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Mon May 02, 2022 7:27 am

Have you guys seen this? This guy got 40 MPGS on a lawn mower carb setup he built himself. This is incredible. I wonder if this can be done for our classic bugs? I wonder if we could hit 60+?

https://www.youtube.com/channel/UC7ssYyYxo88laKkU0tW9j9A

I hope he continues to work this thing out and creates a manifold for our aircooled engines. I would buy one in a hearbeat.

Mon May 02, 2022 8:03 am

Same guy did an AMR300 on a single cylinder engine and mounted it in a Honda insight. Some interesting stuff for sure.

As long as it's jetted correctly and the timing is set up reasonably well you can make small carbs work better than you would expect on larger engines, you'll just be limiting the power overall.

Mon May 02, 2022 8:08 am

ya but a v8 getting 40+? Kinda crazy. Maybe the old rumors of carbs in the 70s being able to get 50-100 mpgs are true. I wonder if the lawn mower carb would be fantastic on a 1800? They aren't all that powerful anyways. in his video he had no problem getting up to 75 mph in a fairly decent time. I dont think most bug owners are going to the track, so this would be perfectly fine.

Mon May 02, 2022 8:16 am

Most of it is hillbilly BS.

A lawn mower carb is intended for a constant RPM engine.

It's an easy trick. If you severely limit flow into your engine your fuel ecomomy will be impressive.

There ain't no such thing as a free lunch.

That was the concept between the old Reagan era 55mph speed limit. We were in an era of two ton cars with carbon- daters (carburetors) and typically V8 engines. Lotta folks drove their two ton missiles as fast as they could. Mashing the gas inevitably sucks fuel.

A modern example:

The 454ci big block in our hauler gets 4mpg at 60 mph, loaded. That's a late model big block with fuel injection and coil packs, no distributor. Keep it under 55mph, it gets 6mpg. That's still lousy but it's easy math... that's 50% better fuel mileage if I keep my foot out of it.

I'm not going to make any wild claims until I re- visit it again but I severely fly cut the heads in the 40 horse in my old '63. I ran a tiny carbon- dater. I have plenty of choices for carbon- daters, milk crates full of old motorcycles carbs, various Dellortos, Webers, Solex-s as well as the occasional Zenith. On the bike side I have Keihin, Mikuni including a few Mikuni- Solex, plenty of Amals, a giant Bing off a Maico... like that.

My old '63 would get 40mpg all day and all night but...

Its high compression required the best gas I could find, usually 100 octane leaded from the airport or the track.

The fun was over at a pedal to the metal 65mph. That's the point where the inlet restriction was such that it would go no faster.

That's the Stupid Pet Trick. Drive a vehicle very, very conservatively, you will get impressive fuel economy. If you use a carbon- dater don't stick your foot in it. If you use a tiny carbon- dater you're effectively limiting throttle opening and flow. It's a built- in restrictor plate.

Design (or modify) a vehicle so you must drive it conservatively, you will get impressive fuel mileage.

You won't be doin' donuts and burnouts in Chrysler ads any time soon. :lol:

Mon May 02, 2022 8:41 am

The record for fuel economy set in the 1970s used to be 376 miles to the gallon. They did it with a 1500cc 1959 Opel Olympia Rekord with a Tillitson carburetor. The car was up for sale about ten years ago. There's a great book from 1977 that covers the modifications. "Fuel Economy of the Gasoline Engine"

Mon May 02, 2022 9:08 am

If you have the carb jetted correctly, and don't have your foot buried in it all the time, you can get excellent mileage. A smaller carb is just a gimmick to limit airflow.

Mon May 02, 2022 10:04 am

Dusty1 wrote: Most of it is hillbilly BS.

A lawn mower carb is intended for a constant RPM engine.

It's an easy trick. If you severely limit flow into your engine your fuel ecomomy will be impressive.

There ain't no such thing as a free lunch.

That was the concept between the old Reagan era 55mph speed limit. We were in an era of two ton cars with carbon- daters (carburetors) and typically V8 engines. Lotta folks drove their two ton missiles as fast as they could. Mashing the gas inevitably sucks fuel.

A modern example:

The 454ci big block in our hauler gets 4mpg at 60 mph, loaded. That's a late model big block with fuel injection and coil packs, no distributor. Keep it under 55mph, it gets 6mpg. That's still lousy but it's easy math... that's 50% better fuel mileage if I keep my foot out of it.

