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Discussion Starter #1 (Edited)
The thread "Exhaust options. F3-B3-Rivale-Turismo Veloce" got me thinking about the difference in exhaust header designs. Years of racing have taught me that things like header length, collector style and volume all play their part. But it's still somewhat of a black art to me. A quick search revealed some different approaches to the problem of gaining horse power and torque for triples.

This is the MV Agusta's 675 race unit.



Notice the outside cylinders Siamese together whereby the middle runs separate. It does however increase in size but there are no balance tubes as such.

This is Termignoni's effort.



Very traditional design with three pipes of near equal length, (middle pipe appears to be slightly longer). Balance tubes are placed adjacent to each other at about 1/3 distance between the outlet port and the collector.

At first glimpse HP Corse's header looks to be a copy of the Termi.



However, looking closer they are quite different. Bends are greater, balance tubes are closer to the outlet port and there is a lack of formal collector.

For comparison here is the stock Triumph 675 beside it's Arrow replacement.



First thing you notice is how much the Arrow unit matches it's stock counterpart. The second being the balance tubes on such an angle.

As I do not build performance exhaust systems for a living anything I say would be pure speculation. However, we do have some experienced types on here. I'm sure we'd all be keen to hear from those who have used different makes as to what their feelings were. What are the possible reason to chose one design over another? Anyone?
 

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Discussion Starter #4


I’ve been researching lots and so far all I’ve managed to do is prove the old adage; “the more I learn the less I know”.
Although this article I've linked is more about auto headers it is probably one of the best / briefest summaries I’ve read so far. It is a little dry but if you read it all the way through while referencing the different photos from my first post you’ll start to understand which change does what.

The Sound and The Fury
 

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pipes?

Stephen;
pipes are simple.....its acoustics, Henry Ricardo got Knighted for figuring it out in 1928
Bill "Grumpy" Jenkins figured out reversion
Daniel Bernoulli figured out flow in 1738

here is the Pipe Formula Program I wrote for an HP 42S calculator ~30 years ago;
http://www.apriliaforum.com/forums/showthread.php?112862-the-exhaust-pipe-formula&highlight=pipe formula

only bikes have crossover pipes:jerkoff::jerkoff:

if you can't make them exactly the same length.....learn to knit

I like "merge" collectors.....they take a little off the top but they widen the torque peak

the posted pictures......

the MV race pipe is a disaster....the pulses are all fucked up by the different lengths and the collector is too small and maybe too short

Termignoni angled crossovers whats with that?
don't like the collector again too small and maybe too short

HP Corse hands down best pipe here.....ditch the crossovers though again collector too small and maybe too short


the collector must be the same length as the head pipe from the exhaust valve to the collector......

its acoustics :drummer:

Stephen in post#4 is that a triple? the outside pipe must go to the top of the collector.....or they have to make a corkscrew out of the middle pipe to eat up the length
 

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I read that whole article and it left me amazed at what people do for a living. Motorcycle headers seem to have the additional challenge of putting it all together in a package that fits in the space inside the fairings.
 

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I read that whole article and it left me amazed at what people do for a living. Motorcycle headers seem to have the additional challenge of putting it all together in a package that fits in the space inside the fairings.
And not just always the most power Chuck, but the most usable too.
 

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Stephen in post#4 is that a triple? the outside pipe must go to the top of the collector.....or they have to make a corkscrew out of the middle pipe to eat up the length
No, that's a YAMAHA M1 4 banger Noel.
 

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That would have to be true when designing for street use...or the track too, I suppose.
 

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No, that's a YAMAHA M1 4 banger Noel.
pipe is still wrong Donsy.....1&4 go to the top of the collector, 2&3 to the bottom......think about it......that is if you want equal length pipes

bet the head pipes are too long too, don't know EO degrees and the power peak, but JR's collector was about even with the crankcase split, NHRA National Champion....we went for peak power and a merge collector
 

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So, watching the BTSport coverage of Moto3 this weekend, and noticed Julian Ryder commenting on the beautiful 916-esque Honda exhausts, and that there are individual pipes for each valve in that single cylinder engine.

Any insight as to that advantage? Lower internal resistance? Any other machines set up like this?
 

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So, watching the BTSport coverage of Moto3 this weekend, and noticed Julian Ryder commenting on the beautiful 916-esque Honda exhausts, and that there are individual pipes for each valve in that single cylinder engine.

Any insight as to that advantage? Lower internal resistance? Any other machines set up like this?
Yes, you can tune a wider power band, at the expense of top end

old Honda XR-500 dirt bikes had different length head pipes, does the same thing
 

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A lot of engineering and R&D goes into exhaust design indeed. Each system is made to fit a specific purpose. Obviously, some better than others. That's why I shake my head sometimes the average guy attacks their street exhaust with a sawsall and a welder.

They finish their abortion and say, " look what I made, or it sounds better". And then never bother getting the bike tuned afterward to actually try and make the bike run well.

That kind of stuff is for choppers. Chopper guys care about how it looks or sounds than if there is a giant flat spot now in the RPM band or your low end torque disappeared.

Nothing wrong with that , I built a chop or two myself changing everything from carb to the end of the muffler. And spent a lot of time getting the tune in spec afterward.
 

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Hmmm, you mean like this:

A Monster S4Rs as new.
DSCN5183r.JPG

It's stock performance.
S4Rs Dyno Run Initial.jpg

After I got out the hack saw and did a Tail Chop and I shortened the exhaust by a solid 5 inches to match the "Chop".
DSCN0618r.jpg

The post chop tune.
S4Rs AFTER Tuning r.jpg

And now the poor thing looks like this:
DSC_2501r.jpg

Like you have said, if you are going to mess about with exhaust, intake or internals...you must tune afterward. Tuning before lets you know if you have gained anything by your efforts.
 

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Yup, it was pretty terrible...but on the agricultural Monster, it wasn't all that noticeable...oddly enough.
 

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Hey Knurl
If those things were corrected on the HP corse, would the gains be noticeable or only for the racers??

Tree MV
 
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