Best way to improve fuel economy?

[Petros]

With the increasing cost of fuel I thought I would see if anyone has any tested ideas that they could share to improve fuel economy.

Primarily you either have to improve efficiency (compression ratio, cam shaft) or reduce loses (induction, exhaust, tires, etc.).

I have raised my CR to 11.2 to 1 the last time I had it apart, I am running about 10 btdc timing. I am still using the stock carb, exhaust and tires and have most of the smog equipment still installed.

I get about 28-29mpg mixed driving and about 32-33 mpg highway. It seems a lot of the modern cars that are heavier with similar sized engines get a lot better MPG, so there should be room to improve even with this older technology car.

What fuel mileage are you getting?

Besides replacing the exhaust system, and running my tires at 50 psi, is there anything to be gained in economy by changing the carb?

Has anyone put in a larger exhaust system, if so what was the economy increase if any?

What about replacing the air filter or air filter housing?

Which of the smog equipment would disabling give the best gain?

[Snax]

I'm trying to figure out the same things. I just replaced my stock carb with the 32/36 DGEV this month. Although it's not as cold weather friendly as the stock one (meaning you will need to manually keep the revs up until it gets a touch of heat in it), I think it will provide a significant improvement in FE for me, but the stocker was just dumping fuel in at startup. Some of my cold weather issue with it could be related to how lean I have the idle mixture set, but I think that is what is going to make a significant impact on my city economy.

One thing I have noticed about my car however is that it seems to have a fairly high rolling resistance. I don't know if that's just from the 4WD system or if my snow tires are just plain mushy even at 45 psi, but I think allot could done there. It seems to lose speed about twice as fast as our Mazda5 even at speeds under 40 mph, so I know that's not an aerodynamic issue.

Aside from that, one of the biggest factors in improving fuel economy for most people is driving habits. Keep the rpms low, coast as long as possible to stops and down hills, and don't leave it idling for long periods.

I've thought about doing things like disc wheel covers and wheel well fairings, but my car almost never sees the highway, so that would be pretty pointless for me. It may make a measureable difference on a highway car however. Certainly, if you have racks on the car and travel on the highway allot, take the racks off whenever possible. Testing has shown that an unloaded rooftop Yakima style rack can knock as much as 10% off of fuel economy.

My first tank of gas only netted me about 24 mpg. I'm hoping the DGEV will push that up to at least 28. I drive so few miles however, it's gonna be about a month before the next fill, so I won't know until then.

[takza]

I manage about 32 mpg mixed in summer with the stock carb and all the nice vac tubing mostly intact. 30 mpg mixed last winter.

* 14" wheels/tires about the same diameter as stock...higher tire pressure

* ~ 2" ID exhaust from cat back thru a glasspack

* advanced ignit

* EGR doesn't work

* warm air intake for winter

* NGK V-power plugs...indexed

* moly additive in transaxle

* synth to part synth engine oil with additives

* air bleed thru dist...ozone air bleed

* newer O2, but will not cycle (?)

* Condensator

Typrus was claiming possibly higher mileage (high 30s freeway) by bypassing all the vac tubing and going simple with vac advance to dist...canister purge at minimum?

The ONLY 4x4 vehicle that you can now buy that gets similar mpg to the T4WD is the Ford 4x4 Hybrid?

There are no easy answers as far as mpg gains...you gain a few % here and there from various mods and changes...but they do add up.

[keith]

Modern cars in the same weight range i.e. Saturn SL get better gas mileage for two reasons, 2wd only and fuel injection. I don't think Toyota ever put fuel injection on the two valve engines.

[Petros]

Yes the 4wd issue occurred to me, you not only have the extra weight of the drive train but on this car the rear axle and drive shaft is always turning. The extra drag on of the rear wheel drive train can not help economy.

There are certain of the emission control system that do effect economy, but many do not, i see no reason to disable all of them, but only the ones that affect economy. Which would they be?

What exactly is the "air bleed through dist." ? How would that help economy?

Does replace the O2 sensor help economy. Mine is likely as old as the car and not working. I am not sure it makes any difference on to the driver. Would it affect economy?

YOu are correct, they never put EFI on this engine/head combo. They did no a later engine with a 12 valve head, though the dist. location would not make it suitable for conversion to this car.

There are some costly aftermarket fuel injection conversions, and someone on this forum installed a Metro TBI fuel injection system on the stock intake manifold. I do not know if it helped the economy. It looks like a nice clean installation however.

