Fuel economy 'how-to' thread

[hrcollinsjr]

Originally Posted by bullmoose ...wasn't any better than 15mpg.

I can only think of a few responses to 15mpg. Your engine is in really bad condition, a sad state of tune (that will probably shorten the engine life), really horrible driving conditions, the brakes are dragging, or you don't know there is a throttle position between idle and WFO.

Harold

[Paul]

Uhhh.... maybe you have a fuel leak...

If you are truely getting only 15 MPGs, then you should be seeing signs of dumping raw fuel out the exhaust... After having the car sit in the same spot while the engine is running... do you have a pattern of black dots being sprayed out of the exhaust? That would be a sure sign of running rich... Also, at 15 MPGs, I'd think you'd be fouling plugs pretty regularly...

[opelnut10]

Something is not in proper tune somewhere or as previously mentioned, maybe a fuel leak. First and easiest thing to check is the choke to see if it is opening all the way at operating temp, next check the mechanical advance on the distributor ( turn the rotor by hand and let it go, it should spring back) take the rotor off and put a few drops of oil on the wick inside the shaft under the rotor. If everything in those two areas are OK then I would look for a leak, fuel pump first, if no sign of it leaking externally put the dip stick and smell it to see if it is leaking into the crankcase (not good for bearings) also if you a running the Solex check the ventura boosters to make sure they are secure and lastly pull the top off the carb. and check in the fuel bowl for a little glass ball.

[bullmoose]

Originally Posted by opelnut10 ...next check the mechanical advance on the distributor.

You nailed it! Mechanical advance was frozen stiff. A bad rotor that moved 1/4 inch all by itself hid the problem. That and the fact that I never bothered to really look as I'd never had that be a problem in the past. I replaced the distributor with another I had. We will see what happens. To time it in the past, I was never able to get a good initial setting, so I just set it for total at around 35. Now I can finally set initial!

I fueled up after the work to see what happens now. After 108 miles, I got 12 MPG.

[bullmoose]

Originally Posted by Paul Uhhh.... maybe you have a fuel leak... If you are truely getting only 15 MPGs, then you should be seeing signs of dumping raw fuel out the exhaust... After having the car sit in the same spot while the engine is running... do you have a pattern of black dots being sprayed out of the exhaust? That would be a sure sign of running rich... Also, at 15 MPGs, I'd think you'd be fouling plugs pretty regularly...

...nope.. No raw gas, no black splatter, no leaks of any kind can I find.. No. 4. plug is a little oil fouled, the rest are dry with a little grey/brown flaky deposits on the electrode. I can't say absolutely the mechanical advance fix was the only culprit, but I will know in about two weeks after I put about 100 miles on the car and top off the tank.

[bullmoose]

Originally Posted by hrcollinsjr I can only think of a few responses to 15mpg. Your engine is in really bad condition, a sad state of tune (that will probably shorten the engine life), really horrible driving conditions, the brakes are dragging, or you don't know there is a throttle position between idle and WFO. Harold

I'm saving the WOT for after I get an exhaust the doesn't scream "Hey Fuzz, I'm over here!

You'll see I found the mechanical advance was bad. Now that I have it working, I can get the car to idle smooth and stable at 700RPM without issue. I think replacing the sloppy rotor made a big difference there too. I have good vacuum. I would check compression, but I can't find the hose portion of my gauge.

I still need to adjust my clutch. After I replaced transmissions a while back, I never adjusted the clutch fork. The pretty red light keeps yelling at me!

[greenopelgt]

After a double road test by Hemmings - why should I change a set of perfectly good factory Solex downdrafts for any reason? One stop for gas from Carlisle to Cincinnati after carrying a half load of premium burning on Platium plugs.

[bullmoose]

So after 136 miles, I filled up.. I've gone from 11.99MPG to 22.82MPG by replacing the bad mechanical advance! Now we're getting somewhere. Every bit of those miles is city driving! Here in a little while I will swap from the 20W-50 to the 5W-30 and see if that's worth anything. I need to replace my exhaust first.

Thanks for the help folks!

[bullmoose]

I am traveling about 1100 miles this week between Kansas and Idaho. My mileage is all over the place, but getting better. Before the trip, I replaced the 20w50 with 10w-30, had the exhaust fixed, took out the weak electric fan and put the original one back on. I got around 22-24 this morning in the midwest, and almost 29 this evening in the mountains. I haven't quite figured out the reason for the difference, but it's all better than the 11MPG I was getting a few months ago. I have noticed that I get better mileage from Conoco and Mirastar stations, but junky mileage from Sinclairs. Am I crazy or is there really something to this?

[jordan]

I was wondering if anyone has tried efi on a 1.1? I was thinking about a simple megasquirt system with a single jenvey or extrudabody on a manifold like the one that Kevin Fier is using on his 1.1 kadett and I was curious about what kind of fuel economy is possible with a high compression 1.1 with a single 2 barrel TB?

