Stroking your crank (Retards the timing)

Duster · #21 (**permalink**) 03-10-2010, 05:01 PM

Quote: Originally Posted by Dust Devil

Quote: Originally Posted by Duster

Quote: Originally Posted by Dust Devil

Will place the piston higher or lower in the cylinder at the time of spark firing...

or Dwell timing...

OK... a clock is a good timing analogy...

lol

...

When it is 12 o'clock... it's 12 o'clock.
(TDC)

It does not matter how big the clock is, or how long the hands are.
(how big the crank is or how long the rod is)

You argument is based on Diesel ignition to compression (TDC)
I'm talking about Gasoline engines using a spark to ignite the fuel/air mixture... (BTDC)

Stroke to Rod Ratio

What causes a clock to speed up or slow down. Longer or shorter arms or stroke.....Longer or shorter stroke cause a different crank angle to piston position in the cylinder....

WHAT THE HECK IS A STROKER?
What the heck is a Stroker Crank?

Quote: Originally Posted by Dust Devil

The stroke of the KFX450R is 62.1mm (The timing for the ignition,fuel injector and the valves are fixed to 62.1mm stroke...) 7 degrees (BTDC)

The Crankshaft (sensor) is fixed and cannot be moved to (any) increase or decrease of stroke displacement... any change to piston linear distance (Stroke) also has to be re-align to (Sensor Rotor) as well as cam chain timing realignment...and extending its length.

Tne crank rotation= 63.1mm piston stroke +1mm
(The timing for the ignition,fuel injector and the valves are (fixed) to 62.1mm stroke...) 8 degrees (BTDC) spark firing...

Degrees vary in measurement as you increase the distance from center

This is an (Example)

Now slam the brakes on... this is what you don't get....

Nothing is "fixed to the stroke"... no-how, no-way.

Ignition timing and valve timing are all fixed to 2 full revolutions of the crankshaft.

You need to go back here and look at the diagrams.

What the heck is a Stroker Crank?

What creates a stroker crank is not advancing or retarding the crank pin position in rotation.

What makes a stroker is increasing the distance between the crank center and the crank pin vertically.

The piston pin is still indexed in the old rotational position, still indexed with the timing chain gear splines and the stator hub.

Here it is compared in motion...

The only thing that really changes in timing is piston dwell time.
Good for pulling in a charge, and good for burning it.

As you can see, the crank still only turns one RPM from TDC to TDC again.
The piston just moves further in that one RPM.

Dust Devil · #22 (**permalink**) 03-11-2010, 12:32 PM

Quote: Originally Posted by Duster

Quote: Originally Posted by Dust Devil

Quote: Originally Posted by Duster

OK... a clock is a good timing analogy...

lol

...

When it is 12 o'clock... it's 12 o'clock.
(TDC)

It does not matter how big the clock is, or how long the hands are.
(how big the crank is or how long the rod is)

You argument is based on Diesel ignition to compression (TDC)
I'm talking about Gasoline engines using a spark to ignite the fuel/air mixture... (BTDC)

Stroke to Rod Ratio

What causes a clock to speed up or slow down. Longer or shorter arms or stroke.....Longer or shorter stroke cause a different crank angle to piston position in the cylinder....

WHAT THE HECK IS A STROKER?
What the heck is a Stroker Crank?

Quote: Originally Posted by Dust Devil

The stroke of the KFX450R is 62.1mm (The timing for the ignition,fuel injector and the valves are fixed to 62.1mm stroke...) 7 degrees (BTDC)

The Crankshaft (sensor) is fixed and cannot be moved to (any) increase or decrease of stroke displacement... any change to piston linear distance (Stroke) also has to be re-align to (Sensor Rotor) as well as cam chain timing realignment...and extending its length.

Tne crank rotation= 63.1mm piston stroke +1mm
(The timing for the ignition,fuel injector and the valves are (fixed) to 62.1mm stroke...) 8 degrees (BTDC) spark firing...

Degrees vary in measurement as you increase the distance from center

This is an (Example)

Now slam the brakes on... this is what you don't get....

Nothing is "fixed to the stroke"... no-how, no-way.

Ignition timing and valve timing are all fixed to 2 full revolutions of the crankshaft.

You need to go back here and look at the diagrams.

What the heck is a Stroker Crank?

What creates a stroker crank is not advancing or retarding the crank pin position in rotation.

What makes a stroker is increasing the distance between the crank center and the crank pin vertically.

The piston pin is still indexed in the old rotational position, still indexed with the timing chain gear splines and the stator hub.

Here it is compared in motion...

The only thing that really changes in timing is piston dwell time.
Good for pulling in a charge, and good for burning it.

As you can see, the crank still only turns one RPM from TDC to TDC again.
The piston just moves further in that one RPM.

A Woodruff key or half-moon key, is a semicircular shaped, removable key that fits into a matching keyway cut into a shaft, leaving a protruding tab. The tab mates with a matching slot on a device mounted flush upon the shaft e.g. a pulley, thus preventing the device from freely rotating about the shaft. It is widely used in machine tools and in the automotive industry. A Woodruff key is also used as a shear pin on some power take off devices and on such implements as snowblowers and marine propellers.

