What type of exhaust for power. (2019)

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Brooking 850 said:
I have a similar set up as storm 42 , JS 2 cam longer rods and lightweight pistons. The Vvs in a RH10 head are standard diameter with 32mm Premier carbs on standard manifolds
Swapping from two separate pipes into open peashooters, a copy of a Maney 2 into 1 gave me more mid range power and torque with very little drop at the top of the range. Ask Fast Eddie for noise levels as he has one my systems.
Regards Mike
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I have heard Nigel's bike run, it is louder than mine, but I must say that your exhaust has the looks over mine, very nice.
 
gortnipper said:
On my bike, Mike's exhaust isnt any louder than my Duc with a Termi exhaust. :D

The Emgo peashooters I had on previously were definitely quieter with the same motor:
FA head flow ported FA head with 1.5mm oversize intake valves
Maney forged 9.5:1 pistons
Webcam 312a
Amal Premiers​
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Ha, I think you would struggle to get either of your bikes through our track noise tests.
 
acotrel said:
Back in the early 1960s, most of the top A graders rode Manx Nortons - the quicker smother guys usually seemed to have bikes that were quieter. It might have been because their cam timings were not so radical and their bikes were more tractable.
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It had crossed my mind that two pipes designed for a Manx but made left and right might work.
 
Chris said:
Ralph
Have you got Steve's silencer kit?
I was too stressed with the standard set up when noise testing. Steve used to warm his bike up then be very steady on the throttle, always passed! I ran plus or minus everywhere I was tested. Basically replaced the end cone with a holder for supertrapp discs. I run them all. Felt safer at noise testing. Strangely when I had to change the engine back to the 750 it was far louder, raspier.
I have a NRP 2 into 1 for the 750 as until Brooking made his set up I couldn't find another Maney exhaust.
Chris
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Same exhaust as me then, I also made the supertrapp discs fit and I think I have 12 in place, but at the last race I had removed them for some reason and forgot about it until it was testing time, it passed but it could have been close if they had done it down near the tech bay.

Is the cam more advanced in your 750?
 
cash said:
Excessively loud exhaust can be caused by an over advanced ignition.
The standard balanced pipes can help reduce the noise but how they will effect power I haven't a clue.
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I run 26deg, shouldn't be that then.
 
Hi Ralph
Early Maney engine. Martin minnovation built it when he & Steve raced. Maney cam nearly 4s. just a harder exhaust note.
 
Ralph your issues going from closed to open throttle don’t sound pipe related to me mate. More likely carbs I’d have thought, second suspect would be ign.

If you’re running Amal’s I’d be saying it was the slide cutaway.
 
storm42 said:
No, but.

............

I might pop over to Nigel's and have a word.
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Do that, but I think you may have another problem that isn't exhaust related and you may need to work systematically through carb jetting from pilot up to 3/4. And check for free and smooth cables/twistgrip.

So, Snotzo told me his is busy moving house but told me I could post the graph you should see here. Emphasising that this is a simulation based comparison of exhaust dimensions provided to him of my NRP single pipes and a Maney 2 into 1. Nothing else is changed and the cam is a PW3 profile.

I think it sort of dispells some myths repeated above about 2 into 1s and indicates what a good job Maney did. As noted before the dimensions of the separate pipes are not wildly different from stuff Thruxton used, but includes input from Nigel, and megaphones almost don't exist today!

Do remember this is a 750, not a 920 which should pick up its power a bit more in the mid range. Your discomfort in the damp conditions is probably when all that extra mid range hits, adding more may not be your best approach o_O

My best result ever at CRMC was a 4th overall in 1300 open classics and post classics at Brands Hatch, I had started 12th and worked my way through....the bike proved fairly easy to ride smoothly in the worst of damp conditions, particularly compared to more powerful bikes, the simulated power delivery may indicate why!
 

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storm42 said:
It had crossed my mind that two pipes designed for a Manx but made left and right might work.
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You can get that silly idea out of your head right now, different valve and ignition timings and cylinder capacity......
 
