Under engine Balance pipe

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Pure co-incidence but I just spent a few days computer simulation a new exhaust system for a new parallel twin 360 engine. Balance pipe modelled 850 mm (33 inches) from the head filled in some nasty holes in the lower rpm torque curve.

Using this software

http://www.vannik.co.za/EngMod4T.htm
 
About as long as there's been engines with dual exhausts ist been known that cross over tube between the long runs always softens/deepens the tone and helps low-mid range power as has two pipes and openings to exit. If possible the x-tube attachments is done at the hottest spots along the exhaust sides usually found by a crayon streak when holding rpms one most interested in. This is not the same thing as tuned length mergers to get one pluse pullling the next out but can be if space allows. Informative to see dyno data of its worth.
 
I just - yesterday - did a 200 mile ride on my 850 with an oem balanced pipe replacing the straight (750 type) pipes for the first time. The bike felt more responsive in every way AND, most interestingly, was able to hit 100MPH in a stretch where it has never been able to do it before. No other changes were made - just the pipes. I was quite impressed with the difference. All I can say is that if you have only ridden your 850 with the typical 750 pipes that we typically use, you will definitely notice an improvement if you fit the balanced pipes.
 
There has been talk here recently of dyno testing a Commando with a balanced exhaust system and an unbalanced system (no connecting pipe),
to compare the torque figures. Unfortunately, it doesn't seem to have happened.

Its near unbelievable that the factory never released similar dyno charts,
given all the talk of the balanced pipes producing more torque low down, etc...
 
Paul Dunstall's book on Norton tuning stated that a balanced pipe system added 4-5 HP per a dyno as I recall. I don't have the book here so I can 't verify that. In any case, his book is what made me determined to find/try a balanced pipe system on my bike. He showed a pic of what he recommended and it looked essentially identical to what Norton implemented a year or two later.

I'd prefer installing a 2-1-2 pipe but since it goes below the engine/frame, it would last here in Mexico for about 5 minutes before being crushed by a speed bump.
 
The under engine cross exhaust of the Laverda 750 SFC seemed to work very well. It wasn't just a simple connecting pipe. I don't believe a 90 degree bend works well. A two into one under engine pipe with the correct collector works vey well if you adjust the cam timing to suit.
 
That was more just a case of suitable pipes lengths ??

mike996 said:
Paul Dunstall's book on Norton tuning stated that a balanced pipe system added 4-5 HP per a dyno as I recall. I don't have the book here so I can 't verify that.
Click to expand...

He may have said that, but the dyno charts to back it up weren't published either ??

His 2-1-2 system, with the double Y-branch under the engines and the hugely long DECIBEL silencers splayed out the back
were developed by Dr Blair of QUB (Queens University Belfast) - and the dyno charts were shown.
They weren't exactly quiet though.
As you say, that pipe underneath was low - and the stock centrestand no longer worked.
Thats a bit of fail, when you tot it all up ?
Did make a unique bike of the Dunstall though, when you add up all the goodies that could be added.
 
years ago i had a dunstall 2 1 2 fitted on my m2a it made no difference that i could detect over the stock system when it rusted through i went to separate down pipes and pea shooters ,more recently on my 750 i changed the down pipes from balanced to unbalanced this did make a difference to the noise level it is a fair bit higher without the balance pipe as confirmed by my girlfriend following on her bike !! but no difference to power that i can notice,i too would like to see a commando on a dyno with no other changes made apart from the balance pipe and also another one with the balance pipe at 28" along the downpipes ,,,,,,,,,,,,,baz
 
The Norton is not the only bike where you can detect no difference with/without the balance pipe.
A few years ago I had two Honda CX650s at the same time, one with the bottom "exhaust collector box" the other without, no difference was detected when I rode them back to back, but somewhere in the midrange power the was probably a difference of a couple of BHP, that would only show up on a Dyno.
 
I'm hoping to get a day on the Dyno within the next few weeks, just got to wait for my velocity stacks to arrive for the FCRs.

If anyone in the UK has a set of balanced pipes... Or a set of 1.5" down pipes lying around, and is interested enough in this topic to lend them to me, I'd be delighted to try them out on the Dyno, and then return them.

My own hypothesis is that they'll make little difference. As Bernhard said, a couple of BHP here or there is almost impossible to detect on the road.

But I would be delighted to be proved wrong and discover that they add 10 BHP !!
 
10 gee gees is highly unlikely, Dunstall only claimed 4-5 bhp in the mid-range on the Atlas/ Commando.
 
Fast Eddie said:
I'm hoping to get a day on the Dyno within the next few weeks, just got to wait for my velocity stacks to arrive for the FCRs.

