Disproportionate intake for fuel mileage.

[Isaac Zackary]

I thought I'd throw out this not-so-common idea. Anyone familiar with the classic VW Beetle knows that the early Bugs (cerca 1940's and 50's) got as much as 35mpg stock without any modification. But by the 70's the fuel mileage dropped down to around 25mpg. But it went back up again in the 90's back to around 35mpg again.

How did they do it?

The early Bugs had little 1100CC engines that produced 25hp, followed by 1200cc "36hp", 1200cc "40hp", 1300cc, 1500cc and finally a 1600cc engine. These were all called single port engines, and were known for their better low end torque and fuel mileage when compared to the later dual port engines. The dual ports also came in 1300cc and 1600cc sizes, so how did the single ports get better fuel mileage?

Well, there's an interesting theory. These engines have a strange intake manifold that starts with a center carburetor feeding into a tee that goes from end to end of the engine. So one long runner feeds the 1/2 head and another the 3/4 head. Timing is 1-4-3-2 so the #2 and #4 cylinders basically start the flow through their ends of the intake tube and the #1 and #3 finish it. This disproportionate intake causes two cylinders to fill a lot more than the other two, basically turning the 4 cylinder engine into a 2 cylinder at highway speeds (also it "super charges" two cylinders at low RPM giving the engine it's low end torque characteristic.)

When VW began looking for better emissions it became apparent that more even cylinder filling would make it easier to control. So they made the dual port engine, which put the split on each end closer to the carb. Fuel mileage and low end torque dropped as a result.

Interestingly, however, by the 1990's VW went even further and made an even intake runner manifold with fuel injection for this same engine. Sold until 1993 in Mexico, this engine ended up getting the best fuel mileage any of the classic Bugs ever had.

[cosmick]

The same concepts have been tried in many American V8s, and some American V6s. All of them, separately and every combination. That induction imbalance has gone the way of the Dodo, and I'm not convinced it helped that much. But thanks for the thought-provoking history. Bugs are fun, once you swap at least 200 HP into them.

[oil pan 4]

This is the motor eilo motors needs to be using.

[Isaac Zackary]

I think it's been superseded by variable length intakes and engines that can disable certain cylinders.

[Chrysler kid]

Originally Posted by Isaac Zackary

I think it's been superseded by variable length intakes and engines that can disable certain cylinders.

You can pretty much rebuild them with a screw driver in the parking lot

one of my regular customers has a 2002? Vw beetle 50th anniversary from mexico. It was a final year production model and it had what looked like jetty style/quality leather seats an upholstery And fuel injection.

He was suprised how fascinated I was with it, he said he could get a dozen more for me if I wanted lol

[Isaac Zackary]

I'm attracted to the classic VW since it was the first successful economy car. I just love it when people brag about how they get 30mpg in there brand new SUV or other and I can rightfully say I get more than that in my half a century old Bug.

True, they're not the most technologically advanced car out there. But if you include the build in your economy figures they are very simple and cheap to build, mainly for being the most popular platform in history thus far. I just spent $100 for new pistons, cylinders, rings, hone and wrist pins of really good quality. I don't know of any other that cheap to rebuild.

[user removed]

Originally Posted by Isaac Zackary

I'm attracted to the classic VW since it was the first successful economy car. I just love it when people brag about how they get 30mpg in there brand new SUV or other and I can rightfully say I get more than that in my half a century old Bug.

True, they're not the most technologically advanced car out there. But if you include the build in your economy figures they are very simple and cheap to build, mainly for being the most popular platform in history thus far. I just spent $100 for new pistons, cylinders, rings, hone and wrist pins of really good quality. I don't know of any other that cheap to rebuild.

I would call the Model T the first successful economy car.

regards
mech

[Isaac Zackary]

Can you get all new pistons and a decent hone job for $100 these days on a Model-T? What king of fuel mileage did those start out at?

[oil pan 4]

Those old model T engines have pretty much all been replaced with small block chevy engines or ford flat head motors by dedicated purists and the original engine were largely used as boat anchors with no line attachment.
Ledged has it that the model T could get high teens in the MPG department. Surprising how little some things can improve in 100 years.

[Isaac Zackary]

Ah! Found it. The Model T was rated from 13 to 21mpg. That was a great improvement over previous cars, or at least that's what I've been told. Beetles (Type 1's) were rated between 26 and 34mpg. Not bad for a 1930's design! I've known a few who've got over 40mpg (HWY) out if them.


Back to the original topic, I don't see any evidence of single port heads actually increasing fuel mileage substantially. Actually, some of the dual ports got better mileage than some of the single ports. Oh well. I guess Ill go back to the drawing board.