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!! 8)
n2o:
Quote from: SOB/DBR on March 11, 2006, 14:42:59 pm
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!!
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