High MPG Ideas / Discussion

[mikedjames]

The other day I completed a tank full of fuel on a fast drive, where the engine was running about 16-17:1 on the flat at around 65 mph around 4100 rpm, and dropping back to 13:1 on hills.

My fuel economy went up about 10% compared with a richer tune, or 22 vs my usual 20 UK mpg.

Because I am running a dreaded progressive, by slightly closing the throttle or opening it, the mixture would go from 14:1 to 17:1 at the same rpm, and same apparent power.

I decided to go for a leaner tune because I have now got a basic CHT measuring setup, one sensor each side in a Brazilian sensor boss.
The bulk metal temperature of the heads hit about 300 deg F.
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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

[Max Welton]

[Juanito84]

[Juanito84]

I noticed something interesting with my stock carb. If I'm going down a steep pass and shut off the shut off solenoid on the carb temporarily the engine vacuum will keep it shut until you give it some throttle. No fuel while engine braking!
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[oprn]

I have not read every post on this thread, just wondering if anyone has tried preheating the gasoline to get better vaporization, more complete burn therefore higher mpg?

[Bugsy61]

I know that my Kadrons run smoother since the air picks up some warm air as it
passes through the turbo. By that I mean just cruising around town, not on boost. Why don't you rig up a heat box around your exhaust and let the carb pull air through it. Maybe have a cable controlled flap to switch to cool air when climbing a hill or accelerating to avoid pinging.
Smokey Yunick was experimenting with heated gasoline when he died. Sounds really dangerous though.

[Alstrup]

[oprn]

[Alstrup]

Search ebay for diesel fuel filter heater. I am a little surprised that so few of the fuel efficiency guys use this option. It works well for preheating gasoline for extreme weather driving.

[oprn]

[bugguy1967]

I'm fairly sure I'm going to take a stab at this MPG venture. I'm going to take a slightly different approach, using some racing knowledge as my basis:

Lower rotating and reciprocating friction - I'll achieve this by using a modern lower-drag ring package, with properly honed barrels for that specific ring pack. The barrels will be Sunnen-honed to a near perfect roundness when torqued in the case.

Modern pistons with moly-coated crown pistons, to reduce detonation, and increase thermal efficiency. 30.9mm compression heights will drastically narrow the engine width.

Re-designing the intake manifold - The goal is to optimize runner and plenum length for the 4500 rpm-max operating range. This means eliminating the factory center section and end castings. I'll adapt a pre-heat system to this manifold that heats the manifold at the beginning of the carb flange all the way to the head.

Use a real merged 1 3/8" header modified for an O2 sensor.

Run negative deck (out of the hole) to aid in more complete combustion.

Small chamber, tight deck, high quench, multi-electrode plug

Programmable crank-fired ignition - Will not only aide in optimizing timing in all ranges, but eliminating gear drag, however minimal. Also timing scatter.

Textured runners, ports, and chambers - To help fuel remain in suspension until combustion. My goal is to eliminate fuel puddling.

The engine will be a 69x86 (1603cc) engine. I'll use the Pipemax program to optimize my inlet and exhaust lengths and diameters.

[Juanito84]

As the engine was breaking in I got about 25mpg, then I measured 28mpg. Now I'm getting a consistent 30.5mpg. Well, part of the reason too is that I'm actually getting oil temps above 140°F. Today they sat right at 180 most of the time with them going up to still below 220 when climbing 4,000ft up Cerro Summit. Head temp never got above 350°F, usually settling at 300 (although when it was below zero my guess is that it was way off due to not being of the compensated type.)

Now I need to start dialing in the carb and the spark table. I notice that the AFR changes a lot with outside temp. I have a stock air cleaner with a vacuum thermostat and carb heat. But of course this kind opens up at full throttle sucking in cold air. So I was getting around 14:1 at full throttle. Now it's sits around 13:1 at full throttle and between 15:1 to 14:1 outside of full throttle. I'm guessing full throttle will become even richer as the days get warmer. I have a 50 pilot jet. I'm not sure what main jet I have.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[[email protected]]

try a 48 idle next.

http://vwparts.aircooled.net/Solex-Kadron-Brosol-and-Bocar-Idle-Jet-Micro-p/solex-idle-jet-micro.htm
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It's just advice, do whatever you want with it!

