EPA has new mpg figures....

keith · Post by **keith** » Thu Mar 08, 2007 4:57 am

Our Tercel got 29 on a trip from California to Tennessee. Since then, It's gotten about 26. Haven't checked since putting in the 4ac with the Weber. I just got a FA meter and will start dialing in the carb soon. Gotta put in that EMPI this weekend.

Interestingly, I usually beat the EPA figures, even the older ones. My Saturn was rated at 29 and 40. The new figures, if I remember correctly are 28 and 36. My last tank only got me 39.5 in mixed driving, 65% highway and 35% town. My worse was 29 in the LA area and best 42 on a cross country. The first 60k, I averaged 37.85, I kept a spreadsheet. My Nissan truck, rated 20 and 25, I averaged 25.5 mixed 50:50. It got its worst mileage on the highway above 65. I only got 18 on one trip where I was running around 80 mph. My old Colt rated at 29 and 36, averaged 37. Only the Hondas did worse than rated, but I always thought they were overrated to start with.

xirdneh · Post by **xirdneh** » Thu Mar 08, 2007 8:38 am

Petros wrote:

How on earth are you getting 40 to 46 mpg!?!?

What have you done to the engine/carb/exhaust syst?

What kind of tires are you running?

Why do you think you are getting such good MPG?

I find it hard to beleive they could even be tweeked to get that good mpg. The best I would hope for on mine is 36 or so, after a number of mods I am planning.

I too could hardly believe other people were getting 40 or more mpg.
Having six of these cars since 1988 only produced a high of 34 mpg on long distance drives. Now i have one that does 40 mpg and i'm not sure why. The engine was reringed at 220,000 miles, carb rebuilt and everything else on it is old. I am a believer now.

Post by **ARCHINSTL** » Thu Mar 08, 2007 8:50 am

Ditto on xirdneh's remarks - as mentioned, I never got close to 40mpg, even when new, even at (the then legal speed of) 55mph, even on trips in the flatlands of IL and IN, and even with the lower ratios of the '83.
Similar comments on the top speeds of then and now...not quite 90mph was my max on the flatlands as well...this mirrors the R&T and CandD tests of the time.
Tom M.

Post by **Petros** » Thu Mar 08, 2007 6:32 pm

We need to determine what the differnace is so we can all try it out. What final drive ratio does your car have?

I would sure love to get 45 mpg! Perhaps there is some part of the emission control system that is disabled or not working? What would effect the cruise economy? The EGR? The vacume retard? The heat riser?

Raising the combustion temp and pressure will improve economy (and power), the vacume retard, the EGR and the warm air intake all serve to lower combustion temps. I have not studied my service manul on what each of the devices on the emission control system does. Not all effect the cruise economy (some only are activated at high temp, high RPM, etc. which will have no effect on ecomony).

I would think with proper tweaking of the factory carb (and the emission control system) you could get even better economy than with the Weber because it is smaller and likely has a better part load efficiency. So now the question is what is different about the several examples that get 40+ mpg.

I was going to replace the whole exhaust system with a free flowing one, which should help both power and economy. I am also considering disabling certain of the EC devices to see what would happen to both the power and the economy. Knowing the difference with these high milage example would be interesting to know about.

takza · Post by **takza** » Fri Mar 09, 2007 3:37 am

Petros wrote:We need to determine what the differnace is so we can all try it out. What final drive ratio does your car have?

As far as Typhrus' car...and it's cam timing vs his mpg...my theory from what I can find is that possibly....retarding the cam riming by maybe 5* or so MIGHT cause the 3AC to run more efficiently in the 2.5K and above rpm range. This would likely reduce torque below 2.5K...but if the ignit timing was tweaked relative to the new cam timing...torque below 2.5K probably wouldn't be any less than with the OEM specs.

The improved mpg would most likely be seen on the highways at cruise maybe in the 3K area or above?

