2 in 1 exhaust system (2010)

From Mike's graph , the drop-off in torque appears to be nice and slow as the revs rise, however how it actually translates in performance terms can only be determined by riding the bike. (How much drop at near peak revs is significant) ?

Rohan, tell me this - how do you know when your overall gearing is not high enough ?

When you are reaching redline, and the horizon is still some distance away ?

But is this a trick question. ??
Are we riding a racing motorcycle here, or a road bike.
On a short circuit, or the Isle of Man.
Don't think there is a one-size-answer-fits all- here, somehow....

Brooking 850 said:

I was running 2 x 1 3/8" ID headers into 'straight through' peashooters and now with a copy of the Maney set of 1 1/2" ID into 1 I have increased my power and torque without changing the cam or cam timing. With the new system I am making power all the way to the rev limiter which is built into my crank mounted ignition system. Just a slight jetting change, although that can change depending on which track I race at.
Regards Mike

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Hi Mike ,

That's a nice curve for a rideable Commando.

For other posters I would comment that the NZ tracks and races are usually short sprints 4 to 6 laps on smaller clubmans type circuits. Hampton Downs being the only circuit that approaches a longer variable international style circuit. Mike also said he is a good rider but maybe not one of the top guys (yet?). So based on my NZ experience he is really going to be best with a broad power band rideable machine which this dyno curve looks like.

My 500 ended up being a pretty highly strung machine with zero power below 4000 rpm. But the rider was very very good with a lot of experience. Most riders would have hated the bike.

Cheers John, like the bike, work in progress with my riding!!!!
See you in NZ when?
Regards Mike

See you in NZ when?
Regards Mike[/quote]

Home for three weeks at Christmas but then back to Romania. Maybe home for good in a year ??? The bike is stored away in Wellington.

acotrel said:

With Brooks bike, I would raise the gearing and try shifting near the revs where peak torque occurs and see if the acceleration is quicker - it can be very deceptive. It helps if you have a reference point such as another rider near you trying hard over many laps.

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I feel obligated to point out that decades of drag racing has proven that quickest straight line acceleration comes from shifting at red-line rpm, typically somewhere around max safe rpm and just past max power. Short shifting on a roadrace track can be useful, particularly if it lets you avoid changing gears at an awkward place in a corner, but it's not the quickest way to accelerate over any significant distance.

Ken

lcrken said:

acotrel said:

With Brooks bike, I would raise the gearing and try shifting near the revs where peak torque occurs and see if the acceleration is quicker - it can be very deceptive. It helps if you have a reference point such as another rider near you trying hard over many laps.

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I feel obligated to point out that decades of drag racing has proven that quickest straight line acceleration comes from shifting at red-line rpm, typically somewhere around max safe rpm and just past max power. Short shifting on a roadrace track can be useful, particularly if it lets you avoid changing gears at an awkward place in a corner, but it's not the quickest way to accelerate over any significant distance.

Ken

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There you go again Ken... bringing logic to the debate... :roll:

What we need are race tracks with no straights, then Norton Commandos would win every race for 500cc to 1000cc bikes ?

When you short shift when you have the right gearing for the circuit - usually the next gear is too high, and the motor goes off the boil. However I suggest that short shifting can tell you if you should raise the overall gearing. If you can short shift and still accelerate quickly, the overall gearing is probably too low. This doesn't depend on circuit length because it is all relative. On a very big circuit you usually run much higher gearing, however the problem of finding the optimum still remains. At present the only place I ride the Seeley is Winton Raceway (3Km in length) and I use very high overall gearing with a very close box. If I have to ride at Phillip Island (3 Miles in length) I think the bike will be useless. I don't know how I would get sprockets to get the gearing high enough.

Brooking 850 said:

Hi pommie John, here is an earlier graph with the 2 x single 1 3/8" upswept headers and open peashooters.
Regards Mike

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That's a great result from just changing exhausts. My own experience with 2 into 1 exhausts has been a big flat spot in the mid range. Obviously they were not very well designed. If I were still racing my Commando I'd definitely have to try a Maney exhaust ( despite my personal experience with him

Seeley920 said:

Steve Maney's system is really good on the track....maybe a little loud for the road depending on where you live , mine was tested at 108db. However like Ken said, it gives a lot more midrange and really good top end. I had a works spec 2-1for years, but had to put a straight can on the end to get around the noise testers, and it cost me a lot of power and screwed up the carburation. Putting Steve's pipe on transformed the motor.
He does also sell an "extra silencer" to add on to the endcan which would make the pipe acceptable for road use (noise wise!)

