MASS moto exhaust custom made,thoughts?

[Anders]

18 hours ago, MartyNZ said:

It looks like a great system, I'm looking forward to pictures of it installed. 

A comment on pipe size: as exhaust gasses travel out, three changes happen.

1.The pulses smooth out slightly as they expand into a larger volume.

2. The gasses cool down due to both expansion and heat loss radiating out of the system.

3. In a constant diameter pipe, the gas flow speed slows due to effects 1 & 2.

This explains why motorcycles with two headers leading into one muffler (eg Griso) do not suffer any power loss caused by exhaust system restriction.

Bigger pipes are less restrictive to gas flow, however, with all other things being equal, gas flow in a big pipe is slower than in a small pipe, so the negative pressure pulses, or extractor effect, can be reduced.

Your aim of 42mm dia pipe all through could be a great idea, or it may just add weight. It will be great to hear how it works out. 

We will see how it works out. I have no technical education,I have mostly read what others have done with the same engine,

like this page for instance:

http://www.bikeboy.org/sport1100_update.html

 

The different thickness of the pipes did some difference,like when the silencers fit the size of the rest of the exhaust.Or thinner headers for instance.

I have seen and read about some 2 into 1 systems that are supposed to be great,but I decided to try this for now.

I will for sure post pictures when it's on the bike.Thanks for the info MartyNZ.

 

[GuzziMoto]

A few thoughts about this.

First, many people think that a larger pipe will keep exhaust velocity up, but that is not how it works. If you were to compare two systems, one with a larger pipe diameter than the other but both close to the right size, the larger diameter pipe system would have lower exhaust gas velocity than the smaller pipe diameter system. There is a max size for exhaust pipe given your displacement and power levels. Anything above that slows exhaust gases down. Really trick systems will use a smaller diameter pipe right out the exhaust port and step up to larger diameter pipe 6 or 8 inches down the pipe. They are counting on the fact that the fuel / air mixture is still burning as the exhaust exits and as such it is still expanding. Because of that, the pipe diameter required for best exhaust flow is less right away by the exhaust port and increases further down the pipe as the air / fuel mixture finishes burning. But any sudden increase in pipe diameter / size will result in a slow down of the exhaust gases. Sadly, the stock exhaust crossover is just such a change in diameter / cross section. But the stock system is built to be cheap to manufacturer while working well enough. After market systems should be able to work better. But how much better can vary.

Next, exhaust gases do no flow out the exhaust in a steady flow, they are pulses. Between the pulses there are waves of negative pressure that flow back up the pipe. Since the Guzzi V twin doesn't fire the two cylinders at the same time the pulses of exhaust from each cylinder are never trying to flow out the pipe at the same time. If the system works well, the negative pressure waves flowing back up the pipe from one cylinder will help the other cylinders positive pressure exhaust pulse exit quicker, which then can cause a stronger negative pressure wave to arrive at the exhaust port of that cylinder. The interaction between positive exhaust pulses and the negative pressure wave happens both between the two cylinders at the crossover and at the exhaust valve. But because a 90 degree V twin doesn't have an even firing interval between the two cylinders the affects of exhaust negative pressure waves are more likely to be back at the exhaust valve from that same cylinders exhaust pulse. But there are systems with complex crossovers, like the Ducati "spaghetti" system that have two separate crossovers to address the differences in timing between the two cylinders.

All I can really say is back in the day I wanted a two into two system for our Ducati 750 twin racebikes (two separate exhaust pipes, basically). I did not think that a two into one system, or a two into one into two system, would work best on a 90 degree V twin. But we ended up having a system built by a guy who built exhaust art. And he didn't build what you told him, he built what he knew would work. We ended up with a two into one system. It maybe did not make the most peak power, that probably would have been from a two into two system, but it made more power under the curve and as such was ultimately faster than other bikes that claimed to make more peak power.

