A Tercel MPG's Question

[emmahumpfritter]

Hi Everyone,

Occasional thread starter, more often silent reader. I've been finding some mixed feedback via the search function regarding Tercel 4wd MPG's. The two I've personally owned (both in the 220K range) get approx. 30MPG easy enough on long freeway trips (if I don't drive stupid) I've pulled up to 33MPG a few times (keeping it at 55MPH) I tend to always TRY to pull as many miles from a gallon of gas possible in every vehicle I own: 88 Toyota wonderwagon van 4wd/5-spd (22-25MPG) 89 Ford Festiva 5spd (40-50MPG) 89 Geo Metro XFi (52-67MPG) 79 Toyota truck 4wd (18-20MPG) 07 Yaris HB 5-spd (38-42...with a fluke 51MPG once) and 29-33MPG in my 86 Tercel 4wd wagon (with a crap carb currently)...Yes I own all of those vehicles at the same time, it's a juggling act I need to get under control.

So my question is: Let's say hypothetically I guy wanted to own one car, that being a tercel 4wd wagon, and wanted to get the max-MPG's possible on long, slow trips, how would he go about setting up the car to do so? I'm not going to say "money is no concern!" but I do always have a few bucks I can throw at worthwhile projects, which my tercel certainly is.

Anyone ever reached 40MPG by chance? Just curious.

Thanks Everyone,
Brenton (Duluth, Mn.)

[ARCHINSTL]

Here is an interesting thread: http://www.tercel4wd.com/forums/viewtop ... gage#p7697
Mind, this was in a new T4WD...
Tom M.

[Petros]

We have discussed this in several threads. But the first few things you can do: Make sure it is in excellent tune, use low visosity synthetic oil, run the ignition timing at 10 deg BTDC, install tires that have low rolling resistance and pump them up to max pressure, install a 2" exhaust system, and find an after market low resistance air filter. Synthetic trans and diff lube might help, but it will not be very noticable I suspect. If you drive a lot of hwy miles, a properly designed spoiler and air dam might help a bit too.

If you want to rebuild or replace the engine there are a few more tweaks, raise the compression ratio, port the head, install a performance regrind cam shaft (this you can do without an overhaul, it can be installed with the engine in the car). A mild performance overhaul on an EFI 4AGE or 4AFE engine, and adapt it to fit might get you up to 40 mpg, as well as get you more power. But that is a pretty involved project, and expensive. I think my 4AGE swap is going to cost me about $1600, doing most of the work myself. I might save some by doing some trades, but it is still not an inexpensive option, so you will likely never recover the cost. If you want a more modern and more powerful engine anyway, than the better economy is a bonus.

[takza]

I have spend a lot of time as a hobby trying various methods to increase mpg....doesn't mean I know what I'm doing though.

Things I think work:

* increase your tire pressures to somewhere below max sidewall, but above the glovebox numbers

* advance the ignit timing...this at least gives maybe 20% more power, but too advanced can hurt mpg as I recently found

* I use radiator blocking, where you close off most openings in front...except for directly in front of the radiator....need to be very careful here...I have an indicator light set up to let me know when the rad fan runs...also an aftermarket mechanical fan switch

* used plastic lawn edging to extend the front "valence" down 3-4"...can still run offroad

* use moly in the trans....will be using synth and Tufoil in the future

* use 91% isopropyl alcohol at 2.5 oz / 10 gallons in the gas...a combo of quality acetone/xylol should work also

* currently testing Restore and now Tufoil in the engine oil

* use a Condensator or PCV jar

I don't really use driving techniques...just easy on the gas...and try to drive consistently...cause I'm always testing.

A lot depends on the type of vehicle and the particular vehicle...a 4x4 is never going to do as well as 2WD. Much depends on wind resistance...I once got 47 mpg with a full tank after a full day of 25 mph tailwinds.

Driving technique and avg speed can make a major difference. One simple thing that works is to set up an extra spring on your accelerator linkage so that you can feel more resistance at a point further down than your typical cruising position...this automatically keeps you in a easy throttle position...and you can over ride it when needed....works like using a vacuum gauge for driving.

There are a lot of fairly simple tweaks and changes that might add 1-2% to your mpg...do several and the results add up.