If anyone in the UK has a set of balanced pipes... Or a set of 1.5" down pipes lying around, and is interested enough in this topic to lend them to me, I'd be delighted to try them out on the Dyno, and then return them.

My own hypothesis is that they'll make little difference. As Bernhard said, a couple of BHP here or there is almost impossible to detect on the road.

But I would be delighted to be proved wrong and discover that they add 10 BHP !!
Click to expand...

Nigel,
I have a set of original balance pipes along with spherical seatings , short exhaust nuts etc that you are welcome to try if you can't get them any closer to you. If you want to borrow em , give me a bell Sunday or Monday after 7pm and we can sort it out. I wouldn't be able to post them off before next w/end.
sam
 
trident sam said:
Fast Eddie said:
I'm hoping to get a day on the Dyno within the next few weeks, just got to wait for my velocity stacks to arrive for the FCRs.

If anyone in the UK has a set of balanced pipes... Or a set of 1.5" down pipes lying around, and is interested enough in this topic to lend them to me, I'd be delighted to try them out on the Dyno, and then return them.

My own hypothesis is that they'll make little difference. As Bernhard said, a couple of BHP here or there is almost impossible to detect on the road.

But I would be delighted to be proved wrong and discover that they add 10 BHP !!
Click to expand...

Nigel,
I have a set of original balance pipes along with spherical seatings , short exhaust nuts etc that you are welcome to try if you can't get them any closer to you. If you want to borrow em , give me a bell Sunday or Monday after 7pm and we can sort it out. I wouldn't be able to post them off before next w/end.
sam
Click to expand...

Top man Sam, will give you a bell. Thanks.
 
There is no doubt that a crossover can increase power on SOME engines/layouts; there are plenty of published dyno tests showing it. But engines are different. On my 850, IMO, there is a difference in the performance that I noted in the speed/distance which I felt was a bit more "evidence" than a "it feels faster/quicker" butt dyno report (which is wrong more often than right). OTOH, as I said, there was no real science - perhaps the carb jetting benefitted slightly from the Bpipes and perhaps that same benefit could have occurred with careful jetting with the regular pipes. Or maybe I was seated fractionally different in some way that produced less wind resistance. IOW, maybe the speed/distance improvement was just luck and the better response occurred because I wanted to believe it! ;) I CAN say for certain that I liked the sound better! :)

In any case. I think it is possible that the balanced pipe on a Commando does increase power. OTOH, 4-5 HP seems a bit high on such a small engine.
 
just thinking outloud here, but a set of the kenny deer 880 under pipes would be a nice starting point if one could get them to feed an x-pipe and then exit just ahead of the normal muffler mounts. , in the end i think it would look a lot like jim comstocks exhaust....

once i get that far i may just tinker a bit,

alternatively use a flex pipe instead of the fixed balance pipe provided by the factory, and maybe it might not self destruct...
 
As mentioned so gleefully above there ain't much but head work than can please as much as getting the exhaust helping out. Peel did not have 8+lb centerstand but could of. Main issue crossing behind forks is bottoming out may ding a header an inch into mudgaurd as I found out so crossing above or below wheel fouling should be kept in mind. Any good exhaust it going to be loud in its power band but found a exit hole in baffle plate a bit bigger 20%? than header collector ID give soft pats down low and non barking aubable pur at curise but roars getting into power band WOT which its response just invites ya too often for any tire economy. Hi Side pipes look-work great on flat trackers but a bit nucance in real life. If not raw off roading these works fine but need modifying route, smaller fender or just leave the factory bashed one on.

Under engine Balance pipe


Under engine Balance pipe
 
I don't believe it is possible for the pipe in the photo to work effectively with any commando camshaft. The dimension after the join is too small. It might make for a bit more safety for the engine by preventing over-revving. It might be better to make a set of pipes that fit right in close under the lower frame tubes and make a Laverda type cross under the gearbox.

' 1972 first 2-2 system with manifold cross under the engine or 2-1 megaphone system.'

http://www.motorsportscenter.com/printer_751.shtml
 
Oh yes I'm payting attention to you 2-1 insight Al. Peels was mainly done out of boredom and wt. loss on her long 1st time re-buld and sure didn't do much but bog down till I happened to get the exit size pretty right as was still so depressed by the prior lack luster performance I thought it was my derpression that prevented me for seriously gripping bars and planting in seat going out my drive way when I gave WOT snap to freaking end up on tail light pissed at my in atttention so settled my nerves locked on and snapped again to only end up on rear of seat pad, WTF!! So did it a 3rd time with more throttle control and the biggest shit eating grin cracked across me face permenently. Use all the clac's you like to get to known zone then tiral error from there. Btw each peashooter side weighs almost 10 lb. counting fittings and muffler mounts. 3lb in the header.
 
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