Anyone else striving for better MPGs by adding HPs?

[oil pan 4]

Ideally you wouldn't run lean or or have a warm air intake at wide open throttle, but this is how a lot of people set up their machines.

[freebeard]

[wandering the forums looking for a thread to comment in...]

I'd point to the HotVWs Mileage Motor magazine series. Based on work by John Karcey, an AA Fuel engine builder, for his Karmann Ghia as documented in VW [Trends or Greats](, I forget) and available at CB Performance; and developed over 8 installments by Bruce Simurda.

The plan involves a stroker crank and high reciprocating mass. Stock pistons and cylinders means better cooling and the 1/4" stroke pulls the torque curve downward. A Freeway Flyer transaxle, electronic ignition, low friction lubricant, &etc.

Karcey used a 50lb Jaguar pulley (prolly a little slow off the line ), I forget what HVWs used; but the motor sitting on my bench has a Gene Berg 8lb crank pulley (and his Type IV cooler upgrade and a spin on oil filter).

HVW's test vehicle started at 28mpg and their goal was to crack 40mpg. They got to 39.99999ohIgive up. And this was with no aerodynamic mods to speak of (IOW Herrod Helper). Karcey claimed 50mpg in his Ghia in the 1970s.

I think a lot of it is in the build quality. Did you know VW racers drill holes in the tops of their pistons to go faster? True story.

Edit: Fixing a typo, but what about this: Entire engine assemblies can be dipped in liquid nitrogen. Apparently it doesn't affect rubber seals and such. Individual part machine better after treatment so maybe it's best to re-crystallize the metal grains and then machine to tighter tolerances before assembly.

All I know is that my brake rotors are holding up great. Some claim 3—4 times the part life. But it doubled the cost of the stock part. So maybe you could assemble an engine too loose or too tight, freeze it to -273°F and have the various alloys settle in together before you fire it up.

[freebeard]

I'm not sure. It's a mixed bag. Aircraft powerplants get torn down and rebuilt based on engine hours with no debate.

I believe there are watercooled V-6 aircraft rated engines. Do you have any example?

2500hp AA fuel engines have a fairly short life span. So do Bug engines rebuilt in the carport with Harbor Freight tools.

Possibly a level playing field is motorcycles; they come in air- water- varieties. Here's a water-cooled Vespa:


http://blog.vintagestyle.eu/ten-inch-terror-meet-the-vespa-husqvarna/

[Frank Lee]

Without a doubt watercooleds live longer. Due to the smaller operating temperature "bandwidth" and greater heat rejection capability, they can be (are) built to tighter tolerance and run leaner to boot.

[freebeard]

But running lean is what kills the #3 exhaust valve. Oh, wait...

You can troll me all you want about 'watercooled's better', but i was hoping someone would comment on the square bore/stroke ratio, high reciprocating mass strategy which yields in the test case, better mpg and added hp.

[freebeard]

The Beetle starts out over-square; the 1/4" stroke just brings it closer to square. The theory being a square bore/stroke has the least surface area, to retain the heat of combustion.

The low end torque possibly compensates for the long-legged transaxle.

How do you think the high reciprocating mass helps?

[Frank Lee]

IMHO most of the action of combustion takes place early on; perhaps whether an engine is square or not is of little consequence, or less consequence than simply what the stroke is because the stroke defines what the piston speed will be and from what I can tell optimal piston speed is 1000-1200 ft/mn. Of course with a longer stroke you get your 1000-1200 at a lower rpm with all the good things that brings.

Perhaps the high rotating mass is helping with lug-a-bility- short shifts, tall gears, and whatnot. Spool it up and it can get moving with those long legs without stalling

[freebeard]

I agree with the conclusion. But surely the most action is taking place 90° after TDC, when the lever arm on the crank throw is at a maximum?

https://www.google.com/search?q=air+vs+water+offroad

Scanning the result here suggests that the advantage goes to water-cooling creeping in traffic or over boulder-sized rocks.

Old racing Porsches started with air-cooled cylinders and water-cooled heads. Some interesting discussion here:

http://rennlist.com/forums/996-forum/202717-what-technical-innovation-led-to-porsche-going-to-water-cooled-engines-on-996-a.html

*noise reduction
*Four valves per cylinder for emissions reasons doesn't leave room for cooling fins
*air-cooling is really just oil cooling anyway
*...and, yes; of course, longevity.

[gumby79]

I'm late to th party i was going to say diesel water cooled.
Working for KAP I found a sorce for turn-key 454cuin 350hpfor 2500usd in Grant's Pass ,Oregon. From a co Named Welcome to Hellgate Jetboat Excusions.
They do a complete r&r for a new carb to oil pan including all boltons, at a 5000hr interval. There insurance company requires them to flow FAA power plant rebuild or replace interval. Its cheape(and easier) to buy a turn-key FAA approved than to rebuild.
Gumby Stay Flexible

[freebeard]

That's interesting—a V8 powered jet boat that follows aircraft regulation?