Old 23rd February 2019, 10:27 PM #1
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Engine braking.

I've had an il4 600 for a few years and have gotten used to the zero engine braking on the down shift.

It'll lock the rear when I get the speed/timing wrong rather than slow the bike it seemed. Got used to it.

Riding a litre V twin now and was expecting the engine braking to be much better but though better it wasn't what I expected.

I had the chance on a tdm 900 over last summer and it had decent engine braking. Was advised to drop a gear going into a corner to avoid loading the front with the brakes as it suited the bike. Seemed to work fine.

The new bike has a euro 4 exhaust and I got around to drilling out the baffles today.

Holy shit now it'll nearly put me over the bars the engine braking is that strong. Not through the whole rev range though. Higher revs it's less noticeable.

So to make a short story long.

Why is that? How can removing a couple of inches long pipes at the end of the exhaust make a dramatic change?

(I am liking the change. Noise and braking. Just curious)
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Old 23rd February 2019, 11:20 PM #2
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Re: Engine braking.

placebo?
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Old 23rd February 2019, 11:27 PM #3
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Re: Engine braking.

The exhaust has been the main area for motorbikes that has kept them within emissions limits,so a lot of the characteristics of the engines have changed to suit the need for the catalisers to burn off unwanted emissions ....v twins and single cylinders are more prone to lose their natural ability to engine brake from the changes,put a full akra on any ktm and you instantly have a different animal,same with the likes of Ducati’s and so on
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Old 23rd February 2019, 11:43 PM #4
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Re: Engine braking.

You Can't ride for shite go away
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Old 24th February 2019, 12:08 AM #5
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Re: Engine braking.

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Originally Posted by jic44 View Post
placebo?
Deffo no.
Been on the bike daily.

Took it for a dart to enjoy the noise and it was clearly different.
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Old 24th February 2019, 12:09 AM #6
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Re: Engine braking.

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Originally Posted by dec c View Post
You Can't ride for shite go away
Not what yer má says
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Old 24th February 2019, 12:12 AM #7
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Re: Engine braking.

No idea why the change to the exhaust would have done that.
Is engine braking a good thing? If so, then why is a slipper clutch a good thing as it lessens engine braking???
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Old 24th February 2019, 12:15 AM #8
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Re: Engine braking.

Quote:
Originally Posted by DavyH View Post
The exhaust has been the main area for motorbikes that has kept them within emissions limits,so a lot of the characteristics of the engines have changed to suit the need for the catalisers to burn off unwanted emissions ....v twins and single cylinders are more prone to lose their natural ability to engine brake from the changes,put a full akra on any ktm and you instantly have a different animal,same with the likes of Ducati’s and so on
I knew about the emissions but didn't consider it would change the character of the bike as much.
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Old 24th February 2019, 12:17 AM #9
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Re: Engine braking.

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Originally Posted by CodeJACK View Post
No idea why the change to the exhaust would have done that.
Is engine braking a good thing? If so, then why is a slipper clutch a good thing as it lessens engine braking???
Stops the back wheel locking up i believe.
What it does to engine braking.....?
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Old 24th February 2019, 12:19 PM #10
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Re: Engine braking.

Given that locking up the rear is not a good thing, unless you're showing off, then a slipper clutch removes the necessity of having to blip the throttle to match revs and wheel revolutions as you come down.
The slipper is favoured by less able riders like myself who never mastered the blipping/ braking combination otherwise required.
And racers obviously
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Old 24th February 2019, 01:20 PM #11
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Re: Engine braking.

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Originally Posted by the dessert fox View Post
Given that locking up the rear is not a good thing, unless you're showing off, then a slipper clutch removes the necessity of having to blip the throttle to match revs and wheel revolutions as you come down.
The slipper is favoured by less able riders like myself who never mastered the blipping/ braking combination otherwise required.
And racers obviously
Locking up the rear has its advantages,can work nicely if you think you’re goin a bit wide! And most of all it looks fucking awesome
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Old 24th February 2019, 03:17 PM #12
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Quote:
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Locking up the rear has its advantages,can work nicely if you think you’re goin a bit wide! And most of all it looks fucking awesome
Not so cool when the rear wheel then tries to overtake the front one.
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Old 24th February 2019, 04:21 PM #13
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Re: Engine braking.

