Gas $5.00/gal. - What kind of mileage motor should one build

[dalland]

[Eaallred]

[DarthWeber]

[raygreenwood]

The milage motor part is actually less hard than the rest of the car. There are lots of engine configs that will deliever very fine gas milage. The original 1.7L in my 411 and 412's delivered upwards to 35 mpg with the automatic...when very well tuned and driven in its sweet spot.

Highly tuned out in later years (better exhaust, ignition and lots of injection massage).....and most importantly with the factory 4 speed and really good tires....it delivered 37-40 mpg highway between 65 and 70.

However....thats on a still day...with an empty trunk. Put the tools and junk in the trunk and it loses about 2-3mpg. Get a head wind and it loses another 3-5 mpg.
All of this with D-jet injection.

So the things that most do not pay attention to while they are worrying about what "motor" to build...is primarily gearing, tires (rolling resistance) and aerodynamics. Lowering the front end slightly...and not for looks....helped immensly (the 411 and 412's need this especially)

Look hard at what new cars are doing. High compression, efficient engines of course....but carefully selected gear ratios to keep rpms down at all speed ranges.

My parents 2011 Audi (has either a 6 or 8 speed),,,but with the 2.0 turbo...at 70 mph...its loafing along at about 1600-1700 rpm and getting about 36-38 mpg.
My 2012 Golf with 5 speed gets about the same on a still day at 70...and rpm at 70 is right at 1900 rpm.

The engine is designed with it peak torque band between 2100 and 3000 rpm....really losing push around 4000. Sounds stupid?...no....when accelerating onto the interstate....4000 in 3rd gear is about 70 mph.

The vast majority of people building milage motors are thinking about the tranmission later...when you should be thinking about gearing first and where your peak cruising ranges are.

Ray

[Eaallred]

[Eaallred]

I think if John offered a "kit" with 85.5's, basically a cam, rocker, and piston set, he would sell a bunch (Imagine a bunch of 40+ mpg VW's cruising around!). Maybe not though. I'm always suprised with what does and doesn't sell in this industry.
_________________
Eric Allred

10.29 @ 131mph
Utah's fastest and quickest VW.

Aircooled.Net
Blackline Racing (Formerly ACE)

[66brm]

[spencerfvee]

you are very right on gearing it has every thing to do with milage . i had a stock vw 3.88 trans. in my bug when i got it .every one thinks that if you have a 3.88 geared trans. your going to get better milage. some times this does not hold true. i put a 4.125 trans in my bug . it ran way better and got better gas milage than the 3.88 trans did .and i pulled hills better with the 4.125 trans . it was just a more street friendly trans . all i can say it worked better for me .and your right on tire size i see guys at vw drag racing shows that have tall tires on there vws and they run like shit on the drag strip . and i feal a tall tire on a street bug would allso hold true and not run that well on the street. and your right guys build there motors first . and some never think about gearing or the right tire size . i see it all the time on vw dune buggies and vw pipe buggies and vw trikes . just my 2 cents spencerfvee

[raygreenwood]

[Eaallred]

Gearing is VERY key.

Anyone wonder why my figure was at 70mph and not 65mph which is the legal speed limit here in Salt Lake City?

70mph was 3600rpm with my car when I did my big mileage run, take a look at why I picked that rpm to cruise at:




The two red areas are my most efficient areas. The lower one is peak torque, the upper one is peak rpm. I cruised at my peak torque rpm to maximize my mileage.

Granted, I did get better mileage at 65 than 70, and even better still at 60 (datalogging showed 50mpg @ 60mph), but 70 was right before mileage dropped off (think bell shaped curve) so that is where I did the real world testing with the GPS to back it up.

Getting good MPG figures at 70mph is so much more awesome than 60mph since it's a much more realistic modern-day freeway speed in comparison.
_________________
Eric Allred

10.29 @ 131mph
Utah's fastest and quickest VW.

