What exactly is cam surge???
What exactly is cam surge???
07-03-2003, 10:47 PM
#3
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Join Date: Aug 2000
Location: North Vancouver, BC
Posts: 4,305
Basicly big overlap at low rpm causes low BEMP / combustion pressure & causes very uneven engine airflow at those speeds cuz air comes in & lots escapes past the exhaust valve, we call this Effective compression, unlike static compression like 10.4:1 which is a stock engine, effective/trapped compression is how much air acctually gets compressed factoring in components like the camshaft, if most of the air escapes past the exhaust valve then you don't have much compression, & you have low power down low, you also suck in some of the exhaust gases back into your combustion chamber, thats why you have a ratical behaviour, as the RPM's climb you start to benifit from overlap because you get to cool your combustion chamber & with more duration you suck in more air, with small overlap you also open the intake sooner & exhaust later & since the air is being sucked in so fast, it doesn't get to excape past the exhaust valve, well atleast most of it doesn't, so these events become a benifit at high RPM as apposed to low RPM since you suck more in & exhaust later.
But basicly thats what cam surge is down low, & to make sure you dont go (so why don't we go stock) I explained the benifits of big cams, you sacrifice down low power for up top
But basicly thats what cam surge is down low, & to make sure you dont go (so why don't we go stock) I explained the benifits of big cams, you sacrifice down low power for up top
07-03-2003, 11:12 PM
#4
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Join Date: Nov 2001
Location: Kansas
Posts: 3,517
i think i know why but its difficult to explain.. here goes.
an aftermarket cam has larger lobes which keep the valves open longer.. this in turn slows down the combustion process. it takes more time for the cam and crank to make a complete revolution. this is most evident in the lower RPMs b/c the combustion isnt fast enough to spin the crank to where its a fluid clean motion and instead gets all choppy which is naturally transfered to the rear wheels... you have cam surge.
an aftermarket cam has larger lobes which keep the valves open longer.. this in turn slows down the combustion process. it takes more time for the cam and crank to make a complete revolution. this is most evident in the lower RPMs b/c the combustion isnt fast enough to spin the crank to where its a fluid clean motion and instead gets all choppy which is naturally transfered to the rear wheels... you have cam surge.
07-04-2003, 12:20 AM
#5
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Join Date: Apr 2002
Location: sebewaing, mi
Posts: 1,309
Originally posted by bunker
Basicly big overlap at low rpm causes low BEMP / combustion pressure & causes very uneven engine airflow at those speeds cuz air comes in & lots escapes past the exhaust valve, we call this Effective compression, unlike static compression like 10.4:1 which is a stock engine, effective/trapped compression is how much air acctually gets compressed factoring in components like the camshaft, if most of the air escapes past the exhaust valve then you don't have much compression, & you have low power down low, you also suck in some of the exhaust gases back into your combustion chamber, thats why you have a ratical behaviour, as the RPM's climb you start to benifit from overlap because you get to cool your combustion chamber & with more duration you suck in more air, with small overlap you also open the intake sooner & exhaust later & since the air is being sucked in so fast, it doesn't get to excape past the exhaust valve, well atleast most of it doesn't, so these events become a benifit at high RPM as apposed to low RPM since you suck more in & exhaust later.
But basicly thats what cam surge is down low, & to make sure you dont go (so why don't we go stock) I explained the benifits of big cams, you sacrifice down low power for up top
Basicly big overlap at low rpm causes low BEMP / combustion pressure & causes very uneven engine airflow at those speeds cuz air comes in & lots escapes past the exhaust valve, we call this Effective compression, unlike static compression like 10.4:1 which is a stock engine, effective/trapped compression is how much air acctually gets compressed factoring in components like the camshaft, if most of the air escapes past the exhaust valve then you don't have much compression, & you have low power down low, you also suck in some of the exhaust gases back into your combustion chamber, thats why you have a ratical behaviour, as the RPM's climb you start to benifit from overlap because you get to cool your combustion chamber & with more duration you suck in more air, with small overlap you also open the intake sooner & exhaust later & since the air is being sucked in so fast, it doesn't get to excape past the exhaust valve, well atleast most of it doesn't, so these events become a benifit at high RPM as apposed to low RPM since you suck more in & exhaust later.
But basicly thats what cam surge is down low, & to make sure you dont go (so why don't we go stock) I explained the benifits of big cams, you sacrifice down low power for up top
i was under the impression that cam surge was just the area below the power band, which doesn't produce the power until you hit the power band. reason for this i think turbo z explained, airflow is blubbered up and doesn't smooth out until higher rpms. same idea as why bigger cams need higher idles.
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