Going to a 4AFE would be not too bad if you can put a distributorless system on it and plug the old dist hole. My Corolla All-trac has a 4AFE with full time AWD in a heaver car and it gets about the same MPG as my tercel! But the dist. location makes the engine swap a PITA, you have to alter the fire wall to get clearance for the dist. I understand those after market distributorless systems are pricey but there might be some later production cars that use them that can be adapted to this engine.

[takza]

There are certain of the emission control system that do effect economy, but many do not, i see no reason to disable all of them, but only the ones that affect economy. Which would they be?

What exactly is the "air bleed through dist." ? How would that help economy?

Does replace the O2 sensor help economy. Mine is likely as old as the car and not working. I am not sure it makes any difference on to the driver. Would it affect economy?

As far as I know the EGR reduces mpg some. An air bleed will help the mpg of a non-feedback carbed car...just leans it out a little. Some bleed thru a jar of water and some thru the dist cap to pickup ozone. I replaced the O2 in mine and when I finally got around to checking the cycling with a multimeter...it doesn't even cycle. A PCV jar might help mpg some and will help to keep the carbon cleaned up. With my Condensator and carbon cleaning I've used about 1/3 qt oil in the last 7K miles or so...usually around 1 qt to 5K.

viewtopic.php?t=3293

A PCV jar might increase mpg a little...keeps your oil, combustion chambers, and cat converter cleaner too.

[hberdan]

I get about 30-32 mpg on summer tires. In winter, with aggressive, but not studded snows, a ski rack and this absolutely awful oxygenated gas we are forced to endure on the Colorado front range, I get a dramatic drop in mileage, down to about 26-27 mpg--sometimes even less if I have to warm up a lot, or drive in the mountains, or travel long distances in heavy snow in 4wd.
I'm running with every thing as factory equipped, including the regular carb, and 13" (Hankook W409) tires.
I do a lot of mountain driving; combined with a carburated vehicle at altitudes between 6000-10000', and 290,000+ on the original engine, I think I'm doing ok for now. It beats having car payments AND paying for gasoline.

The only current SUV things that are close in concept to our Tercels use full-time all wheel drive, which cuts down on mileage quite a bit. It's a shame that those weren't made with a 2wd override switch so the awd feature could be disabled for normal driving...but I digress. Foresters get 24-27 mpg, same as the Honda CRV.

[TuffGong]

I went from getting 20-21mpg on average when I first bought my terc. The warm air intake hose? was missing so I replaced it giving on average 24 mpg. I made some mods to my car and got 31.705 mixed highway/city/and a few miles of offroading and not driving as conservative as I could. I also have a PCV jar/filter as well.



and



I haven't really done any tests though and I still need to troubleshoot some things. My acceleration is a bit odd as it bogs with heavy acceleration in higher gears i.e. I have to rev high in low gears to get good acceleration which effectively kills my gas mileage. My main engine fuse is working with a blown fuse in it and the hot wire from the radio attached to it. If I put in a good fuse, the car won't shut off.

I have a long way to go to fine tune my system but I'm slowy getting there.

http://www.tercel4wd.com/forums/viewtop ... 79&p=30823

[Typrus]

I saw low 40's on my long highway trips running 87 octane oxygenated fuel at 75+mph.
My car was a rolling paradox. It got worse fuel economy driving gently than my normal style. And if it was still running, I'd challenge any one of you to ride with me for a few thousand miles and challenge that statement. Period. For some strange reason, thats just how it was.

My vacuum goodies were bypassed, for the most part. EGR still worked, canister purge still worked, and the dizzy was hooked up, but as I later found, my vac advance was dead.


Go read takza's "heresay, theoretical, unrealistic, mythical" posts testing various methods. lol. Anyone can gripe at him for testing the latest fad, but guess what? He does root out what works too.

Some good mods? Aerodynamic mods. Yes, I've been told that trying to make a brick aerodynamic is kind of pointless. Well, there is always room for improvement.
A full underbody bellypan would definitely help. The biggest concerns are clearing moving suspension members, and allowing for exhaust heat to either be contained in the pipe or vented away from the space between the body and pan.
Yes, a wheel disc would help, but if you drive like me, your front brakes will melt. lol. Maybe something like a Civic Hybrid wheel. With small vents. Then, incorporate into the bodypan some ducts to feed air to the brakes. Will definitely help.
Get the rare H4 Euro-style flush headlights. Not the 9007 POS USDOT headlights, but the same flushness with the Euro lens and better bulb. Eliminating the recesses on the leading edge will help reduce some turbulence. Getting the Euro ones will help improve aesthetics as well, versus say a plexiglas cover to smooth it out, which will distort the light as well as look strange.
Get a sort of cowl-cover for the wipers. If you do it where it smooths airflow at resting position as well as increases downforce, you'll be golden. No more 70+mph wiper lift. Just don't overstress the wiper motor with weight or resistence downforce.

