[philgoodscrambler]

Had my FTP for nearly two years now (from new) and done about 11,000 miles.

Termignoni racing exhaust fitted pre-collection and always ran without baffle, except for California Superbike School at Brands one year ago and recently IAM Skills Day at Thruxton.

Left baffle in after Thruxton. To me the bike goes better all round and uses less fuel doing it. Recorded 127mph and not hitting the limiter. Why is this so?

PS Doesn't sound quite so good but willing to give this up for improved performance.

 

[AdminBot47]

Perhaps baffles are helping with exhaust scavenging.

 

[Gort]

Baffles increase backpressure or reversion, as some people call it. Having a too-free flowing exhaust will rob you of some midrange. “Drag-pipes”, popular on H-D’s back in the day, were great on top end but horrible on midrange as there was no backpressure. Here’s a dyno chart of a 100 hp bike with straight pipes and with our baffles. Big difference in midrange. Your exhaust is obviously tuned to work best with the baffles.

 

[philgoodscrambler]

S

Perhaps baffles are helping with exhaust scavenging.

Scavenging?

 

[Max Kool]

It's not just "backpressure". An exhaust can be seen as tuned system, like a saxophone. Change the metrics (dimensions, lengths) and it will flow different amounts of gas at different rpms and throttle openings. The first thing you should do before you draw to conclusions is optimize the fueling after making changes to the exhaust.

A freeer flowing exhaust that could give better performance given optimized fueling, may perform worse than a stock exhaust with the oem map.

 

[philgoodscrambler]

The termignoni came with its re-mapper.
So the bike was re-mapped for the baffles in and I've been running it with them out?
Has any damage been done?

 

[Max Kool]

I don't think any damage has been done. If it runs fine and gives good economy, right?

That upmap would still be a compromise between with, and without baffles. Maybe it just hits the sweet spot better with baffle in.

(ps, your dash says "RACE" when you switch on the ignition?)

 

[philgoodscrambler]

I don't think any damage has been done. If it runs fine and gives good economy, right?

That upmap would still be a compromise between with, and without baffles. Maybe it just hits the sweet spot better with baffle in.

(ps, your dash says "RACE" when you switch on the ignition?)

Yeess (if you ask me on a Monday). :cat-21:

 

[Gort]

It's not just "backpressure". An exhaust can be seen as tuned system, like a saxophone. Change the metrics (dimensions, lengths) and it will flow different amounts of gas at different rpms and throttle openings. The first thing you should do before you draw to conclusions is optimize the fueling after making changes to the exhaust.

A freeer flowing exhaust that could give better performance given optimized fueling, may perform worse than a stock exhaust with the oem map.

Never said it was just backpressure, but all engines need some restriction somewhere in the system, else why would a two-stroke expansion chamber be designed the way they are. Read the “two stroke tuners handbook”, it gives a good read on tuning and restrictions. If you don’t have a properly constructed exhaust system, no amount of fueling adjustment will provide an optimized system.

 

[Max Kool]

Ja Ja Ja I understand (this a four stroke btw, with very little valve overlap)

 

[AdminBot47]

S

Scavenging?

The "sucking/pulling" that a pulse of exhaust does to the pulse of exhaust behind it by means of the vacuum state between the two pulses

"Exhaust scavenging makes an exhaust system more efficient because as your exhaust gases pulse out of the engine (from each exhaust stroke of the engine), you have a high pressure area leading the exhaust pulse, followed by a low pressure area (with a transition). This low pressure area helps to pull the next exhaust pulse out, meaning the piston has less work to do when it’s forcing out the exhaust gases. Ultimately the goal is to have the fastest exhaust velocity with the least amount of restriction (which of course isn’t as simple as writing that sentence)."

Engineering Explained: Exhaust Systems And How To Increase Performance

 

[firstducati]

Had my FTP for nearly two years now (from new) and done about 11,000 miles.

Termignoni racing exhaust fitted pre-collection and always ran without baffle, except for California Superbike School at Brands one year ago and recently IAM Skills Day at Thruxton.

