quest for better mileage

[Challenger]

one thing dawned on me this weekend
the White car is the only one that does not have power steering.

For anybody wondering, removing the power steering belt still leaves these cars very driveable. It's not the typical heave-ho like most cars with power steering. I'd put it back on for any serious off-roading however. It's there for a reason.

I´d recommend keeping the power steering belt off. I´ve been driving T4wds with manual steering for 5 years and you should see my biceps...

But seriously its interesting that the one that hasn´t got power steering gets the best milage. I have a ´90 corolla alltrac and its much thirstier on fuel than my Tercels. In fact I´ve heard others here say the same thing. All the alltrac corollas here have power steering but none of the Tercels do. I always thought that the Tercels got more MPG because they don´t have full time 4wd.

[Neu]

Yeh, i've been thinking about removing my power steering, on a 5.0l+ engine it doesn't make a difference, but on a measly 1.5l i bet it sure does.

I'll probably take it off sometime today.

[Snax]

One of the things I am wondering about is the effect of rpm on fuel economy. Since the day I bought mine, I've always tried to keep them as low as possible and in the highest possible gear, but now I'm thinking that it may not be the most efficient way to drive a carbureted vehicle. My thinking is that the air velocity through the carburetor has a significant impact on atomization, so there is probably a point where lower rpms simply don't mix it up enough. Fuel injected vehicles don't have the same issue because they use high pressure and the injectors are responsible for the majority of atomization.

I'm conducting my own experiment by using lower gears than usual. I.e., no more cruising in 5th at 40 mph. Instead I'm seeing what happens in 4th.

Any thoughts or experience with this?

[sdoan]

One of the things I am wondering about is the effect of rpm on fuel economy.
Any thoughts or experience with this?

Yes! It's the throttle opening that counts. The wider the throttle the more fuel and air per time. I get better gas mileage driving with a very light foot and down shifting when the car starts to slow. If I step into it, I can almost see the gas gauge drop. I've come to this conclusion over 120,000 miles in the little beast and lots of long trips.

Back to the original question - does the car with the poorest fuel economy have the loudest stereo? My gas mileage dropped significantly when I got the good stereo...

[ARCHINSTL]

Back to the original question - does the car with the poorest fuel economy have the loudest stereo? My gas mileage dropped significantly when I got the good stereo...

An emphatic YES !
You see, when you beat on the dash/steering wheel to keep time with the drums, there is actually a slowing effect applied to the car because of the impacts absorbed and consequently transmitted to the wheels, quite proportional to the decibels emitted.
You could look it up...
There - another case made for Yanni tapes !
Tom M.

[takza]

One of the things I am wondering about is the effect of rpm on fuel economy. Since the day I bought mine, I've always tried to keep them as low as possible and in the highest possible gear, but now I'm thinking that it may not be the most efficient way to drive a carbureted vehicle. My thinking is that the air velocity through the carburetor has a significant impact on atomization, so there is probably a point where lower rpms simply don't mix it up enough. Fuel injected vehicles don't have the same issue because they use high pressure and the injectors are responsible for the majority of atomization.

When you have an O2...they need to cycle and typically they don't unless your manifold vacuum is high...and this only happens when throttle is just off idle. Noticed with an early EFI TB setup that you only get O2 cycling if the rpms are UP and the throttle position is just off idle....LOW LOAD conditions.

So your mileage might be better if the kept the rpms in the 2000 to 2500 range and the pedal down just far enough to keep moving?

My guess is that most small displacement engine are most efficient under these conditions with the load need to move.

Buy a vac gauge and drive for best vac and keep the rpms up?

[Snax]

I'm just going to avoid lugging it for this tank and see what happens. The best economy I've gotten before and after installing the Weber while sticking to low rpm is a paltry 26 mpg.

[splatterdog]

There won't be any o2 sensor voltage fluctuations without a stock feedback carb. With a weber aim for .5 volts while cruising steady for a good baseline. I am surprised your weber isn't doing better. My two get 30 and 32. The 32mpg is on the 84 which has out of the box jetting and the tallest 13's I could find and of course the highway gears for that year. There is a 300 rpm difference between the two at speed. So I would say reduced rpm does help mpg slightly(not to metion reduced interior noise). I almost wished the 85 needed treads so I could slow it's engine down too. I don't race anybody(except metro's and grandmas) unless it's snowing so a little less bottom end doesn't bother me!

[takza]

I'm just going to avoid lugging it for this tank and see what happens. The best economy I've gotten before and after installing the Weber while sticking to low rpm is a paltry 26 mpg.

Well with a weber...forget the O2. Probably need to rejet it? Shift in the 2000-3000 range, but use a light foot?

[Petros]

some 28 years ago I did dyno testing on a number of both stock carb, EFI and Turbo charged engines, almost always the best economy comes when the engine is at low RPM with throttle near full open. That is, when you are always lugging the engine. If you end up with a lot of pre-ignition however, you could damage valves and head gaskets, which means there will be no savings. So the most you can lug without getting pinging should deliver the best economy.