Another really cool exhaust technology is merge collectors. If you want to learn more, google that. Merge collectors put a lot of effort into merging the different exhaust pipes into a single pipe while controlling and maintaining the size / cross section the whole way. They don't really have a lot of benefit for a 90 degree V twin like a Guzzi, but they are exhaust art.

[Anders]

Thank you for alot of information GuzziMoto.I'm learning alot from this.Wow you have done racing too? It must have been tons of fun!

About the inlet of the headers,I noticed that the headers I got with this system has an entrance of 38mm,only for about 1" into the pipe though,like most headers I've seen for Guzzis.I guess that serves a purpos maybe a little bit then?

Other than I suppose that part needs to be really strong.(the pipe walls is twice or more thicker too).

With this order I was kind of hoping for what happened to you with the exhaust for your Ducati 750.Mainly telling them what I wanted it to do,and to use an exhaust I know work well as a reference.I guess they built what they think will do best (the x pipe),but still they did it with an ID of 42mm,probarbly mainly because I specifically asked for that.I wonder what they would have built if I only told them I want something that is great between 2500-6000rpm.Probarbly a better exhaust.

I will read about Merge collectors too,thanks.

 

 

[GuzziMoto]

14 minutes ago, Anders said:

Thank you for alot of information GuzziMoto.I'm learning alot from this.Wow you have done racing too? It must have been tons of fun!

About the inlet of the headers,I noticed that the headers I got with this system has an entrance of 38mm,only for about 1" into the pipe though,like most headers I've seen for Guzzis.I guess that serves a purpos maybe a little bit then?

Other than I suppose that part needs to be really strong.(the pipe walls is twice or more thicker too).

With this order I was kind of hoping for what happened to you with the exhaust for your Ducati 750.Mainly telling them what I wanted it to do,and to use an exhaust I know work well as a reference.I guess they built what they think will do best (the x pipe),but still they did it with an ID of 42mm,probarbly mainly because I specifically asked for that.I wonder what they would have built if I only told them I want something that is great between 2500-6000rpm.Probarbly a better exhaust.

I will read about Merge collectors too,thanks.

 

 

Racing was tons of fun, that was when we were kings.....

While some exhaust systems are made more for looks and more to a price, in general I have learned that when you have people that know what they are doing you should let them do what they know works. I don't try to tell them how to do something I came to them to do.

I do want to build an exhaust pipe for my Aprilia 550, I think that would be a fun experience. I would love to make a double exhaust pipe for it, two separate pipes one for each cylinder, with some sort of megaphones on the end leading into the mufflers. I always liked the look of the old XR750 Harley flat track bikes exhaust systems. But it would be hard to beat the look of the underseat exhaust it has stock.

[po18guy]

I think we should wait until the MASS Moto system is installed and tuned for. It might be far better than expected. I measured the outside diameter of the V11s OEM head pipes @ 1.77 inches. That is rather large, given the cylinder's displacement and PRM range - but they must know what they were doing? That is big block Chevy size.

[Anders]

 

1 hour ago, GuzziMoto said:

Racing was tons of fun, that was when we were kings.....

While some exhaust systems are made more for looks and more to a price, in general I have learned that when you have people that know what they are doing you should let them do what they know works. I don't try to tell them how to do something I came to them to do.

I do want to build an exhaust pipe for my Aprilia 550, I think that would be a fun experience. I would love to make a double exhaust pipe for it, two separate pipes one for each cylinder, with some sort of megaphones on the end leading into the mufflers. I always liked the look of the old XR750 Harley flat track bikes exhaust systems. But it would be hard to beat the look of the underseat exhaust it has stock.

I know,I generally let people who know what they are doing just get on with their work.It was more a precaution because I didn't know that much about their work other than a system with conical headers on the website (It's gone now)for the v11.A good example of why that is a good idea,I think, is why the music industry was so much better in the 70's compared to now.Some guy believed in a band or a singer and just let them create.

I'm looking forward to reading about your exhaust for the Aprilia.

