Pin,
Getting back to your 650 project/ IgniTech: Vacuum advance??! Doesn't the mechanical advance satisfy any partial throttle/mileage issues ? I'm not familiar with your project, so let me apologize in advance.
The reason that I'm psyched about the GM ignitor is that I can make it "plug and play". In other words, I can easily stow another Hei module with some dielectric grease in the event of failure at the worst possible time. Because, as I'm sure you know, THAT is the time when Oki ignitors are likely to fail....
I agree completely about the GM ignitor system. However, as Kit said, I just can't leave well enough alone.
I've read articles most notably by David Vizard that stated that a correctly operating vacuum advance can increase mileage by 20% by itself.
HERE is the article.
Neither the canister on the distributor nor the MAP sensor, if you have an EFI engine, is there for decoration. Too many street rodders see that the pro racers use distributors without vacuum advance and figure if it’s good for the winning car it’s good for them. Unfortunately this is not so. Although a drag race car may not realize much in the way of an advantage, none of it performance related, it’s about the only type of race car that falls into this category. Here’s how the puzzle fits together.
When you back out of the throttle the manifold vacuum goes up. This means the compression pressure at the end of the compression stroke is way lower. When a spark timed for a normally fast burning charge (as it is at WOT) fires under these circumstances it is going to occur far too late for the pressure to be at it’s peak at 15 degrees after TDC. This means that less than optimal use of the energy content of the fuel has been made. That in turn means burning more fuel to get the level of power being demanded by the driver at that particular moment. By having vacuum advance pull in appropriately more timing you can let out of the throttle more and consequently cruise on less fuel.
...For you circle track racers here is something I want you to think about. If your car’s engine had vacuum advance it would get about 20% more mileage on the yellow flag laps. Just how many times have we seen a lead car run out of fuel with just half a lap to go?...
Just in case you want to take a look,
HERE is the main thread. The cylinder head is outlined
HERE and the pistons have been worked by Soos as shown
HERE.
Called out by a pinhead.
LOL!