[keithrulz]

I just drove to college and back 225 miles each way in my newly rebuilt 1.9/4 speed to school and only used 7.16 gallons of 89/90 octane mix. which figures out to be 31.42 miles per gallon. i got that each way and hit many stop lights in the process and about 2 hours of that cruising was at 4k rpm in 4th. I didn't think a 1.9 could get mileage like that!?? i think I'm going to try the acetone idea to see if it increases even further.

[66kadett]

I love the Chemistry here, but the simplest things for economy are best accomplished by the driver. I suspect that most Opelers are enthusiasts, but sometimes I have overlooked the obvious looking for a magic bullet.

1. Plugs, wires, and air filter. Yeah, I know unleaded fuel has made plugs a lot more long-lived, but how many times have people seen fuel economy drop 10%, then not checked the plugs, wires, or air filter? A five-hundred dollar exhaust system is worthless if the engine isn't getting any air!

2. Back out of it. You haven't won squat by outdragging a soccer mom in a Cherokee. Part of the fun of owning an Opel is being seen in an Opel. Let 'em take a good look, and check out how many people ask "What the hell is that thing?" as they go by.

3. Steady speed is good. Unless honour requires the ritual smoking of Beavis' Civic, get quickly to top gear and stay there. At a steady 60-65 a 4-speed '73 Manta 1900 should turn in the low 30s.

4. Love the 1100, respect the 1100. Yes, the 1100 is a slug compared to the 1900, but an 1100 will turn 5-10 mpg more than a 1900. For somebody with a long commute at moderate speed and traffic, an 1100 may be a better choice. It's also lighter and gives better balanced handling. But the weak acceleration may be too much of a deal breaker.

HTH, the ole professor

[GTJIM]

5. Stay away from those wide tyres - a set of 165SR-80 X 13 tyres pumped up to 32 to 35 psi will help mpg heaps. Better yet try and find a set with modern silica blend ('green') rubber as they alone are worth 3 to 5 % increase.

[PROPEL]

Water for gas, anyone?

[PROPEL]

Air Car

[opelwasp]

Originally Posted by PROPEL Water for gas, anyone?

Originally Posted by PROPEL Air Car

On the water for gas I call BS.

But the compressed air engine shows real promise. I would definitely buy one. It looks like it may even be possible to build your own.

[RallyBob]

Maybe time to revive this thread? It seems more pertinent now than ever.
I've even been contemplating putting together a high fuel mileage car just for those days the Kawasaki is not suitable (rain, hauling stuff, or long trips).

I have a 60% complete engine that should make tons of low end torque and has high compression (milled 1.5 head with 1.7 block with 2.2 crank).

Maybe a custom intake with two downdraft Solex carbs (from 1.2 Manta)? 3.18 final drive? Getrag? Tall skinny tires with full Moon flush wheel covers? Gutted interior to reduce weight? And the real clincher, my California GT that was slated for Bonneville. With nothing more than detail work like the aforementioned wheel covers and tires, plus a lower ride height and front air dam, I wonder how good I could get it to perform...mileage-wise? 40 mpg? 45 mpg? Is it worth the effort?

Bob

[Gary]

I can remember getting 42 MPG in my '69 GT on a trip back from Maine. Stock with a Solex.

[jeff denton]

Originally Posted by RallyBob Maybe time to revive this thread? It seems more pertinent now than ever. Bob

Absolutely, but hurry! Need a recipe before gas price averages $5/gal, which, according to the news, people polled think will be soon...

Don't the higher mileage engines start as a very undersquare (small bore, long stroke) design?

My engine tinkering has NEVER been about good mileage. Always just want to GO FAST.

So this would be whole new game to me. Sounds fun, and sensible, too!

[hrcollinsjr]

How about a 1.7 1 bbl. manifold and some type of throttle body injection system on it?

Harold

[RallyBob]

Originally Posted by jeff denton Don't the higher mileage engines start as a very undersquare (small bore, long stroke) design?

Sure do. That's why I went with the 1.7 block. Punched out from 88 to 89 mm, and with a 77.5 mm stroke, it's far closer to a modern engine in terms of bore/stroke ratio. Why have a massively oversquare engine if you're gonna keep the revs below 5500 rpms?

Bob

[RallyBob]

Originally Posted by jeff denton Absolutely, but hurry! Need a recipe before gas price averages $5/gal, which, according to the news, people polled think will be soon...

Working on it! It's basically going to be my 'stock class' racing engine I never got to finish (sold the car). Really built for torque. I'll revise it for economy somewhat, but I think it can make some good numbers installed in a streamlined GT.

Originally Posted by hrcollinsjr How about a 1.7 1 bbl. manifold and some type of throttle body injection system on it? Harold

I didn't get a 1-bbl intake with the engine, so I have none to work with. I'm debating over a modified Weber 32/36 (sleeved primary venturi for economy and bored secondary venturi if you need some 'oomph'), or a custom intake with a Manta 1.2 1-bbl Solex carb (I have 4 new ones!).

EFI would be awesome but I don't want to spend any more money on the engine. Just use what I have laying around or whatever I can fabricate. I have an older 'Air Sensors' throttle body programmable EFI system from the late 1980's...I used to have it on my Toyota pickup with a supercharger. But it's fairly large and flows decent air. I doubt it would be very economical, it sure wasn't on my truck! Maybe that was my right foot's fault?

