Backfire/coughing

[po18guy]

I must admit that I have not had a pop back since switching to ethanol-free 92 octane. Here is a website which shows many US and Canadian locations for ethanol-fre gas.

https://www.pure-gas.org/

Costs more but my fuel tank says it likes it.

[p6x]

3 hours ago, po18guy said:

I must admit that I have not had a pop back since switching to ethanol-free 92 octane. Here is a website which shows many US and Canadian locations for ethanol-fre gas.

https://www.pure-gas.org/

Costs more but my fuel tank says it likes it.

But it brings back the discussion we had about minimum Octanes for our high compression ratio engines. The V11 is considered high compression ratio, and recommended octanes is 91 using the US calculation.

Some Ethanol free gas station sell below 91 Octane gas. Actually, in Texas, 87 seems to be the norm.

 

[GuzziMoto]

To make it even more confusing, my wife's V11 manual listed octane required using the Euro numbers. So that added to the confusion.

Europe uses the RON number, the US uses an average between RON and MON. That results in the European number being higher.

[po18guy]

There is a farm co-op in my state. They sell 92 octane E-0.

[Daveguzzi1]

I did not know this would digress into a fuel conversation as I stated in one of my first post.I run one hundred octane sunoco ethanol free. When on a longer ride I run the best available. When I put the bike away I siphon the shit California gas out and put some good stuff in. I get my fuel down the street from a gas station. They sell a lot of race fuel so it is fairly fresh. 10 bucks a gallon 

[Lucky Phil]

It's pretty easy to remove the ethanol from the Tainted stuff you get in the USA to keep corn growers in business. I wouldn't want to do it for commuting to work but for day rides it's doable.

 

Phil 

[docc]

On 3/20/2024 at 9:11 PM, Daveguzzi1 said:

I have a 2003 v11 Lemans. I have an off idle cough/backfire through the intake that is consistent to 3000 rpms. It is worse when the bike is fully warmed up. When rolling on the throttle and going thru the gears it doesn't occur but holding the throttle steady at 3500 or below it hiccups and coughs. New plugs properly set valves clean air filter. Plugs look good when pulled after running. The exhaust crossover has the special seals so it doesn't leak and headers are tight and not leaking. 23k on odo. She's done this for a while but getting worse. We have a dealer in our town but I have a factory service manual and would prefer to fix myself.  Thoughts????? DaveG

No mention of CO setting, TPS setting, or throttle body balance. Highly recommended baseline procedure:

 

[p6x]

On 4/10/2024 at 8:33 AM, GuzziMoto said:

To make it even more confusing, my wife's V11 manual listed octane required using the Euro numbers. So that added to the confusion.

Europe uses the RON number, the US uses an average between RON and MON. That results in the European number being higher.

We discussed this in a topic related to running the V11 with regular fuel.

At the time, I took a picture of an adhesive on my rear mudguard. The recommended fuel for the V11 is 91 RON+MON/2. So in the USA, we should be using 91 Octane fuel. In Europe, the minimum Octane is 95; the equivalent of "premium gas" octane is 98.

I have run the V11 with 87 Octanes without the engine knocking. Not by choice. I was in West Texas, running low on gas, and the only station within my reach only sold regular and diesel. After a complete setup of the V11 earlier this year, my engine no longer cough at 3000, but the engine knocks if I really pull hard on it.

 

[p6x]

13 hours ago, Daveguzzi1 said:

I did not know this would digress into a fuel conversation as I stated in one of my first post.I run one hundred octane sunoco ethanol free. When on a longer ride I run the best available. When I put the bike away I siphon the shit California gas out and put some good stuff in. I get my fuel down the street from a gas station. They sell a lot of race fuel so it is fairly fresh. 10 bucks a gallon 

 

[GuzziMoto]

Without getting off into the weeds about octane and the pro's / con's of running 100 octane race fuel in a bike not made for it, I would agree with docc that a good place to start when you are having running issues is the Decent Tune Up that he linked to.

Has it always done this or is this new, @Daveguzzi1 ?

[Lucky Phil]

It's pointless discussing fine tuning a Guzzi for the subtle operations such as fine throttle response, idle and coughing when you are trying or indeed running it on 100 octane race fuel. The higher the octane rating the less volatile the fuel and the more likely you are to have low speed throttle response and idling issues. Low volatility is great for anti knock but bad for pretty much everything else. The greater volatility of lower octane fuels also helps with intake temps due to better evaporation in the inlet manifold which also is the reason the higher octane fuels often exhibit poor low speed running. We ran some race engines on 100LL Avgas back in the day on injected Ducati Superbike engines and they exhibited poor low speed running especially when the engine was cold and the only advantage it offered was consistency. In the IOM years ago the guy in the next garage to us was using it in his Kawasaki production bike and it was a bitch to keep running properly on start up even with choke at 0430 in the cold weather before the 5am practice started. The Sunco 100 race fuel is actually 104 RON octane and the highest pump fuel we have here is 98 Octane, so it's a decent jump. America uses some average number of RON and MON for their ratings. So on a Guzzi engine I'm pretty confident the Sunco fuel will result in worse low speed running especially at cooler OAT's and poorer starting as well. It's street legal in the US but mostly used by massive boost road car nutters you have there. 

[Tomchri]

Yes it took awhile before lesson learned about the octane hunt. Back in the days it was possible to get 110 octane from a buddy working offshore. 
Cheers Tom.

[Gmc28]

22 hours ago, Lucky Phil said:

It's pointless discussing fine tuning a Guzzi for the subtle operations such as fine throttle response, idle and coughing when you are trying or indeed running it on 100 octane race fuel. The higher the octane rating the less volatile the fuel and the more likely you are to have low speed throttle response and idling issues. Low volatility is great for anti knock but bad for pretty much everything else. The greater volatility of lower octane fuels also helps with intake temps due to better evaporation in the inlet manifold which also is the reason the higher octane fuels often exhibit poor low speed running. We ran some race engines on 100LL Avgas back in the day on injected Ducati Superbike engines and they exhibited poor low speed running especially when the engine was cold and the only advantage it offered was consistency. In the IOM years ago the guy in the next garage to us was using it in his Kawasaki production bike and it was a bitch to keep running properly on start up even with choke at 0430 in the cold weather before the 5am practice started. The Sunco 100 race fuel is actually 104 RON octane and the highest pump fuel we have here is 98 Octane, so it's a decent jump. America uses some average number of RON and MON for their ratings. So on a Guzzi engine I'm pretty confident the Sunco fuel will result in worse low speed running especially at cooler OAT's and poorer starting as well. It's street legal in the US but mostly used by massive boost road car nutters you have there. 

Amen.

Way, way back octane choice had a more visible effect in some ways (pinging, fuel econ), in my opinion, but that was way back, when carburators were the norm and ECU’s were not, etc.  25 plus yrs now I’ve run only regular in all my Italian and Germanic machines, 2-wheelers and 4, with zero differences other than a lower fill-up cost.  LT, the somewhat well-known Ducati guru, says he never runs premium in any of his machines.  I run it only in my less-ridden V11’s now, but only because it’s the only ethanol free gas I can get. All my other machines, and even the Guzzi’s on a road trip, just run regular.

Sorry PO, Daveguzzi1, that we digressed into an octane discussion!  But mixed in here is the good stuff/advice on the “decent tune up” to establish the baseline, so more specific troubleshooting ideas can be focused.  Your choice to run 100 octane may as Phil says be making things either worse, or less clear.