AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,978
- Reaction score
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Go look into your Passenger-side primary throttle bore, and find the spark port.
The Spark port will not deliver signal to the Vcan until your throttle opens up to very near to the port.
As the throttle exposes the port fully, you will get max signal to the V-can.
From then on, the signal is governed by manifold vacuum. As the rpm climbs and the throttle goes towards WOT, the manifold vacuum will fall towards zero, taking the signal with it.
With a factory Vcan, you can delay the signal to the Vcan And in some instances, prevent the maximum amount from coming in, if you max the adjustment; but not all will do that, and there really is no good reason to try it.
The max amount of Power-Timing varies with the efficiency of the combustion chamber,cylinder pressure, local hotspots, AFR, altitude, Inlet air temp, and even coolant temps.
Factory open-type, cast-iron,chambers might accept 36*, but that doesn't mean, she wants it all the time. Some days she might accept it at 3000, others not until 3500 or even higher.
With timing; it's not the case of throwing as much at it as you can, as fast as you can, and hope she likes it. That's a good way to break parts. One more time; sneak up on it. Give the engine a chance to protest, before the damage gets done.
In first gear, the tires are gonna spin most of the way, if not all the way thru it. So, if sub-optimum timing loses you 10hp at 5000rpm, yur never gonna know it. And if the engine loses 10hp at 5000, that might translate to 5hp at 2500, which is gonna be close to the stall rpm. If the tires spin when you mash it, even your engine doesn't care about the 5 hp.
If you run the engine to redline, with a 904, on the 1-2 shift, the Rs will fall to 59% .. If you shift at 5500, that will be 3250, and your engine will be near to max timing. This is the time to try to be accurate about Power-Timing...... cuz with 3.23s say, this will be 50 mph, and second gear will go to 85@5500. That's a long pull, so every horsepower is gonna count. But if your power=timing is too much, not only will your car be slower, detonation is hammering your engine parts for the whole time,cuz at WOT in second gear, it's really hard to hear detonation. Like I said earlier, it is better to be 3 or 4 degrees short than even 1* too much.
Your power-Timing only becomes important in second gear from either stall, or to whenever the tires stop spinning, whichever comes first ...... to about 3500. In first gear, your engine is only gonna be in that zone for milliseconds, so it doesn't have to be perfect, as long as it ain't too much.
But in second gear, with tires NOT SPINNING, it could be in that zone from 50 to 55 mph (still with 3.23s) or up to a couple of seconds, So again, the timing doesn't have to be perfect in that zone, as long as it's not too much.
There is exactly one time when timing below 3500 is important, and that is while cruising. At this time, you want to be as close to perfect as possible. Thankfully, the window of perfection is an easy 4 to 6* wide .
So in all of this; the take-away should be, that the Power-Timing after 3500 is the one place where the timing should be as close to optimum as possible without being too much.
All other timings are built on top of the Power-Timing, by the advance starting point, the rate of advance springs, and by the V-can at PT.
The Spark port will not deliver signal to the Vcan until your throttle opens up to very near to the port.
As the throttle exposes the port fully, you will get max signal to the V-can.
From then on, the signal is governed by manifold vacuum. As the rpm climbs and the throttle goes towards WOT, the manifold vacuum will fall towards zero, taking the signal with it.
With a factory Vcan, you can delay the signal to the Vcan And in some instances, prevent the maximum amount from coming in, if you max the adjustment; but not all will do that, and there really is no good reason to try it.
The max amount of Power-Timing varies with the efficiency of the combustion chamber,cylinder pressure, local hotspots, AFR, altitude, Inlet air temp, and even coolant temps.
Factory open-type, cast-iron,chambers might accept 36*, but that doesn't mean, she wants it all the time. Some days she might accept it at 3000, others not until 3500 or even higher.
With timing; it's not the case of throwing as much at it as you can, as fast as you can, and hope she likes it. That's a good way to break parts. One more time; sneak up on it. Give the engine a chance to protest, before the damage gets done.
In first gear, the tires are gonna spin most of the way, if not all the way thru it. So, if sub-optimum timing loses you 10hp at 5000rpm, yur never gonna know it. And if the engine loses 10hp at 5000, that might translate to 5hp at 2500, which is gonna be close to the stall rpm. If the tires spin when you mash it, even your engine doesn't care about the 5 hp.
If you run the engine to redline, with a 904, on the 1-2 shift, the Rs will fall to 59% .. If you shift at 5500, that will be 3250, and your engine will be near to max timing. This is the time to try to be accurate about Power-Timing...... cuz with 3.23s say, this will be 50 mph, and second gear will go to 85@5500. That's a long pull, so every horsepower is gonna count. But if your power=timing is too much, not only will your car be slower, detonation is hammering your engine parts for the whole time,cuz at WOT in second gear, it's really hard to hear detonation. Like I said earlier, it is better to be 3 or 4 degrees short than even 1* too much.
Your power-Timing only becomes important in second gear from either stall, or to whenever the tires stop spinning, whichever comes first ...... to about 3500. In first gear, your engine is only gonna be in that zone for milliseconds, so it doesn't have to be perfect, as long as it ain't too much.
But in second gear, with tires NOT SPINNING, it could be in that zone from 50 to 55 mph (still with 3.23s) or up to a couple of seconds, So again, the timing doesn't have to be perfect in that zone, as long as it's not too much.
There is exactly one time when timing below 3500 is important, and that is while cruising. At this time, you want to be as close to perfect as possible. Thankfully, the window of perfection is an easy 4 to 6* wide .
So in all of this; the take-away should be, that the Power-Timing after 3500 is the one place where the timing should be as close to optimum as possible without being too much.
All other timings are built on top of the Power-Timing, by the advance starting point, the rate of advance springs, and by the V-can at PT.
