Re: 123 Ignition Tune
Posted: Wed Aug 29, 2012 9:57 pm
You measure MAP (manifold absolute pressure) and manifold vacuum at the same place on an engine. A MAP sensor is measuring absolute pressure, a vacuum gauge measures it relative to air pressure.
RPM tells you what speed you are at it does not tell you whether you are accelerating, cruising or decelerating. Or put another way whether you are wide open throttle (WOT), partial throttle or closed throttle.
Adding a MAP sensor into the equation allows this unit understand what is currently being asked of the system.
As Vernon(2) says this is what a vacuum dizzy did back in the day.
It may well be that taking a MAP reading from a single barrel causes issues. Not because this is inaccurate as all your barrels _should_ be doing the same thing. But as Vernon(2) says perhaps low rpm pulsing would be an issue. However since the unit obviously knows the RPM they should be able to apply a suitable filter (doesn't mean they have!). That said there are folks over on Keith's yahoo site having fun and success with mechanical vacuum advance units so my hunch is that you would be OK.
Vernon(2) is correct in that the points in the picture are specifically for testing airflow at each barrel not the actual adjusters.
As to what sums the 123tune might be doing we would have to look closer (I will be). In a mapped ignition system you would ideally be able to specify the advance on a table with RPM on one axis and MAP on the other. Then you could optimize all the points. Of course a really comprehensive system should be looking a trends in an attempt to predict what to do next, eek! Before we get too tweaky we are forgetting that we have no active control over the fuel. In an injected system (like what V2 has) the MAP is used to measure the air mass and instruct the system on how much fuel to deliver to achieve max power or max efficiency depending on the demand. So the 123Tune has to hope that the webers are providing a suitable mixture in the first place - hmm I wonder how to do this...
Still the idea of this unit appeals even if the MAP proves somewhat difficult to do. If I needed a new dizzy right now I would get one of these (assuming it fits). Of course I'm a sucker for this kind of stuff!
Simon
RPM tells you what speed you are at it does not tell you whether you are accelerating, cruising or decelerating. Or put another way whether you are wide open throttle (WOT), partial throttle or closed throttle.
Adding a MAP sensor into the equation allows this unit understand what is currently being asked of the system.
As Vernon(2) says this is what a vacuum dizzy did back in the day.
It may well be that taking a MAP reading from a single barrel causes issues. Not because this is inaccurate as all your barrels _should_ be doing the same thing. But as Vernon(2) says perhaps low rpm pulsing would be an issue. However since the unit obviously knows the RPM they should be able to apply a suitable filter (doesn't mean they have!). That said there are folks over on Keith's yahoo site having fun and success with mechanical vacuum advance units so my hunch is that you would be OK.
Vernon(2) is correct in that the points in the picture are specifically for testing airflow at each barrel not the actual adjusters.
As to what sums the 123tune might be doing we would have to look closer (I will be). In a mapped ignition system you would ideally be able to specify the advance on a table with RPM on one axis and MAP on the other. Then you could optimize all the points. Of course a really comprehensive system should be looking a trends in an attempt to predict what to do next, eek! Before we get too tweaky we are forgetting that we have no active control over the fuel. In an injected system (like what V2 has) the MAP is used to measure the air mass and instruct the system on how much fuel to deliver to achieve max power or max efficiency depending on the demand. So the 123Tune has to hope that the webers are providing a suitable mixture in the first place - hmm I wonder how to do this...
Still the idea of this unit appeals even if the MAP proves somewhat difficult to do. If I needed a new dizzy right now I would get one of these (assuming it fits). Of course I'm a sucker for this kind of stuff!
Simon