stock mpg motor build counter-weighted crank or stock crank

[Pruneman99]

Just my opinion that is just a guess:

If I was going after a MPG engine I wouldn't worry about the crank being counterbalanced or not. I would focus on balancing everything. Vibration is wasted energy. I would use the lightest pistons with the thinnest ring pack I could use.

Tight tolerances, very light oil. How much HP is wasted pushing that 20/50 tar some people like to use?

Mild cam, light spring pressures. Maybe light beehives so you can go lighter on the nose pressure.

[spencerfvee]

[spencerfvee]

[spencerfvee]

[spencerfvee]

[spencerfvee]

[oprn]

[modok]

Not perpetual motion
Reduced bearing loading means reduced friction.
Will that happen? Probably not. But maybe. As a basic idea the crank mass is proportional to the stiffness, but that can be broken if the crank is lightened in particular ways.

But if we talk about reducing the mass of the rods and pistons I don't think you would have any objection.

What about the RATIO of the rotating to the reciprocating masses.
A VW engine with a heavy crank and light pistons and rods is super smooth and quiet. Vibration and noise is caused by lost energy right?

[oprn]

[Alstrup]

Well said. However, both sgl and dual carbs can do well on the fuel efficiency side. Most people feel that it is easier with duals, because for some weird reason the stock carbs and intake system is massively misunderstood, as you also point out.
An old friend of mine, from who I learned a lot, had a ´67 or 68 1500S type 3 many years ago. He was an ace with carbs and he understood the VW engine better than most. He had no problem averaging 15 km/l in daily driving. Bear in mind that that was while most other did something like 11,5-12 km/l.
Making an engine that will do 34 mpg or better (approx 14,5 km/l) after the KISS method will take some effort, but lets see where it goes.
On the other hand, if you go into heating up the intake air and leaning it out and adjsting the vacum timing accordingly you can come a long way. I have done 40 mpg (17 km/l) with detailed 1600´s and over 45 mpg (20 km/l) with detailed 1200 engines. In type 1´s that is. Ghia´s are somewhat easier. 37 mpg out of a nice and not too spec´d out 1600 is quite easy. The last 3 mpg is much more work.
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[Floating VW]

[spencerfvee]

[Alstrup]

Yes, trimming the hot air mix is the way to go, especially with a header.

Storytime. This has absolutely nothing to do with chasing mpg as such, but bear with me.
Some years back I was approached by a guy who had a ´71 vert which was imported from the States (but that´s not the story) The story is that they got it MOT´d much to my surprise, because when it came here it ran like crap to put it mildly. The previus owners had done just about everything they could to make it run better. What they had done in reality was making it run worse. Soo, first things first:
The preheat was cut off of the manifold because they were clogged anyway (accoring to owner)
The stock DVDA dizzy was replaced by a knock off 009.
Plug wires had 4,5 K Ohm resistance. (Belonged on a Mazda or something.)
The muffler was about the worst period stock look alike period piece of crap I had seen for a long time period.
Finally the carb had seen better days.

A compression check showed that the engine itself was in reasonably good shape, so it was worth throwing some money after it.
So out came the engine. Intake manifold was replaced with a good used, - with - heat risers. Muffler was replaced with a decent Ernst muffler. I rebuilt a 113 905 205S distributor and added electronic points. (I don´t like points) along with replacing the ignition coil to an appropriate for the rest, and replaced the ignition wires to some std Bosch 1 K Ohm and regapped the plugs. I also cleaned the oil bath mesh since it looked like nobody had done that for a decade or so. Carburettor was of course also cleaned and jets checked and verified.
Engine back in. Ran miles better than before, but still had some off idle and midrange stumble. Carb off again. Increased main jet by 0,25. Better, but still not acceptable. Shortened the timing curve to 10-30 mechanical. Now the midrange hesitation was just about gone. Aircleaner off and recheck the mixer thermostat. It was a little low, so I adjusted it to 10 degrees C. hotter intake air on cruise and low speed. Bingo! Now the engine ran smooth everywhere.
This was a full 2 day job, but it often takes much longer to fix a problem others have tried to remedy the cheap and easy way.

Bottom line is that yes, the hot air intake can definitely be played with to get the final result perfect.
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[Floating VW]

[spencerfvee]

[spencerfvee]

[esde]

No idea if it makes a difference in MPG at all, but almost everything I build gets a CW crank that's balanced with a lightened flywheel. The actual weight gain is very little, and the weight is where it's needed.
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modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that.

[spencerfvee]

[quote="esde"]No idea if it makes a difference in MPG at all, but almost everything I build gets a CW crank that's balanced with a lightened flywheel. The actual weight gain is very little, and the weight is where it's needed.[/quote.....................................................................................................................................its like this theres people that stand by a CW crank and there people that like stock cranks ... when i worked in a vw shop we sold more stock cranks than CW cranks . most went into pipe buggy motors . street dune buggies some vw cars .. i think why we sold more stock cranks was because they were cheaper than a CW crank . for me a stock crank will work . because its not going over 4,500 rpm . i will be going 3,500 rpm on the high way spencerfvee

[oprn]

Back when I had my '71 Super Beetle (34 mpg) I followed the How To Hot Rod your VW book to the letter. Yes I removed the thermostat, blocked the heat riser, bought a 009, extractor exhaust, Holley Bug Spray carb, threw away the stock air cleaner and I gained a bit of power - maybe 4 or 5 HP. But just like the Beetle Alstrup told us about (he described my Beetle perfectly), it ran like total CRAP at anything less than full throttle. It was virtually undrivable in the winter and mileage was in the 15 mpg range!

Also if you are truly committed to a mileage engine do not forget to put a thermostat and flaps back on. It is vital to keep that engine hot enough to run on a lean mileage mixture! I know you will say otherwise but even in summer weather a VW engine without temperature control will run too cold at light throttle and a cold engine will always require a fat mixture to run smoothly.

...And of course a properly matched vacuum advance assisted distributor. Building a mileage engine is not that hard but it does require sheading the "1/4 mile time is God" mentality.
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We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[spencerfvee]