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[Juanito84]

[[email protected]]

when dealing with elevation changes, you have to jet for "worst case", which is the LOWEST elevation you see. It will be a little rich up high, but that doesn't hurt anything.
_________________
It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net

[Juanito84]

Well I jumped clear to a 45 idle jet. at 55/60mph I'm getting around 15.5:1 at 7,7000 and 15.9:1 at 5,800ft. At around 40mph I'm getting about 0.5:1 leaner. I haven't touched the main jet yet since I'm still waiting for the weather to warm up to see what kind of high load AFR's I'll get with warm air.

I'm also positive I need to rebush this carb. I got the mixture screw all the way out and am idling at around 20:1. If I put a propane tank to either side of the throttle shaft the AFR drops down to around 14:1. That's only putting propane to one bushing at a time!

I also have advanced the timing quite a bit. I have total, full throttle timing at 35°! With testing I've got part throttle advanced even more too, up to as much as 50°! A few test drives and I'm seeing better acceleration time. Going from 20mph to 45mph in 3rd gear I've knocked off a whole second. I haven't noticed any pinging. I do wonder if this engine won't explode like a stick of dinamite with all I'm doing to it. I have the CR up at 9.5:1, running leaner than 13:1 at full throttle and the timing advanced pass all common sense and using this car to climb steep mountain passes!

I still need to do some more runs to get my fuel mileage numbers put together. But from the looks of it I'm well over 30mpg now.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[Juanito84]

So I'm getting 34.9mpg average (US miles and gallons.) Not bad! That's about a 70% highway 30% city mix. And by "highway" I mean mountain passes over the Colorado Rockies, as much as 20,000ft change up and down in less than 150 miles.

But I think I'm going to give the Bug a rest for a while. I got my 1985 Golf diesel running again and it gets around 55mpg.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[oprn]

Thanks for keeping us up to date on your mileage journey! Interesting stuff.

The pinging issue is worrysome to me as my ears are older and Bug engines tend to the noisy side especially with better flowing exhauses. I am working on a visual indicator solution to track engine vibration with the hopes that I can catch a change in vibration as an early indicator of aproaching pinging.

Yes the VW diesels deliver some pretty sweet mileage numbers. Our '04 Jettas delivered 55 to 57 regularly with 61 possible with judicious use of the load peddle. The '02 we have now is in the 59 to 60 range normally with 63 achievable on careful driving! Pretty hard to beat that on gas!(this push to get rid of diesel cars is so bogus and backward... don't get me started!! )

I gave the pre-heated gas a quick unscientific try the other day. I did about 6 wraps of plastic fuel line around the oil filter and insulated it with a rag and taped it in place. after warm up my heat gun showed about 10 degrees warmer on the gas line and 8 higher on the carb bowl. this of course is on an open bodied dune buggy at temperatures below freezing.

No fuel mileage results were attempted yet as it is still too cool for this old cat to go for lengthy rides but I learned 2 things. 1) I need better heat transfer than the plastic line affords. 2) even without any mileage figures the engine ran remarkably better in the cold even with just a few degrees warmer gas.

I think warming the gas has some real possibilities that need further testing. Yes warm air helps both with winter running and mileage but are we not trying to get the gas warm by adding heat to the air? Why not concentrate directly on getting warmer gas?

[Juanito84]

Warming the gasoline sounds interesting, especially in a place like where I live where temperatures can get down to as cold as -40°F (-40°C) at times. I just might try it some day. However, I would guess that there's more benefit in warming the air since normal AFR's are around 5% to 8% fuel and 92% to 95% air. But that's not to say that warming the fuel wouldn't help.

Here's a thought about louder, lower restriction exhausts and intakes. They can improve efficiency, especially in a case like mine where I tend to be near full throttle because of the steep grades. But still, a lot of my driving is in top gear cruising along at moderate speeds, which is where you won't benefit much, if at all from lower restriction intakes and exhausts. This is because you just don't have the flow necessary to create a lot of back pressure in the exhaust. And as far as the intake goes, anytime you're driving at part throttle your biggest restriction is your throttle plate. Plus I wonder what some of these exhaust systems do to air drag.

I got my 34.9mpg with stock intake and exhaust. I might try a zoom tube or something similar one of these days. But like you said, louder exhausts make it harder to listen for pinging.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[Bugsy61]

Glad to hear the advanced timing is working out for you. As for pinging, there is J and S Safegaurd for $75 and there is water injection for $300. Tough to save enough gas to pay for a $300 water injection system, so I guess it depends on whether you are doing this to save money, or for the sake of experimentation.