Dyno runs before and after engine mods

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Quarter mile MPH numbers are a better indication of HP than ET.... Traction, slow or fast shifts, short shifting, over revving, among other things effect ET much more than MPH... imo. Not that we all don't like low ET's.
 
FWIW, unless you are experienced motorcycle drag racer at the drag strip (NOT playing drag racer with your friends on a back road), you won't get close to the ETs listed for any motorcycle in a road test or advertising copy. As I mentioned in post 34 and Rweb stated in post 41, the trap speed won't vary much even when the ET does so trap speed is a much better indicator of engine power.
 
rweb said:
Quarter mile MPH numbers are a better indication of HP than ET.... Traction, slow or fast shifts, short shifting, over revving, among other things effect ET much more than MPH... imo. Not that we all don't like low ET's.
Click to expand...
Good reaction times are one of the big keys and good ones win many races. Great reaction time with good ETs gets you to the next round of eliminations or your packing the bike to go home.
 
I remembered there was another bike tested on the same Dyno:

www.accessnorton.com

Dyno run (2017)

Had the "Nortan 850" dyno'd last week with very interesting results. The engine is standard apart from a Fullauto Technologies head, a PW3 cam and a VM34 Mikuni. The rapid dip in the torque curve is interesting. The motor is very strong in the low end and mid range as you would imagine with 50...
www.accessnorton.com www.accessnorton.com

'The engine is standard apart from a Fullauto Technologies head, a PW3 cam and a VM34 Mikuni'
Makes me think what makes the difference. Twin carbs? Higher compression?
 
While I'm disillusioned to learn that my MKII only makes 41 hp, the torque curve explains why I have such magnificent throttle response in the low revs. I've scrapped with 1300 CC metric cruisers and they can't touch me until the long straights. So I guess 41 hp is enough.

I'm still gonna tell people that she makes 60 though, even if it's a lie.
 
MexicoMike said:
FWIW, unless you are experienced motorcycle drag racer at the drag strip (NOT playing drag racer with your friends on a back road), you won't get close to the ETs listed for any motorcycle in a road test or advertising copy. As I mentioned in post 34 and Rweb stated in post 41, the trap speed won't vary much even when the ET does so trap speed is a much better indicator of engine power.
Click to expand...
Back in the day, everyone hired Jay Gleason
www.google.com

Drag Legend Jay 'Pee Wee' Gleason Passes

The legendary Jay 'Pee Wee' Gleason has passed away this weekend. In the '80s Jay was THE MAN to hire if you wanted to know just how fast your bike was in the quarter mile.
www.google.com www.google.com
 
Joachim said:
'The engine is standard apart from a Fullauto Technologies head, a PW3 cam and a VM34 Mikuni'
Makes me think what makes the difference. Twin carbs? Higher compression?
Click to expand...
Yes, both of those ! Notice how it flattens off at 5,000 to 6,000. I never dyno’d mine when it had the single Mik but that’s exactly what it felt like. I’m not knocking the single Mik, it suits many folks riding needs perfectly, but it def stops that BHP line climbing after 5,000.

Ken‘s figures would clearly have been boosted by that fact he’s used one of his heads too. Unless you’re a porting genius there’s no way you’ve got yours flowing as good as his !
 
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According to the graph, at 4500 rpm this engine is making just 32 HP.
The single carb is not holding it back at 4500. Long before this dyno run , when this engine first went together, the dyno tested -5 HP @ 4500 rpm with a PW3 info was mentioned.

Glen
 
Carl H said:
Good reaction times are one of the big keys and good ones win many races. Great reaction time with good ETs gets you to the next round of eliminations or your packing the bike to go home.
Click to expand...
I never rely on reaction times when I race. I always look a long way ahead and I don't ride fast into corners where there are guys going in all sorts of directions. Adrenalin causes psychological time dilation. If an incident happens, you usually have tons of time to react, but I don't rely on that. I am always smooth steady and systematic.
Some guys don't know how to race-change up through as gearbox. If the gears are wide ratio, it is more difficult to be smooth. I usually race with my motor revving between 5,500 RPM and 7000 RPM. And that is even in the slowest corners.
Due to a heart problem, Take beta-blocker medication. If an incident occurs while racing, I simply manage it in the cold hard light of day. When I approach any corner, I know what it should look like. If I go in too hot, it is never a problem, because I stay in control.
If you watch Marquez - he finds out how fast he can get around corners by crashing in practice. I usually only go fast enough to scare myself. That is smarter
 
acotrel said:
I never rely on reaction times when I race. I always look a long way ahead and I don't ride fast into corners where there are guys going in all sorts of directions. Adrenalin causes psychological time dilation. If an incident happens, you usually have tons of time to react, but I don't rely on that. I am always smooth steady and systematic.
Some guys don't know how to race-change up through as gearbox. If the gears are wide ratio, it is more difficult to be smooth. I usually race with my motor revving between 5,500 RPM and 7000 RPM. And that is even in the slowest corners.
Due to a heart problem, Take beta-blocker medication. If an incident occurs while racing, I simply manage it in the cold hard light of day. When I approach any corner, I know what it should look like. If I go in too hot, it is never a problem, because I stay in control.
If you watch Marquez - he finds out how fast he can get around corners by crashing in practice. I usually only go fast enough to scare myself. That is smarter
Click to expand...
The conversation is about drag racing Al. The are no guys going in all sorts of directions, no bends, no braking, etc… slow reactions in a drag race means an early finish for the day…!
 
