Dr. Blair on Dyno Hill- Place your bets!

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worntorn said:
It went slower than with the balance pipes. Four runs were made, all netted 108 kmh at top. I then tried jetting up and down, both slowed the bike even more, so the 260s were correct.

The balance pipes with the same silencers netted 110kmh. The balance pipe with cross pipe plugged netted 113 kmh, the very best result found.
The separate Interstate pipes with these open silencers fitted also netted 113.
It seems most folks already have the best combination for midrange power, separate 1&3/8" pipes with open peashooters.
I tried nine other combinations and they all came up short.
I did not have a Maney type exhaust to try, that would be interesting.
It appears there are lots of ways to slow things down with the exhaust configuration but getting more out of a stock bike with a stock pre black cap exhaust is tough to do.
The quiet silencers killed performance the most.

Glen
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So the SS pipes may look cool but the stock setup is still king? when you say cross pipe plugged , can we infer that to be the same as unblanced stock pipes?
 
Yes, the blocked balance pipes and the separate pipes both gave the best result, 113 kmh top of hill. Both with the same open peashooters fitted.
I tried the same with open short emgo silencers and the bike slowed a bit, even though the emgos are 7 lbs lighter than the peashooters (3.5 lb saving each)

Glen
 
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My Maney replica gave impressive gains with the JS#1. This has a lot of duration. But when the same tests were done after having tighter radius ground onto the lifters, reducing the duration, the Maney no longer had those gains over the stock 1 3/8 none balanced pipes and peashooters.

Thus my hunch is a stock cam bike won’t see massive gains with a Maney pipe.
All only IMHO and of course YMMV.
 
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It's good that the manufacturer got it right for a long time- but then they went so terribly wrong with the MK2a and MK3 exhaust.
I guess they were forced to comply to the noise regulations in the big US market.
Glen
 
Fast Eddie said:
My Maney replica gave impressive gains with the JS#1. This has a lot of duration. But when the same tests were done after having tighter radius ground onto the lifters, reducing the duration, the Maney no longer had those gains over the stock 1 3/8 none balanced pipes and peashooters.

Thus my hunch is a stock cam bike won’t see massive gains with a Maney pipe.

Which therefore means that the best set up for a stock motor is probably the 1 3/8 pipes and peashooters.

All only IMHO and of course YMMV.
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What radius before and after?
 
worntorn said:
Yes, the blocked balance pipes and the separate pipes both gave the best result, 113 kmh top of hill. Both with the same open peashooters fitted.
I tried the same with open short emgo silencers and the bike slowed a bit, even though the emgos are 7 lbs lighter than the peashooters (3.5 lb saving each)

Glen
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Hi. How did you block the balancer pipes?
 
worntorn said:
Yes, the blocked balance pipes and the separate pipes both gave the best result, 113 kmh top of hill. Both with the same open peashooters fitted.
I tried the same with open short emgo silencers and the bike slowed a bit, even though the emgos are 7 lbs lighter than the peashooters (3.5 lb saving each)

Glen
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Glen,
More info on those "short" Emgo silencers please. Are you referring to Emgo's Dunstall pattern silencers? Or another style of silencer?
 
Glen, how do you approach Dyno Hill? Forth gear at some RPM or road speed? Then what, roll the throttle to WOT?
 
Fourth gear at 100 kmhr GPS to a driveway at toe of the hill, then full bore in 4th to a traffic sign at top of hill.
Unless I make an exhaust or tuning change, nine times out of ten the GPS will show the same result at top of hill.
Now and then it will be +- 1 kmhr, never any greater variation than that.

Glen
 
chaztuna said:
Glen,
More info on those "short" Emgo silencers please. Are you referring to Emgo's Dunstall pattern silencers? Or another style of silencer?
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These are the Emgos I tried.
They are very light, straight thru and quite harsh sounding.
The bike dropped 2 kmh vs the open peashooters.

Glen
 
worntorn said:
These are the Emgos I tried.
They are very light, straight thru and quite harsh sounding.
The bike dropped 2 kmh vs the open peashooters.


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Glen,
Thanks for the link. The 2017 Emgo Classic Bike catalog does claim those [P/N 80840-51] to be a "Dunstall" replica. I'm no Dunstall expert, so perhaps that syle was produced by Dunstall at some point. That said, P/N 80840-50 is what I've used on British bikes for 35 years. This part number is what I know to be a pattern of the Dunstall "Decibel" silencer. These are about 5/8" shorter than the "pea shooter" silencers. See page 9 from the catalog linked below.