Aircooled.Net
Blackline Racing (Formerly ACE)

[JeivoPE]

[Bewitched]

In holland one liter of unleaded fuel cost $2.40,thats almost $8.40 per gallon

[808OvalGreasemonkey]

ACVW engines are dinosaurs,especially with carburation,they can be efficient but nearly as efficient as modern high pressure direct injection motors. These engines make incredible HP for their displacement as well as great gas mileage.
They do require premium gas for the turbocharged ones. The trick is making something that is efficient and can use crappy (cheap)gas,and if you guys can pull it off,Kudos to you.

[andy198712]

[andy198712]

[dawie]

Maybe someone (CB, etc), can sponsor a competition to find the most fuel efficient aircooled VW? Driving in convoy at 65- 70 mph for a few hundred miles, repeating the test, and have independent people scrutinize the cars and oversee the results. Categories using (A) a beetle, and (B) a VW bus.

If we can get experts like John, Eaalred, Mark Harney, Darth Weber, Jake, and the many other experts to participate... and make this a yearly event. Maybe even the followers of the blue book can demonstrate the "efficiency" of their 6.5:1 semi-hemi techology

So many old wives tales and controversy floating around in the performance aftermarket. (Gear ratios, "bigger is better", lean mixtures especially at cruising, cam selection, compression, deck height, overheating, etc.)

As they say "the proof of the pudding is in the eating". Drag racing guys have their results in seconds. Will be nice to have independently monitored mileage runs (at realistic speeds- maybe 70mph for beetles and 60-65 mph for vw buses?

Darth Weber took the words out of my mouth- If John could find a way to mass-produce his Super Squishies in 85.5mm size.

Think the ideal "mileage cam" does not exist off the shelf. One way of thought suggests early intake valve closing to maximize torque at low rpm's.
But this increases dynamic compression, meaning static compression has to be lower. Resulting in lower expansion ratio. Some say this could be one reason why some gasoline engined commercial vehicle engines have lower than expected fuel efficiency.

On the other hand, keeping the inlet open longer, enables us to use higher static compression, and increases expansion ratio. (At the expense of a bit less torque at low revs). Which is'nt necessarily a bad thing. Resulting lower torque at very low revs may also help reduce possibility of damage to the engine from "lugging" at low revs when oil pressure is low). "Semi over-expansion cycle", making better use of remaining exhaust gas pressure, which would otherwise be lost. However going too far is not good, as this will hurt efficiency at very light loads. Like if you were running full "Atkinson cycle", which is only efficient at full load (as when used in a hybrid).

By the way, i was inspired by Jon Carcey and built a slightly different small mileage engine for my beetle some 20 years ago. Still going fine after over 100 000 miles. It did not fail, melt or explode as some "experts" predicted years ago. Easily cruises at 80mph all day long, while cht's remain cool. Being more efficient, a larger percentage of the fuel is converted to useful mechanical energy and therefore less is wasted as heat to the heads.

Think that, now 30 years later, some improvements to the Carcey type mileage engine concept may be: Fuel injection, improved squish, different camshaft, and 5 speed box. Maybe some of the coatings available nowadays will help as well.

[spencerfvee]

hi dawie . that sounds like a great thing to do . we have vw drag racing . i am for a show down on who can get the best MPG out of a air cooled vw motor .i would like to see dean kirsten of hot vws . get into this and report on it in hot vws . . there could be a contest between the 50 states . the cal. guys are allways talking about how they are the leaders in performance . how could they place in a MPG contest mmmmmm????. and the over seas guys . they could have there own MPG contest and there winners could go agaist the USA winners after all high cost of gas is not just in the USA its all over the world .the over seas guys allways come up with some great motor combos. after all they have been dealing with MPG cars for years . great going dawie GO AFRICA this is something i could get into spencerfvee .

[spencerfvee]

hay greasemonkey . we vw guys are like the ford flat head forever guys . air cooled forever . if this contest gets going. i would be willing to bet that a air cooled motor can get better MPG than any new water pumper sold today at a dealers show room. spencerfvee

[spencerfvee]

hay john .what do you think about that reply john . now cant we all just get along lol lol spencerfvee

[spencerfvee]

wow is all i can say. if our gas is going up . your surely will go up to. that sucks big time spencerfvee