Timing advance at idle
#11
09-16-2007 | 12:16 PM
RE: Timing advance at idle
ORIGINAL: Dalton
Couple of things - Going with a long duration cam especially with a stock engine will do nothing but kill torque and low end performance.
And cam "lift" does have a lot to do with performance,I am running 10.5:1, 2.0" valves, 50mm throttle body with SE high flow injectorsand a Woods .650 lift cam with short duration. It is a torque monster and builds great Hp even with the short duration, the cylinders fill efficiently due to the high lift. If lift didn't add to performance, no one would make high lift cams.
ORIGINAL: sonar_chris
IMHO cams would be the safest way to accomplish the sound of the older carb bikes. As stated above, EFI bikes idle is set higher to make sure that the charging system is getting enough juice back to the battery. Also I believe factory idol is set to around 1000 rpm, another reason is oil flow to the motor. When you slow down the idol, you dont get as much oil and pressure to the motor, which will cause your bearings to start to go and so on. An S&S 510 cam is about the largest can you can bolt in a bike with no mods to the motor. What your really looking for in a cam for lope at idol will be its durration, not its lift. I know Ill catch some flack from some people around her by saying this, but lift doesnt have much to do with a cams performance, its really how long you can keep that valve open to get gas in and exhaust out. The size of the intake and exhaust runners will always stay the same size, thus lift of the cam will really wont make much of a differance as compared to durration.
Chris
IMHO cams would be the safest way to accomplish the sound of the older carb bikes. As stated above, EFI bikes idle is set higher to make sure that the charging system is getting enough juice back to the battery. Also I believe factory idol is set to around 1000 rpm, another reason is oil flow to the motor. When you slow down the idol, you dont get as much oil and pressure to the motor, which will cause your bearings to start to go and so on. An S&S 510 cam is about the largest can you can bolt in a bike with no mods to the motor. What your really looking for in a cam for lope at idol will be its durration, not its lift. I know Ill catch some flack from some people around her by saying this, but lift doesnt have much to do with a cams performance, its really how long you can keep that valve open to get gas in and exhaust out. The size of the intake and exhaust runners will always stay the same size, thus lift of the cam will really wont make much of a differance as compared to durration.
Chris
And cam "lift" does have a lot to do with performance,I am running 10.5:1, 2.0" valves, 50mm throttle body with SE high flow injectorsand a Woods .650 lift cam with short duration. It is a torque monster and builds great Hp even with the short duration, the cylinders fill efficiently due to the high lift. If lift didn't add to performance, no one would make high lift cams.
Chris
#12
09-16-2007 | 09:56 PM
Outstanding HDF Member
Joined: Jul 2007
Posts: 2,609
Likes: 1
From: Indy area
RE: Timing advance at idle
Modifying the distance the valve opens will also change the rate at which it moves. If you went from .5 to .6 inches with the same durations the second one would be at .5 inches sooner and stay at least that much open longer. I don't have the expertise to describe/compare the results exactly but they will definitely differ between the two cams.
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60Gunner (08-08-2020)
#13
09-18-2007 | 12:42 AM
Novice
Joined: Aug 2007
Posts: 19
Likes: 1
From:
RE: Timing advance at idle
You guys need to go to CAMs 101. Most if not all answers are incorrect.
Lift is free hp, provided that the ports can handle the increased flow.
A longer duration will bleed off cylinder pressure and without an increase in compression, will kill low end.
The greatest event that controls the level where the engine makes its power band is the closing of the intake valve, period.
If you want to make some serious lope, without killing your low end, you need to look for a camshaft combination with a tight lobe center, say in the 105 to 108 degree area. This will do two things. 1. it will allow an earlier closing of the intake event and boost the mid range of the engine's power band. 2, it will increase the overlap of the intake and exhaust events, and give you that rough idle that you are looking for.
The flip side is a tight lobe center will narrow the power band of the engine, whereas a wide lobe center will smooth out the idle and have a flatter torque curve in the engine, and possibly make a bit more power in the upper end of the engine.
