Dr. Blair on Dyno Hill- Place your bets!

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Reggie said:
The rods on the link arm with the little wheels (that lift the slide) came loose on the left hand carb. That part was £80, so not cheap.
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Thanks for the info. That sounds like a bad day. Never much fun when one cylinder isn't running right.

Nothing is particularly cheap about the FCR carburetor set up for a Norton engine. I'm thinking about using them, but that's as far as I've gotten.
 
That's another big question in my mind, do expensive carbs of the same dimensions make more actual power or just look cool?
After all, when at full bore, carbs are all just a round hole.
Probably an oversimplification but one does wonder about these things. Dyno hill could sort that out. My suspicion is that the exhaust type could make more difference than changing to another (same size) carb.
Anyway, got the exhaust fitted loosely last night, off to button it up & test.

Glen
 
worntorn said:
That's another big question in my mind, do expensive carbs of the same dimensions make more actual power or just look cool?
After all, when at full bore, carbs are all just a round hole.
Probably an oversimplification but one does wonder about these things. Dyno hill could sort that out. My suspicion is that the exhaust type could make more difference than changing to another (same size) carb.
Anyway, got the exhaust fitted loosely last night, off to button it up & test.

Glen
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Brilliant
I can't wait to hear the results
 
The Dunstall exhaust is a fair bit louder than the balance pipe /open peashooters setup at low revs but similar at full bore. Both are very loud at full bore.
It runs nicely with the Dunstall setup.
It did not make any additional power, in fact it showed slightly less speed than the balance pipe set up.
The balance pipe /open peashooters managed 110 km at crest, the Dunstalls did 3 runs at 109 and one at 108.
The plugged balance pipes did 3 runs at 113 and one at 114.

I'm going to try 270 mainjets with the Dunstalls. There are 260s in there now, that is optimum for the balance/open peashooters.
I'm not expecting a huge improvement with the 270s, but the hill will be the judge!

Glen
 
Glen, could you please refresh my memory on the particulars of dyno hill? Approx entry speed?
Distance to exit?
Approx entry to exit pull time?

Thank you.
 
Glen, the early Dunstall's had removable baffles, you could add or remove exhaust lagging to suit when it came to noise.
 
worntorn said:
My friend said these are not Dunstall silencers. He also said they are more open and louder than Dunstalls. These just have a perforated 15/8 tube running through, no cap at end.
I'm also hoping to try a pair of the little Emgo reverse cones on here. If the performance and sound is OK, the Emgos would give a further 5 lb reduction vs the Dunstall look alike silencers.
The exhaust tubing is all Dunstall.

Glen
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Glen,
Emgo also makes [or made] copies of the Dunstall Decibel silencers. The chrome was pretty good. I installed them on half a dozen Triumphs and Nortons back in the 1980s. They were light weight and held up quite well.
They had a removable perforated tube, with fiberglass wrapped around the tube. The fiberglass would blow out after a time. They would then be a bit louder. I would sometimes use the pink fiberglass house insulation to wrap around the perforated tube. I just wrapped mechanics wire around the fiberglass to hold it in place. I preferred to have the insulation in the mufflers whenever I planned on a trip.
You might want to see if Emgo still makes them.

Charlie K
 
WZ507 said:
Glen, could you please refresh my memory on the particulars of dyno hill? Approx entry speed?
Distance to exit?
Approx entry to exit pull time?

Thank you.
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The speed at bottom is 100km/hr. The grade is 12.5%
I don't know distance or time.
So far, I've just been using the hill for tuning rather than generating a HP number. I know I've hit paydirt when the bike goes over the top at a higher speed.
For relative tuning it seems a pretty consistent method as the hill never changes.
I also use it to check the performance on my old standard Rapide every now and then. If it feels a bit off I'll run it up the hill to see what's up. I have the tuned speed recorded in a log book, so if it is below that, even a couple of kms, it's time to tune.

