Disproportionate intake for fuel mileage.
 

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.

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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.

This is the motor eilo motors needs to be using.

I think it's been superseded by variable length intakes and engines that can disable certain cylinders.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

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

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?

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.

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.
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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.

First, that's not impressive. If you could do it in a '65 Chevy Suburban, then that would be impressive, but that's been done, thanks to an LSx / T56 swap.

Second, total number of original style Beetles still falls short of the GM B-body cars. Sorry, GM wins, as usual. Better yet, V8 B-bodies outnumber the Beetle, without including the few rare 6-cylinder versions. Part of why the SBC V8 is the best selling engine of all time, as most B-bodies had one, and most of them were the 350.

My family loves Chevys. My brother just got his rebuilt 350 running yesterday!

Regardless, to me a car designed in the 1930's that gets nearly 35mpg with no modification or eco-driving and can get over 40mpg with some jetting and being easy on the throttle is impressive to me. Of course that's a matter of opinion. If my brother could get 18mpg out of his Chevy truck with the newly rebuilt 350 that would impress him.

I'm not saying this is the best car and engine out there or that everyone should like them. But I think they're a neat concept and are very affordable and easy to work on.

Yes 30mpg in a Suburban would be impressive. Kind of like me getting over 50mpg in my Golf Diesel yet only 24mpg in my Chevy Astro yet I can haul twice as many people and things in the Astro for less than double the price to fuel the Golf.

Back to the original topic. I see that with the unequal intake runners it would be optimal to have different spark curves for each cylinder (or eliminate the inequality and go with fuel injection.) interestingly VW actually had made different cylinders run at different timing on the single port engines, namely, the #3 cylinder being different than the rest. This was in part to the 3/4 head being behind an oil cooler inside the fan shroud. Therefore, the air reaching those heads was pre-heated, so they lacked the cooling the 1/2 head received. But only the #3 cylinder actually ran retarded. You the might ask yourself why both cylinders weren't retarded being that both were put on the hot side. But again, the unequal intake obviously would fill the #3 more than the #4 making it run hotter for that reason too.

Later VW repositioned the oil cooler when the dual port engine came out. Now the 3/4 head receives as much cool air as the 1/2 head and the intake is now more even with the dual port.

As of now I have a programmable spark map distributor (21x21) that I want to play with to see what kind of fuel mileage I can get from this antiquity. But my dream would be to figure out how to use an Adrino with perhaps a Ford TFI module and a crank trigger in order to adjust specific cylinder timing.

This reminds me of a story my friend loves to tell about his old neighbor in Oregon who would swap the engine between a VW Bug and Van every time he would want to take a trip in the van. Which happened to be pretty much every other Friday. Then Sunday afternoon it would go back in the Bug when he got back home.

Hehe! Ya, I've got it down to about 15 minutes either putting it in or taking it out! Four bolts a couple of wires, a fuel line and the throttle cable and violà! Plus the engines light enough I can pick it up myself.

Have you ever seen the top gear where Jeremy clarkson tries to drive a model T? The throttle is on the steering column and you have to push and pull a bunch of levers.

He got it up to 31mph on unpaved roads and said it was ludicrous to even go that fast. You hit a rut, large bump, or have to stop fast and you end up in a ditch destroying the car and getting ejected into a field where you die of cholera

Hehe! The Bug's not the greatest road handler either, but my manual says it has a top speed of 81mph. I've never gone over 65mph in it. First drive I took it on I got slightly over 30mpg, and that was with it in poor shape. We'll see what she does with the rebuilt motor and engine mods I'm doing.