I'm not going to make any wild claims until I re- visit it again but I severely fly cut the heads in the 40 horse in my old '63. I ran a tiny carbon- dater. I have plenty of choices for carbon- daters, milk crates full of old motorcycles carbs, various Dellortos, Webers, Solex-s as well as the occasional Zenith. On the bike side I have Keihin, Mikuni including a few Mikuni- Solex, plenty of Amals, a giant Bing off a Maico... like that.

My old '63 would get 40mpg all day and all night but...

Its high compression required the best gas I could find, usually 100 octane leaded from the airport or the track.

The fun was over at a pedal to the metal 65mph. That's the point where the inlet restriction was such that it would go no faster.

That's the Stupid Pet Trick. Drive a vehicle very, very conservatively, you will get impressive fuel economy. If you use a carbon- dater don't stick your foot in it. If you use a tiny carbon- dater you're effectively limiting throttle opening and flow. It's a built- in restrictor plate.

Design (or modify) a vehicle so you must drive it conservatively, you will get impressive fuel mileage.

You won't be doin' donuts and burnouts in Chrysler ads any time soon. :lol:

That 55 mph speed limit was initiated by Nixon his last year in office. Reagan had nothing to do with it. You are in a time warp!

Mon May 02, 2022 10:15 am

I don't know about using a lawn mower carb on a Type 1, but I used a 28PICT carb on both 1300 and 1600sp engines. The throttle response was much better with a noticeable increase in torque off the line. It was limited in the higher rpm range however. Fuel economy was typically 10% higher.

Mon May 02, 2022 10:27 am

I think the biggest factor for both the economy and driveability of the guy's setup is the air bypass valve he incorporated into the intake. It senses the AFR and uses an automatic controller to admit extra air downstream of the lawnmower carb to achieve a stoich mixture across all rpms and throttle positions.

Mon May 02, 2022 10:34 am

mukluk wrote: I think the biggest factor for both the economy and driveability of the guy's setup is the air bypass valve he incorporated into the intake. It senses the AFR and uses an automatic controller to admit extra air downstream of the lawnmower carb to achieve a stoich mixture across all rpms and throttle positions.

Ya he said he created his own app to control air fuel ratio. He kinda created his own fuel injection system with a carb. He basically has a controlled vacuum leak. He explains it halfway through his drive. He also said when you want to punch it, the car gets up and goes, its not always locked into wimpy performance cause his app adjusts on the fly. He was driving 2500 rpms on the highway at 75 mph.

Mon May 02, 2022 10:44 am

lawn mower carbs are not efficient at all. hell mine never seems to make it past the other side of the street. build a big vw motor right and the car &gearing&tires right it will get good mpg if your foot will let it. possiably over 40. my 2332 was about 35 on the highway with some city & a few stabs.. it could of been more if I had put more cr into it. my 2028 was about the same with different raitos&tires. it too could of been more. if you build a disposable slug that can hardly pull it's self than you deserve the bad mpg.

Mon May 02, 2022 10:47 am

FarmerBill wrote: The record for fuel economy set in the 1970s used to be 376 miles to the gallon. They did it with a 1500cc 1959 Opel Olympia Rekord with a Tillitson carburetor. The car was up for sale about ten years ago. There's a great book from 1977 that covers the modifications. "Fuel Economy of the Gasoline Engine"

There was some sort of economy record car for sale in New Hampshire recently.

It's not a complicated recipe. Shed as much weight as you can. Eliminate as much drag as you can. Use a tiny engine.

Drive it downhill never uphill. Wait for a tailwind. :lol:

Rich Latsch wrote: That 55 mph speed limit was initiated by Nixon his last year in office. Reagan had nothing to do with it. You are in a time warp!

Thanks for the history lesson.

Reagan era. It took decades for interstate speed limits to get de- restricted in many areas.

Reagan era cars had 85mph speedometers 'cuz faster that that was politically incorrect and illegal.

I can think of a few stretches of interstate where you better be able to sustain 85mph or you'll get run over. :roll:

It's easier to sell "luxury" than it is to sell economy. American automakers always build larger heavier vehicles until they're confronted with the next fuel crisis.

.

Rich Latsch wrote: I don't know about using a lawn mower carb on a Type 1, but I used a 28PICT carb on both 1300 and 1600sp engines. The throttle response was much better with a noticeable increase in torque off the line. It was limited in the higher rpm range however. Fuel economy was typically 10% higher.