Glen
 
Reggie said:
They seemed to be inconsistent with the choke. One day the engine would be chugging when cold and in traffic queues near my house, so I would turn the choke off and then it was spitting back until it warmed up, then another day it behaved much better. snipped
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Reggie, I installed Mk IIs on several Triumphs. The choke problem is that the choke jets were great..... if you lived in Antarctica! The Mk II choke jets are the same style as the early Mk I Concentric idle jets. Amal sent them out with #50 choke jets. The bike would start OK, but slowly start to foul the spark plugs due to the excessively rich mixture.
I was living in the Buffalo, NY area at the time. For that area, I found #35 jets worked really well. The bike would now start & go to a fast idle. You could drive away immediately with the chokes on. After 2 or 3 blocks, I could turn the chokes off and it would idle slightly low, but normal. After about 7 blocks, it warmed up enough to idle normally.

Charlie K
 
worntorn said:
That's another big question in my mind, do expensive carbs of the same dimensions make more actual power or just look cool?
After all, when at full bore, carbs are all just a round hole.
Probably an oversimplification but one does wonder about these things. Dyno hill could sort that out. My suspicion is that the exhaust type could make more difference than changing to another (same size) carb.
Anyway, got the exhaust fitted loosely last night, off to button it up & test.

Glen
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When i was doing my rebuild s few years ago, i needed to replace my knackered out Amals. I was thinking about FCRs. I talked about it with a few respcted folks, including Mr. C. who did my head work, and most thought i wouldnt make more power with them vs. properly set up Premieres.
 
Hi Glen
From my engineering days you need to take in various things on the day of the test such as air temperature, air pressure , fuel any other changes etc, plus a few other things I have forgot now. There are formulas that can bring things back to square, so long as you record the various changes, if you have "Tuning for Speed" Phil has some good information on how to achieve reliable results with your Hill tests.
I like these sort of tests as they don't cost much other than time and a enthusiasm.
Looking forward to your final result.
Burgs
 
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Right, the dyno operators use correction factors for this.
In places where temp and humidity varies a lot the CF is quite high at times.
Fortunately the climate here in Vancouver during riding season and even year round is very moderate ( 961 owners might say bland:) so I don't see any measurable difference in top of hill velocity day to day, same bike, no changes.
That is with the TomTom GPS set for km/hr, which gives a fairly sensitive reading on speed.
I have wondered about this and concluded it must be due to our fairly constant humidity and temperature levels. It would be interesting to try the hill on a day when the atmospheric conditions would have a dyno operator using a large correction factor.

Glen
 
If'n I could weld, had a pipe bender, and wanted to copy that exhaust, I'd make the diameter of that section in the middle of that pipe 2 inches minimum. Would be a lot of work making the collectors if it was a mistake, but I kind of doubt it would be if going over the top of that hill faster was the goal.

My thoughts about FCR carburetion are... The 35mm FCR's would make better power on an 850 or larger displacement engine than any non-pumper carburetor of similar size if setup right. You might even be able to run a quicker turn throttle, if you like that kind of thing. 35mm bodies might be pushing it on a 750 street bike, but OK on a 750 road racer. Anybody with 35mm FCRs on a 750 want to chime in?
 
Hi Glen
Don't want to say this but
Top speed only?
I suggest it's time for a stopwatch! Lol
Time to the top is more important
 
Might also explain why there was no appreciable difference on the balance pipe test, the balance pipe made a difference from very low revs on mine.
 
Chris said:
Hi Glen
Don't want to say this but
Top speed only?
I suggest it's time for a stopwatch! Lol
Time to the top is more important
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I don't see it as necessary.
The ability to accelerate against the grade is what I'm after, the more the better.
If I can get my Norton to enter the hill at 100 and exit at 115 and you are beside me with an untuned Norton that enters at 100 and crests at , say, 108, my Norton will be ahead. By quite a bit. It's pretty simple out there on those big grades, you either have the power or you don't.
But the hill is an easy cheap way to optimize things.
Searching for another 270 jet, I only have 1 in my collection.

Glen
 
If it were a race, time would be THE important factor, NOTHING else would matter. Many things influence time, tyre grip, suspension, rider skill etc, etc.

But it’s not a race, it’s a power test. And SPEED needs POWER.

Yes, aerodynamics would have a big effect and would have to be taken into consideration if comparing a JPN to a Hi Rider for example. But so long as we’re talking about the same rider, on a ‘normal‘ naked bike, we can pretty much rule this out for our purposes.

So, Glen is measuring pure speed up a fixed gradient. I believe that within the confines of our interest (ie practical, real world relevance) this is pretty bloody good test.

My main criticism is that he clearly needs a better stocked jet collection !
 
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