Let's get down to basic...Horsepower!!
n2o:
I'm a slow learner, sorry. So what you are saying is that you would like to have 30 +/- degree advance in at low rpm (like 2000rpm?), even under heavy load?
Regards to tuning, I can agree on tuning after the mph on timeslip, but "feel of the pants" usually means pre-igniton.....futher down the road.
n2o:
Quote from: SOB/DBR on March 12, 2006, 16:38:03 pm
The quicker the advance can be all in, the torquer it will be, as it builds cylinder pressure and cylinder pressure is torque....or pre ignition..... a fine line to walk. Happiness is a Hot VW!!
This I do not understand. Cylinderpressure is a function of a lot of things, and each of the "cycles" need correct timing. So what you are saying is that the engine needs more advance to build pressure, but to me that means the engine is not very efficient?
Jon:
Hi SOB, I love these tech talks were I know nothing more than I have much to learn.
I feel it would help to know what a fast timing curve is.. I assume you end up on 30° at the end of that curve... but when will a fast curve be "all in"... 2500?
Is all cylinder pressure good cylinder pressure...? If you have TO much advance compared with the revs. you build a lot of pressure, but that pressure must be working against the piston...and slowing it down. What I guess you mean is you want the right timing, and by building the engine so it is efficient on low revs, you enabels the engine to take unusually much advance relatively early?
I other words, this is something you "do" in the build, not some trickery with the ignition at a later stage?
Just trying to figure out this ignition curve thingy...
SOB/RFH:
A locked distributor has no advance built in to it. A 010 has all advance in by around 2000 rpm and a 009 has all advance in by around 3500. Please note that there are diffrent versions around so just take the numbers as a ballpark and do a serious search for fact, please. Anyway, to build cylinderpressure we need as much advance as early as possible. Cylinderpressure gives a quick throtle respons and acceleration is quicker. Thatīs the good case. On the other hand we have pining, and that is a no-no. So we need a curve for the engine we have that fullfills our dreams of high cylinderpressure. Here are some baselines I have come up with, other may have other experiences but keeping things simple and staying away from the latest trick gives a good working engine:
On a stock stroke engine with long (stock) rods the 009 is a good choice
On a long stroke engine with short rods you need the 010 or quicker curve
Then comes variabels as compresson ratio. Low compressione ratio and you need less of an advance curve and on a high compression engine you need more. Example a 9:1 2275cc engine with good heads and a 320 deg cam can get away with a locked distributor and my own 11,15:1 2633 cc engine with big bore and very short duration (256@.050") have a total advance of 11 deg and all is in by 1100 rpm. I think bouth are short curves in anyones book.
If you go to Cal-look.com there is a article written by john Connaly about optimizing the ignition curve that is good for the home mechanic. Read it and I hope it open up the eyes of how ignition work.
Most people belive in technicaly advanced solution to a problem that is simple if you get the physics behind it. You will get a long way with common sence and knowledge. These last centences are written politly so that no one reads it and thinks i am a besserwisser and has there day spoiled. I hope this helps!! Happiness is a Hot VW!!
Berger:
This is very interesting! Do You have any experience with magnetos? I use a Joe Hunt magneto with my 2276(FK87/SF heads 11:1). I know it has a total advance of 10 deg, but don`t know when it has all advance in?
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