And mill a new slot in the proper location on the crankshaft.

A keyway is a longitudinal slot or notch usually milled into the outside of a cylindrical machine shaft, or into the inside hole of a pulley or gear, all of which indentations are intended to accept a small rectangular metal key or semi-circular bit of metal (known as a Woodruff key). This provides one way of locking pulleys, gears, and other parts to shafts so as to prevent relative angular movement, but either relative axial movement is allowed, or other means are needed to prevent relative axial movement. A "Scotch Key" also provides a keyway not by milling but by drilling axially into the part and the shaft, so that a round key can be used.

You can use a degree wheel or the alternator rotor timing mark (TDC) without the key so the gears on the crank can move showing the new location for the "Keyway"...

(It's the only way to reset "All timing" to factory spec's)

ICS cutting tools ICS Cutting Tools - woodruff key seat cutters

Then the KFX450R stand a chance against the KTM 525 until they decide to up-grade their stroke....

P.s All timing is fix to the crankshafts keyway preventing the cam chain gear and the alternator rotor from moving or to be moved...

and "All" of the electronic timing is "fixed" the a non-adjusting crankshaft sensor and a locked rotor by way of the "Woodruff key"...

not like the good ol' days being able to adjust a "Magneto" or CDI...

capacitor discharge ignition....

(See manual) electrical system 16-35.

Dust Devil · #23 (**permalink**) 03-12-2010, 12:03 PM

"Sorry" for the confusion I'm mean that stroking your crank will advance your timing and will cause Pre-ignition and severe "Detonation" to occur...
"Again Sorry" I just want to clearify....

Ignition timing - Wikipedia, the free encyclopedia

"Timing advance" refers to the number of degrees before top dead center (BTDC) that the spark will ignite the air-fuel mixture in the combustion chamber during the compression stroke. Retarded timing can be defined as; changing the timing so that fuel ignition happens later than the manufacturer's specified time. If the ignition timing,

Retarding the cam timing can also lower cylinder pressures to reduce detonation at low r.p.m., but doing so hurts low speed torque which is not recommended for street engines or cars with automatics.

You can't adjust your initial timing setting,which will throw off all of your ignition timing curves causing "Detonation" to happen.

4. Check for over-advanced ignition timing. Too much spark advance can cause cylinder pressures to rise too rapidly. If resetting the timing to stock specifications doesn't help, retarding the timing a couple of degrees and/or recalibrating the distributor advance curve may be necessary to keep detonation under control.

Instead of the fuel igniting at the right instant to give the crankshaft a smooth kick in the right direction, the fuel ignites prematurely (early) causing a momentarily backlash as the piston tries to turn the crank in the wrong direction. This can be very damaging because of the stresses it creates. It can also localize heat to such an extent that it can partially melt or burn a hole through the top of a piston!

Detonation
Under normal conditions, the combusting air and fuel mixture inside the combustion chamber ignites in a controlled manner. The mixture is ignited by the spark, normally in the centre of the cylinder, and a flame front moves from the spark towards the outside of the cylinder in a controlled burn. Detonation, or engine knock, occurs simply when fuel pre-ignites before the piston reaches scheduled spark ignition. This means that a powerful explosion is trying to expand a cylinder chamber that is shrinking in size, attempting to reverse the direction of the piston and the engine. Causing sudden pressure changes in the cylinder (Up to 10x that normally experienced), and extreme temperature spikes that can be very damaging on engine pistons, rings, rods, gaskets, bearings, and even the cylinder heads.
Even the best engine components cannot withstand severe detonation for more than a few seconds at a time. More severe detonation obviously leads to more severe forms of engine damage. If there is enough heat and pressure in the combustion chamber, detonation can begin to occur before the spark plug even fires, which would normally initiate the combustion. Under these circumstances, known as "pre-ignition", the piston may be travelling up towards a wave of compressed, exploding gas. These are the worst kinds of detonation conditions, and can bend con-rods and destroy pistons.

Duster · #24 (**permalink**) 03-12-2010, 11:28 PM

Man the cam timing and spark timing will be the same.

The only way you could mess that up would be to move the pin location forward/backward in position in relation to the crankshaft spline indexes for the cam chain sprocket and stator rotor hub.

And there is absolutely no reason why anyone would want to do that. There is no point to it... and if they did, no one would ever want a stroker. It would be too much trouble/work to get the timing right, and trial/error would be at the expense of the whole top end. The piston and valves would hit! There is typically not very much tweaking room on valve timing without contact... and it is typically advanced... for earlier valve opening.

Anyways, good support for both is this... consider the Sparks timing advance key sold for the Honda 400EX. It's a 6 degree advance in valve timing... about the max.

Dust Devil · #25 (**permalink**) 03-13-2010, 01:12 PM

Quote: Originally Posted by Duster

Man the cam timing and spark timing will be the same.