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seeley 920,send pm

we used the same works spec exhaust on our outfit and it really worked well , from around 3700rpm to 7000isch , without megafonitis and good torque from standstill
later we copied a maney one (from a friends race solo , yves van buylaere ,)and that was even better but we went up in cc,s as well so could not objectively say wich one works beter
the works 2 into 1 was imho neater and smaller , not so obvious and show-off for a raodbike , and on an outfit the smaller is the better

lab why can,t i edit older posts of me ??????????????

I only get to see the back of Mikes Commando at Hampton Downs.... :cry:
Off Topic...I've run two pipes and Commando pea shooters on the BMW and previous to that a horrible 2 into 1, The 2 into 2 seems to give a better spread of power.
I'm making a 2 into one with a merged header so interesting to see how that goes.
You going to Puke Mike?
Won my first race there....back in 2012
The mile long back straight suits the BMW.
Sorry OP

72Combat said:

I only get to see the back of Mikes Commando at Hampton Downs.... :cry:
Off Topic...I've run two pipes and Commando pea shooters on the BMW and previous to that a horrible 2 into 1, The 2 into 2 seems to give a better spread of power.
I'm making a 2 into one with a merged header so interesting to see how that goes.
You going to Puke Mike?
Won my first race there....back in 2012
The mile long back straight suits the BMW.
Sorry OP

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Hi 72Combat, did you end up making your 2 into 1? I have one on a MK3 that I'm trying to get back on the road after 30 odd years, and am interested to hear how they go. Mine is a Bub system from the states, came on the bike, can't find a lot of info about them, but it has a triumph TT style spread and tuck under sort of look to it. Quite a good looking single muffler out the right side. I'm sure it'll sound great, no idea if it will help with power at all. ANy pointers or if anyone knows of the Bub system i'd be keen for feedback/pointers. Has amild porting jpb done and runs a single vm34 mikuni.
Cheers

If the tail pipe on a 2 into 1 exhaust system is not as big as the sum of the two header pipes in cross-sectional area, you lose too much top end. Bur if it is big enough, the pipe often makes too much noise.

Bmunro said:

Hi 72Combat, did you end up making your 2 into 1? I have one on a MK3 that I'm trying to get back on the road after 30 odd years, and am interested to hear how they go. Mine is a Bub system from the states, came on the bike, can't find a lot of info about them, but it has a triumph TT style spread and tuck under sort of look to it. Quite a good looking single muffler out the right side. I'm sure it'll sound great, no idea if it will help with power at all. ANy pointers or if anyone knows of the Bub system i'd be keen for feedback/pointers. Has amild porting jpb done and runs a single vm34 mikuni.
Cheers

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Might find this thread on the BUB exhaust interesting


Ken

Bmunro said:

Hi 72Combat, did you end up making your 2 into 1? I have one on a MK3 that I'm trying to get back on the road after 30 odd years, and am interested to hear how they go. Mine is a Bub system from the states, came on the bike, can't find a lot of info about them, but it has a triumph TT style spread and tuck under sort of look to it. Quite a good looking single muffler out the right side. I'm sure it'll sound great, no idea if it will help with power at all. ANy pointers or if anyone knows of the Bub system i'd be keen for feedback/pointers. Has amild porting jpb done and runs a single vm34 mikuni.
Cheers

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Like I said in the other 2 into 1 BUB pipe thread where you asked the same question, the BUB pipe works with modification, but if in your shoes, I'd run with standard OEM style twin exhaust. You'll make better overall useable power with less noise and effort tuning wise using the twin exhaust. Plus you'll be able to access everything on the engine and use the center stand like you would a factory bike. The only thing negative about abandoning the BUB pipe is cost.

The BUB pipe as delivered from BUB won't be an improvement on power up top. For the most part just the opposite. You'll find out once you get it running.

For the record, my ole P11 is a Atlas turned Combat. It is Mikuni 34mm twin carbureted in custom length intake manifolds with a 2S cam and a FBS ported head. Point being I know how the BUB pipe works on a warmed up Combat motor. I don't know how the BUB pipe works on a Norton Combat motor with a 34mm single on it. I had a Commando with a single Amal on it for a while, and my P11 made the single carbureted, factory cam, stock head Commando feel like I was pulling a Zamboni down the street. (comedic exaggeration of course) Yours should be better than that, but I wouldn't expect a lot with that BUB pipe on there.