performance mod comparisons

[dave]

I cant help but be curious about engine mods. While I support clean living, I am also a romantic about internal combustion engines... burbling spool downs, the smell of fuel in the air, ect. I have been looking over old posts and the dyno thread for a while but am having trouble piecing together a clear picture of the gains and trade-offs of different tinkerings. The main monkey-wrench in my ointment (love me a shaken metaphor) is that while there are clearly folks out there who have done their homework and know, the background noise is too much. I particularly like the threads that some of the clearer thinkers have methodically collaborated on only to meltdown into goo. I have spoken to Mike Rich but would like to understand why one bike with cam, port, twin plug and tummy rub will dyno similarly to one that just has a dialed in ecu and exhaust. I understand all bikes and test conditions are different, but after 12 years there should be a bell curve showing up like a shimmering rainbow somewhere. .

 

Any pseudo scientific insight would be welcome both as data and just for an enjoyable read by a non-racer who appreciates those who do.

[docc]

Reading Greg Field's account of the development of this engine (Moto Guzzi Big Twins, MBI Publishing, 1998), I am left with the impression that the designers and engineers brought it to a pretty high state of tune for a big, air-cooled, push-rod twin. Properly tuned, they do run very, very well, yet benefit from free flowing exhaust cans and, perhaps, a little better air flow.

 

Beyond that, it looks like big bucks and high effort for rather incremental gains.

 

Being an incurable motorhead , a good friend finally convinced me that turning my attention to the bike's suspension would give me far greater performance gains than anything I could do to the motor.

[dave]

Reading Greg Field's account of the development of this engine (Moto Guzzi Big Twins, MBI Publishing, 1998), I am left with the impression that the designers and engineers brought it to a pretty high state of tune for a big, air-cooled, push-rod twin. Properly tuned, they do run very, very well, yet benefit from free flowing exhaust cans and, perhaps, a little better air flow.

 

Beyond that, it looks like big bucks and high effort for rather incremental gains.

 

Being an incurable motorhead, a good friend finally convinced me that turning my attention to the bike's suspension would give me far greater performance gains than anything I could do to the motor.

 

I could not agree more that handling is vastly more important and a better value than pure power. That said, it does not keep me from being curious or grinning to myself over the possible fun to be had by tweaking the motor. If the gains are incremental but the outlay high, it will still be interesting knowledge. If there are some real world gains for reasonable outlay, all the better.

[gstallons]

There is an old hot rodder's maxim. "Speed costs , how fast can you afford to go?".....

[GuzziMoto]

My wifes V11 has had some work done on the motor (and the suspension).

So far the heads have been ported, the cylinders machined to match deck heights, the heads skimmed to increase squish and compression. It has a oiled cotton air filter, slip-on mufflers, and a Power Commander. I have a set of gears for the cam drive yet to install, and would like to get one of the cross-overs in the future.

So far the bike makes about fifteen more Hp then it started with. It wasn't cheap but all in all it was much cheaper then getting that kind of % power increase out of a more modern motor. It is pretty fast, but if some is good more must be better.

[dave]

My wifes V11 has had some work done on the motor (and the suspension).

So far the heads have been ported, the cylinders machined to match deck heights, the heads skimmed to increase squish and compression. It has a oiled cotton air filter, slip-on mufflers, and a Power Commander. I have a set of gears for the cam drive yet to install, and would like to get one of the cross-overs in the future.

So far the bike makes about fifteen more Hp then it started with. It wasn't cheap but all in all it was much cheaper then getting that kind of % power increase out of a more modern motor. It is pretty fast, but if some is good more must be better.

 

Thanks! That is a good start. Can you say if you lost any power from the bottom end?

 

Thanks again

[Guzzirider]

Tuning a two valve motor V11 motor is very expensive- you could bolt in a Centauro or Daytona motor with a little effort, put in fast cams and have 100bhp at the back wheel for much cheaper than throwing thousands of dollars at your existing motor.

