Donate!
Welcome, Guest. Please Login or Register :: View Members
Pages: 1
Send Topic Print
info video about exhausts (Read 83 times)
IslandRoad
Serious Thumper
*****
Offline

It doesn't vibrate,
it purrs!

Posts: 1059
The Kiewa Valley, Australia
Gender: male
info video about exhausts
12/30/19 at 18:40:28
 
I came across this video about some of the complexities of exhaust systems on bikes. It's very simple and concise and it probably won't be very informative to the old-timers here. But Newbies (like me) might find it useful. It discusses back pressure, noise, performance etc. The example is for a modern sports bike, but the basic concepts are still applicable.

https://www.youtube.com/watch?v=3QCIIDSYJLc

A couple of points caught my attention:

1. The exhaust in the demo has a back-pressure valve. I assume we get our back pressure from the muffler itself. So no baffle = no back pressure?

2. the example here is for bikes with EFI but the basic concept of tuning for the exhaust still applies.
Back to top
 
 

S40, 2015, Dyna, Raptor, 52.5/152.5, spacer mod, sea level, cat-eye LED tail light, bullet style halogen turn signals, 31" drag bars with custom risers, modified stock seat, Metzeler tyres.
  IP Logged
batman
Serious Thumper
*****
Offline

SuzukiSavage.com
Rocks!

Posts: 3652
osceola new york
Gender: male
Re: info video about exhausts
Reply #1 - 12/30/19 at 20:49:26
 
In most cases the Savage exhaust can't be tuned , due to the fact that the stock cam and cams reground from them( web standard - and stage 3) have no overlap . Back pressure is something we're stuck with, but it can be reduced ( a Dyna muffler etc.)  A reduction in back pressure is a two way street . There are rpm ranges where the tuning could harm power production.  A straight pipe will have little or no back pressure, it would probably give the highest hp but only at very high speeds (wide open throttle ) the rest of the time the torque curve would be very peaky, and you would find that you needed to shift more often to keep the bike at high rpms in each gear to make power. A Dyna or other muffler ,would lower back pressure slightly and it's weight being about half that of the stock muffler would add power ,but keep the torque curve flatter  ,letting the motor run smoother,and build more speed in each gear before needing to shift .  You can have loud,  or power,  but not both, unless you feel you can ride at WOT all the time. That's why we favor the Dyna for a stock bike ,it adds a bit of power ,but still allows the bike to be drivable ,and your neighbors will still talk to you. Wink
Back to top
 
 

my old work mates called me MacGyver
  IP Logged
IslandRoad
Serious Thumper
*****
Offline

It doesn't vibrate,
it purrs!

Posts: 1059
The Kiewa Valley, Australia
Gender: male
Re: info video about exhausts
Reply #2 - 12/30/19 at 23:57:55
 
Aaaaaand, it looks great on the Savage 😎
Back to top
 
 

S40, 2015, Dyna, Raptor, 52.5/152.5, spacer mod, sea level, cat-eye LED tail light, bullet style halogen turn signals, 31" drag bars with custom risers, modified stock seat, Metzeler tyres.
  IP Logged
IslandRoad
Serious Thumper
*****
Offline

It doesn't vibrate,
it purrs!

Posts: 1059
The Kiewa Valley, Australia
Gender: male
Re: info video about exhausts
Reply #3 - 12/31/19 at 00:03:41
 
Batman, I have a question for you. I'm going to install a high-compression piston. I believe I read, here somewhere, it could add up to 10% more horsepower.

Looking beyond that, what would you suggest would be the next mod, if any, to make the most of the bike?

I like the set up generally as it is - the torque, gearing etc. I would just like to make the most of what it can do without going so far as to re-bore.

I'm already running a Dyna with stock intake setup.

Cam? Carb? Any other suggestions?
Back to top
 
 

S40, 2015, Dyna, Raptor, 52.5/152.5, spacer mod, sea level, cat-eye LED tail light, bullet style halogen turn signals, 31" drag bars with custom risers, modified stock seat, Metzeler tyres.
  IP Logged
batman
Serious Thumper
*****
Offline

SuzukiSavage.com
Rocks!

