I believe it went to just over 4,000 rpm at top.
Might try again at a higher speed and also try a 3rd gear pull.
Glen
Balance pipe and Dyno Hill
- Thread starter worntorn
- Start date
- Status
I believe it went to just over 4,000 rpm at top.
Might try again at a higher speed and also try a 3rd gear pull.
Glen
Tornado
VIP MEMBER
- Joined
- Dec 5, 2017
- Messages
- 4,822
Interesting work Glen. I should have a pair of muted peashooters available for you to test out in the near future if you'd like to redo your tests. I scored a set of original non-muted peashooters locally a few weeks ago...these will be finding their way onto my bike shortly.
- Joined
- Feb 7, 2010
- Messages
- 4,195
This
"It's possible that a bit more could be gained by trying different mainjets with the non balanced setup."
- Joined
- Aug 8, 2005
- Messages
- 2,819
I found that I had to go up to 270 mains with my 74 when I changed out my balanced pipes to 750 type singles on my RH10 head. I am going to give a pair of 280 mains a try this spring.
Yes I will play with mainjets with the individual pipe exhaust, but not to " restore lost power".
Just to clarify, the individual pipe setup gave me a little boost over the balanced, right off.
As far as trying bigger and smaller mainjets with the balanced exhaust, I did that a few years ago using dyno hill and the GPS. The best size was 260 for this elevation. That's what is in the bike right now.
I suspect it's the right size mainjet for the individual pipe exhaust as well, but you never know.
I thought I knew how the balanced /unbalanced test would go, sure had that wrong!
Glen
Fast Eddie
VIP MEMBER
- Joined
- Oct 4, 2013
- Messages
- 21,546
Well I’m pleased how your tests went Glen, cos I’ve never been a fan of balanced pipes (on Norton’s or Triumphs) as I prefer the looks and the ease of fitting of unbalanced!
I also can’t help but think it’s not good for cylinder head cooling to have a big hot tube blocking the air flow to the head.
And, years ago Dave Degens told me that to make a Triumph go well you need long straight through pipes and no balance pipe... pretty much like the stock unbalanced unmuted Norton peashooter set up...
I also can’t help but think it’s not good for cylinder head cooling to have a big hot tube blocking the air flow to the head.
And, years ago Dave Degens told me that to make a Triumph go well you need long straight through pipes and no balance pipe... pretty much like the stock unbalanced unmuted Norton peashooter set up...
- Joined
- Feb 10, 2009
- Messages
- 2,959
They may originally have fitted the balance tube for no good reason at all, or because other bikes had one and then made up some sales talk about torque, quietness, economy, increased libido, etc.
Don’t forget how illogical the factories could be.
Don’t forget how illogical the factories could be.
Fast Eddie
VIP MEMBER
- Joined
- Oct 4, 2013
- Messages
- 21,546
Increased libido is a good point...
Glen, can you re visit the test please...?
Glen, can you re visit the test please...?
Perhaps one reason the balance pipe was introduced was to help hold the pipes in the head and take some of the stresses off the thread in the head for the rose nuts. My Royal Enfield Interceptor has lugs welded on the bottom of the exhaust pipes near the head for inserting tie bar which is held on by tightening nuts each end for helping to hold the pipes in the head. Sixties BSA Twins had a similar tie bar to attach the pipes before they went with a balance pipe around 1969 for the twins.
Doctor Gorden Blair of Queens University did some development work for Dunstall way back in the 1960s to find out what advantage the balanced pipe had, I believe his conclusion was 4-5 bhp gain on mid - range. Although I never noticed any difference, I also rode 2 Jap twins I had, one with balance pipe, one without, no noticeable difference. He also developed the 2-1-2 Dunstall exhaust.
- Joined
- May 7, 2005
- Messages
- 7,119
What tuning area on the carb that needs looking at depends on the throttle opening Worntorn used on his run to 4000rpm, WOT would be main jets. When I changed from balanced to unbalanced back in the 90's the main jets stayed at 260 and I did a WOT plus plug chop run to check, what I can't remember is what changes I made if any to the needle position.
- Joined
- Feb 10, 2009
- Messages
- 2,959
That 5 bhp could make a bike feel better to ride.
I expect it’s also possible to design and fit a balance tube wrongly, so you don’t get any benefits.
Agreed. I cannot get any explanation on how the two different exhaust setups share the same silencer, surely, one will require to act more like an extractor exhaust whilst the other is just as it is. Yes, I do understand that a "tuned" exhaust can have benefits over any old junk bolted on there, but as it is now over 50 years since Queens University did these tests, technology has moved on in leaps and bounds and someone somewhere could possibly improve upon the old system?
- Joined
- Feb 7, 2010
- Messages
- 4,195
260s are what came in my '73 with crossover, but 230s seem to work best for the SS's MkIII engine which has high individual pipes. I just wondered if the 'over-jetting' with the plugged crossover and peashooters had anything to do with pulling the hill faster. I thought about plugging the '73's crossover to see what the result would be, but it was picked up by the new owner a couple of days ago.
Glen - if we assume you top the hill at 4100 (you suggested a bit over 4000 rpm), then you would be entering the hill at ~ 3600 rpm (at 100 km/hr) and gaining about 500 rpm during the test? Since we have no idea what gradient you are ascending, approximately how long (time - seconds) does it take to make the ascention and gain the 500 rpm? Thank you.
On holidays right now but once home, I'll try some different jets with the unbalanced exhaust and post results
The grade is 12.5%, very steep. This soaks up a lot of power without speeds going too high.
Time and distance are unknowns, I just aim for best acceleration resulting in highest top speed at the top marker.
It would be possible to put hp numbers on it with time and distance known.
I don't know how accurate a bhp number would be. Probably not terribly accurate as the first part of the hill is a curved lead in to the main 12.5% grade.
As it is, for simple tuning, the hill and km/hr GPS speedo seem to give really consistent results.
When I make little changes to ignition timing it shows up immediately in speed at top.
I could time the run easily, will do that on my next go round.
Glen
Last edited:
- Joined
- Jan 31, 2010
- Messages
- 3,093
The info re increased power/reduced noise was published independently in several publications, including the Dunstall performance book, two years before Norton began installing the balanced exhaust. When Norton did so, they copied the design that was in the Dunstall book as far as placement of the crossover.
A quote from 1971 re the Norton engine: "By far the best system for fast roadwork is separate exhausts joined by a balance pipe up close to the cylinders." They go on to point out that a racing-type megaphone system can produce more 2-3 more HP on the dyno at 7000 RPM compared to the crossover system but the crossover system produced nearly 6 HP more than the racing system at 5500 RPM.
I'm not disagreeing with any statement here where folks observed different results; If they did, they did. I am saying that the crossover system was not some "invention" by the factory for marketing purposes. There was independent testing/use several years prior that induced the factory into incorporating it into the 850.
I can say from personal experience with a lot of competition car engine building and a LOT of dyno testing on all manner of changes, properly designed crossover pipes DO increase power and reduce noise. Nowadays they are usually use X pipes rather than the H pipes since the X provides a power boost over the H.
Last edited:
- Status