Smooth the airflow at the rear to help reduce the large amount of drag at 50+ mph.

Bear in mind the Terc4wd has a great coefficient of drag for what it is. Hey, it could be worse. It is more aerodynamic than an Excursion. lol.


ALSO....
Low rolling resistence tires are a place to start. Harsher ride, not offroad friendly.

Get 4 all-new wheel bearings. Get new bearings inside the rear axle and diff. Get everything super clean. Replace with a high-quality full synthetic lube. I'd vote Amsoil or Schaeffer's.
Get new u-joints. You'll need to pay a driveline shop (who is willing to do the work) to remove the old ones, find matching ones, and replace them and re-stake them in. Or maybe even get a custom drive-shaft made with replaceable u-joints.
It was $350 or so to get a one-piece shaft made for our lifted F-250. So a custom one here shouldn't be too bad.
Either get a new carrier bearing on the rear driveshaft, or get a 1-piece made to kill the carrier.

Make sure your front diff has good bearings.

If you can, have a local good tranny shop bust into your tranny and replace the bearings (and probably synchros while in there) and if the budget allows, get EVERYTHING in the tranny cryo'd. It'll help it last a lot longer. And maybe handle better than 100HP/100ft-lb.
Again, high quality synthetic lubes. Amsoil is good as a straight synthetic, Schaeffer's is on par with Amsoil, PLUS it has molybdenum and other goodies in it.

Good shocks, struts, and springs will help also.

If you haven't, flush your engine. I'm going to do a write-up on it here in a minute or so. Then use good oils. I used either Schaeffer's Supreme 7000 15W-40 or Valvoline Deep Blue synth 15W-40 with Purolator PureONE filters.

Use a good air filter. If you still have the Aisan carb, either get a K&N filter, or get the Fram filter. NOT THE STP. The STP has a good 1/2" less filtration area. The foam ends come up the paper further.
Generally, the biggest air filter your can make work will work best and for a longer time.

Good fuel filter will help.

Make sure your thermostat is good.


I had a 2" manifold-back exhaust installed on Silver. About 2 weeks before I wrecked it lol. Mileage went up in my 2 tanks in that time by maybe 1 or 2 MPG. It'll either be going on White when I get the time, or it'll go on my next T4WD. Be warned, with a 2" system and a generic turbo-muffler, you will get a ricey drone for a couple hundred RPM window. It goes away pretty quick, but it is there. A better muffler would probably help. I spent about $550 on a whole system. New muffler, new cat, etc.

If you look it up, takza did a flex-tube system. Much cheaper than what I did. Though, getting a 2" downpipe bent and welded would be quite helpful.

GET A GOOD ALIGNMENT.

Replace all of your suspension bushings to maintain proper alignment. All of them. You can get most through the dealership for a reasonable price. You can only really get the control arm inner bushing and sway to body bushings at the parts houses.


Did I mention check for proper differential lash to reduce resistence?


If you can, replace as much of your cars wiring with thicker wires. Headlights and stereo in particular. Why? To reduce voltage drop. Thus reducing load on the alternator, and thereby reducing resistence on the crank. Not to mention cleaner stereo sound and brighter, whiter lighting.


If you can, get the manifolds and head cleaned up. Remove casting seams, rough spots, etc. Not necessarily a full-on port job, but enough to get airflow cleaned up.

Also, our heads have a lot of port inconcistency. A LOT. Get them evened up if you can.

Somender Singh's Grooves. Look them up.



I know of a few more, but my brain is off right now.

[splatterdog]

Whew! Don't forget to pull unneccessary seats,carpet,headliner,interior trim,spare tire and jack,replace windows with plexi,smaller lighter lawn tractor battery, only drive with a tailwind,go on a diet.....

Some of the previously mentioned strategies in this thread would fit into this category. Some might take years to "pay back" if ever.

If you can't get satisfactory mileage out of a tercel, it might be time for a 3 cylinder Metro or smaller.

Sorry to seem negative, but this year has worn this topic out beyond belief. Small in-tune roadworthy car and light foot. Any questions?

[Typrus]

If I'm not mistaken, the question was how to improve economy? Not whether anyone liked the topic?
The underbody bellypan can be done with sheet plastic or sheet metal. Not like its a several hundred dollar undertaking.

