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Peter Williams on PW3 cam
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Very interesting even if I don't fully understand some of the theory. Put one in mine January and set it to specified lift at TDC by advancing 5 degrees. It worked fine but produced a very blatty and noisy exhaust and it didn't seem to perform that well. I have a 'ported' Combat head with 9.3:1 (030" spacer under barrels) and 32mm carbs. Have since put it back to std timing marks and it's a lot nicer and more flexible. What I have noticed is that it was necessary to drop the needles to the top notch to cure cruising throttle (1/4 and 75-80) and initial accel richness. I'm wondering if the lower compression is inhibiting full benefit?
It does perform better than std but doesn't have the mad rush of the 2S I once had. Would be nice to get the bike on a Dyno but I'd feel silly with modern bike riders watching 50hp coming up on the screen!
It does perform better than std but doesn't have the mad rush of the 2S I once had. Would be nice to get the bike on a Dyno but I'd feel silly with modern bike riders watching 50hp coming up on the screen!
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That link is really interesting, thanks for it.
I think that maybe most racers will agree that the PW3 cam is best, higher RPMs are possible, when everything else for the high RPMs is also installed. however my friend has a 750 with the PW3 cam. I think he has around 9.5 to 1 compression. His engine is in good condition. That bike doesn't seem to have any more power than my standard 850 with a single mikuni 34mm and the RH10 head. I think that maybe for the PW3 to work properly the compression should be at least 10.5 to 1.
Probably for road use the 2S cam is beter. Now days if you want to go faster on the road probably it is better just to buy a faster bike.
I think that maybe most racers will agree that the PW3 cam is best, higher RPMs are possible, when everything else for the high RPMs is also installed. however my friend has a 750 with the PW3 cam. I think he has around 9.5 to 1 compression. His engine is in good condition. That bike doesn't seem to have any more power than my standard 850 with a single mikuni 34mm and the RH10 head. I think that maybe for the PW3 to work properly the compression should be at least 10.5 to 1.
Probably for road use the 2S cam is beter. Now days if you want to go faster on the road probably it is better just to buy a faster bike.
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The "blatty" aspect of exhaust note is due to large overlap, that period of crank rotation when both intake and exhaust valves are open simultaneously. Until the breathing, rpm and compression come together to produce max hp, the motor sort of fires straight out the pipe. Big overlap is good for racing where most of the time is spent in the higher rpm ranges, but for the street, it's a bit of a waste. Ducati advertises the engine in their new 1200 Multistrada as the 11 degree engine, meaning 11 degrees of overlap as opposed to the nearly 40 degrees utilized in the 1198 sportbike engine.
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keith1069 wrote;
You're expecting as much as 50bhp??
I have fitted a PW3 this year and a Maney big valve head. My bike is runing very rich, and the power increase has not been all that noticable. Unfortunately I have not had very much spare time this year to try and get it sorted properly, but I had thought that the fact that I am probably running approx 8.5:1 compression ratio is a contributory factor.
You're expecting as much as 50bhp??
I have fitted a PW3 this year and a Maney big valve head. My bike is runing very rich, and the power increase has not been all that noticable. Unfortunately I have not had very much spare time this year to try and get it sorted properly, but I had thought that the fact that I am probably running approx 8.5:1 compression ratio is a contributory factor.
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Very informative review. I've had to study up on this to try to get away with stuff I shouldn't. The common denominator in above tales, not getting the most out of an aggressive cams is lack of enough Compression Ratio. There also seems to be a kick start meanness threshold some where after 10.5 CR. Small ports and valves tend to tame long duration cams' low end roughness but may limit the top end. Advancing the cam tends to help low end and spread power band at cost of max peak power.
Review Dyno Daves cam profile pages, most hot cams are 2S based. Hot cams need hi CR and like extra octane to keep the ignition timing advanced for best torque.
Owners who thought they'd detune a Combat by standard cam but retaining 10CR got detonation as public octane got diluted. It'd be hard to dyno various cams in same engine because other factor must be altered to get most of each cam in its intended zone. Good for side car may not be for hill climber. I sure liked my 2S cams, good idle, easy to creep on hi throttle and always eager to pull hard the higher you rev, no torque drop off till past normal red line. My 2S Combats got an extra piston kicking in about 6800, about where everything else needs beefing up of lightening up to stand this and higher. When snicking shifts over red line it tends to just reset engine back to its best power wind up again, oh yum.
