What causes a lumpy cam?
what makes the cam have that lumpy sound? The overlap of the exhaust valve closing and intake valve opening causes the engine to be inefficient at low speed which results in the lumpy idle. The closer the Lobe Seperation Angle the more the overlap, the more duration the more (typically) the overlap.
How do you get lumpy idle?
You can get a lumpy idle by retarding the timing and adding too much fuel.
What does lobe separation do for a cam?
Typically, narrower lobe separation develops peak torque at lower rpm and widening the separation tends to build peak torque higher in the rpm range. Nitrous engines, which make plenty of power and torque, often run wide lobe separation angles to moderate cylinder pressures and temperatures.
What is engine lope?
We say an engine “lopes” or “surges” at idle when RPMs cycle unsteadily up and down. For example, a car may surge at idle between 600 and 1000 RPM.
What causes lopey idle?
Lope is a result of the intake and exhaust valves both being open at the same time. This is called overlap. Mild cams have little or no overlap at any valve opening that makes a difference. Hotter aftermarket type cams have a lot because it aids high RPM breathing.
Does retarding the cam timing increase compression?
Effects of Changing the Cam Timing This changes the cylinder’s ability to build pressure. On the other hand, if the camshaft timing is retarded, the intake valve will close later (usually sometime during the compression stroke). It should be no surprise that this drops cranking compression and hurts low-rpm power.
What causes loping idle?
Many different problems could result in a rough idle for your car or truck, including: dirty fuel injectors, clogged air filters, bad spark plugs, and a variety of exhaust system issues. Let’s go over each of these causes in more detail and learn how they can be remedied.
Why do cammed cars lope?
Again, keeping all else constant, more duration will make the engine less efficient at low rpm, with more overlap dilution of the induction charge, and the later intake valve closing reducing the trapping efficiency. Therefore, a long-duration cam will cause rough running at idle (lope) and a loss of low-rpm torque.
Should I advance my camshaft?
One way to improve the low-speed torque on a camshaft with too much duration is to advance the intake lobe in relation to the exhaust. Advancing just the intake lobe opens and closes the intake valve sooner which is one way to help improve the low-speed torque.