It would be great if we could hit the big numbers with old technology and of course we can.

The VW Bug is one of the original "economy" cars. Regardless of vintage they're designed for good flow velocity at relatively low RPM. Good flow velocity and a 4.37 differential makes the car feel stronger than it is.

Didn't take long for VW owners to figure out our Porsche designed engine was capable of Porsche performance by methodically eliminating the built- in restrictions.

A carbon- dater (carburetor) almost always works but almost never works perfectly. The intake tract must be designed to preserve the vacuum signal. A carbon- dater won't carbon- date without vacuum.

Fuel injection facilitates port volume that would defeat carburetors at anything besides a very narrow RPM band.

"Digital" fuel injection facilitates fuel flow "map" that can be tuned to be close to ideal.

Combine digital fuel injection with four valves per cylinder and variable valve timing. The cam timing can be actively tweaked to be close to optimum.

Add a turbocharger or two to make our small engine "bigger".

Our small engine doesn't need to be that big if we're making 200hp / liter. :idea:

Our small engine doesn't need to be that big if we make our vehicle as light and as aerodynamic as possible.

None of this is rocket science although...

Our theoretical "ideal" engine quickly outgrows the hardware constraints of 60- 80 y.o. designs.

Oh, wait. Some of it is rocket science.

The land speed record guys figured out that aerodynamics would make you go faster when you were at the limits of your motor.

Going "further" instead of faster is just a matter of tweaking a few variables.

.
.

Mon May 02, 2022 2:08 pm

Maybe he got 40 mpg from a V8, maybe he didn't. His story and he can tell it how he wants.

Ya you can do impressive things at a give load, rpm, fuel/air flow but at the end of the day... is it drivable? A fellow we know built a gasoline vapor carb for his Chrysler New Yorker back about 30 years ago. He drove from Edmonton to California and claims he averaged 75 mpg. Did he? I don't know, his story...

Anyway, I asked him if he was still running it. "No, I took it off when I got home." was his reply. So I asked him why. He said "It's not something you can send the wife to the store for groceries with."

Not drivable! Therein I believe is the rub.

Mon May 02, 2022 3:23 pm

Put a block of wood under your throttle pedal. Limit your rpm to 2500. Same thing.

Mon May 02, 2022 3:33 pm

bsairhead wrote: Put a block of wood under your throttle pedal. Limit your rpm to 2500. Same thing.

I prefer to conceptually have a two pound over- ripe tomato under the accelerator. 8)

Brakes just slow you down. You can boost economy by preserving momentum.

Drive it like a Peterbilt. Modern diesels have engine management that won't let you do anything harmful to the engine. The computer won't let you over- rev it. The computer won't let you over- heat it. Heck, the way I heard it the computer lets you drive ten hours with very little wiggle room. Then it shuts you down.

Mon May 02, 2022 3:36 pm

Way back I bought a new 1981 Pontiac Lemans with a 265 V8. This was the 4th model year of the downsized version and it had a 2 barrel Holley carb that was computer controlled. The car was considerably lighter than the pre-1978 models. It wasn't much on power but ran very smoothly. Initial gas mileage figures were 18 local and 25 highway. There were 3 minor things I did almost immediately. I plugged the EGR vacuum line to make it inoperable, removed the catalytic converter and replaced it with a "test pipe", and punched the guts out of the A.I.R. pump so it was essentially an idler pulley. The new gas mileage figures were 20/28 which would be impressive for a V8 even now. If I had toyed with it further, I'm sure the figures would have been higher. There was no emission testing until I no longer owned the vehicle.

Mon May 02, 2022 4:09 pm

Lessons in the laws of thermodynamics are good for everyone.

Mon May 02, 2022 5:21 pm

HIGH mpg is easy on a straight windless road with no intersections or traffic.
Then we go into the real world, on real roads, trying to do real things and it all falls apart.

Mon May 02, 2022 5:23 pm

modok wrote: HIGH mpg is easy on a straight windless road with no intersections or traffic.
Then we go into the real world, on real roads, trying to do real things and it all falls apart.

My wife said it does really good going down hills, :lol:

Mon May 02, 2022 7:31 pm

modok wrote: HIGH mpg is easy on a straight windless road with no intersections or traffic.
Then we go into the real world, on real roads, trying to do real things and it all falls apart. Got stopped today for rolling a stop sign. Cop asked me why. I said it doesn't matter now.