Emgo 2017 Classic Bike Parts Catalog

The 80840-50 has a removable baffle, so that you can replace any blown out fiberglass packing. The 80-840-51 units baffle is not removable. I like to leave the glass packing out when riding locally. I'll install new packing for long rides/trips.
 
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It'll be interesting. Since the black caps (and plastic airbox) uses smaller OEM main jets, it seems "obvious" that they reduce performance compared to the ham can/peashooters with their larger mains. Maybe just the mufflers won't have that effect. OTOH, since they are not appreciably larger than peashooters and they are much quieter, I would expect a noticeable reduction in performance. Quiet mufflers can produce just as much power as a loud muffler but they generally have to be larger to do so.

In fact, sometimes quieter mufflers produce more power than loud mufflers but that's a function of muffler design/application. I did (car) dyno tests years ago where a pair of straight-through, very loud "performance" mufflers produced less power than the OEM mufflers. ;)
 
Exhaust pipe design goes hand in hand with the whole ‘system design’ and especially the camshaft design.

Modern production vehicles therefore have very highly developed and finely tuned systems. As such, swapping the OEM silencer for some horrid straight thought things will not usually give big gains unless it is accompanied by other changes. That’s why performance cams can make a big difference, it’s not about it being a ‘race cam’ it is often just about it being a cam that is not designed to minimise noise etc!

Fuelling can also throw up surprises. Better tuning can sometimes require weaker mixtures. I found this with the Maney pipe, on the set up where it worked well, it needed weaker settings. Although the opposite is most likely the case with modern lean burn engine settings.

Exhaust silencer design wasn’t so advanced in the early ‘70s and Norton made no attempt to modify the camshaft etc to suit the more restrictive silencers in fact the Commando kept what was essentially a 1960s sports cam design.

So… all things being equal, my money is on the black caps yielding a performance drop.
 
I reread some period roadtests of the MK2A last night.
The MK3 was fitted with the same airbox and silencers, why was it found to be so sluggish while the MK2A didn't get that same reputation?
It could be the in way the tests were written.
The MK2a acceleration test results in the Gold portfolio are very poor. Quarter mile time was 14.2 seconds with a terminal speed of just over 90 mph.
A JPN bike that was essentially a MK2A was similarly sluggish.
The testers shrug off the lack of performance with a lot of " who needs to go that fast anyway?" type logic.
But the numbers are there, a huge decrease in power output from the earlier 850 to the MK2A and MK3.
I don't think the airbox is the culprit.
It was designed to have very low restriction and large size which meant lower air speed and less noise.
The plastic airbox likely is less restrictive than earlier aircleaner types.
One other thing came to light.
One tester talked about the power reduction with the quiet pipes. He was told by Norton that the RH10 head on the MK2A was designed to work with the restrictive silencers to restore some of the lost power.
Strange that Norton did not continue to use that head with the MK3.


Glen
 
worntorn said:
I reread some period roadtests of the MK2A last night.
The MK3 was fitted with the same airbox and silencers, why was it found to be so sluggish while the MK2A didn't get that same reputation?
It could be the in way the tests were written.
The MK2a acceleration test results in the Gold portfolio are very poor. Quarter mile time was 14.2 seconds with a terminal speed of just over 90 mph.
A JPN bike that was essentially a MK2A was similarly sluggish.
The testers shrug off the lack of performance with a lot of " who needs to go that fast anyway?" type logic.
But the numbers are there, a huge decrease in power output from the earlier 850 to the MK2A and MK3.
I don't think the airbox is the culprit.
It was designed to have very low restriction and large size which meant lower air speed and less noise.
The plastic airbox likely is less restrictive than earlier aircleaner types.
One other thing came to light.
One tester talked about the power reduction with the quiet pipes. He was told by Norton that the RH10 head on the MK2A was designed to work with the restrictive silencers to restore some of the lost power.
Strange that Norton did not continue to use that head with the MK3.


Glen
Click to expand...

Glen
I agree that the airbox is not the culprit. I have 2 x mk 3s one with plastic box and one with the ham can, it is the stuffed up silencers that kill the power as I've had pea shooters and black caps on both to check the difference. I haven't done anything like your runs but the black caps restricted both bikes when fitted.
 
Curious if anyone's tested an Interstate with the low pipes (not black caps). My buddy's combat interstate can't keep up with my 850 MKII and I have no idea why.
 
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