40 mpg engines

nanometer · Posted: Fri Oct 02, 2015 6:54 pm Post subject: 40 mpg engines

I came across a site that's advertising air cooled engines (would fit something like a 1971 bug) that will get 40 mpg Hwy. They want over $4000. Then there's a kit from CB for a little under 4K. $4000 would buy a lot of fuel.
Isn't there some way to get at least 35 mpg that's more home brew and I don't have to hold up a bank to do it ? Thanks . . . Alan

Eaallred · Posted: Fri Oct 02, 2015 7:05 pm Post subject:

Going for max MPG is fun for the challenge of it, but it's a bell shaped curve on reaching the point of diminishing returns as you've already touched on.

30mpg or so is easy to get with a fairly stock and mild engine. Hitting 40 or higher is going to take a substantial amount more effort.
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Boolean · Posted: Fri Oct 02, 2015 7:16 pm Post subject:

Building an engine for good MPG is usually not worth it if the car is not a real daily commuter. And actually not even then.
Doing it for other reasons may be something else, but don't expect to save any money when the build is included.
Good ignition and fuel control is key to good MPG numbers, but so is driver proficiency.
I bet a stock bug could do 35 MPG with just skinny tires and an egg under the foot.
My first bug was a stock -69 1300 SP which usually did between 25-30 MPG.
As a teenager at the time, I drove it like there was no tomorrow.
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bluebus86 · Banned Joined: September 02, 2010 Posts: 11075

My 61 1200 would get 30-35 mpg on regular gas back 35years ago, that was before the government mandated ethanol in the fuels, which lowered the energy content, reducing mileage by 10-15%. I had several cars at the time they switched the gas, and all suffered loss in mpg in the 10-15% range.
of course the new gas costs more per gallon, and actually introduced more CO2 into the air than if petroleum was put back in the gas if one takes into account the CO2 released during ethanol production. (you got to distill it , that takes heat) of course I think global warming is not true anyway.

This bad fuel forced on us shows the corruption of the government, for they told us the change in fuel was for CO2 reduction, for the Earth, climate change. In reality they did it cause they were bought off by the corn farmer lobby. further the new fuels, which cost more, give lower mpg, and create MORE pollution, also will corrosively attack some fuel system parts used in older cars, causing fuel leaks and breakdowns, additionally the switch of crop land for food to crop land for fuels has driven up the price of food, even cattle fed cost more, which can be attributed to the increased use of corn based fuels.

"I am from the government I am here to help you..." Most frightening words ever spoken.
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jpaull · Posted: Fri Oct 02, 2015 8:45 pm Post subject:

Bluebus yes very true. Looks like your in beautiful Cali also where we have all kinds of government "helpers".

30-35 mpg can be done. The gas does suck but dual icts on any mild motor with good ignition and everything dialed has a chance. I would not go for 4000 motor. Build your own and have some fun with it.

Jeff
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GTV · Posted: Fri Oct 02, 2015 9:33 pm Post subject:

Have you priced a stock engine lately? It's not the 80's anymore.
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67jason · Posted: Fri Oct 02, 2015 9:48 pm Post subject:

ive gotten real close to 32mpgs with my 2180. avg speed 68 mph for an entire tank of gas on a road trip. i regularly see 29-30 mpgs with mixed driving. if i forget im an adult and drive it "crazy" i get in the 27mpg area.
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mark tucker · Posted: Fri Oct 02, 2015 9:54 pm Post subject:

I got over 35 with my 2332.and over 33 with my 2028. the 2028 has a different trans&smaller tires. big motors work less.of corse if I was to keep my foot in it all day long like I lived at the drag strip.(boy do I miss those days)...it would possibly run out of gas.

Randall · Posted: Fri Oct 02, 2015 10:08 pm Post subject:

Here's a thread with a 10 year history on the same subject.

http://www.thesamba.com/vw/forum/viewtopic.php?t=97269&postdays=0&postorder=asc&start=0

Alstrup · Posted: Sat Oct 03, 2015 5:37 am Post subject:

Hello
As said, 40 mpg is a challenge. 35 mpg is absolutely doable. You do not menthion your engine size, but a a homebrewed detailed and fine tuned 1200 would do the job nicely. Sgl port engines are generally easier to make super efficient.
Also think correct alignment, correct tyre pressure, low friction tyres, low friction oil in both transmission and engine.
15 years ago I built some 1200 engines with 1300 dual port heads, more cam CR, exhaust and dual 36 Dells. 65 ish hp. They did really good, approx 33 mpg in everyday driving (without "thinking" in fuel economy) 40 mpg on longer tours with 55-60 mph.

andk5591 · Posted: Sat Oct 03, 2015 2:56 pm Post subject:

Hot VWs did a series a few years ago called Mileage Motor or something like that. They got real close and most of the combinations seemd to give fairly decent performance. Something to remember that its not just the engine, but the car as well. Fat tires suck up gas as do poor aerodynamics. I seem to recall that that the played with a thing called Herod's helper(?) that made a noticable difference.

If I was totally after milage, would research the Hot VW series, lower the car, skinny and hard tires with a freeway flyer type tranny. And the hardest part is keeping your foot out of it....Driving style makes a huge difference.

And $4k is not a boatload of money for a turnkey anymore.
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Juanito84 · Posted: Sat Oct 03, 2015 3:10 pm Post subject:

Might I add:

High MPG Ideas / Discussion
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

miniman82 · Posted: Sat Oct 10, 2015 7:06 am Post subject:

Diesel conversion.
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mark tucker · Posted: Sat Oct 10, 2015 10:18 am Post subject:

it also depends on what car or rail it is in and the trans and tires and driver and location and.......I dont think it's hard to do with a unlimited budget.

buggnuttz · Posted: Wed Oct 14, 2015 1:51 pm Post subject:

about twenty years ago I built a motor for a 1974 bug using 87mm bore stock fuel injected heads I built the center section to use a 30pict-1 carb hooked to smoothed out end pieces .used fuel inj. exhaust ,I had it and like heat.it got 38-41mpg on hwy. sorry don't remember jet sizes .it also had a auto stick svda dist set at 32degrees full advance with vacuum line off.
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Juanito84 · Posted: Wed Oct 14, 2015 3:08 pm Post subject:

The main thing is tuning. Not just the AFRs but the ignition timing curves. Try this:

1. Make sure you've got good emulsion (fuel into air closer to the combustion chambers, heated intake air and tract, rough surfaces, etc).

2. Get an O2 sensor and AFR gauge and tune you're low load AFR to around 16:1 or leaner and your high load AFR 13:1. Of course a good electronic inductive ignition set up would be a must.

3. Tune the heebee-geebees out of your ignition. Something digital with a spark table would be nice. The goal is to get the most torque out of any load/rpm combination. If at 2,400RPM and 65 kilopascals intake manifold pressure you have an AFR of 16.7:1 and you get the most torque at 31* BTDC, but at 95 kp you have an AFR of 13.2:1 and the most torque you get now at 19* BTDC yet at 3,200 RPM at 85 kp you get an AFR of 12.9:1 and you get your most torque at 31*, then with each small change in manifold pressure or RPM (better have you're AFRs set) you need your ignition timing to hit each of those perfect timing marks perfectly, less a few degrees from pinging for safety's sake. Obviously that's going to be hard to measure with your seat-o-pants meter and much harder to dial in by fiddling with springs and stops and such. If you have access to a dyno and a digital ignition box that would make this much easier to achieve.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?


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