[Anders]

13 minutes ago, po18guy said:

I think we should wait until the MASS Moto system is installed and tuned for. It might be far better than expected. I measured the outside diameter of the V11s OEM head pipes @ 1.77 inches. That is rather large, given the cylinder's displacement and PRM range - but they must know what they were doing? That is big block Chevy size.

Yes I agree.I haven't put it on and tried it yet.I don't think they would sell something that they didn't approve.I'm sure it will work, maybe they would have made suggestions what would work and what wouldn't.But they told me I should get good results.

Yes,1.77 inches is about 45mm,and maybe (41,7mm ID)that's about 1.64 inches.If it's optimal or not I don't know,but probarbly close to I guess as the 1100sport headers are about the same size.

[Tomchri]

Curoius,,   has it been an inspection inside the crossover - xover ,, whats happening there  

Cheers tom.

[Tomchri]

Pressure thing,,  just rememberd, before any electronic world, putting a new dual exhaust on the 440, and put a stripe of white paint  on the fresh pipes after the Hooker headers,, go for a sporty trip,, most burnt spot got a crossover.  I'm sure it was fun  

Cheers tom.

[po18guy]

5 hours ago, Anders said:

About the inlet of the headers,I noticed that the headers I got with this system has an entrance of 38mm,only for about 1" into the pipe though,like most headers I've seen for Guzzis.I guess that serves a purpos maybe a little bit then?

The smaller diameter inner pipe at the cylinder head may be for strength, as that is the focal point of vibration and mounting stress. As well, smaller pipes leading to larger pipes provide a sort of "expansion chamber", which technically can help in scavenging the exhaust. IIRC, the expanding gas as it enters the larger pipe, produces a bit of a lower pressure behind it, which helps draw the rest of the exhaust out of the cylinder. 

[Anders]

11 hours ago, Tomchri said:

Curoius,,   has it been an inspection inside the crossover - xover ,, whats happening there  

Cheers tom.

I'm sure there should be some youtube clip somewhere of someone testing and explaining that.Maybe not for a Guzzi engine though,but maybe some similar where you can see roughly what is happening when used.

[Anders]

10 hours ago, po18guy said:

The smaller diameter inner pipe at the cylinder head may be for strength, as that is the focal point of vibration and mounting stress. As well, smaller pipes leading to larger pipes provide a sort of "expansion chamber", which technically can help in scavenging the exhaust. IIRC, the expanding gas as it enters the larger pipe, produces a bit of a lower pressure behind it, which helps draw the rest of the exhaust out of the cylinder. 

OK thanks.

[Tomchri]

10 hours ago, Anders said:

I'm sure there should be some youtube clip somewhere of someone testing and explaining that.Maybe not for a Guzzi engine though,but maybe some similar where you can see roughly what is happening when used.

Sorry, still curious ,bad innlish, meant looking inside with some fancy equipment, or feeling with a steel wire or something for the opening's in the crossover- xover ?

 Cheers tom.

 

 

 

 

[GuzziMoto]

On 6/29/2020 at 6:51 PM, Tomchri said:

Curoius,,   has it been an inspection inside the crossover - xover ,, whats happening there  

Cheers tom.

I am pretty sure there is nothing inside you can't guess by looking at the outside. I would bet if you rolled a golf ball down the pipe (or whatever size ball would fit) it would roll right through the crossover. If you held the crossover at the right angle it would go straight through. But if you held it at a different angle you could probably get the ball to fall out the other pipe. There is surely no baffling or anything else in that crossover. It is basically two pipes weld together so that they cross in an X pattern.

The stock crossover is welded up of stamped steel and has a baffle of sorts in it. But this one looks to be made better and likely flows better.

[Tomchri]

Yes, that would be a safe bet with the golf ball there. Just another old habbit of mine, wondering or checking    ,, what does it look like inside     

And, it will be nice to see it on the bike,  hear it to.

Cheers tom.