A new carrier bearing is somewhere around $100-150 last I checked. Its something that should be done to prevent driveline failure. If you don't want it at all, shell a little extra money to have the driveshaft reworked into a 1-piece. Not too tough or unrealistic.

The tranny rebuild may be pricey, but most are pretty likely to need it at this point. Cryo dip isn't that expensive either. A 7.3L Powerstroke block is only a hundred or so to do last I heard from the folks who've done it. So a tranny can't be that bad.

The bearings are another preventative maintenance deal.


You do realize that a lot of what was recommended was just bringing the Terc up to like-new quality, maybe with a few improvements?

New headlights not only look good and help cut resistence, but they also cast a better light pattern, improving safety. How valuable is your life?

Wiper cowl? Want to keep it simple? Stiff plastic.

Wiring isn't that expensive either.

If you have the head off, groove it. If not and you don't need a gasket, leave it be.



Heck, I'm paying $1.69/gal right now, which is getting close to the lowest price I've ever paid ($1.50) so maybe you're right. Spending $50 would take a while to earn back. Lol.



Oh well. I find it fun to mod what I have. And if it can be done relatively inexpensively, then all the better.


We'll spend almost $400 on a new carb but get scared about a few hundred dollars in other stuff. Seems a tad strange to me.


As for things like the exhaust, it likely could have been done cheaper. Look at takza's flexi-tubing system. A lot less than mine. Not to mention mandrel bent (even though the surface does lend to turbulence) and heck, if you don't care about the brown cloud over your local big city, you could punch out your current cat, cut off the end tubes, and make it so you could weld a 2" tube through the middle of it so it's essentially a super-stealth straight-pipe. Slash $100 off your bill there, unless the DOT finds out. lol. You could always also go cherry-bomb on the muffler and spend $15 on it. Theres $100 less than I spent on my muffler. Look, we're already cutting the dollars back!


But if you wanted, and like to offroad, you could do an aluminum bellypan. More expensive for sure, but it would protect your valuables.


But what do I know. 42mpg must not be all that great.

[takza]

One idea I'll be testing next summer is bubbling air thru a jar of 1 to 1 water and isopropyl alcohol. You can get 91% iso at Walmart for a bit over $2 / qt. One guy claimed a 4 mpg gain doing this.

Was seeing 35 mpg mixed using 2.5 oz 91% iso per 10 gallons gas.

[ARCHINSTL]

One idea I'll be testing next summer is bubbling air thru a jar of 1 to 1 water and isopropyl alcohol.

What - the air entering the carb is the air of which you speak above? I would have thought the carb's demands would suck the solution as well.
Bernoulli was not one of my favorite mentors.
Tom M.

[splatterdog]

We'll spend almost $400 on a new carb but get scared about a few hundred dollars in other stuff. Seems a tad strange to me.


.

Not trying to offend Typrus, but a full driveline rebuild in the hopes of a tiny bit more mileage to me doesn't make any sense. Yes a $400 carb does make sense to me as everyone knows how much fun the OE one is,which is also almost $400 from most suppliers. I did it for the driveability. Mileage is a direct byproduct. My 84's was a 8mpg bolt on. Perfect sense there and paid for itself in less than a year. Fact is my weber has probably put my 84's total cost of ownership in the negative vs. running the very fussy stock carb that one had.

If I tried to sell "maintenance bearings" my credilbility as a tech would fade fast. Bearings are bad or not bad. Also, new bearings are always tighter than broken in so I don't see any benefit out of that approach.

Deep driveline repairs are out of many peoples grasp both in ability to do it oneself or paying 80+ an hour + parts. That's what got me going. And everything on your list would be far more than a few hundred even when done by yourself.

Just because someone claimed they gained 4mpg by sucking alcohol fumes on a forum doesn't make it true. I've seen platinum solution bubblers back in the 80's. Don't see em anymore. Humm... Just look at the massive amount of HHO b.s out there. Good carb vs. bad carb is far more realistic as far as gains. I feel that people want to believe in some of these methods so bad it becomes reality for some.

Now I don't want to step on any more toes so I'll just shut up on this topic. I knew I should've left this one alone...

[Typrus]

If you want to keep your Terc running, you'll run into drivetrain problems eventually. Wouldn't hurt to fix it anyway. Will removing resistance from the driveline help reduce parasitic loss? Yes. It will. It'll also help keep your Terc on the road. Good idea? You tell me?


Does pumping propane into your diesel help power, egt's, and fuel economy? Why, that must be a voodoo idea! If it worked, why haven't OEM's been doing it for years?

Let it be tested then given the thumbs up or down.