2 into 1 exhaust - Page 2

Bitza · 13-02-2024, 03:47 PM

Thanks for the feedback, all pretty interesting. Had a thought myself, one issue seems likely to be the size of silencer required to achieve comparable dB levels to a 2 - 2system. My thinking is that the gases have to pass through twice as fast i.e, giving half the time to do the silencing bit. If you need double the size of silencer then maybe the weight saving potential ain't so great. Another issue might be the restriction created, maybe larger internal dia? but then reducing the gas to baffle contact, meaning more length again?

Darren69 · 13-02-2024, 04:54 PM

[Kinda my thoughts too 1 big dustbin sized can vs 2 smaller ones weoght saving will be negligable unless they're standard oem cans which are very heavy, 2 small carbon race cans very light and easy to source.

900Rebuilder · 14-02-2024, 07:01 AM

Utopia it would be interesting to know what Silmotor system you have as my headers which have the cross over pipes are only around 45mm from memory but are very light compared to the stock pipes. I've got some unbranded 2/3 length oval carbon cans for my bike so the system is much lighter than original and potentially will be quite loud. My purchasing was led totally by the look I wanted to maintain with a secondary nod to sound and performance.

Darren69 · 14-02-2024, 07:35 AM

45 mm headers is ok 50mm over specced esp for a 750 but Ducati messed with 70mm headers on the 999/1098 to reduce noise I think, i can't think of any other reason for it.c

utopia · 14-02-2024, 02:07 PM

I bought my Sil-Moto system secondhand so I don't know exactly what it is.
I've only ever seen one other like it.
It came from America and had clearly been crashed as it was quite damaged when I got it.
It was cheap though and the basic design was almost exactly what I was after so I took a punt on being able to repair it.
It needed a section cutting out and replacing from the front header which was seriously scraped and half flattened.
I would have had to cut the front header to shorten it to fit the 750 anyway, so it wasn't so bad.
And yes, the headers are overkill (probably) at 50mm bore although I didn't realise this at time of purchase. And the whole thing is 1mm wall thickness (I think the std headers on my 750 were 1.5mm wall) and its extremely light..
The tube is actually the same size spec as the std hi-level link pipes from an S4R. I know this because the replacement section that I used was taken from a link pipe given to me by Capo which came from the original system on his bike.
I measured the length of the headers and was pleased to find that they are both the same length.

I don't do photos much but there's a pic on post #4 on this thread from the 2019 weekender.
http://ukmonster.co.uk/monster/showthread.php?t=57395

I didn't notice any particular gain or loss in performance after fitting the Sil system but I must admit that I did nothing to tweek the fuelling so I may not be getting the best from it.
In my defence this was because I had a pair of Kehin flatslides to go on and I was waiting until they were fitted before heading to a dyno.
Then covid and life got in the way and the Kehins are still waiting (yes I know ... shame on me).
But it does seem to run ok as it is.

Bitza · 14-02-2024, 07:25 PM

Just came across an interesting fact(?), crossover pipes on twin exhausts are apparently very effective in reducing db's.

Darren69 · 14-02-2024, 08:41 PM

My 50mm full Termi would disagree but there's nice loud and nasty loud. My neighbour came out one time, didn't complain about the noise, just said you're shaking my windows!

900Rebuilder · 15-02-2024, 06:57 AM

Quote:

Originally Posted by Darren69

My 50mm full Termi would disagree but there's nice loud and nasty loud. My neighbour came out one time, didn't complain about the noise, just said you're shaking my windows!