You can alter engine braking with fueling.

Eg the s1000rr slick mode half's the engine braking.

They add a little fuel off the throttle which eases the braking.


Other thing is a long stroke vtwins will have more engine braking than say a Ducati short stroke twin
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Old 24th February 2019, 04:33 PM #14
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Re: Engine braking.

Quote:
Originally Posted by me2 View Post
Not so cool when the rear wheel then tries to overtake the front one.
Need to know when to let off the brake pedal and feed in a bit of clutch to stop that going too far.....then it still looks cool 😎
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Old 24th February 2019, 05:49 PM #15
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Quote:
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Need to know when to let off the brake pedal and feed in a bit of clutch to stop that going too far.....then it still looks cool 😎
Seems to be a slight misunderstanding between us. My looking a bit like a whirling dervish might look cool but it certainly doesn't feel cool. In all honesty, I've only ever gotten it right by accident.
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Old 24th February 2019, 06:11 PM #16
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Re: Engine braking.

Quote:
Originally Posted by me2 View Post
Seems to be a slight misunderstanding between us. My looking a bit like a whirling dervish might look cool but it certainly doesn't feel cool. In all honesty, I've only ever gotten it right by accident.


Ah I see said the blind man...
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Old 24th February 2019, 07:03 PM #17
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Re: Engine braking.

Quote:
Originally Posted by corkgsxr View Post
You can alter engine braking with fueling.

Eg the s1000rr slick mode half's the engine braking.

They add a little fuel off the throttle which eases the braking.


Other thing is a long stroke vtwins will have more engine braking than say a Ducati short stroke twin
Before I got a slipper it took two trouser changes to do a lap of Mondello on my 916
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Old 24th February 2019, 07:03 PM #18
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Re: Engine braking.

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Before I got a slipper it took two johnnie changes to do a lap of Mondello on my 916
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Old 24th February 2019, 08:26 PM #19
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Re: Engine braking.

Quote:
Originally Posted by Chickenhawk View Post
The new bike has a euro 4 exhaust and I got around to drilling out the baffles today.

Holy shit now it'll nearly put me over the bars the engine braking is that strong. Not through the whole rev range though. Higher revs it's less noticeable.

So to make a short story long.

Why is that? How can removing a couple of inches long pipes at the end of the exhaust make a dramatic change?

(I am liking the change. Noise and braking. Just curious)
Most likely explanation. You've changed the scavenging effect.
My simplified understanding of it is when your cylinder 1 is exhausting it pushes out a pressure wave of gas that flows down the exhaust. When it reaches the header junction where the pipe from cyl 2 meets the cyl 1 pipe, it continues flowing out the back but it also sucks some of the air out of the other pipe. (This also happens at other points in the exhaust system due to other effects, e.g exup valves, crossover pipes, baffles, etc. It's hideously complicated science)
Some clever fella over in Japan spent thousands of hours figuring out how long it takes that "suction" to go back up the pipe to cyl 2 and then tuned the length of the pipe so that at a certain rpm that "suction" reaches the exhaust valve just as it is opening and helps evacuate the cylinder. This means that the engine doesn't have to waste as much power pushing the exhaust gases out.
I assume what you've done is a) removed a restriction from the exhaust so it takes less power overall to push the gas out and b) moved the net scavenging rpm higher up in the rev range so it takes more power to push the exhaust gases out at lower rpm. Hence more engine braking.
Thats my 2c anyway.

TLDR: It's fooking magic
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Old 25th February 2019, 11:53 AM #20
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Re: Engine braking.

are you sure your breaks arent dragging / sticking
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Old 25th February 2019, 06:45 PM #21
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Re: Engine braking.

Brakes are good. No binding.

The improved engine braking is welcome.
It was just something I wasn't expecting from what I was doing.

I'm gonna go with the magic explanation. I was probably asking a question above my level of understanding.

And every time I lock the back wheel it's never I purpose.
But I always cack myself when I do.
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