Dumb Question of the day

[OUTFXD]

Sorry about this,  my brain just went blank

 

Doing timing on Jacquiline.

 

"Advanced"  means before top dead center and "Retard" means AFTER top dead center. 

 

Is that correct or do I have it backwards?

 

[capt den]

correct

[keithb7]

Think of it like this: When the spark fires, the air/fuel mixture ignites. The flame starts at the spark plug and travels away from it.  The flame burns at a pretty constant rate of speed. It needs to burn at just the right time as the piston moves up and down.  If if ignites too soon if will impede piston travel. Ic it fires too late we don’t get good use of the combustion process. Wasting power. The flame travel speed stays the same. Yet piston travel speed varies widely as engine rpms rise and decrease. 
 

When a piston travels faster we need to advance the spark timing. So it fires sooner. The slow burning flame isn’t able to keep up with piston speed. So in an attempt to burn the air/fuel mixture at precisely the right time to match piston speed, we advance the timing. The spark fires sooner.   When the engine is turning over slow the timing is retarded so the spark fires later. 
 

In old cars, they manually retarded the timing by way of a lever at the steering wheel. So the driver could start the engine easier, with a hand crank.  You’ve got a slow turning engine when cranking iit by hand, so timing needs to be retarded. It also prevents a possible engine backfire. So you didn’t break your arm, hand, thumb or dislocate your shoulder . 
 

Later they invented a vacuum pot. It has a spring inside it. When the engine is not running the spring mechanically retards the timing. Holding it back. The operator need not do anything but hit the starter. As soon as the engine is running vacuum is created in the intake. A steel line from the intake (at base of the carb) travels over and hooks up to the vacuum pot at the distributor. Immediately the vacuum created by the running engine sucks the vacuum pot linkage, pulling it. Overcoming the spring in the pot. Removing the spark advance that the spring is putting on the timing.  Timing sits there till the engine revs up. Vacuum then drops as throttle valve opens. Now mechanical centrifugal weights take over. Creating spark advance as the engine revs up.

 

Its all very cool.  I am still very impressed by the developments they came up with so long ago. Delco-Remy were leaders and made massive improvements to the ignition system.  DelcoRemy deserve massive credit for what they achieved. 

Edited December 23, 2022 by keithb7

[rallyace]

Advance means earlier in the cycle, retard means later in the cycle.

[Loren]

For your entertainment:

Delco-Remy was of course two companies at one time. Remy had a perfectly awful reputation while Charles Kettering's Dayton Electric Co. had a perfectly awesome one. Billy Durant was cognizant that his Buick buyers first trip in their new cars was to the Bosch dealer to replace the crummy Remy ignition. Durant who was more of a stock market guy than a car guy wheeled and dealt until he owned both companies. He merged a sick company to a strong one and got Kettering in the bargain, which by itself proved to be the best part of the deal.

The point type ignition, more accurately called Battery Coil Ignition was invented by Mr Kettering ( along with the self starter, a host of other key automotive innovations not the least of which was the perfection of Winton's 2 cycle diesel engine which became Detroit Diesel )

Delco-Remy benefits to this day from Kettering's legacy of scientific research which just in time for World War ll included Tetra-Ethyl-Lead fuel additive for high compression engines. We owe the development of the post war High Compression Overhead Valve V8 engines to Mr Kettering's fuel research.

 

Billy Durant's stock speculation brought together all of the best people to create General Motors and they all seemed to have passed through Buick at one time. Charles Nash and Walter Chrysler both went on to create their own cars. Durant was thrown out of GM not once but twice. His major contribution to the company was the people he brought to it by his stock market activities which ultimately was his down fall.

[OUTFXD]

3 hours ago, rallyace said:

Advance means earlier in the cycle, retard means later in the cycle

 

Thats what blocked my brain up.  My brain wanted "Advance" to mean advance the timing to later in the cycle and retard to mean reduce the timing to earlier in the cycle.

 

Let that be a lesson! Never trust your brain!