Intake Length?

[jwinwi]

Howdy All,

Doesn't a longer intake tract (in theory at least) improve LOW rpm throttle response? Bought the velocity stacks for VHBs and installed on the V7S with new individual K&N filters.
Didn't notice any improvement above 4500 rpm. Maybe a little improvement from 3000 to 4000?

Seems that performance above 4500 was better before these with K&Ns attached to carb bodies... Anyone had a similar experience?

[Murray]

Without retuning the motor to match the changes you are unlikely to get a significant change. The other issue is it's most likely measured in single digit percentages. On something making 190hp thats significant, on something making 50-60 at best at the flywheel, no so much.

[jwinwi]

Without retuning the motor to match the changes you are unlikely to get a significant change. The other issue is it's most likely measured in single digit percentages. On something making 190hp thats significant, on something making 50-60 at best at the flywheel, no so much.

OK, but adding length to the intake tract is supposed to help at lower RPMs, not higher, right?

[Chuck in Indiana]

OK, but adding length to the intake tract is supposed to help at lower RPMs, not higher, right?

Yes. Remember the Mopar cross ram with 2 four barrels on opposite sides of the engine compartment? Airplanes use extremely long intake manifolding for low rpm torque to drive a prop.
For what you are talking about, I doubt if it makes much difference.

[Wayne Orwig]

It is also true that a LARGE air box improves overall performance. Individual filters usually remove the advantage of a large air box, so you lose power. Unless you use filters that are only straining out the large chunks, and not very effective.

[Two Checks]

Quote from: Chuck in Indiana on Today at 10:18:18 AM

Yes. Remember the Mopar cross ram with 2 four barrels on opposite sides of the engine compartment? Airplanes use extremely long intake manifolding for low rpm torque to drive a prop.
For what you are talking about, I doubt if it makes much difference.

They had long tube and short tube versions on the Sonoramic Commandos.

[John A]

remember that the distance from the end of the stack to the closed end of the filter needs to be 2.5 times the diameter or it will hurt performance in the upper ranges.

[jwinwi]

remember that the distance from the end of the stack to the closed end of the filter needs to be 2.5 times the diameter or it will hurt performance in the upper ranges.

 Thank you John! The end of the stack must be awfully close to the closed end of the filter currently...

[Charles in Lake Charles]

Just cut them. That's what I did on the 850T and the Mighty Vert.

[jwinwi]

remember that the distance from the end of the stack to the closed end of the filter needs to be 2.5 times the diameter or it will hurt performance in the upper ranges.

There's only about 26 mm from the end of the stack to the closed end of the filter and the ID at the end of the stack is 36 mm, tapering down to 30 at the carb body.

Admittedly we're talking about small differences in performance but it just didn't seem to pull as hard above 5000.

[guzzisteve]

Just cut them. That's what I did on the 850T and the Mighty Vert.

That what I've been doing since they were made. All you need is smooth entry.

[Huzo]

All you need is smooth entry.

Sounds like good advice !!!

[Rough Edge racing]

 My 650 Triumph land speed racer has spent  hours on the chassis dyno looking for any power gains...Now an old Triumph isn't a Guzzi, but they are both engines more similar than different.....The intake,exhaust and cam timing all work together as one...If you change intake length ,to get the most benifit you will also have to play with the exhaust and possibly cam timing. On occasion, a change in intake length will make a noticeable chance because the other factors were already there....