Let's get down to basic...Horsepower!!

[SOB/RFH]

I like to build my engines with lot's of torque. That makes them pull from low rpm all the way up to a least 6500 rpm. Big engines can be built with the new age low durtion/high lift cams or just 120/125 with 1,35:1 rockers. Short rods on long stroke and rather big ports. If I was to build a Cal-look beast engine with longivty this is my favorite combo. a 7000 rpm puller:
Mag case and 26 mm oil pump full flow and big 3,5qt external sump
84*94 with 5,5 rods (preferebly Porsche journals)
W130 with 1,25 rockers, solid shafts
40*35,5 or CNC round port heads. 11:1 compression ratio if 98 RON gas is availible. Long (non big foot) intakes and IDA:s with 40 chokes.
MSD digital 6 and billet distributor set for fastest timeing curve (no silly 009 curve for this baby)
1 5/8" exhaust and swedish Apple racing 2,5" muffler
This combo works with a stock geard box and will make you a happy camper with lots of 12 second time slips if the tires are sticky and wheels are light.....Happiness is a hot VW!! 
 

[n2o]

MSD digital 6 and billet distributor set for fastest timeing curve (no silly 009 curve for this baby)
 

I am not a big fan of the 009 either, but what do you mean by " set for fastest timing curve"?

[SOB/RFH]

Trying to cleraify. All advance should be in as quick as possible, the quickest is locking the distributor but my experience is that some advance is needed with 11+:1 in compression ratio. 010 is mouch quicker then 009 for example. 009 works great with stock short stroke and long rod combos. Happiness is a Hot VW!!

[n2o]

I am not shure if I understand. If  you have a "tourqy" engine pulling from low rpm, I guess to much of advance would lead to pre-ignition? Is it possible to have a general "rule of tumb" regards to ignition-curve? The tendency to knock/ pre-ignite depends on a lot of factors like quality of fuel, air/fuel ratio, engine temperatures,rpm, design of engine and engine power output. It's seldom to see 2 engines respond to exact the same ignition curve. What kind of advance (degrees)are we talking about?

[SOB/RFH]

Advance is an effect of reaction time in the combustion. A long reaction time and you need more advace (igniting erlier). So if we have an engine that is efficent we don't need to mouch advance as reaction is lesser. The reaction time is also changed due to the speed of the engine and on the other perimeter you have the high speed ignition taking place at rpm:s above 7500. I don't build engines that rev above 7500 as they are aimed for the street and therefor I lack knowledge in that area.

What is the maximum degree of ignintion. Combustion chamber, cylinder diameter and efficiancy if induction system are the major considerations. On a type 1 I go for 28-32 deg and on a type 4 I go for 30-40 deg. I use Statoil gasoline that gives 98 octane Ron and I have good results from BP Super Green when we coluld buy it in Sweden. I have yet to test Shell V-Power, but think it is a good product. My engines use compression ratio from 10:1 to 11.8:1 in street trim. All have IDA:s and either Scintilla or MSD ignition systems. So I usally go by the feel in the pants or the speed from the timeslips when I set up the engines. 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!! 

[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]

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. That´s 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?

[Tony China]

What John Connaly said is what we all "knew", but to me it sounds like you want max advance from idle to peak. I can not understand that this can be correct.

[Jon]

I have read the Connoly text before and that's how I intend to set up my Magneto.
What John C fail to mention is that the magneto has a series of weights, and therefore has a fine "resolution" in lack of a better word, to allow a curve following the curve you find by locking up the distributor.

As Connoly says...  with conventional tuning of distributors you are lucky to hit optimum performance once. With a "designed" curve you can get much closer to optimum, for a longer period of time...  even if you just actually hit optimum one time in that case to.


Both he and you SOB talk about the rod ratio in relation to this... does this come down to the way the piston turns, that gives the "snap" in the intakes... (that provide excellent "signals" to the carbs) like we have talked about earlier SOB?

And remember guys, I guess most of you know it already, not all detonation can be heard over the engine noise... as Clyde Berg once yelled over at Cal-look.com :-)