Posts: 3652
osceola new york
Gender: male
Re: info video about exhausts
Reply #4 - 01/13/20 at 20:40:35
 
The higher compress piston is the biggest boost in power ,it's the cake, consider a higher performance cam as the icing . You'll have to determine how much performance you want and balance that against reliability /cost.
  The 94mm piston from Lancer shouldn't require boring of the cylinder, ( you should use a ridge reamer -the piston sets higher in the bore, and you should hone the cylinder wall) a mild cam could be a Webcam standard, I think Armen uses that one ,and I would too. '
     the Savage rocker arm ratios are intake-1.3   exhaust-1.352   stock  cam lobes .254/.244  =    .330 /.330  -.005 valve clearance  .325/325
     WEBCAM lobes .256/.256 = .333/.346 - .005 -.328/.341
It gives higher lift mostly to the exhaust valve  keeping it farther out of the exhaust path and the cam has slightly longer duration, just what the doctor ordered.  It should allow you to use the Dyna muffler and the CV carb , you could always go to a 36mm VM later if you choose to. Tuning your intake is also a way of boosting hp and torque.

10% more hp is a bit high, it's more like 5.5% if you raise compression from 8.5 to 9.5  that maybe all you'll get from the savage but that isn't counting  the cam.     If you tried to get to 10.5 compression you'd get only 7.7% more hp   (It's like getting 15 people in a VW bug the next 2 gets much harder Grin)
Back to top
 
 

my old work mates called me MacGyver
  IP Logged
IslandRoad
Serious Thumper
*****
Offline

It doesn't vibrate,
it purrs!

Posts: 1059
The Kiewa Valley, Australia
Gender: male
Re: info video about exhausts
Reply #5 - 01/14/20 at 19:16:03
 
Hey Batman, thanks for taking the time to reply so comprehensively.

From what you've mentioned here, any small increase in HP beyond that achieved by the high-comp piston is going to come at a cost in reliability etc. I like the VW analogy!

I'm doing the piston partly for the experience (It's a fun project for a newbie) and partly for the real world gain of a little more power.

I think embarking on an upgraded cam would bring me into territory that I'm not particularly keen to enter. I came to a similar conclusion while researching the VM carb on here. I would LOVE the throttle response of a 'direct cable slide' but it seems the VM carb also adds the need for quite a bit of 'fiddling' that I think outweighs the gain.

Beyond the piston, I think I'll stick with playing with the asthetics and ergonomics to appease my tinkering bug!

... although ... there was that terrific post that Gary from NJ wrote about upgrading the suspension!!  Cool
Back to top
 
 

S40, 2015, Dyna, Raptor, 52.5/152.5, spacer mod, sea level, cat-eye LED tail light, bullet style halogen turn signals, 31" drag bars with custom risers, modified stock seat, Metzeler tyres.
  IP Logged
batman
Serious Thumper
*****
Offline

SuzukiSavage.com
Rocks!

Posts: 3652
osceola new york
Gender: male
Re: info video about exhausts
Reply #6 - 01/15/20 at 08:05:36
 
the piston is a good move ,the higher compression will show gains in hp/torque throughout your entire rpm range < but you have to remove the top end to replace the piston, so adding the cam makes sense, and neither of these upgrades will affect your reliability.. webcam designed the cam for use in the savage ,the dr650 cam is cheaper , but I feel it doesn't address the  poor performance of our exhaust channel as well.The DR has equally as good intake and exhaust channels in the head allowing similar balanced cam lobe lifts , the Savage has a bad exhaust channel ,the web cam deals with this by keeping the intake lobe only slightly higher (to make up for the room the valve stem takes up at the port ) and greatly increases the lift and a bit more duration(2 degrees) to allow more time to remove spent gases .
Back to top
 
« Last Edit: 01/16/20 at 12:58:47 by batman »  

my old work mates called me MacGyver
  IP Logged
Pages: 1
Send Topic Print


« Home

 
« Home
SuzukiSavage.com
02/20/20 at 07:55:47



General CategoryThe Cafe › info video about exhausts


SuzukiSavage.com » Powered by YaBB 2.2!
YaBB © 2000-2007. All Rights Reserved.