[oldopelguy]

Originally Posted by RallyBob I didn't get a 1-bbl intake with the engine, so I have none to work with.

I do have that 1-bbl CIH intake that I was running the Holley carb on still, The stock Solex for a 1.1 will bolt right up, as will the bigger of the VW air-cooled Solex/Brosal carbs. I'd be willing to loan it out for the sake of an experiment.

[hrcollinsjr]

It looks like more MPG may be achieved by non gearheads simply by doing a little research for low rolling resistance tires. Seems like the auto makers are clamoring for the tire manufacturers to produce tires that will increase their CAFE ratings. I believe there are some bills being introduced hoping to establish some type of ratings to help us compare the efficiency of tires.

Harold

[RallyBob]

Okay, so here's what I have come up with so far for my 'economy' engine. One thing to remember here is that I already own 85% of the parts, so I'm just using what I have!

*1.7 litre Opel block (88 mm bore stock). Bored to 89 mm. A smaller bore in this instance means better flame travel and more complete combustion. New displacement is 1928 cc's.
*Opel 2.2 crankshaft. It's 77.5 mm stroke vs. a 1.9's 69.8 mm. It's also about 2.25 lbs lighter than a 1.9 crank, so less mass to spin up. And more stroke means more torque at lower rpms.
*2.4 Opel rods. I already have them, might as well use them! They're lighter than a 1.9 rod, and have a smaller pin end (22 vs 23 mm), and the pin end is also bushed for full-floating pins. They're longer than the 1.9's too....134 mm compared to 128 mm. So the rod ratio is now 1.729:1
*Isuzu 2.0 turbo pistons, .040" oversize (89 mm). Dished piston for turbo use, and much lighter than a 1.9's thanks to the smaller pin diameter, shorter compression height, and smaller bore. Being cast, there will be better ring seal than a forged racing-type piston. I'll probably try the Total Seal gapless top rings on these pistons. These pistons will stick appreciably above deck with the previously mentioned crank/rod combination, so the tops have to be milled down. As they are for turbo-use, theres' plenty of meat up top, and the top ring lands are far enough down to not be an issue as well. Still, even after milling over .100" from the piston a dished top remains. That's good, because a small dish is more efficient than both a domed piston and a flat-top piston.
*1.9 flywheel, very slightly lightened. It weighs 19 lbs. In theory, a heavier flywheel would be better for highway use, as once the mass in in motion it tends to stay in motion. But since I do 80% of my driving in stop-and-go conditions, less inertia is a better thing. Less to accelerate.
*1.5 litre head, angle milled .080", fitted with 2.0 intake valves and 1.9 exhaust valves. Very modest bowl porting will be done to improve airflow slightly but retain port velocity. I'll only remove material where there is a significant restriction, no enlarging of the port will occur! Chambers are a tiny 33.8 cc's, so compression should approach 11.2:1 with the dished pistons and long stroke shortblock. I'm using 2.0 litre spring retainers (stronger) and slightly stronger than stock 2.4 Opel springs.
*Keeping hydraulic lifters because I have them. The camshaft has .426" intake lift/.420" exhaust lift, 212° intake duration @ .050"/ 208° @ .050" exhaust duration. The duration is just a bit more than a stock Opel solid lifter cam, but with added lift. Plus, the emphasis is on intake flow to compensate for the Opel head's tendency to be exhaust-flow happy. Too much exhaust flow wastes fuel BIG TIME.
*I'm keeping stock rocker arms so I don't waste the roller rockers on such a mild engine. But I will have the rocker arms Micro-blue treated. This drastically reduces friction, so I'm hoping there's a significant reduction in oil temps as well.
*Intake manifold. This will either be a long-runner custom fab'd intake with one or two (haven't decided) Solex 1-bbl carburetors, OR a modified stock intake with a 32/36 DGV Weber on it. If I go the Weber route, I'm thinking about boring the secondary venturi out to 31 mm for more airflow when I 'need' it. But I'm also comtemplating sleeving the primary venturi down a bit to improve signal strength in the carburetor, and jet it very lean for fuel economy when running on the primary.
*Exhaust. Probably going with a 1.375" long-tube header (since I already own the tube bends), MAYBE 1.25" primaries if I feel like spending money. 39" long, leading into a merge collector, then to a 2" exhaust with my trademark 2.5" over axle pipe.
*Ignition. Gonna use whatever I have laying around. I'll have to check my inventory, but I might have a spare Compufire (1st choice), then an XR-3000 (2nd choice), and I know I have a factory Bosch breakerless ignition (3rd choice). If I can't find any of these systems I'll go with Pertronix and a Summit multiple spark box. Pretty nice unit for the money. I'll probably use a 1971 distributor and retain the vacuum advance for improved part-throttle driveability and economy. I'll have to limit the total mechanical advance due to the higher compression ratio (30-33° estimated), and will likely bump the timing to 4-6° initial timing thanks to the slightly hotter cam.

That's most of the details for now. Of course anything could change at any moment!

Bob