What happens in a straight line on race circuits is irrelevant. What happens in the corners is much more important. The faster you get around the corner, the faster you enter the next straight. If you have 10 MPH on the next guy as you enter the next straight he usually needs monster horsepower to pass you before the end of the straight. It is the reason that 500cc Manx Nortons won more races than 650cc Tritons ever did.
 
Drag racing does not mean anything and it does not prove anything. It is simply'how fast can you afford to go. Which is faster - several smooth gearshifts in quick succession or a couple in slow succession ? In road racing, the bike with close gear ratios accelerates faster than the one with wide ratios. First guy to the first corner has an advantage. I now have 6 gears, but massive horsepower and a high first gear is probably faster ?
 
I'm totally with Nigel on the "going flat at 5000 rpm" thing with a single Mikuni. My own mildly tuned 850 struggled to overtake my brother's 650 single carb Triumph, so equipped. Now with twin Amals it leaves it for dead.
On Joachim's pondering on the contributors to the power differences pre and post rebuild, surprised no one has mentioned cam timing? John Baker when prepping the NVT Commando paid a lot of attention to getting this spot on. I don't know how the 5 degree correction was achieved (vernier cam sprocket?), but the original cam could easily have been out by that much, who knows? Also what were the compression readings prior to the rebuild, before the valve seating was refreshed?
I guess what I'm saying is the devil is in the details. I also doubt the PW3 is the main contributor, it's supposed to take out of the midrange what it adds to the top end (as nearly all fiercer cam timing does), but that dyno chart shows more power everywhere?
Incidentally, not knocking the dyno runs, think it's great data. I also fully understand the arguments for pw3s and single miks.
 
"Drag racing does not mean anything and it does not prove anything. It is simply'how fast can you afford to go"

Drag racing at the pro level requires skills that very few people have - just like every other sport at the pro level. ;)
 
wavey_davey said:
I'm totally with Nigel on the "going flat at 5000 rpm" thing with a single Mikuni. My own mildly tuned 850 struggled to overtake my brother's 650 single carb Triumph, so equipped. Now with twin Amals it leaves it for dead.
On Joachim's pondering on the contributors to the power differences pre and post rebuild, surprised no one has mentioned cam timing? John Baker when prepping the NVT Commando paid a lot of attention to getting this spot on. I don't know how the 5 degree correction was achieved (vernier cam sprocket?), but the original cam could easily have been out by that much, who knows? Also what were the compression readings prior to the rebuild, before the valve seating was refreshed?
I guess what I'm saying is the devil is in the details. I also doubt the PW3 is the main contributor, it's supposed to take out of the midrange what it adds to the top end (as nearly all fiercer cam timing does), but that dyno chart shows more power everywhere?
Incidentally, not knocking the dyno runs, think it's great data. I also fully understand the arguments for pw3s and single miks.
Click to expand...
You can get 5 degrees by remeshing the gears and changing the no of link spacing on the sprocket. I don't have the process in my head but it's on the NOC side and elsewhere.

I don't like verniers at all on the camshaft because they are just not strong enough. If yiu need a less than 5 degree step then either an offset key or I beleive RGM sell sprockets with the keyways offset.
 
johnm said:
You can get 5 degrees by remeshing the gears and changing the no of link spacing on the sprocket. I don't have the process in my head but it's on the NOC side and elsewhere.

I don't like verniers at all on the camshaft because they are just not strong enough. If yiu need a less than 5 degree step then either an offset key or I beleive RGM sell sprockets with the keyways offset.
Click to expand...
My 312a is timed at 104.5 by moving the idler and cam sprockets 12 pins apart. Idler gear is now 5 teeth counter clockwise from stock.
 
wavey_davey said:
I'm totally with Nigel on the "going flat at 5000 rpm" thing with a single Mikuni. My own mildly tuned 850 struggled to overtake my brother's 650 single carb Triumph, so equipped. Now with twin Amals it leaves it for dead.
On Joachim's pondering on the contributors to the power differences pre and post rebuild, surprised no one has mentioned cam timing? John Baker when prepping the NVT Commando paid a lot of attention to getting this spot on. I don't know how the 5 degree correction was achieved (vernier cam sprocket?), but the original cam could easily have been out by that much, who knows? Also what were the compression readings prior to the rebuild, before the valve seating was refreshed?
I guess what I'm saying is the devil is in the details. I also doubt the PW3 is the main contributor, it's supposed to take out of the midrange what it adds to the top end (as nearly all fiercer cam timing does), but that dyno chart shows more power everywhere?
Incidentally, not knocking the dyno runs, think it's great data. I also fully understand the arguments for pw3s and single miks.
Click to expand...
Good point about cam timing. I found the timing chart of the stock cam I took before I disassembled the engine:



That was done by measuring with a dial gauge straight onto the followers. So not considering valve lash.


Regarding the timing of the PW3. When I put it all together as per manual, just using the timing marks, the cam lobe center was at 100 degrees but was supposed to be 106 degrees. With moving the timing chain sprocket one tooth forward (15 degrees) and the crank timing pinion two teeth (2x 5 degrees), I am still 1 degree out. Dont ask how many times I checked that!
After riding for a while I was questioning my measurments and did it all again, with a degree disc and the dial indicator on the valve spring top cap. Same result.

Many people here have way more experience with that stuff than me, but I cannot understand where this negative opinion about the PW3 comes from. I know a few people who have one. And their bikes all run really strong.
 
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