 

Saying that, a V11 motor is one of the best engines to ride that Guzzi have ever produced and will have a nice spread of power for the road in comparison to the Daytona engine.

[GuzziMoto]

My wifes V11 has had some work done on the motor (and the suspension).

So far the heads have been ported, the cylinders machined to match deck heights, the heads skimmed to increase squish and compression. It has a oiled cotton air filter, slip-on mufflers, and a Power Commander. I have a set of gears for the cam drive yet to install, and would like to get one of the cross-overs in the future.

So far the bike makes about fifteen more Hp then it started with. It wasn't cheap but all in all it was much cheaper then getting that kind of % power increase out of a more modern motor. It is pretty fast, but if some is good more must be better.

 

Thanks! That is a good start. Can you say if you lost any power from the bottom end?

 

Thanks again

No power lost, just more. The motor pulls hard from 3 grand and just keeps pulling harder. I don't usually get to ride it (it's the wife's bike) but last weekend we went for a ride and while she was riding her Lario I ended up on her V11. I had forgotten how fast it is.

And while tuning any motor ain't really cheap I find that the V11 motor is an easy motor to tune and mod. Most of the basic parts are already there, bigger valves, ports, and throttle bodies. Plus there are a fair number (for a Guzzi) of parts made for the motor like high compression pistons and even bigger valves. Yet most parts from the older two valve motors should also fit. Plus, air cooled push rod motors are generally easy to work on (so you can do much of the work yourself) and finally, Guzzi got much of the motor in the ball park but did not finish it out so there is still much to be gained with relatively basic (and cheap) work like setting deck height and squish.

I have, not counting the gear drive, less then $2500 (everything including exhaust) in the motor and I got over a 20% increase in power. That is cheap Hp.

[AndyH]

Just an observation: it's always an option to pare down the weight in search of more performance...

I chose to take 25 pounds off the rider this year: big difference in acceleration and handling.

 

Just made myself really popular, I guess.

 

Anyone for a pie and a pint?

[Skeeve]

I have spoken to Mike Rich but would like to understand why one bike with cam, port, twin plug and tummy rub will dyno similarly to one that just has a dialed in ecu and exhaust.

The devil is in the details: while someone may have thrown $$ at a motor & not really dealt with getting everything to work together well, the guy who "just put on a pipe & dyno-tuned PCIII" may have in fact done a lot of blueprinting, or just gotten lucky and gotten an engine that had everything just right from the factory [it could happen! ]

 

The fact of the matter is, stacking of tolerances & parts mismatches can go a long way toward reducing the efficiency of a motor: this is why Mike Rich can sell his pistons for so much money, because Guzzi redesigned the heads for the V11, but never put in the matching pistons to take advantage of proper squish, etc. Dual-plugging is a band-aid for poor combustion chamber topography; look at what efficiencies Harley-Davidson was able to achieve Shovel->Evo->Twin Cam, all with better combustion chamber design: those motors were all 2v & air-cooled, but the Shovel was lucky to get 25mpg, the Evo would regularly do 40, and the TC is up around 50, despite big increases in displacement w/ each generation.

 

The 2v Guzzi mill is like a slice off the end of a ohv V8, only w/ air-cooling instead of liquid, and will respond to the same sort of attention to detail and performance niggles that have been laboriously worked out in racing those engines over generations:

1) Fill the cylinder efficiently.

2) Burn the mixture as quickly & completely as possible.

3) Get the exhaust out of the cylinder.

4) Eliminate parasitic drag.

 

Intake restrictions are 1 & 4. Exhaust pipes are 3. Porting the intake is 1 & 4; porting the exhaust is 3 & 4. Sloppage sheets are primarily a reliability issue, but also help w/ #4. Keeping your tires properly inflated is 4. Using no more of the correct wt. of oil than necessary is 4. Dialing in the efi is 2. Servicing the water pump is 4 [oh wait, that's already been done for us by Ing. Carcano! ] & so on...

 

Ride on!