Prostock engines run in the 9000 plus range and even with intake and exhaust timing at over 295 degrees at .050 lift, they idle really smooth due to lobe centers at well over 116 to 118 degrees. A short track motor is rough idling, even though the duration at .050 is in the 250 to 260 degree range.
Lastly, lift for the most part can't hurt HP, only help it, when the duration is the same. Its referred to the area under the curve. The only parts that take a beating however is the valve springs and lifters that have to deal with the increased load on them.
Adjusting the timing with a split combination as suggested is micky mouse at best. I'd opt for looking for a cam that has a marginal increase in duration at .050, with a tighter lobe center to get you what you want.
As a side note, all my race motors run locked out timing, so we have anywhere from 36 to 38 degrees in them from idle on. No problems typically if you don't lug your engine. My current 06 Street Glide is anywhere from 22 to 24 degrees as idle, which helps cool the motor down substantially due to the simple fact its making more power on less fuel, and the fuel is burned more completely prior to the piston going down the hole, which heats up the motor. However, you run a higher NOX and CO emission.
End of class.
Lift is free hp, provided that the ports can handle the increased flow.
A longer duration will bleed off cylinder pressure and without an increase in compression, will kill low end.
The greatest event that controls the level where the engine makes its power band is the closing of the intake valve, period.
If you want to make some serious lope, without killing your low end, you need to look for a camshaft combination with a tight lobe center, say in the 105 to 108 degree area. This will do two things. 1. it will allow an earlier closing of the intake event and boost the mid range of the engine's power band. 2, it will increase the overlap of the intake and exhaust events, and give you that rough idle that you are looking for.
The flip side is a tight lobe center will narrow the power band of the engine, whereas a wide lobe center will smooth out the idle and have a flatter torque curve in the engine, and possibly make a bit more power in the upper end of the engine.
Prostock engines run in the 9000 plus range and even with intake and exhaust timing at over 295 degrees at .050 lift, they idle really smooth due to lobe centers at well over 116 to 118 degrees. A short track motor is rough idling, even though the duration at .050 is in the 250 to 260 degree range.
Lastly, lift for the most part can't hurt HP, only help it, when the duration is the same. Its referred to the area under the curve. The only parts that take a beating however is the valve springs and lifters that have to deal with the increased load on them.
Adjusting the timing with a split combination as suggested is micky mouse at best. I'd opt for looking for a cam that has a marginal increase in duration at .050, with a tighter lobe center to get you what you want.
As a side note, all my race motors run locked out timing, so we have anywhere from 36 to 38 degrees in them from idle on. No problems typically if you don't lug your engine. My current 06 Street Glide is anywhere from 22 to 24 degrees as idle, which helps cool the motor down substantially due to the simple fact its making more power on less fuel, and the fuel is burned more completely prior to the piston going down the hole, which heats up the motor. However, you run a higher NOX and CO emission.
End of class.
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Dagobert (12-23-2019)
#14
09-18-2007 | 02:03 PM
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5th Gear
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RE: Timing advance at idle
You my friend are a genious.....
I have noticed that since i increased my timing curve to be higher at idle to 1200 rpm it is much cooler runing did not change much for the idle or rumble........but the bike is much more powerful from traffic lights! I understand your cam class do you know any cam part #'s that you would suggest, keeping the rest as stock as possible. Thanks guys.
[IMG]local://upfiles/41767/E3C575EFBE2042048D39BE987C1A42CE.jpg[/IMG]
I have noticed that since i increased my timing curve to be higher at idle to 1200 rpm it is much cooler runing did not change much for the idle or rumble........but the bike is much more powerful from traffic lights! I understand your cam class do you know any cam part #'s that you would suggest, keeping the rest as stock as possible. Thanks guys.[IMG]local://upfiles/41767/E3C575EFBE2042048D39BE987C1A42CE.jpg[/IMG]
#15
09-18-2007 | 05:33 PM
Novice
Joined: Aug 2007
Posts: 19
Likes: 1
From:
RE: Timing advance at idle
I'm not sure of the exact specs of your cam, but I would guess its in the 215-220 degree range at 050 with a wide lobe center of say 112 to 115 degrees. I'm sure someone has the exact specs out there, and I belive I have seen them myself.
