Another Mileage Project

[cal 67]

The other one's really old. Wanted to start a new one.

Last year I built my 1776 for mileage only. There's some things that went into my engine which in retrospect, probably weren't the best for max efficiency i.e., counterweighted crank (extra weight + overkill for only 4000 max rpm), stock weight parts, there's something else too. Can't remember right now.

Instead of tearing it down, I wanted to start anew. Here's what I was thinking....

74 non-C/W Chevy Journal
Chevy I beams (lightened)
Stock (cast? lighter?) 85.5 clearanced pistons, true-honed barrels, and low-drag rings
Profiled straight-cuts
Engle stock grind, stroker clearanced for weight savings, profiled lobes
Light lifters
Aluminum Low Bugget Pushrods
Stock heads, fresh valve job, intakes cleaned up, stainless valves with generous back-cuts if possible, titanium retainers, and chamber work for a tighter deck
1.4:1 rockers
36mm Weber IDFs

It's less ccs than my current engine but I feel that the power should be the same or more than my 1776. So what do you think? Anywhere where you think I could improve the efficiency w/o spending a fortune?

[Marc]

Methinks you are assuming that lightweight valvetrain components will improve fuel economy greatly - actually reducing reciprocating weight has little effect at lower/steady RPM, you'd have to drive many, many miles to see a return on the investment in titanium retainers. No point in whittling down the cam either IMO (74 stroke/Chev rod should only need minor clearancing). It's your money, but you could probably find better places to spend it. What exhaust/heater boxes do you have in mind? Do you want to be able to run cheap gas, or will this be a Premium-fuel motor? What's the vehicle, and do you do mostly highway or around-town driving?

[cal 67]

It's going in my 67 Bug. My car's probably 200 lbs lighter than stock. I do mostly highway driving. 44 + miles a day. I want to continue using 87.

How do you KNOW that modifying almost every single part for efficiency won't improve mileage greatly? Is there any concrete evidence, or do you have any, or know of anyone who has had any past experiences with using lighter parts and failing? I ask because when it comes to automotive theory, people's ideas are usually all over the place and it's hard for a person to hear just one right way of doing things. I'm simply applying common-knowledge drag-engine ideas to my new engine.

[Piledriver]

...
Ring friction is ~50% of losses. Cam/lifter friction is probably next.

Look for the elephant in the room, worry about the ~1% stuff last.

Your stated goal is "mileage" you are not building a drag engine, or running at high RPM.
High RPM==friction. Friction is enemy#1.

Ti retainers and taking a few grams off the cam would be silly.

Keep the RPM down (friction) keep the displacement down, CR up, deck as tight as practical.

Rings-- low tension. Case evac, you can do a lot with manifold vacuum and a proper PCV setup, requires sealed case (crank seals)
Perhaps some Nickasil jugs...

Keep spring tension to a minimum, consider beehives from a late Ford, would work with a mild cam, and you have tiny/light retainers.

[raygreenwood]

All of what pile noted.....and think very hard about GEARING and tire diameter...when you decide on the cam and where you want your torque band to be for most efficient cruising. You can have the most efficient engine in the world and waste it all with poor gearing and tire size.

Think hard about using fuel injection if you already are not. In that case....think of a cam that keeps manifold velocity high....with a good intake manifold design and an excellent exhaust system.

Instead of a lot on some of the other 1%'s you are playing with, get a better ignition, polish the insides of the intake system, spend alot of work on balancing chamber volumes, reciprocating weights. High build quality, balance and velocity work will be better than any silver bullet.

Most "common knowledge" drag engine theory is not very useful at all for street engines....much less milage engines. Much different power curves. The straight cut gears lend virtually nothing but noise to the equation. Cam and crank thrust on a street engine cruising is not much of a power loss to speak of. Ray

[cal 67]

Ok. I'll take those things into consideration. Thanks.

[harryset]

How would flywheel weight figure in?

[Steve Arndt]

... polish the insides of the intake system

Keep it German.

[Piledriver]

...Just dont polish anything past the injectors, you want uniform texture, 60 grit or coarser.

[Piledriver]

How would flywheel weight figure in?

If anything a light FW woudl help economy in city traffic, and hurt it on the freeway.

Probably talking <2% either way though.

[cal 67]

I never even said anything about polishing the intakes. I said clean them up. I meant of casting flaws; like how a set of ported - only heads look.

Also, to clarify, I meant modifying parts for max efficiency; balancing, blueprinting, etc when I mentioned drag engine theory. Of course the powerbands of a drag engine and fuel economical street engine are going to be different.