A good Combat geared right and run in 6500-7500 can give them too easy front lifting sports bike a real run for the money till power runs well over the ton.
I find it takes rather more G' force thrust to lift Commando's than sports bikes, so tends to leap ahead of them w/o let off, if you are willing to wring the neck out of hot camshaft.
Review Dyno Daves cam profile pages, most hot cams are 2S based. Hot cams need hi CR and like extra octane to keep the ignition timing advanced for best torque.
Owners who thought they'd detune a Combat by standard cam but retaining 10CR got detonation as public octane got diluted. It'd be hard to dyno various cams in same engine because other factor must be altered to get most of each cam in its intended zone. Good for side car may not be for hill climber. I sure liked my 2S cams, good idle, easy to creep on hi throttle and always eager to pull hard the higher you rev, no torque drop off till past normal red line. My 2S Combats got an extra piston kicking in about 6800, about where everything else needs beefing up of lightening up to stand this and higher. When snicking shifts over red line it tends to just reset engine back to its best power wind up again, oh yum.
A good Combat geared right and run in 6500-7500 can give them too easy front lifting sports bike a real run for the money till power runs well over the ton.
I find it takes rather more G' force thrust to lift Commando's than sports bikes, so tends to leap ahead of them w/o let off, if you are willing to wring the neck out of hot camshaft.
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hi keith,reggie,ive got to agree with hobot,the fact you,re not getting the best out of the pw3 is the lack of cr ,i would think at least 10 to 1 or maybe a bit more,the pw3 is a race cam and needs more compression,most race cam makers ive seen specify you must use race pistons [to get the most benefit] my idea of a race piston is high compression with deeper valve pockets to allow for the extra lift.fitting a race cam in a road bike with 8 or 9 to 1 cr will most likely reduce power compared with a std cam,if you,re thinking why would a race cam need high comp pistons or skimmed head have a look at the intake closing after bottom dead center of a std cam and a race cam,
Chris
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Hi
My cam has always been the 4s. Good drive god top end. My 750 race bike has Steve Maneys cam which he says is based on a 4s.
We ran a Pw3, a 4s & a 7s on my mates sprint bike with very little diference in times. However feel told you that the pw3 had a better spread of midrange power. The 7s had less & only gave the better top end on the rolling mile. Compression ratio is fairly high & to get the best out of each cam it shows you have to match up the rest of the package.
Chris
My cam has always been the 4s. Good drive god top end. My 750 race bike has Steve Maneys cam which he says is based on a 4s.
We ran a Pw3, a 4s & a 7s on my mates sprint bike with very little diference in times. However feel told you that the pw3 had a better spread of midrange power. The 7s had less & only gave the better top end on the rolling mile. Compression ratio is fairly high & to get the best out of each cam it shows you have to match up the rest of the package.
Chris
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The lobe centers on the PW3 cam are too wide at 107 degrees. Other race cams have closer lobe centers and run better at around 104. For comparison - a stock Commando cam is around 101 or 102. There are no valve clash problems with the PW3 and there is no reason for the lobe centers to be so wide. For instance - the Axtell #3 could be had with lobe centers anywhere from 102 to 105. 102 being the hottest but requiring custom machined valve clash clearance. 105 being intended for street bikes. 104 was the most popular for racers who wanted a drop in cam.
It would be easy to make the PW3 cam with closer lobe centers. PW3 lovers would get better performance. The problem is that you're still stuck with those high wear, HP robbing, heat producing, obscenely heavy flat lunks of iron - Norton lifters. The longer lasting cam setup for lightweight BSA type radiused lifters is a much better idea.
It would be easy to make the PW3 cam with closer lobe centers. PW3 lovers would get better performance. The problem is that you're still stuck with those high wear, HP robbing, heat producing, obscenely heavy flat lunks of iron - Norton lifters. The longer lasting cam setup for lightweight BSA type radiused lifters is a much better idea.
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Anyone know how many degrees are the lobe centers for a Megacycle 5600 cam?
lcrken
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highdesert said:
The lobe separation angle for the 560-00 cam is 104.5 degrees. When the cam is timed to Megacycle specs, the intake lobe center is 104.5 degrees atdc, and the exhaust lobe center is 104.5 degrees btdc.