Also consider trying to drive without using your brakes, that is allow it to cost up to stops and lights, watch ahead for traffic, signals, etc. and match speed to signals and other traffic, and use VERY slow acceleration away from stops, and never accelerate up hill if possible. These will improve economy about 10-20 percent. But it is hard to do in heavy traffic.

[Snax]

I go so far as to do engine-off and neutral coasting, as well as limited warm-ups, and I use a block heater. I think there's just something else I should be looking at.

[takza]

* increase tire pressures to the point that you can corner and not have slop...stay under the max press on the sidewall.

* synth oil in engine...rear diff...trans I'd stick with regular gear oil plus an additive.

* check your brakes for freeness...roll up to a stop at about 1 mph...you'll notice any sticking...should stop and roll back if on a slight slope.

* best mpg I ever got was with high pressure in cheapo tires....driving very lightly at no more than 45 mph...like having an egg under the right foot.

* check for aero issues...best mileage ever (not valid) was 47 mpg driving all day with a 25 mph tailwind...600 lbs in the car and with some stuff on top.

* carbon clean...oil flush...PCV jar.

[Petros]

I want to revive this thread because of the rising cost of fuel.

Anyone have any other ideas for mods to improve fuel economy?

A home made induction system that attaches to the stock carb?

How about some external aerodynamic mods, front spoiler? I was considering blocking off the grill since there is enough room to plenty of air to the radiator from below the bumber (a high pressure area anyway), and also covering the head light recess with clear plexiglass (or go to the '87 type head lights). Fill-in or flaten the rain gutter (guess I will not be using a ski rack again). fill all body gaps with weather strip tape. Any other ideas, would a spoiler on the back help?

Ideas, ideas, we need ideas.

[takza]

I think that the key to getting better mpg is finding a way to lean out the fuel mix...while at the same time using certain mpg mods such as fuel additives...fuel heat...PCV jar...etc.

This page has specific info on the T4WD:

http://www.maryngroup.com/Archives/Arti ... omemag.htm

I'd like to find a way to manually control the HBCV or whatever it is on the pass fender that the ECU/O2 uses to control the mixture by introducing air into the fuel flow. Find out the ECU voltage(?) range to the HBCV...duplicate and control it using an adjustable resistor and you could theoretically control the mix from the dash. You'd run at cruise and lean it out till you see a stumble and then richen it up some. A lot of the 50% + gains from the HAFC (HHO plus sensor modes) are from sensor tweaking. If you had this set up then you could tune the mix in to whatever mpg enhancing mods you were using.

You could even use batteries or one of those 12V voltage converters for your base voltage. My guess is that it is a voltage range that is used.

Other ways to lean:

* add an air bubbler (thru water) I gains a couple mpg with a '76 Corolla (no O2)...though with the 3AC...any extra air at idle makes it NOT idle

* solder the "power valve" closed ala LaPointe

* install smaller jets?

IMO...mpg gains usually come from using a variety of methods combined...increased tire pressure...driving slower...reduced weight...fuel additives...etc...

A fuel additive I will eventually test:

* 24 oz cheap canola oil per 10 gallons and 3 oz acetone per 10 gallons...not sure if this will make your car smoke or carbon up the plugs/O2. Some have claimed good gains and little extra smoke. Due diligence required.

* 3oz 91% isopropyl per 10 gallons...from Walfart...need to use some top lube with this...will give more power...need to keep off the throttle...said to work even with 10% ethanol gas.

* other mods that might work? magnets....ozone injection...

* an air dam down almost to the ground...messes up the off road stuff though

One method that works for me....combine trips and just don't drive.

I need to fix my vac diaphrams so they work.

BLUEPRINT this Tercel?

White tercel 36-38 mpg 120-125 psi 15 deg pinging

Then there is always this mod:



What with the NWO and disaster capitalism in action...we'll ALL be doing this fairly soon.

[Snax]

Hmm, not so sure the emissions from that last suggestion would be a step in the right direction . .

As for aerodynamic mods, I think it would be tough to make a marked improvement to the Tercel shape without some signficant changes to it. Volvos have more slippery lines IMO.

I installed a partial grille block on mine in this last fall. It covers only the top half and is a thin sheet of ABS that's held on with double sided tape. I don't think it really did anything for fuel economy, but It helped warmup slightly.

I've also had the tires jacked up to 45 psi since I got the car, but they are skinny little M&S tires that seem to have the rolling resistance of marshmallows. Perhaps it's something else that's causing the problem, but my car has a deplorable coast down rate. I think that is where allot of improvement could come from, but I don't know that I'm really going to sweat it at this point since we have two other cars that are better for daily drivers both in comfort and economy. (I'm still only getting mid-20 mpgs with the Tercel.)

I think there is simply allot of extra drag from the 4WD system on these cars, and getting much over mid-30 mpg would be miracle work. My Escort wagon in contrast can push into the 40 mpg range with little effort. So if it's highway economy you are concerned about, I suggest finding something more suited to highway driving. The Tercel simply is neither slick, nor an easy roller. It's saving grace around town is the small displacement and low weight. Ours is pretty much going to be relegated to snow duty cargo hauling from here on out. (Or perhaps a lift kit. )