I would say I'd increase your duration no more than 10 degrees if you are doing nothing else to the motor, otherwise you will have a very lazy soft motor. I could care less about articles that boast peak HP numbers, because we all rarly ever drive in the 5000 - 6000 rpm range, plus once you shift you are well below the torque curve.
I'd call any of the cam companies and tell them you want a tighter lobe center to pick up the mid range. One company (comp cams) has come out with a series for cars (harleys too?) where the lobe centers are really tight to give a really rough idle. I think they are in the 102 to 104 range.
Side note, lobe center is the point where the valve is at maximum lift in the cycle of the piston, as well as the amount of degrees between intake and exhaust maximum lift. Smaller lobe centers mean you are delaying the exhaust opening, and opening up the intake sooner as well as closing the intake sooner (remember I mentioned in the previous post that the greatest important event is the closing of the intake valve). What happens is your overlap period is longer with both valves being open at the same time longer, so at low rpms you have more reversion in the intake tract which gives you the lump lump due to exhaust dilution.
Last note, since the intake is opening later and the exhaust is closing sooner, you have to really watch your piston to valve clearances.
I'm glad the timing helped. Harley really has a retarded timing which makes me think its emissions, and nothing else. Heck, in some motors with vacuum advances, we are able to get 50 plus degrees as part throttle, as long as the mixture isn't too lean.
I would say I'd increase your duration no more than 10 degrees if you are doing nothing else to the motor, otherwise you will have a very lazy soft motor. I could care less about articles that boast peak HP numbers, because we all rarly ever drive in the 5000 - 6000 rpm range, plus once you shift you are well below the torque curve.
I'd call any of the cam companies and tell them you want a tighter lobe center to pick up the mid range. One company (comp cams) has come out with a series for cars (harleys too?) where the lobe centers are really tight to give a really rough idle. I think they are in the 102 to 104 range.
Side note, lobe center is the point where the valve is at maximum lift in the cycle of the piston, as well as the amount of degrees between intake and exhaust maximum lift. Smaller lobe centers mean you are delaying the exhaust opening, and opening up the intake sooner as well as closing the intake sooner (remember I mentioned in the previous post that the greatest important event is the closing of the intake valve). What happens is your overlap period is longer with both valves being open at the same time longer, so at low rpms you have more reversion in the intake tract which gives you the lump lump due to exhaust dilution.
Last note, since the intake is opening later and the exhaust is closing sooner, you have to really watch your piston to valve clearances.
I'm glad the timing helped. Harley really has a retarded timing which makes me think its emissions, and nothing else. Heck, in some motors with vacuum advances, we are able to get 50 plus degrees as part throttle, as long as the mixture isn't too lean.
ORIGINAL: Racerx296
You my friend are a genious..... I have noticed that since i increased my timing curve to be higher at idle to 1200 rpm it is much cooler runing did not change much for the idle or rumble........but the bike is much more powerful from traffic lights! I understand your cam class do you know any cam part #'s that you would suggest, keeping the rest as stock as possible. Thanks guys.
[IMG]local://upfiles/41767/E3C575EFBE2042048D39BE987C1A42CE.jpg[/IMG]
You my friend are a genious.....
I have noticed that since i increased my timing curve to be higher at idle to 1200 rpm it is much cooler runing did not change much for the idle or rumble........but the bike is much more powerful from traffic lights! I understand your cam class do you know any cam part #'s that you would suggest, keeping the rest as stock as possible. Thanks guys.[IMG]local://upfiles/41767/E3C575EFBE2042048D39BE987C1A42CE.jpg[/IMG]
#17
12-23-2019 | 09:13 PM
Intermediate
Joined: Aug 2019
Posts: 49
Likes: 6
From: the Netherlands (Holland) _ Leiden (your 'Founding Fathers' original city of residence)
You guys need to go to CAMs 101. Most if not all answers are incorrect.