The only way you could mess that up would be to move the pin location forward/backward in position in relation to the crankshaft spline indexes for the cam chain sprocket and stator rotor hub.

And there is absolutely no reason why anyone would want to do that. There is no point to it... and if they did, no one would ever want a stroker. It would be too much trouble/work to get the timing right, and trial/error would be at the expense of the whole top end. The piston and valves would hit! There is typically not very much tweaking room on valve timing without contact... and it is typically advanced... for earlier valve opening.

Anyways, good support for both is this... consider the Sparks timing advance key sold for the Honda 400EX. It's a 6 degree advance in valve timing... about the max.

[quote=Duster;45706]Man the cam timing and spark timing will be the same. Correct!

But the piston is (Placed) in a new location (at the spark timing) due to the addition of the displacement. Adding stroke! Adds Displacement or (CC)

The trick to the ignition system is in when the spark actually occurs at the spark plug. This is the ignition TIMING. Timing is controlled by the relationship of the position of the piston to when the spark occurs. If the ignition spark occurs too soon it can actually push against a piston traveling up the cylinder as it is compressing the fuel/air mixture. This causes detonation, lost power, much higher combustion temperatures, backfires out the carburetor, and early internal engine part failures. If the spark occurs too late, the ignition of your fuel mixture occurs after the piston is traveling back down the cylinder. This is wasted energy, unburned fuel, high emissions, and lost power.

How do you control the timing you ask? Well, late model cars use computers that monitor engine load, piston position, incoming air quality and temperature, engine RPM, and more. The computer then tells the ignition system what the engine needs based upon those inputs from the sensors and a pre-determined MAP within the computers' programming. On older OEM engines, and most race cars with aftermarket distributors, the ignition system used a simple mechanical advance (or a combination of mechanical and vacuum advance) system built into the distributor. You would set "initial" idle timing with a timing light looking at the balancer mark and timing tab indicator. As RPM increases, the mechanical advance (weights and springs) moves due to the inertia occurring within the distributor, thereby changing the timing causing the point that the spark plug receives voltage to also change in relation to piston location. You can tune your timing curve (shown later on this page) for your engine's optimum performance curve by changing initial, mechanical as well as vacuum advance settings and parameters.

What this means is that if you have your initial timing setting at 10° advanced, your ignition is firing that cylinder at ten degrees "before" top dead center (BTDC). TDC is where the piston is at it's highest point in the cylinder. As engine RPM increases there is less time to be able to fire the cylinder. The parts are moving faster so you must get the spark in there sooner, but not too soon that it will cause detonation or engine damage.

Say for example that you have that 10° initial timing and then you have mechanical advance of 24°. This means you have a "Total" timing of 34°.

10 + 24 = 34

Now, that 34° does not happen all at once ... the "Timing Curve" is the staging of advances, or increases, in your timing. Remember, as the RPM increases it puts inertia against the weights and springs that move in the distributor causing this added timing. All of these values are adjustable by changing initial settings, the weights that control the MAX advance, as well as the spring pressures that control the RATE (or speed) of advance..

Now, when adding vacuum advance to the equation you would have the total (34 degrees) PLUS the additional vacuum advance. On a street application, adding 8-10 degrees is plenty. But, each individual application will vary slightly.

What is Initial Timing and Total Timing?

Initial timing is that setting you make while your engine is idling with a timing light. This is typically between 4° ATDC (After Top Dead Center) to 16° BTDC (Before Top Dead Center). For performance applications "in most cases" you want as much initial timing as the starter can handle (the more timing the more cylinder pressure that the starter must overcome to crank the engine). Too much initial timing, besides the starter load, can also run the HC (Hydrocarbon) emission levels beyond legal or breathable levels <hint to the smog machine as a tuning tool above>.

Total timing is the calculation of the combined initial and mechanical advance timing settings (max). This "can" also include your vacuum advance though, I like to describe it as "total timing plus vacuum advance". Since vacuum advance is a nearly inconsistent value I like to use it after I have set up the correct mechanical values in the distributor. At times I must use the vacuum advance to generate the timing values I require, but I try to only use it as an "economy" tool to give a street driven vehicle more efficiency and throttle response by this addition. Electronic Timing Controls and Retards serve as an added feature to making sure that the timing curve is "exactly" what your engine demands to make maximum horsepower and torque and prevent engine damage when using high power engine upgrades such as nitrous, superchargers, etc. Electronic timing controls in many cases give you full computerized programming capabilities of your timing curve, eliminating the sometimes binding and inaccurate mechanical advance controls. The timing retards allow you to select degrees of retard based upon your engine demands. From a high speed retard (your engine needs a bit less timing in many instances in racing applications at high RPM or top gear), to retarding the timing based upon the amount of boost from superchargers to the use of selected retard settings upon activating a nitrous system. This retard also works well l as based upon exceeding normal engine loads or fuel quality in street use towing applications to eliminate engine damage from detonation and other occurrences.