Shortened silencer

britincali · Post by **britincali** » March 3rd, 2008, 3:10 pm

A few weeks ago I got bored and decided to chop down the silencer on the GSS bike. I got roughly 2.5-3" off the end and re-riveted it back together, it definatly sounds better and should help over-rev a little

pimp559 · Post by **pimp559** » March 3rd, 2008, 3:47 pm

I was thinking of doing the same thing to gain a little more bottom end. Do you notice anymore bottom end?

britincali · Post by **britincali** » March 3rd, 2008, 4:10 pm

pimp559 wrote:I was thinking of doing the same thing to gain a little more bottom end. Do you notice anymore bottom end?

In theory it will loose bottom and gain top end.

I havent run it yet.

iggys-amsoil · Post by **iggys-amsoil** » March 3rd, 2008, 6:07 pm

Ah..... I don't think the feds are going to like that.

Take the sticker off so its not so obvious.

britincali · Post by **britincali** » March 3rd, 2008, 11:16 pm

iggys-amsoil wrote: Take the sticker off so its not so obvious.

Too much hassle

CR480R · Post by **CR480R** » March 4th, 2008, 1:01 am

britincali wrote: In theory it will loose bottom and gain top end. I havent run it yet.

Are you sure about that? I always thought shorties were for bottom end gains at the expense of over-rev...

Post by **AlisoBob** » March 4th, 2008, 6:29 am

The length has less to do with it, the diameter much more.

Many " Factory" shorties have larger I.D.'s. than the oem silencer their replacing.

Brits "Barstow" shortie does not.

Slow old Fart · Post by **Slow old Fart** » March 4th, 2008, 6:39 am

I always found when I cut the stinger it moved the power foward.

pstoffers · Post by **pstoffers** » March 4th, 2008, 6:52 am

The shorter the stinger is the more bottom you will have.
The longer the stinger is the more topin you will have..............

redrocket190 · Post by **redrocket190** » March 4th, 2008, 7:01 am

I always thought that shorter fatter pipes favored top-end, and longer slimmer pipes favored not so much bottom-end as a broader power band. I have a PDF of the Two-Stroke Tuners' Handbook if anyone wants it....

dannygraves · Post by **dannygraves** » March 4th, 2008, 8:11 am

I think you guys have been hanging out with brit too long

shorter=topend longer=low end torque
longer creates more back pressure which would create more bottomend. why do you think FMF and PC sell shorty silencers with rev pipes and long silencers (like the 500 ones) with torque pipes like the gnarly. if shortys made more down low, FMF and PC would sell shortys for the 500, not these huge-ass foot+ long ones.
DeWayne told me to cut back my silencer 4" when I get my rev pipe from him. He also told me to pack it with something denser, can't remember what he said right now though.

britincali · Post by **britincali** » March 4th, 2008, 8:11 am

I dint really do it for performance I did it 'cos I was bored

As an added bonus it definatly sounds meaner

britincali · Post by **britincali** » March 4th, 2008, 8:13 am

dannygraves wrote:cut back my silencer 4" .

You aint gonna get 4" off unless you relocate and make a bracket for the rear mount.

britincali · Post by **britincali** » March 4th, 2008, 8:13 am

dannygraves wrote: shorter=topend longer=low end torque
longer creates more back pressure which would create more bottomend. .

Thats what I was always told.

dannygraves · Post by **dannygraves** » March 4th, 2008, 8:14 am

britincali wrote:
dannygraves wrote:cut back my silencer 4" .

You aint gonna get 4" off unless you relocate and make a bracket for the rear mount.

yup

pstoffers · Post by **pstoffers** » March 4th, 2008, 12:13 pm

Okaaaaaaaa...

Kids these days...

shortys are for supercross period........

Slow old Fart · Post by **Slow old Fart** » March 4th, 2008, 3:59 pm

It will make the powerband start a few hundred RPM earlier and sign off a few 100 RPMm earlier.

britincali · Post by **britincali** » March 4th, 2008, 4:11 pm

Did some searching and came across this on wiki...

The length of the pipe determines at what time the waves arrive back at the cylinder. Longer pipes require more time for the waves to traverse and so will be tuned to a lower rpm than a shorter pipe. The shorter the pipe the higher the rpm it is tuned to.

redrocket190 · Post by **redrocket190** » March 4th, 2008, 4:19 pm

Slow old Fart · Post by **Slow old Fart** » March 4th, 2008, 4:43 pm

britincali wrote:Did some searching and came across this on wiki...

The length of the pipe determines at what time the waves arrive back at the cylinder. Longer pipes require more time for the waves to traverse and so will be tuned to a lower rpm than a shorter pipe. The shorter the pipe the higher the rpm it is tuned to.

Go research the stinger. That is one of the reasons a newer CR 500 revs out further than a older model because Honda specially made that super long silencer to do that, besides quiet that was the main reason. Longer stinger means more topend. They are talking about the back of the pipe and how it deflects the wave back not the stinger it is seperate

Slow old Fart · Post by **Slow old Fart** » March 4th, 2008, 4:47 pm

pstoffers wrote:Okaaaaaaaa... Kids these days...

shortys are for supercross period........

Rigft because it starts the powerband going a touch earlier and they need that instant power for drive to the next double or triple right as they come out of a corner.

britincali · Post by **britincali** » March 4th, 2008, 4:51 pm

Then why do all drag bikes have tiny or non-existent silencers?

And why on my AF (when the silencer fall of) did the bottom end all but dissapear but it would scream its ass off on top end?

redrocket190 · Post by **redrocket190** » March 4th, 2008, 4:53 pm

The end of the stinger produces a wave form that combines with the the waves returned by the different parts of the diffuser. The timing and strength of that wave is a function of the stinger diameter and its length. I have a Pro-Form "torque" pipe on my Elsinore and the pipe is longer than stock, and then the silencer is longer still. More mid-range, less top.

britincali · Post by **britincali** » March 4th, 2008, 5:00 pm

I just got of the phone with glen from GSS he told me the main job of the silencer is just that, to quieten things down.

As far as length it does pretty much squat, the stinger section of the expansion chamber is the biggest contributing factor.

ou812 · Post by **ou812** » March 4th, 2008, 6:00 pm

Then why do all drag bikes have tiny or non-existent silencers?

Because they were designed with no silencing in mind. Dirt bike pipes were designed to take into account a silencer.

BannedCR500Riders.com

Shortened silencer

Shortened silencer