Lift is free hp, provided that the ports can handle the increased flow.
A longer duration will bleed off cylinder pressure and without an increase in compression, will kill low end.
The greatest event that controls the level where the engine makes its power band is the closing of the intake valve, period.
If you want to make some serious lope, without killing your low end, you need to look for a camshaft combination with a tight lobe center, say in the 105 to 108 degree area. This will do two things. 1. it will allow an earlier closing of the intake event and boost the mid range of the engine's power band. 2, it will increase the overlap of the intake and exhaust events, and give you that rough idle that you are looking for.
The flip side is a tight lobe center will narrow the power band of the engine, whereas a wide lobe center will smooth out the idle and have a flatter torque curve in the engine, and possibly make a bit more power in the upper end of the engine.
Prostock engines run in the 9000 plus range and even with intake and exhaust timing at over 295 degrees at .050 lift, they idle really smooth due to lobe centers at well over 116 to 118 degrees. A short track motor is rough idling, even though the duration at .050 is in the 250 to 260 degree range.
Lastly, lift for the most part can't hurt HP, only help it, when the duration is the same. Its referred to the area under the curve. The only parts that take a beating however is the valve springs and lifters that have to deal with the increased load on them.
Adjusting the timing with a split combination as suggested is micky mouse at best. I'd opt for looking for a cam that has a marginal increase in duration at .050, with a tighter lobe center to get you what you want.
As a side note, all my race motors run locked out timing, so we have anywhere from 36 to 38 degrees in them from idle on. No problems typically if you don't lug your engine. My current 06 Street Glide is anywhere from 22 to 24 degrees as idle, which helps cool the motor down substantially due to the simple fact its making more power on less fuel, and the fuel is burned more completely prior to the piston going down the hole, which heats up the motor. However, you run a higher NOX and CO emission.
End of class.
Lift is free hp, provided that the ports can handle the increased flow.
A longer duration will bleed off cylinder pressure and without an increase in compression, will kill low end.
The greatest event that controls the level where the engine makes its power band is the closing of the intake valve, period.
If you want to make some serious lope, without killing your low end, you need to look for a camshaft combination with a tight lobe center, say in the 105 to 108 degree area. This will do two things. 1. it will allow an earlier closing of the intake event and boost the mid range of the engine's power band. 2, it will increase the overlap of the intake and exhaust events, and give you that rough idle that you are looking for.
The flip side is a tight lobe center will narrow the power band of the engine, whereas a wide lobe center will smooth out the idle and have a flatter torque curve in the engine, and possibly make a bit more power in the upper end of the engine.
Prostock engines run in the 9000 plus range and even with intake and exhaust timing at over 295 degrees at .050 lift, they idle really smooth due to lobe centers at well over 116 to 118 degrees. A short track motor is rough idling, even though the duration at .050 is in the 250 to 260 degree range.
Lastly, lift for the most part can't hurt HP, only help it, when the duration is the same. Its referred to the area under the curve. The only parts that take a beating however is the valve springs and lifters that have to deal with the increased load on them.
Adjusting the timing with a split combination as suggested is micky mouse at best. I'd opt for looking for a cam that has a marginal increase in duration at .050, with a tighter lobe center to get you what you want.
As a side note, all my race motors run locked out timing, so we have anywhere from 36 to 38 degrees in them from idle on. No problems typically if you don't lug your engine. My current 06 Street Glide is anywhere from 22 to 24 degrees as idle, which helps cool the motor down substantially due to the simple fact its making more power on less fuel, and the fuel is burned more completely prior to the piston going down the hole, which heats up the motor. However, you run a higher NOX and CO emission.
End of class.
Thank you Hasselbach !
Very Interesting lesson, I can learn a lot from you...!
I noticed that you havent been here for more then 11 years now.
Are you still alive?
Are you still available?
Please let me know, I like to ask some questions about this.
Greetings,
Jochem
Leiden _ the Netherlands (your 'Founding-Fathers previous city of residence')
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