Here is a good source for mpg info...emphasis is mostly on aero and driving techniques...check out the garage for claimed mpgs and mods...

http://ecomodder.com/forum/

I'm probably reaching the limits of simpler methods to use with the T4WD...will next go with a 2WD vehicle and try for mid 40s and 50 mpg.

[Petros]

Brenton,

Another couple of ideas occurred to me. Make sure the vacuum advance on the distributor is working (most are not on a car this old). This will advance the spark timing when at part load condition, such as hwy driving, and improves ecomony. Depending on the year of your car, there is also one or two vacuum retart ports on the distributor. these come on a various conditions for the sake of emissions. If you disable the vacuum retart lines, and only have the vac advace one working you will improve the economy. This can be done by by-passing the TVSV, read up in the FSM how this works and install the vac advance line directly to the vac advance port on the distributor. This can also be done if your TVSV valve is malfunctioning, it will drive normally without the TVSV in the system, except you will get better fuel economy.

Also, if you disable your EGR valve so no exhaust gas is recirculated into the intake it should also improve economy and power output. You can either remove it all together and block off the port, or just disconnect the device so it always stays closed.

Most of the emissions control devices do not affect the economy much, and several actually improve the economy. Like the fuel shut-off solenoids, these cut off the fuel supply during down shift or a rapid throttle closing to prevent fuel being sucked into the engine when you do not want power (as in using engine braking in a down shift). So I do not recommend whole removing of all emission control devices, but the TVSV that allows vacuum retarding the spark, and the EGR valve both affect economy, and if disabled it should improve the economy some.

BTW, I forgot to mention those are some pretty impressive economy number you get out of those cars.

[emmahumpfritter]

Thanks for this Petros and A... I just drove my tired 86 tecel 4wd wagon from Mn. to my brother's place in Nor-Cal. When keeping it at 60mph or less, I got 35MPG on the nose. When kicking it up to 65-75MPH I got 30-33. I find this amazing for many reasons, most notably the fact that this car is literally falling apart. The CV's are gone (clicking while NOT turned) the carb has the typical issues, it has 230K on it. The clutch is shot. I did pump the tires up to 44psi (helpfull on the rest of my rigs) and I drive very nice (slow take-offs, etc.) My goal is to rebuild this car with the help of the parts 86 I just picked up (for $150 bucks) and pull a 40MPG tank.

Brenton

[splatterdog]

I just drove my tired 86 tecel 4wd wagon from Mn. to my brother's place in Nor-Cal. When keeping it at 60mph or less, I got 35MPG on the nose. When kicking it up to 65-75MPH I got 30-33. I find this amazing for many reasons, most notably the fact that this car is literally falling apart. The CV's are gone (clicking while NOT turned) the carb has the typical issues, it has 230K on it. The clutch is shot. I did pump the tires up to 44psi (helpfull on the rest of my rigs) and I drive very nice (slow take-offs, etc.) My goal is to rebuild this car with the help of the parts 86 I just picked up (for $150 bucks) and pull a 40MPG tank.

Brenton

Not bad, it is a T4 though, they are survivors. Your carb trouble must be idle and or cold engine related? All that highway keeps you in the sweet spot. Do you have oversize tires? 195/75/14's shave about 200 rpm's off. Since you don't launch hard, the taller tires that are a little harder to turn shouldn't be an issue. If you do any hardcore mudding you will wish for a bigger engine and a stronger clutch. Got mine stuck in a ditch this summer along with a bobcat during a leveling job "on the farm". My friend was working, I was playing(and having much fun) until he started stirring up juicy wet black soil. It was like glue. Could not spin the tires.I smelled clutch that night. Good thing we had a tundra to pull everything out. I had grass growing out the bottom of my bumper for a while!

Anyway, getting off course here. I think 40 could be do-able but it won't be easy. Not in real world situations. Too many things against you. Were you loaded or empty? That makes a big difference. All my mileage calc's have been done with at least medium load. I measured my worst ever on an Ely trip a while back. Me, my two little ones, and the entire rest of the car stuff sacked with a packed large cooler and camping gear. Drove much harder than usual, maintaining 70-85mph only dropping down to 65 on the home stretch(169). Still managed 30.5mpg. Next trip up there was slightly lighter and slower and I pulled 34.8mpg. My recipe has been proper tune,synthetics,taller tires, and my favorite, the weber. The rest is up to my right foot and I'm way past traveling light.