High MPG Ideas / Discussion

[Juanito84]

That makes sense. A seat-of-your-pants dyno.

Ideally I would use a regular dyno. That way I could just set the RPM and then throttle to a specific manifold pressure (or should I say vacuum) and then adjust timing to the point I get the most torque without any pinging or overheating. And I would just keep doing this at several RPM/load combos until I figured the most ideal mechanical and vacuum curves.

But at $600 a day, and at an altittude much lower than mine, renting a dyno is not worth it. I have been tempted to make my own with a large PTO hydraulic pump. Prince makes one that puts out 40gpm at 2000psi. That's about 40hp. Obviously I wouldn't be able to test high loads or high RPM, depending on how it's geared. But it's the lower loads and RPM I'm mainly concerned with.

But for now, the seat-of-your-pants dyno will have to work.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[jimw]

I didn't read every post so apologies if this was noted before. But it seems counter intuitive to run anything other than a turbo for an added boost to combustion.
To start with if your fans provide less forced air than a turbo you'll impede air flow. A turbo provides airflow that is stronger than the natural vacuum of any engine. That is what gives the boost.
Secondly tho, if it's electric it will cause drag on the engine.
So does the wider foot print I've read about that seems desirable to so many. As has been said here or maybe not, properly inflated narrower tires, accurate tuning specific to each engine with good parts, properly functioning CV joints, transaxles, wheel bearings and brakes are about as good as you can get. Wider tires naturally = more drag
With one of my buses years ago I joked about having the BIG mirrors hanging on the doors and how they weren't terribly aerodynamic.
Oh yeah, and rain-x on your windshield.
Well I thought it was funny anyway.

[Juanito84]

[modok]

Can also use a vacuum gauge.........dash mounted.
Cruise at a constant speed and time and jet it for highest vacuum reading.

They used to sold as an accessory for MPG freaks.

[Juanito84]

[mikedjames]

Instead of varying weights use a hill that gets steeper as you climb it.

I have a nice hill like this that I can get my bus up to just over 60mph on the first section starting the hill at 20 mph ..and can make it at 45 mph over the top in 4th when my engine tune is good.
When things are bad it ends up at 40mph in third..
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Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[Juanito84]

One idea mentioned in this thread is a warmer intake. I was thinking one way to get a warmer intake would be to increase heat transfer between the dual port intake manifold ends and the heads.

But would it be better to just not use a gasket, or to use a thin smear of silicone, or some soft copper cut to shape like an intake manifold gasket?
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[air-h2o-air]

use the factory type gasket.....the metal version..will transfer heat just fine....and NO RTV on them....which doesnt hold up to gasoline and does act as an insulator

[Juanito84]

I'm moving this to the correct thread since it's straying away from the Jet-A-Vator idea.

[Bugsy61]

I'm running 17.5 AFR on my Chevy engine with a Megasquirt and TBI. Wish I could tell you the actual mileage, but my odometer doesn't work. It runs very smooth at steady speeds, even though it is running lean. It would likely do even better with regular port fuel injection. Whether or not you would save enough gas to pay for the change over depends on how many miles you drive a day.

[Juanito84]

[ps2375]

I used to run my MS'd Rabbit as lean as 18:1 at certain cruise loads. BUT, it had plenty of cooling for the head (water and oil). Dunno how lean you'd want to go on an ACVW motor w/o or even w/ a CHT gauge. I had it very lean and a lot of timing advance, it would cruise well on the flat but really wouldn't pull much of a hill w/o getting out of the really lean tuning (to the tune of 30+mpg @80mph).

[Brian_e]

[Alstrup]

[74 Thing]

Yes, Brian E is correct. The CB is meant to be run off manifold vacuum (below the throttle plate).

[Brian_e]

[Juanito84]

[Bugsy61]

[/quote]
Anyhow, a lot of people don't know this, but other than at idle the vacuum advance and manifold vacuum signals are the same on a carburetor designed for a vacuum and mechanical advanced distributor.[/quote]
I've found ported vacuum varies a bit from manifold vacuum. I agree it comes from the same source. Ported will drop off as the throttle plate moves away from the vacuum port at a higher rate than manifold vacuum drops off as the throttle opens. Other than that, I think your statement is well said.
Back to AFR, if you do a search for "lean to peak, aircraft" you'll come up with a lot of interesting reading about how aircraft engines are run all the time at 16:1 or 17:1 AFR at steady, fairly light loads without any damage, and fuel consumption drops by 20 percent. This is usually accompanied by very advanced spark timing. Good stuff.

[Juanito84]

[Bugsy61]

I run somewhere around 14 to 16 btdc initial timing. Once you stray away from a stock engine in any way, you no longer have any reason to set initial timing at 7 btdc. Some of the draw through turbo guys used to run 24 btdc, locked. I'm not suggesting that you do that, but it's just an example of giving the engine what it wants depending on how much it's been modified.