Inlet Ports

[Charlie J]

I have posted this question in the Griso Bella section but without response,so I ask it here.My 06 1100 Griso's Inlet ports are bigger than the inlet elbows thus creating a step when coming from the valve back to airbox. Is this step there for a reason? thanks for your help.

 

[GuzziMoto]

Well, I think you are asking if the step is there for a GOOD reason. The step is certainly there for a reason but likely not for a good reason. Guzzi are not know for their high degree of refinement and finishing. Often there are mismatches like that along with basic design shortcomings that lead to a relatively mediocre power output for the engine design and size. You could certainly remove the step and you might see a small gain in power but without approaching the engine breathing as a whole you likely will not see a noticeable gain.
My wifes V11 had the heads ported, including removal of the steps in the intake tract, heads and cylinders decked to improve the squish band,and a valve job, and it gained about 10 hp. You could feel the improvement but it was not night and day.

I doubt that step is there on purpose and I would think that removing/blending it would be a good thing. Sometimes it is actually better to add material then to remove material to smooth out the flow. In your case it sounds like removing would be the main option.
I have seen steps there on purpose in the exhaust tract but not in the intake tract.

 

[Charlie J]

Thank you Guzzi Moto. Yes a GOOD reason was what I intended.I wasnt sure whether the step was there to stop gases coming back up the inlet,you made me think ease of manufacture was the reason its being there. I intend to fit "Uniflow" foam pods to inlet pipes that have been mandrel bent,clamp these to the T/B's,clean up the inlet ports and check out the squish and see how that goes. I am not expecting a rocketship as a result,rather a sweet,healthy motor.Hopefully all benefitting the mid range.
As a result of using inlet pipes between pod and T/B, the pods will be under the seat where the stock air box was,and out of the rain. The bloke at Unifilter told me that "The volume between the throttle butterfly and the underside of the filter element must be at least 1.3 times that of the volume of the cylinder/s serviced by that air filter". The inlet pipes I am making will acheive this.Thanx for your help.

 

[Chris R]

Was it intentional? Hard to say - air in an enclosed pipe is really tricky. What is downstream affects what is upstream and the other way around. Laminar flow pretty much never happens.

You'd think sticking a small valve stem would help flow - in my experience frequently not. Same goes with big valves.

The only way to know is with a flow bench and a dyno or a setup like Cosworth has where you can send a continuous pulse of very low pressure air.

The step may be something clever - like an anti-reversion valve, or just sloppiness. I disagree that Guzzi's are crude - they are just crude enough for the purpose. Harleys are crude.

Amazing that Guzzi had a wind tunnel since the 50s but didn't have a flow bench until quite recently - I think that is a Dr. John innovation or maybe the result of the various mergers. I would think with something as modern as the Griso it has been extensively studied.

 

[GuzziMoto]

Harley's may be a lot of things, but the Harley motor that was in a Buel X1 I used to own was a brilliant motor. It made more power and got way better fuel mileage then any of our Guzzi's. And it sounded good.
I am not surprised that Guzzi has not had a flow bench until recently. Now if they could only figure out how to use it.

 

[Chris R]

Any comment about Harley is bound to raise feathers and I don't want to start a pissing match.Don't get me wrong - I like, appreciate and groove on crude and if you look at the stock head casting for Harley they are lumps! The amount of development the aftermarket has put into the Harley motor is amazing - they get some real power out of a design that goes back to the dawn of the airplane age.

I've had use of a Buell as well and agree that it is a powerful motor with great torque. Didn't find the fuel economy any better or worse than the Guzzi to be honest.

And I too wonder about the whether there is anybody at Guzzi who understands how to actually use a flow bench.

 

[GuzziMoto]

No pissing match required.
I was just saying that Harleys, for all their low tech outside, are not so low tech on the inside. The combustion chamber shaper and port design for my Buell's motor was very good. It allowed it to make about 80 hp at the rear wheel and still return 50+ mpg. The best my Guzzi get is about 45 mpg. And from what I hear the new 8 valve motors are worse, of course they do make more power. The FI on the Buell was also brilliant, fueling smoothly. And watching it correct for a change in exhaust or intake was always a treat. Why can't my Guzzi do that.
The Sportster motor and the 2 valve Guzzi motor are not that different. The new 8 valve motors and the new HD motors like the twin cam motors are pretty different and of course the V rod motor is its own.
I would own another Buell (but not a Harley), but I prefer Guzzi's. That does not mean that I do not wish Guzzi would climb closer to the top of the heap with regard to engineering. There was a time when they were up there, not so much anymore. Their bikes still have more style and character then anyone else's bikes. but sometimes it would be good to have the engineering to go with that.