One cylinder hotter than the other

[Bob LeClair]

2002 V11 Lemans. After an hour ride I thought I'd check the cylinder temperature, and the left was about 50 F hotter than the right. Didn't notice any running problems, power seemed smooth, but this was the first real ride on the bike. Is this a tuning issue? Bike has Guzzi headers and aftermarket crossover and mufflers. It had a Power Commander III when it came to me but I've removed it. Previous owner had installed it along with the pipes. I've been reading about the tuning procedures using cables and a laptop with Guzzidiag. Not a computer savvy guy so it's a little scary to contemplate reprogramming the ECU. I have no complaints about how she runs, but I have no baseline to compare. Any suggestions for my next steps?

[docc]

Basic starting point (includes balancing the throttle bodies = important!):

 

[footgoose]

My rudimentary knowledge of combustion tells me hot can mean a lean mix. First thing I'd look at is a possible air leak into the hot side intake. Like the cap (if you have one) on the balance nipple for the hot side throttle body. Those tend to dry rot. If not that, I would do the check involving a flammable spray onto the intake boot area while idling. While yer at it make sure you have no exhaust leaks. 50 deg doesn't sound like a lot. Is there any color difference to the head pipes? After that ... I'd ask the smart guys.

[Bob LeClair]

I did replace all the rubber boots but I haven't checked the balance screws yet. Weekend project. 

[Lucky Phil]

2 hours ago, Bob LeClair said:

I did replace all the rubber boots but I haven't checked the balance screws yet. Weekend project. 

Well of course the other suggestions are valid but it depends on when you checked the head temps. The only real way is on the move riding. As soon as you stop other variable come into play. My bike also runs a little different temp one side to another but its also in the nature of the engine architecture. That's why the right cylinder fuel map is different to the left which is the base map and the right has corrections based on the left. The right cylinder's header pipe and intake are different lengths compared to the left due to the cylinder offset due to side by side rods. You can of course adjust the right cylinder offset via Tunerpro. Here's the offset map for a std V11 Sport map MY2000 showing the different injector pulse times compared to the Left cylinder. 

 

Left cylinder base map.

 

 

Ciao

[Chuck]

My understanding is the left works a little harder than the right because of the firing order. (?)

[Bob LeClair]

7 hours ago, Chuck said:

My understanding is the left works a little harder than the right because of the firing order. (?)

??? The firing order is 1-2-1-2, evenly spaced. 90 degree v twins have perfect primary balance, unlike that American brand. 

[Bob LeClair]

12 hours ago, Lucky Phil said:

Well of course the other suggestions are valid but it depends on when you checked the head temps. The only real way is on the move riding. As soon as you stop other variable come into play. My bike also runs a little different temp one side to another but its also in the nature of the engine architecture. That's why the right cylinder fuel map is different to the left which is the base map and the right has corrections based on the left. The right cylinder's header pipe and intake are different lengths compared to the left due to the cylinder offset due to side by side rods. You can of course adjust the right cylinder offset via Tunerpro. Here's the offset map for a std V11 Sport map MY2000 showing the different injector pulse times compared to the Left cylinder. 

 

Left cylinder base map.

 

 

Ciao

I wish I understood that better, it's all Greek to me. I'm sure a comprehensive tuning would wake up the beast. 

[LowRyter]

55 minutes ago, Bob LeClair said:

??? The firing order is 1-2-1-2, evenly spaced. 90 degree v twins have perfect primary balance, unlike that American brand. 

For one time in my life I'll clarify what Chuck said about a mechanical thing.   I think the better term is firing interval (instead of firing order).   The bike has a 270/450 degree crank, meaning that one cylinder goes 3/4 of a turn to fire while second one goes 1 1/4 turns to fire.   

In other words, consider twice around the clock for firing a 4 cycle engine.  The first cylinder fires at 9am and the second fires a midnight.

So the first cylinder works a little harder than the 2nd one.  For sure, I've noticed that my EV runs hotter on one side.

[Chuck]

Semantics.. but you are right, John.. firing order is 1-2-1-2, but they are *not* equally spaced.

[po18guy]

The real problem arises when the firing order is 1-1-1-1 or 2-2-2-2.  In ('03 >) bikes(?) the forward crossover helps, but it helps one cylinder more than the other. If the exhausts were entirely separate, the temps and tuning would be closer but probably still not identical, due to the amount . 360º British twins have that 1-2-1-2 every 360º firing order and interval.  The heavy flywheel helped make up for the odd firing interval, but dampened not only crank speed fluctuations, but rider enjoyment. As in politics, everything related to internal combustion is a compromise. 

[docc]

Well, now y'all have me interested in this temperature difference between the cylinders. I have one of those (cheap) infra-red temp readers.  But where to take the temperature? The lateral cylinder wall just below the spark plug (not the head)? Or dead on the exhaust flange?

Bad Scientists want to know . . .

 

[LowRyter]

23 hours ago, Chuck said:

Semantics.. but you are right, John.. firing order is 1-2-1-2, but they are *not* equally spaced.

I really appreciate that.  

[LowRyter]

20 hours ago, docc said:

Well, now y'all have me interested in this temperature difference between the cylinders. I have one of those (cheap) infra-red temp readers.  But where to take the temperature? The lateral cylinder wall just below the spark plug (not the head)? Or dead on the exhaust flange?

Bad Scientists want to know . . .

 

BTDT.  I was at the Salida CO rally and had just gotten the EV.  I mentioned it to Matt Forslund and he hit both cylinders with a temp gun and shrugged his shoulders.  Of course, there could be all kind of reasons unrelated to the topic, like a slight difference in ignition timing or one side being leaner...... all the Guzzi black magic stuff.

[docc]

32 minutes ago, LowRyter said:

BTDT.  I was at the Salida CO rally and had just gotten the EV.  I mentioned it to Matt Forslund and he hit both cylinders with a temp gun and shrugged his shoulders.  Of course, there could be all kind of reasons unrelated to the topic, like a slight difference in ignition timing or one side being leaner...... all the Guzzi black magic stuff.

South'n SpineRaid TechSession?  We'll generate a Venn Diagram . . . or a Bell Curve. Or a shrug and another round of brews . . .