Rev Limit
Thread Starter
|
Road Captain
Joined: Nov 2005
Posts: 571
Likes: 0
From:
Rev Limit
Most riding occurs well below 3500-4000 RPM's. Can someone explain the relevance of increasing the rev limit on a bike? I am sure there is a very good technical reason. Seems like the only time you would need it is for rapid acceleration in lower gears.
Cruiser
Joined: Jan 2006
Posts: 173
Likes: 0
From: Maryland
RE: Rev Limit
On a stock street bike, to go from 5800 rpms stock to 6200 rpms with upgraded download serves no purpose, IMHO. I think I've hit the rev limiter one time in 22500 miles. But, it sounds macho while drinking a beer with the boys, and everyone's dick is hanging out.
Thorns
Thorns
Tourer
Joined: Nov 2005
Posts: 339
Likes: 4
From: Tallahassee Florida
RE: Rev Limit
ORIGINAL: Thorns
..... But, it sounds macho while drinking a beer with the boys, and everyone's dick is hanging out.
Thorns
..... But, it sounds macho while drinking a beer with the boys, and everyone's dick is hanging out.
Thorns
If Thorns invites you to a party....... Decline humbley !
Budds...............
Cruiser
Joined: Jan 2006
Posts: 167
Likes: 0
From:
RE: Rev Limit
It is the "easiest" way to claim higher horsepower ratings, if that type of thing matters. Why? Because the formula for calculated HP is tourque in lb ft X rpm divided by 5520. So if you do some things to the engine to increase rpms by even a few hundred, you can see how this makes the hp # increase a lot more than if you increase the torque number, even if a rise in torque actually makes you acclerate faster starting at lower rpms. Just math.
This seems to be prevalent in the race bike arena these days, as competing brands are racing for hp #'s too. Alot of technology is going into lighter pistons, shorter strokes with wider bores, lighter valves with stiffer valve springs, etc. This way the engine can rev higher without making more torque per stroke and end up with higher hp.
Will it make the bike pull harder? Yes, in a way. Because accleration is also a factor of how quickly the engine will increase its rpms, not just how much push per revolution. In an engine that starts its power band at 9 or 10K, then increasing redline from 14.5 K to 16K does make a difference. On the race track, you are riding those bikes at between 8.5K and redline the whole time. In the real world, it doesn't translate the same way.
You can quickly see that for an engine like the HD Vtwin that pulls nicely at 2500 rpm and revs out at 5K, a few more rpms won't make as much difference.
Hope that explanation helps.
Bones
This seems to be prevalent in the race bike arena these days, as competing brands are racing for hp #'s too. Alot of technology is going into lighter pistons, shorter strokes with wider bores, lighter valves with stiffer valve springs, etc. This way the engine can rev higher without making more torque per stroke and end up with higher hp.
Will it make the bike pull harder? Yes, in a way. Because accleration is also a factor of how quickly the engine will increase its rpms, not just how much push per revolution. In an engine that starts its power band at 9 or 10K, then increasing redline from 14.5 K to 16K does make a difference. On the race track, you are riding those bikes at between 8.5K and redline the whole time. In the real world, it doesn't translate the same way.
You can quickly see that for an engine like the HD Vtwin that pulls nicely at 2500 rpm and revs out at 5K, a few more rpms won't make as much difference.
Hope that explanation helps.
Bones
Road Captain
Joined: Jan 2006
Posts: 566
Likes: 3
From:
RE: Rev Limit
Increasing the rev limit on the bike will not increase hp numbers. Why? Because peak hp reached before the stock rev limit anyway. The bike will still probably accelerate better with increased rev limit because you can use for example 2nd gear longer. That is, you can use the lower gearing provided in 2nd to reach a higher speed before you have to go to 3rd.
The above is true assuming the engine torque doesn't drop so low above 6000 rpm that you would actually be better off gearing up a notch. This would happen if the engine torque in the 3rd gear would be so much higher than in 2nd that it makes up for the loss in the gearbox (due to the longer gear ratio in 3rd gear).
