How do the hot rodders achieve their "thumpy" idle?
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Re: How do the hot rodders achieve their "thumpy" idle?
Lobe seperation angle. The lower the LSA (say a 108) the more over lap u have the more down low power u will make because there's more scavenging effect. The higher the LSA (say a 116) the less over lap u have which makes for a broader power band with good power up top. U want a higher lsa on a boosted car also so you don't have alot of wasted air going through the motor on over lap. I'm sure one can get into much more detail about this but thats kind of the gyst of it.
Mike
Mike
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Re: How do the hot rodders achieve their "thumpy" idle?
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#10
Re: How do the hot rodders achieve their "thumpy" idle?
Lobe seperation angle. The lower the LSA (say a 108) the more over lap u have the more down low power u will make because there's more scavenging effect. The higher the LSA (say a 116) the less over lap u have which makes for a broader power band with good power up top. U want a higher lsa on a boosted car also so you don't have alot of wasted air going through the motor on over lap. I'm sure one can get into much more detail about this but thats kind of the gyst of it.
Mike
Mike
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Re: How do the hot rodders achieve their "thumpy" idle?
just run big cams untuned with not enough fuel delivery at idle lol i think the point everyone is making is the lumpy idle isn't something you want to try and achieve if anything you want a idle thats as smooth as a baby's bottom
#13
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Re: How do the hot rodders achieve their "thumpy" idle?
Youtube vtec killers to get an idea of idle sound. And they don't come on cam till about 5000ish so driveability is gonna blow
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Re: How do the hot rodders achieve their "thumpy" idle?
It has very little to do with "crap" carburetors. My EFI V8 lopes just like a carbureted V8 with a large cam.
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Re: How do the hot rodders achieve their "thumpy" idle?
Very good answer! That late intake closing point is the primary cause to that lope too. At low speeds, that intake valve hangs open long enough for some of the burned exhaust gases to enter the intake manifold and basically cause a mild misfire in some cylinders.
It has very little to do with "crap" carburetors. My EFI V8 lopes just like a carbureted V8 with a large cam.
It has very little to do with "crap" carburetors. My EFI V8 lopes just like a carbureted V8 with a large cam.
#16
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Re: How do the hot rodders achieve their "thumpy" idle?
Very high compression and very big cams
http://www.youtube.com/watch?v=dHVCyj4GqPo
http://www.youtube.com/watch?v=KW7m-...9&feature=plcp
http://www.youtube.com/watch?v=dHVCyj4GqPo
http://www.youtube.com/watch?v=KW7m-...9&feature=plcp
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Re: How do the hot rodders achieve their "thumpy" idle?
Mike
#18
Re: How do the hot rodders achieve their "thumpy" idle?
Regarding both the same amount moves power up the band. Advancing both the same moves power down the band.
Since a lot of people advance the intake and retard the exhaust at the same time your original comments would apply to most situations, just not for the reason you thought.
#19
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Re: How do the hot rodders achieve their "thumpy" idle?
Yeah. I like The Pro 1s idle, as well as the Pro2s.
http://www.youtube.com/watch?v=Q0yMd...eature=related
http://www.youtube.com/watch?v=Q0yMd...eature=related
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#22
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Re: How do the hot rodders achieve their "thumpy" idle?
lol....all of those engines ARE 4 cylinders. The point is, it's not "cool" to make that noise, the ones that do are either purpose built or they are put together incorrectly and don't/won't run right. In this section, the general goal is to maximize all motor performance. I don't think wanting to make your car idle "lumpy" for no other reason than it sounds cool, really fits with this sections ideals.
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Re: How do the hot rodders achieve their "thumpy" idle?
lol....all of those engines ARE 4 cylinders. The point is, it's not "cool" to make that noise, the ones that do are either purpose built or they are put together incorrectly and don't/won't run right. In this section, the general goal is to maximize all motor performance. I don't think wanting to make your car idle "lumpy" for no other reason than it sounds cool, really fits with this sections ideals.
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Re: How do the hot rodders achieve their "thumpy" idle?
It has a larger cam, 235 degrees @ .050" to be precise.
#25
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