guzzis you're starting with anything but a clean slate you are limited. You can either throw a lot of money at the head or you can enjoy it for what it is.

[GuzziMoto]

Just about every engine faces the same issue, having to put the valve somewhere in the port. At some point in a traditional valve train that valve is going to bisect the port. Given that working on the Guzzis you're starting with anything but a clean slate you are limited. You can either throw a lot of money at the head or you can enjoy it for what it is.

While I do agree that you have to work with what you have, I disagree with the notion that you have to throw a lot of money at a Guzzi to make noticeable improvements in performance.

I spent around a grand on motor work for the wife's V11, porting, along with cylinder and head machining, and the results were nice. It would be hard with a better, more modern, engine to get as much improvement for the same amount of money.

I have said it before and I will say it again, as long as your expectations are realistic (you are never going to turn a Guzzi into a Hayabusa eater) Guzzi's are a great candidate for motor work as there is so much unrealized potential. You will get more performance increase for your dollar modifying your Guzzi motor than you would get throwing that money at a Hayabusa. Sure, if you have the money you can double the power output of a Hayabusa. But it will cost you massive amounts of money. On a per dollar spent ratio the Guzzi lump is a good return on investment when it comes to head work and other performance mods.

Or you can enjoy it as it is. But I just ain't like that.

[ScuRoo]

With regards to researching (relatively) large port losses - (p24) Ram Tuning port velocities produce maximum power @ 700 feet per second!

 

Whoever said, “You’ll get alot further shaping for velocity than cutting for flow!” might have been referring to our V11’s lazy ‘ol poop chutes!

[r3datom9]

Hi Kuni,

 

My V11 has a built engine, no port work done though.  

 

We are both in the Bay, if you want to see how it feels compared to your Rosso, lets meet up and hit some back roads in Marin.

 

Haven't ridden a Rosso, but this is my second V11, the first a red frame and my current a black, the original owner had the engine built when the "fuzzy" engine cases were replaced under warranty.  Carrillo rods, high comp pistons, and cams - all built by Moto International in Seattle and dyno tuned.  Runs like a scalded ape compared to my old red frame.  Engine pulls hard up to the factory red line and revs freely.

 

Take it for a spin and see if it can give you a good baseline of work you might want to do. 

 

I have all the invoices from the work done so you can see the parts if you want to add them to your work order.

 

Only demand is I need to ride your Rosso:)

 

I only have Ohlins on the rear and have always wondered how the front end feels.

 

-Nick

[r3datom9]

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.

[GuzziMoto]

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.

That is odd with the detonation / pinging. I assume it was the heat, as generally increased elevation reduces the need for high octane and the detonation resistance of it.

[LowRyter]

Too much ignition timing vs compression, lean mixture, heat, octane and altitude. 

[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.

[Chuck]

 

 

 a symptom of local fuel quality.

Possible. I was coming home from Florida on the Centauro one time, and after a fuel stop it just wouldn't idle. Nothing below 1500 or so. By the time I got to Tennessee or so, it was back to normal. Got a load one time going to California that made Harley Bob's hawg run *really* bad. The Big Guzzi filter stopped that one.. it was probably just dirt.

[r3datom9]

 

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.

 

That was the general area that I fueled up before heading up into the mountains.

 

Coincidence?  

 

I have always had issues with gas inconsistencies in the bay area.  

[GuzziMoto]

Yeah, bad gas can cause pinging. Elevation, as mentioned, actually reduces the need for higher octane. I have been out west in the mountains where the only two choices for octane were 85 and 87. But even with something that wants 91 octane or better I had no issues at that altitude. And running something that wants 87 octane I was able to run on 85 octane with no issues.

But when you are above 8,000 feet your octane requirements seem to drop a fair bit.

[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

[Chuck]

The rule of thumb is at 7500 feet, full throttle will give you 75% power.

[Lucky Phil]

The rule of thumb is at 7500 feet, full throttle will give you 75% power.

Ok Chuck thanks. Seems to tally from my flying around days with the 737-800's and them having around 25% of Sea Level thrust at 40,000 feet. Climb and accell was fairly leisurely at those altitudes as was engine response to the thrust levers.

 

Ciao