Left baffle in after Thruxton. To me the bike goes better all round and uses less fuel doing it. Recorded 127mph and not hitting the limiter. Why is this so?

PS Doesn't sound quite so good but willing to give this up for improved performance.

Fifty-six years of street riding and dirt racing tells me, "back pressure is your friend." Every time you go for louder pipes it hurts your low and mid range power, with marginal gains on top end.

 

[Hui]

Never said it was just backpressure, but all engines need some restriction somewhere in the system, else why would a two-stroke expansion chamber be designed the way they are. Read the “two stroke tuners handbook”, it gives a good read on tuning and restrictions. If you don’t have a properly constructed exhaust system, no amount of fueling adjustment will provide an optimized system.

Ah, now you just showed your limit.
The two stroke expansion chamber sends a pulse backwards to stop the charge fuel falling out into the exhaust before the port closes. And no, engines do not need a restriction somewhere. A crossover pipe can help with mid-range scavenging in a four stroke and the closer to the exhaust port the better. Where some modifiers fall down is making the 1st section diameter too big which slows the exit rate down. Fast is good and hot is fast, hence the header wrap in racing. The trick is to go big without causing ‘any’ restriction but small enough to keep the max gas exit speed rate.

 

[mrjoepete]

On a different note, if you don’t like the whistle noise that you get with the baffle in, you can cut that bar inside of it and that will make it sound so much better. I did that with mine and it totally got rid of that whistle noise and it’s perfect!

 

[gcarper]

I have 30K miles on my Icon that I purchased in June of 2017, Fuel mileage has remained the same with stock exhaust, Delkivic and Danmoto, Your top speed? is that what the speedometer showed? or GPS? Speedometer is way off on mine. 60 mph is 55 on GPS, 90 mph is 82 on GPS.

 

[AdminBot47]

I have 30K miles on my Icon that I purchased in June of 2017, Fuel mileage has remained the same with stock exhaust, Delkivic and Danmoto, Your top speed? is that what the speedometer showed? or GPS? Speedometer is way off on mine. 60 mph is 55 on GPS, 90 mph is 82 on GPS.

I was going to make a post about this today. I didn't get up to 90 (or 82), but 60 on the speedo similarly showed 55 on the GPS.

 

[Gort]

Ah, now you just showed your limit.
The two stroke expansion chamber sends a pulse backwards to stop the charge fuel falling out into the exhaust before the port closes. And no, engines do not need a restriction somewhere. A crossover pipe can help with mid-range scavenging in a four stroke and the closer to the exhaust port the better. Where some modifiers fall down is making the 1st section diameter too big which slows the exit rate down. Fast is good and hot is fast, hence the header wrap in racing. The trick is to go big without causing ‘any’ restriction but small enough to keep the max gas exit speed rate.

I agree with you on principle regarding two strokes, and have built several systems following Jennings formulas with good results, but what is at the end of an expansion chamber? Oh yes, a restriction as the pipe becomes smaller than the head pipe. Regarding four stroke exhaust systems, you are mistaken, otherwise, why are there not crossover pipes on every header? No one does this. Also, how do you explain our dyno chart if a restriction (baffle as an example), is bad. It sure provides a boost in midrange. Oh, and what is at the end of every four stroke can out there? A baffle. Guess all those engineers don’t know what you know, huh?

 

[Max Kool]

Regarding four stroke exhaust systems, I think you are mistaken, otherwise, why are there not crossover pipes on every header? No one does this.

BMW S1000 exhaust headers.... crossovers (most likely to add midrange, and close at high revs..) Nuff said.

long story short, there's more to exhaust design than you may think.

 

[Gort]

BMW S1000 exhaust headers.... crossovers (most likely to add midrange, and close at high revs..) Nuff said.

View attachment 40791 View attachment 40793


long story short, there's more to exhaust design than you may think.

Right, one bike out of how many hundreds? Try harder, bro. Restrictions at the end of an exhaust work.

 

[Max Kool]

Crossover tubes have been on motorcycles for decades. Some had them, some didn't. But you can believe whatever you want.


(just don't spread it as facts please, "bro")