Help me -stock crossover modification

[Guest SteveT]

Anyone out there that can explain how the stock crossover works? I found one on E-bay for $13.00 so I thought I'd modify it for use on my 02 Lemans. When I cut it open you see a thin layer of steel wool type material, then a screen, then you come to the two post, another screen on the bottom with the packing behind it.

I expected to see some type of baffle in there but there is none! It appears it's straight flow through except for the two post. The screens and packing are on the top & bottom and I don't see how the exhaust would be forced to flow through this area. I thought I read that this would give the bike a little more sound (but I don't see how removing the screen. packing, or post could have much effect now that I can see the insides of this thing).

How's this thing work??? Could the screen and packing on the top & bottom of collector just be there to keep the heat down?

Any thought on this are appreciated...I've attached a picture of the inside of the crossover.

Thanks,

Steve Thoerner

[docc]

The screens and packing will recuce noise like acoustic tile in a big room. The added surface area provides for this without much restriction in flow.

[Lex]

Docc answer is, at least as far as I know, correct but I would add that I would love to see a dyno run with a stock cross-over and one with the "stuff" removed. You would need to reprogram the ECU or add a well set-up PCIII for the results to mean much. It would be very interesting to see how opening up the "boom box" to allow each cylinder easy access to both mufflers would change the power output.

 

More on top? More down low? No change? Who knows? If it works well keeping the stock look, saving the cost of an after market X-over would be an interesting option. Who knows, old stock X-overs might be valuable some day.

 

Cheers,

 

Lex

[Guest Bob in CT]

I removed the mesh, top & bottom and the two post. Welded a top back on. Seat of the pants feels better and a litle more throatier. I already had a PC, but didn't change anything. That mesh causes drag by deflecting the exhaust, the same as a muffler.

 

Bob

 

Tenni

Sport1100

G5

[Guest SteveT]

I went ahead and gutted the inside of the box and welded a new stainless plate back in on the top and bottom of the collector.

To see what kind of sound difference I'd get I made some measurements with a sound meter. All measurements were with the bikes at 1500RPM standing about 5 feet behind the bike or 5 feet to the side of the motor.

Stock Guzzi V11 Lemans: 97dB from the rear 92dB from the side

with modified crossover 99dB at the rear 96dB from the side

both measured before the bike warmed up. After a ride with the modified crossover hot I measured 95dB from the rear and 92 from the side...these bikes must quiet down as the motor gets hotter.

 

To give a refrence point I measured my BMW R1150RT: 89dB from the rear and 89dB on the side (way quiet). My brothers H-D Road King loud aftermarket pipes but some baffling 111dB from the rear 107dB from the side at 1500RPM's. When he cranked to 2000RPM's it hit about 120dB. I advised him to get some earplugs!!!

Really no difference in the performance so all in all I'm not sure this modification is worth the effort...I'll probably put my stock crossover back on.

I wanted to get a little more sound from the bike but not give myself headaches on long rides. This modification isn't noticable without the sound measuring instrument. If anyone has some spare Lemans pipes they want to let me have for a reasonable price I'll do the mods and post the measurements on them.

 

Glad I only invested a few bucks on the used crossover....

Steve Thoerner