What will retarding timing do?

Ignition timing retarding causes the spark plug to fire later in the compression stroke. The effects of retarding ignition timing include reducing engine detonation, which is combustion inside the cylinders after the spark plug fires. This is also known as engine knocking.

What are the effects of retarded cam timing?

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 does retarded ignition timing mean?

Retarded timing can be defined as changing the timing so that fuel ignition happens later than the manufacturer's specified time. For example, if the timing specified by the manufacturer was set at 12 degrees BTDC initially and adjusted to 11 degrees BTDC, it would be referred to as retarded.

What does retarding a camshaft do?

Advancing or retarding the cam pushes the centerline of the camshaft to one side or the other of the crankshaft centerline. This changes the Timing of the valve opening and closing events, in relation to the position of the piston in the cylinder.

Does advancing timing increase idle?

Our experience shows that connecting the vacuum advance to a manifold vacuum source will add timing at idle and improve idle quality in gear with an automatic transmission. Milder applications can also benefit from this idea but will require some experimentation.

IGNITION TIMING SIMPLIFIED | The secrets of spark tuning revealed

Does advancing a cam increase compression?

Overlap causes a "scavenging effect" as the engine RPM increases. This is why performance cams "come alive" at higher RPMs. It's not "just" the cam making the power, it's the cam's scavenging effect working as the RPM increases which increases cylinder pressure (dynamic or effective compression).

What does advancing a cam 2 degrees do?

If you advance your cam 2 degrees based on the numbers shown on the degree wheel, you are physically advancing the cam only 1 degree, though it will show up as two degrees when you check the intake or exhaust timing at . 050, as compared to the cam card.

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.

How much HP affects compression?

The generally accepted gauge for adding compression is that one full point of compression can add between 3 to 4 percent power. So, if an engine is making 50 horsepower and we add a full point of compression (from 11 to 12:1 for example), this could potentially push the power to 51.5 horsepower.

What is the compression ratio for 93 octane?

However, general guidelines would be that if you car has a high compression ratio, above 8.5:1 you should use 95, and if your car has a compression ratio below 8.5:1 you should use 93.

What octane do you use for 10 1 compression?

Most stock gas engines have a compression ratio around 10:1 and run just fine on regular 87-octane gas.

What is the compression ratio for 91 octane?

The generally accepted conservative estimate is 8.0 to perhaps 8.5:1 dynamic compression ratio for 91 octane pump gas. This tends to be true for older, traditional engines with less effective combustion chambers. But for later model engines with better chambers, that could be improved to 9.0:1 dynamic.

Why are cams ground with advance?

Ground-in advance opens the intake valve sooner. This moves the torque peak lower in the rpm range. Camshafts designed for street and towing vehicles will often have ground-in advance. Follow this link to learn more about Advancing a Camshaft.

Can Cam Timing cause low compression?

If the camshaft timing is very wrong, it can also cause the valves to hit the pistons and bend them in most engines, which will cause no compression in your engine. If you have low compression on all cylinders, it is definitely time to check the camshaft timing.

How does cam centerline affect performance?

Put simply, we can say that a tight LCA cam produces a power curve that is, for want of a better description, more "punchy." At low rpm when off the cam, it runs rougher, and it comes on the cam with more of a "bang." A cam on wide centerlines produces a wider power band.

Why is intake lobe centerline important?

By advancing or retarding centerline, you can change your engine's entire powerband. For example, advancing intake centerline will shift the rpm range downward; retarding the intake centerline will move the range upward.

What happens if timing is too far advanced?

Overheating: If the air and fuel mixture is ignited too soon in the combustion process, the heat generated will increase. This can damage different parts of the engine. Low Power: Ignition timing that is retarded too far can result in the spark plug igniting the mixture too late.

Does advancing timing increase mpg?

It advances the timing when there is vacuum in the intake manifold, except during idle (on most vehicles). It is needed for maximum efficiency because the fuel mixture burns slower when the pressure in the cylinder is lower. If it doesn't work, the engine will still make normal power but its fuel economy will go down.

When should you advance ignition timing?

In most cases, full advance (32 to 36 degrees) will have occurred before 3,500 rpm. An engine with camshaft duration of above 240 degrees, but less than 260 degrees of duration @ 0.050-inch valve lift, will respond well to 18 degrees of initial timing; however, the total timing will remain the same (32 to 36 degrees).

How does cam lobe separation affect idle?

“On a naturally aspirated engine, the lobe separation angle has an effect on whether the engine reaches peak torque a little earlier or later in the rpm range. Typically, narrower lobe separation develops peak torque at lower rpm and widening the separation tends to build peak torque higher in the rpm range.

How does LSA affect idle?

Tight LSA cams make excellent low-end torque and have a beautiful power curve. But nothing comes without a cost, and idle vacuum suffers as LSA shrinks. This causes the engine's street manners and tuning to become fickle.

How does valve overlap affect engine performance?

Valve overlap is designed into the engine and is most useful at higher speeds. At higher speeds, the extra amount of intake charge brought into the combustion chamber provides a substantial increase in available power. The amount of time that both valves are open in directly related to engine rpm.