Ralph
Stupid thought on my side.
On my bike, I ran it to acu regs, ie dead throttle. If you fall off engine stops. Well being a bit big & the Seeley being a bit small I find braking & hanging on while blipping the throttle difficult. To the point that sometimes the big engine cuts out at the end of the back straight at Donington. All the Commando racers I spoke to seem to have the throttle stops set to keep the motor ticking over well. A couple of the good ones had a tickover of 2,000 revs! Well bike doesnt stall anymore at the end of the back straight when hard on the brakes & banging down the gears but the big difference is how smooth it is in the wet when feathering the throttle. Carbs not right but ridability improved.
Nige
I run all of the plates Steve supplies, ie the loudest setting complete with open end cap. My reasoning was that I could then remove plates if I was too loud. At the meetings I have run in the past 5 years, my bike passes dead on 105 plus or minus. Cadwell is the only track I have been to where I got wildly different reading but then again so did everyone else.
One day lol. I will run the 750 with the minimum plates & the blank end cap but only because Steve told me you only lose a few horse power & I have a registration & can run it on the road!
Steve
You are right, all the old measurements given by the Norton Works measurements work but again as you say, it's about where you want the power to be & the rest of the package to make it work.
Al
Please read a set of Crmc regs for our bikes.

For Gods sake!!

Run some Wal Phillips injectors then slip in a fully programmable injection package! Do you then lie on the eligibility form where it says make & size of carbs!!
 
Chris
you should understand that in Australia there is something known as the 'Dreamtime'........ particularly relevant to the Benalla region it would appear
 
storm 42 Yes I have dyno results I will dig them out.
I posted on here some years ago a breakdown of it all. A lot of naysayers with dyno results though so expect some flack!!!
 
storm42 said:
Hi Mike. Do you have dyno charts?
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Hi ralph , the dyno charts from April 2018 are on this forum somewhere along with the video of the wheelie off the start line , Jim schmidt posted them; Jim was concerned as to the length of the inlet tracts, so I shortened them, It never felt as good after that . The NRP pipes were part of the package of mods I made that year which produced a 10 bhp gain , of course Nigel took credit for all of the 10!!!
 
Moto55UK said:
Hi ralph , the dyno charts from April 2018 are on this forum somewhere along with the video of the wheelie off the start line , Jim schmidt posted them; Jim was concerned as to the length of the inlet tracts, so I shortened them, It never felt as good after that . The NRP pipes were part of the package of mods I made that year which produced a 10 bhp gain , of course Nigel took credit for all of the 10!!!
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Various 'observers' have told me my inlets are too long.....not going to change them.

10bhp at the rear wheel is a huge gain, would you credit the exhaust with 50%?
 
SteveA said:
Various 'observers' have told me my inlets are too long.....not going to change them.

10bhp at the rear wheel is a huge gain, would you credit the exhaust with 50%?
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The upgrades included a crank mounted ignition, new R&D valve springs , 37 from 35 carbs with extra long inlet tracts, JS2 smooth ramp cam & radiused std followers, took 0.040" of the head ( I had been using JS 0.003" copper rings previously but found they were destroyed when the head came off so i shaved the head and went back to the 0.040" copper gasket)( the heads not been off for two seasons now and recently we dynoed it again and it had only lost 1 bhp ) and of course fitted the NRP exhaust system which I had no input , I left the Bike with Nigel and he did his magic. Off to the dyno and when it went over 80bhp i nearly wet myself!!!!
I also spent a lot of time setting the pushrod length to 90 deg to the valve at 65% full lift as per steve Maneys suggestion. What % is due to what I dont know ,im just very pleased .
 
Separate pipes with megaphones is the extreme situation. If your bike has a pronounced power band and gives a kick when it comes on song, with separate pipes with megaphones that will be even more pronounced. If you use separate pipes with mufflers, the effect is slightly lessened. But overall the power you get when the motor is on song, should be better than you get with a 2 into 1 pipe. The downside is the bike becomes more difficult to ride very well. If you were doing a land speed record, the megaphone exhausts might be better. But on a race circuit, a lot depends on getting the power down smoothly. For racing separate pipes with mufflers should be OK. But that is not the choice I would make. My 850 with the 2 into 1, has good power from whoa to go. I expected it to run out of power at high revs, but it goes straight through the top - very difficult to avoid over-revving. Every time I have raised the overall gearing, it has gone faster.
 
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