Other than lightening the valvetrain components, how would one go about reducing cam lobe and lifter face friction? Also, what's the best ring package (brand names) for the above mentioned engine?

[cal 67]

Piledriver, there's another thing I have a discrepancy with. FW and pulley talk are so back and forth wherever you look. I asked to very well known and reputable crankshaft makers in our industry and I got the same reply, and that was that torque is made from the crankshaft and nothing else. It seems to me that the only time you could take advantage of a flywheel's stored energy is as soon as you release the clutch, in gear or when you release the throttle and coast. At a steady RPM, the flywheel is not pushing the car down the road. I may be wrong but I have an example:

Let's take two identical Bugs with identical weights and rolling resistances. One red, one blue. Both cars have the same condition engines but the red Bug is using a 16 lb. flywheel and 6 lb. pulley. The blue is using a 10 lb flywheel and a one lb. Santana pulley. So a 22 lb setup vs. an 11. Also, let's add an 11 lb. brick in the blue car to make things even.

If the cars were at a dead stop and both dropped their clutches at let's say 2,000 RPM at the same time, with the same amount of throttle, the red Bug would pull harder. Ok, so now the red Bug is out in front and both vehicles are accelerating with the same amount of throttle. The blue Bug with it's lighter assembly will catch up with the red. Right? Now both vehicles are evenly side by side and begin to depress their throttles at the same rate to any given cruising speed. The red Bug will travel at a higher speed for longer than the Blue bug. When they finally do reach their cruising speed, the red Bug will be out in front.

Now let's throw a hill into the mix:

They begin to ascend onto a hill. Maybe, only for a brief moment will the red Bug have the momentum to pull ahead even further, but in no time, the Blue Bug would have the advantage of 11 lbs less of rotating mass.

I'm just now imagining a theoretical 1,000 lb. flywheel. It would take our tiny engines forever to get our RPMs up but once we did, and dropped the clutch, it would grenade our transmissions!

So in conclusion, I believe that flywheels were most likely made heavier for driver comfort/ease of driving. A lighter flywheel has the advantage of acceleration and hill climbing.

Does this make any sense?

[harryset]

After reading around a little bit tonight: The heavier flywheel is needed to overcome the inertia of the car body. A lighter flywheel would necessarily require higher rpms to get moving and a raise in rpms when shifting as the engine will slow noticeably when the clutch is engaged. The heavier flywheel keeps the engine rotating better between shifts. Also, the lighter flywheel would only be decent for flat surfaces, not hills, as you are adding weight to the car when going uphill, or at least the engine thinks you are.

[Turbinepowered]

...Just dont polish anything past the injectors, you want uniform texture, 60 grit or coarser.

Past the injectors as in inside the heads and engine ports?

[Darth Weber]

Cal 67, I think you're going the right direction. What do you want to achieve, 40mpg, 50mpg, 60mpg? You don't need very exotic parts or a complex FI system to do it. Have you read the Hot VW's Mileage Motor series? http://www.cbperformance.com/articles.asp They got about 38.5 mpg using Weber ICT carbs on their 1745cc motor with, of all things, an 009 distributor. If they would have added an SVDA they would have got the 40 mpg they were trying for.

If you want more mpg you need to go back to John Karcey and his Karmann Ghia with a 1415cc motor, 77 x 76mm. He was, at one point, getting 60 mpg but the motor was on the ragged edge for reliability so he richened the A/F ratio and lowered the compression ratio to 7.8:1. This reduced his fuel mileage to "only" 54 mpg. He also used Weber ICT carbs.

Both these mileage motors used mildly worked heads. Some exhaust port work, but mostly just smoothing the ports and chambers combined with a 3 angle valve job and stock valve springs.

HVW's used what was essentially a '71 - '74 Karmann Ghia gearbox, what people get sold as the "Freeway Flyer" box. Karcey used taller than stock 1st and 2nd, stock 3rd and an 0.82 4th from a Bus and a 3.875 R&P. To compensate for the extra tall 0.82 + 3.875 combo a larger diameter crank pulley was used to return the cooling fan speed back to what it was with stock gearing.

I think Karcey picked up a fair amount of mileage by using a recurved Bosch 205 SVDA distributor with an MSD 5 ignition box (which I don't believe is made anymore).

HVW's used the CB Cheater cam, Karcey had Web Cams grind him a custom cam, 101 is the grind number.

HVW's tried to use light weight forged pistons, H beam rods, titanium retainers and straight cut gears to pick up mileage but Karcey used basically all stock VW components. Both motors used the same CB 76mm crank, stock full weight flywheels and heavy crank pulleys.