Neighbour poked his head over the fence when I first moved into my house and fired up my old 996 - cor that sounds bloody lovely was his response much to the chagrin of my ex who hated the open pipes

13-02-2024, 03:47 PM	#1
Bitza Bronze Member Join Date: Jul 2006 Location: Poole Bike: M900ie Posts: 470	Thanks for the feedback, all pretty interesting. Had a thought myself, one issue seems likely to be the size of silencer required to achieve comparable dB levels to a 2 - 2system. My thinking is that the gases have to pass through twice as fast i.e, giving half the time to do the silencing bit. If you need double the size of silencer then maybe the weight saving potential ain't so great. Another issue might be the restriction created, maybe larger internal dia? but then reducing the gas to baffle contact, meaning more length again? __________________ Bitza

13-02-2024, 04:54 PM	#2
Darren69 Transmaniacon MOC Join Date: Sep 2013 Location: Sutton In Ashfield Bike: Multiple Monsters Posts: 6,026	[Kinda my thoughts too 1 big dustbin sized can vs 2 smaller ones weoght saving will be negligable unless they're standard oem cans which are very heavy, 2 small carbon race cans very light and easy to source. __________________ Roast Beef Monster! Termignoni and Bucci - Italian for pipe and slippers! S4 Fogarty, S4R 07T, 748, Series 1 Mirage

14-02-2024, 07:01 AM	#3
900Rebuilder Registered User Join Date: Sep 2022 Location: Beeston Bike: M900 Posts: 299	Utopia it would be interesting to know what Silmotor system you have as my headers which have the cross over pipes are only around 45mm from memory but are very light compared to the stock pipes. I've got some unbranded 2/3 length oval carbon cans for my bike so the system is much lighter than original and potentially will be quite loud. My purchasing was led totally by the look I wanted to maintain with a secondary nod to sound and performance. __________________ Ducati Monster 900 - Yamaha tdr125 & dt200wr - Ford GPW

14-02-2024, 07:25 PM	#6
Bitza Bronze Member Join Date: Jul 2006 Location: Poole Bike: M900ie Posts: 470	Just came across an interesting fact(?), crossover pipes on twin exhausts are apparently very effective in reducing db's. __________________ Bitza

14-02-2024, 08:41 PM	#7
Darren69 Transmaniacon MOC Join Date: Sep 2013 Location: Sutton In Ashfield Bike: Multiple Monsters Posts: 6,026	My 50mm full Termi would disagree but there's nice loud and nasty loud. My neighbour came out one time, didn't complain about the noise, just said you're shaking my windows! __________________ Roast Beef Monster! Termignoni and Bucci - Italian for pipe and slippers! S4 Fogarty, S4R 07T, 748, Series 1 Mirage

14-02-2024, 07:35 AM	#4
Darren69 Transmaniacon MOC Join Date: Sep 2013 Location: Sutton In Ashfield Bike: Multiple Monsters Posts: 6,026	45 mm headers is ok 50mm over specced esp for a 750 but Ducati messed with 70mm headers on the 999/1098 to reduce noise I think, i can't think of any other reason for it.c __________________ Roast Beef Monster! Termignoni and Bucci - Italian for pipe and slippers! S4 Fogarty, S4R 07T, 748, Series 1 Mirage

14-02-2024, 02:07 PM	#5
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	I bought my Sil-Moto system secondhand so I don't know exactly what it is. I've only ever seen one other like it. It came from America and had clearly been crashed as it was quite damaged when I got it. It was cheap though and the basic design was almost exactly what I was after so I took a punt on being able to repair it. It needed a section cutting out and replacing from the front header which was seriously scraped and half flattened. I would have had to cut the front header to shorten it to fit the 750 anyway, so it wasn't so bad. And yes, the headers are overkill (probably) at 50mm bore although I didn't realise this at time of purchase. And the whole thing is 1mm wall thickness (I think the std headers on my 750 were 1.5mm wall) and its extremely light.. The tube is actually the same size spec as the std hi-level link pipes from an S4R. I know this because the replacement section that I used was taken from a link pipe given to me by Capo which came from the original system on his bike. I measured the length of the headers and was pleased to find that they are both the same length. I don't do photos much but there's a pic on post #4 on this thread from the 2019 weekender. http://ukmonster.co.uk/monster/showthread.php?t=57395 I didn't notice any particular gain or loss in performance after fitting the Sil system but I must admit that I did nothing to tweek the fuelling so I may not be getting the best from it. In my defence this was because I had a pair of Kehin flatslides to go on and I was waiting until they were fitted before heading to a dyno. Then covid and life got in the way and the Kehins are still waiting (yes I know ... shame on me). But it does seem to run ok as it is.