FWIW, the lobe separation angle on the 4S cam was specified as 101.5 deegrees. The one I measured back in the '70s came out at 102 degrees.
Of the Norton cams that I have measured, the widest lobe separation was 106 degrees, on an old HPI #7 cam, and the shortest was 100 degrees, on a Sifton 460 cam. Both of those were serious race cams, and both worked pretty well in race engines. Even with the difference in lobe separation, they had about the same amount of overlap, because the Sifton had more lift.
Ken
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hi ken,can you explain what you mean by lobe seperation angle,im nowhere near a cam expert,but im under the impression from what ive read on the subject that lobe centers is just another way of setting cam timing,and probably the best,but it does,nt really tell us if a cam is hot or not,my 4s cam timed by conventional method then checked by lobe center method comes out at roughly 99 deg inlet 104 exaust,ie inlet valve is fully open at 99 degrees atdc exhaust fully open at 104 degrees btdclcrken said:
lcrken
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Chris,
lobe center is where the center of the lobe, intake or exhaust, is in relation to top dead center, measured in crankshaft degrees. The most accurate method of checking cam timing is by lobe centers, adjusting until the the lobe center is at the point specified by the maker, typically somehwere between 99 and 108 degrees after TDC for the intake, and the same for the exhaust lobe, but measured before TDC. You see cams with timing outside those limits, but not too many. The lobe separation angle is the number of camshaft degrees between the intake and exhaust lobe centers. You calculate it by adding the intake lobe center value to the exhaust lobe center value and dividing by two. For most cams, the lobe center numbers are the same for both lobes, but not for all. The reason it get's confusing is that when the lobe center angles are the same for both lobes, the lobe separation angle is the same value as the lobe centers.
The easy formula for calculating lobe centers is to subtract the opening number from the closing number, add it to 180, and divide by two. For example, The 4S spec for .020" lift is opening at 65 btdc and closing at 83 atdc. Subtracting 65 from 83 gives you 18, which added to 180 is 198, and divided by two is 99 degrees atdc, so that's where you would set the lobe center when timing it. The exhaust opens at 88 atdc and closes at 60 btdc. If you do the same calcs on it, you get a lobe center of 104 btdc. Add the two, and divide by two, and you get a lobe separation of 101.5 degrees.
Looks like your 4S is timed right where it should be.
In the case of the 560-00 Megacycle, they specify both lobe centers at 104.5 degrees, so the cam also has a lobe separation angle of 104.5 degrees.
Ken
lobe center is where the center of the lobe, intake or exhaust, is in relation to top dead center, measured in crankshaft degrees. The most accurate method of checking cam timing is by lobe centers, adjusting until the the lobe center is at the point specified by the maker, typically somehwere between 99 and 108 degrees after TDC for the intake, and the same for the exhaust lobe, but measured before TDC. You see cams with timing outside those limits, but not too many. The lobe separation angle is the number of camshaft degrees between the intake and exhaust lobe centers. You calculate it by adding the intake lobe center value to the exhaust lobe center value and dividing by two. For most cams, the lobe center numbers are the same for both lobes, but not for all. The reason it get's confusing is that when the lobe center angles are the same for both lobes, the lobe separation angle is the same value as the lobe centers.
The easy formula for calculating lobe centers is to subtract the opening number from the closing number, add it to 180, and divide by two. For example, The 4S spec for .020" lift is opening at 65 btdc and closing at 83 atdc. Subtracting 65 from 83 gives you 18, which added to 180 is 198, and divided by two is 99 degrees atdc, so that's where you would set the lobe center when timing it. The exhaust opens at 88 atdc and closes at 60 btdc. If you do the same calcs on it, you get a lobe center of 104 btdc. Add the two, and divide by two, and you get a lobe separation of 101.5 degrees.
Looks like your 4S is timed right where it should be.
In the case of the 560-00 Megacycle, they specify both lobe centers at 104.5 degrees, so the cam also has a lobe separation angle of 104.5 degrees.
Ken
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hi ken,thx for your reply,its much clearer now,the thing what confused me was the lobe seperation angle thx again
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