2010 12GS/GSA - is there more engine braking?

[JohnnyBoxer]

For those who have ridden it, most have commented on the stronger mid range, courtesy of the exhaust valve, but is there any more engine braking when you throttle off??

 

[Spout]

but is there any more engine braking when you throttle off??

You've misspelt "breaking"

 

[Deleted Member I]

You've misspelt "breaking"

 

[Deleted Member I]

For those who have ridden it, most have commented on the stronger mid range, courtesy of the exhaust valve, but is there any more engine braking when you throttle off??

Don't do it Johnny .. it will just ruin your day

 

[SURMANATOR]

Don't do it Johnny .. it will just ruin your day

No Slightly higher revs though 3,500 @60mph on the 210 3,400 on the 08 The lower final drive ratio would account for that plus some of the added acceleration

 

[2 wheel humvee]

For those who have ridden it, most have commented on the stronger mid range, courtesy of the exhaust valve, but is there any more engine braking when you throttle off??

Do you really think the valve in the exhaust silencer is responsible for the additional power and torque-rather than the raised compression and more efficient valve train with higher rev limit
As I read it, the valve in the exhaust silencer is a "by pass" to allow more noise at larger throttle openings and nothing more,or am I misinformed

Cannot comment on the engine braking or engine breaking

 

[karlp]

Do you really think the valve in the exhaust silencer is responsible for the additional power and torque-rather than the raised compression and more efficient valve train with higher rev limit
As I read it, the valve in the exhaust silencer is a "by pass" to allow more noise at larger throttle openings and nothing more,or am I misinformed

Cannot comment on the engine braking or engine breaking

yes

The flow in an exhaust system is pulsed and every time a pulse of exhaust gas runs through the pipe it causes area of vacuum behind it.

How big this vacuum is depends on the gas velocity. The higher the velocity, the bigger the vacuum the pulse has behind it.

This pulse can be used to scavenge the engine and the maximum scavenging effect is achieved if the gas velocity is high. By maximizing the scavenging effect it helps to pull pulses out of the combustion chamber, i.e extract the exhaust gas

This has the most effect when there's lots of time between the pulses...i.e., at low rpm. As the revs rise, the pulsed flow becomes more and more like constant flow, and consequently the scavenging effect is reduced.

So, at low rpm you need a small pipe to maximize scavenging, and at high rpm you need a big pipe to minimize pressure drop. The exhaust pipe can only be one size, so it's a compromise. Therefore for a given engine, one pipe diameter will be the most effecient at a certain rpm.

Torque is related to gas velocity and ideally you need exhaust components that are not restricive.

This can be achieved by using a flap to effectively make the exhaust pipe diameter smaller at low rpm (i.e. increase the gas velocity )and then open the flap for higher rpm where you need to reduce resistance to the gas flow.

 

[London Mole]

yes

The flow in an exhaust system is pulsed and every time a pulse of exhaust gas runs through the pipe it causes area of vacuum behind it.

How big this vacuum is depends on the gas velocity. The higher the velocity, the bigger the vacuum the pulse has behind it.

This pulse can be used to scavenge the engine and the maximum scavenging effect is achieved if the gas velocity is high. By maximizing the scavenging effect it helps to pull pulses out of the combustion chamber, i.e extract the exhaust gas

This has the most effect when there's lots of time between the pulses...i.e., at low rpm. As the revs rise, the pulsed flow becomes more and more like constant flow, and consequently the scavenging effect is reduced.

So, at low rpm you need a small pipe to maximize scavenging, and at high rpm you need a big pipe to minimize pressure drop. The exhaust pipe can only be one size, so it's a compromise. Therefore for a given engine, one pipe diameter will be the most effecient at a certain rpm.

Torque is related to gas velocity and ideally you need exhaust components that are not restricive.

This can be achieved by using a flap to effectively make the exhaust pipe diameter smaller at low rpm (i.e. increase the gas velocity )and then open the flap for higher rpm where you need to reduce resistance to the gas flow.

So does it mean having an after-market Y-piece without a "balancing pipe" is having an effect on the torque?

 

[karlp]

So does it mean having an after-market Y-piece without a "balancing pipe" is having an effect on the torque?

I am not an expert on exhaust design just know a little about the theory.

balance pipe usually reduces noise as it evens out the pulses and broadens the torque curve

Most aftermarket headers do not have the cat - hence the greater flow but it is possible to get catalytic convertors that have a high flow rate

 

[Deleted member TF]

Never really noticed to be honest,too busy thrashing the tits off it.

 

[Deleted account 190920001]

yes

The flow in an exhaust system is pulsed and every time a pulse of exhaust gas runs through the pipe it causes area of vacuum behind it.

How big this vacuum is depends on the gas velocity. The higher the velocity, the bigger the vacuum the pulse has behind it.

This pulse can be used to scavenge the engine and the maximum scavenging effect is achieved if the gas velocity is high. By maximizing the scavenging effect it helps to pull pulses out of the combustion chamber, i.e extract the exhaust gas

This has the most effect when there's lots of time between the pulses...i.e., at low rpm. As the revs rise, the pulsed flow becomes more and more like constant flow, and consequently the scavenging effect is reduced.

So, at low rpm you need a small pipe to maximize scavenging, and at high rpm you need a big pipe to minimize pressure drop. The exhaust pipe can only be one size, so it's a compromise. Therefore for a given engine, one pipe diameter will be the most effecient at a certain rpm.

Torque is related to gas velocity and ideally you need exhaust components that are not restricive.

This can be achieved by using a flap to effectively make the exhaust pipe diameter smaller at low rpm (i.e. increase the gas velocity )and then open the flap for higher rpm where you need to reduce resistance to the gas flow.

Couldn't have said it better myself. Other benefits are because the valve partially closes of the exhaust it silences the bike more so you can run a less restrictive silencer and still pass the noise regs. Since the regs as metered at fairly low revs this works out nicely. This is also why there are reports of a more fruity exhaust note higher in the revs. In effect the silencer might well be the same spec as an Acro but in and around town because of the EXUP valve its still quiet.

 

[The Nutter]

Hi Johnny,

in an attempt to answer your question, I can't say that I noticed any more in the way of engine braking when I took out the GS and GSA on saturday. That could be down to the fact I was just excited by the new engine and ESA. Get a test ride and try it-just be prepared to love it.

 

[Owen Snell]

Good description Karl. Yamaha started the EXUP valve thing to improve torque at low revs by creating a low rev resonance with the valve closed but allowing high flow for top end power when the valve is open. It is no coincidence that Yamaha also make very good musical instruments, so tuning pipes comes naturally to them.

 

[JohnnyBoxer]

Thanks chaps..............

Guess I'll have to try one again and see................my last 12GSA was a bit lacking....................in the engine braking dept

 

[Wapping]

For those who have ridden it, most have commented on the stronger mid range, courtesy of the exhaust valve, but is there any more engine braking when you throttle off??

Yup, loads.