The above is true assuming the engine torque doesn't drop so low above 6000 rpm that you would actually be better off gearing up a notch. This would happen if the engine torque in the 3rd gear would be so much higher than in 2nd that it makes up for the loss in the gearbox (due to the longer gear ratio in 3rd gear).
Banned
Joined: May 2005
Posts: 14,496
Likes: 156
From:
RE: Rev Limit
Lots of good info here, I feel that upping the limit doesn't help much at all because you run out of cam before you hit the limiter on a stock motor so all you are doing is spinning it over. The "B" engine will live much longer without the extra RPM's also.
Trending Topics
Road Captain
Joined: Jan 2006
Posts: 566
Likes: 3
From:
RE: Rev Limit
ORIGINAL: TCSTD
Lost of good info here, I feel that upping the limit doesn't help much at all because you run out of cam before you hit the limiter on a stock motor so all you are doing is spinning it over. The "B" engine will live much longer without the extra RPM's also.
Lost of good info here, I feel that upping the limit doesn't help much at all because you run out of cam before you hit the limiter on a stock motor so all you are doing is spinning it over. The "B" engine will live much longer without the extra RPM's also.
Does anybody have a link to a dyno chart I can look at.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Outstanding HDF Member
Joined: Oct 2005
Posts: 2,981
Likes: 1
From: Los Angeles, CA (live in Manteca, CA)
RE: Rev Limit
Good write up.
ORIGINAL: BBDeluxe
It is the "easiest" way to claim higher horsepower ratings, if that type of thing matters. Why? Because the formula for calculated HP is tourque in lb ft X rpm divided by 5520. So if you do some things to the engine to increase rpms by even a few hundred, you can see how this makes the hp # increase a lot more than if you increase the torque number, even if a rise in torque actually makes you acclerate faster starting at lower rpms. Just math.
This seems to be prevalent in the race bike arena these days, as competing brands are racing for hp #'s too. Alot of technology is going into lighter pistons, shorter strokes with wider bores, lighter valves with stiffer valve springs, etc. This way the engine can rev higher without making more torque per stroke and end up with higher hp.
Will it make the bike pull harder? Yes, in a way. Because accleration is also a factor of how quickly the engine will increase its rpms, not just how much push per revolution. In an engine that starts its power band at 9 or 10K, then increasing redline from 14.5 K to 16K does make a difference. On the race track, you are riding those bikes at between 8.5K and redline the whole time. In the real world, it doesn't translate the same way.
You can quickly see that for an engine like the HD Vtwin that pulls nicely at 2500 rpm and revs out at 5K, a few more rpms won't make as much difference.
Hope that explanation helps.
Bones
It is the "easiest" way to claim higher horsepower ratings, if that type of thing matters. Why? Because the formula for calculated HP is tourque in lb ft X rpm divided by 5520. So if you do some things to the engine to increase rpms by even a few hundred, you can see how this makes the hp # increase a lot more than if you increase the torque number, even if a rise in torque actually makes you acclerate faster starting at lower rpms. Just math.
This seems to be prevalent in the race bike arena these days, as competing brands are racing for hp #'s too. Alot of technology is going into lighter pistons, shorter strokes with wider bores, lighter valves with stiffer valve springs, etc. This way the engine can rev higher without making more torque per stroke and end up with higher hp.
Will it make the bike pull harder? Yes, in a way. Because accleration is also a factor of how quickly the engine will increase its rpms, not just how much push per revolution. In an engine that starts its power band at 9 or 10K, then increasing redline from 14.5 K to 16K does make a difference. On the race track, you are riding those bikes at between 8.5K and redline the whole time. In the real world, it doesn't translate the same way.
You can quickly see that for an engine like the HD Vtwin that pulls nicely at 2500 rpm and revs out at 5K, a few more rpms won't make as much difference.
Hope that explanation helps.
Bones