All theory unless tested. I could take my extra cam gear...drill some new index holes in it using my trusty protractor...leave the top belt cover off...and test this out this summer...unless someone manages to do this before I do...hint...hint.

misc:

A guy autocrossing a V6 non-turbo...tended to retard the cam by maybe 4-5*. Car had poorer response below 2K rpm. He also did some intake/exhaust/mixture tuning for a final 33% HP gain.

quotes:

"On my car with the gears at +3, midrange power increase was awesome but all power died by just over 5K. I'll be changing them to -3 over the winter."

"small advance brings the torque down, good for turbo cars who naturally peak at higher rpm...small to medium retard allows more air to enter and exhaust to leave on n/a cars improving efficiency"

Typrus · Post by **Typrus** » Sat Mar 10, 2007 1:52 pm

lol.
again I say lol.
(finishes breakfast)
Ok. My timing WAS at roughly 15-30 degrees at the crank. So maybe in the 9-18. degree retarded range? It was pretty far over.

I averaged 26 with my home-to-town wacky driving, and could see high 30's on the freeway.

I fixed the cam timing, and applied that extra grunt to the tensioner, remember? My instructor said he remembers them adjusting themselves 4-6 degrees retarded if you didn't put a little extra snug up on the tensioner.
I'll be taking the upper cover off at some point so that I can inspect coolant stuff, while I'm in there I'll check out timing.

I recently super-flushed my cooling system. I used Zerex Super-Cleaner for several running hours (in the system for days) and consequently had to go through and replace my water pump and various gaskets. Did the timing belt while I was in there. After the super-flush with pressurized water, I re-filled with green Propylene Glycol for environmental purposes, but also aids in longer coolant life and longer-lasting lube/anti-corrosion packaging.

I have all of my vacuum hoo-hah detached from the VSV and the TVSV, distributor aside. Whatever sources into the side of the carb is still there. Hoses are plugged and fitting capped where needed. Dist bypasses the HACV and utilizes the ported vacuum source above the 2ndary in the side of the air horn above the butterfly valves.

I regularly clean my system out with SeaFoam and/or distilled water. I check my sparkers regularly and do my valve lash about every 10000 miles, as per recommendations from my instructor. Remember, my instructor is a multiple-ASE Master certified tech who worked on Terc 4wd's from their inception to their end.
My spark plugs are indexed and 1 heat range colder than normal. Denso u-channel plugs.

I have a 2-inch muffler with 2-inch piping about 6 inches up from it. I have stock otherwise. I have an exhaust leak at the manifold-downpipe flange, at the rear cat-intermediate flange as well. I am hoping to eventually run a full 2-inch or 2.25" system.

Intake is essentially stock. Heat-riser tube is missing is about it.

I'm riding on 175/70R13 Hankook Snow Tires, studded, though most of the studs are missing at this point. They are pretty tired after 15k or so miles, most of it summer driving (I don't have money to put rubber on my 15" aluminum rims)

I drive "spirited". I'm getting a little more tame, out of fear of losing the license, but I still don't take it easy. Free-way driving is 70-90mph. I actually get better mileage there than lower down. Figure that out.

The engine has roughly 210k original miles on it, rebuild free. 140-ish compression if I remember right, biggest difference being 1PSI, and thats #1 being low.
Carb has probably 30-35k rebuilt miles on it. Thank you Charley! Still works great if you ask me. I'd like to have a Weber, but ATM I'm pretty satisfied.

I run Schaeffer's Supreme 7000 15W-40 in my engine, and ATM Walmart's SuperTech in the tranny. I want Schaeffer's in there, but I don't have money right now. Rear diff is unknown. >.<

She's an 84, so she has the 3.727:1 diffs. My 86 got the same mileage though, with literally the same engine. The 84 has the 86's engine. So diff's haven't made a lot of difference for me. Though, with the cam timing fixed, that might be a different story.

Why do I think I'm getting such good mileage? You tell me. The only change I've made recently was to fix cam timing. Remember, both keyways pointing straight up! I drive wacky and yet she treats me well.

BTW, use QUALITY fuel from a station with good patronage (fresh fuel in their tanks at all times) and use midgrade or higher if your engine wants it. Use quality additives regularly (BG Power Service and SeaFoam come to mind) both via fuel tank, crankcase, and direct introduction. Go look up my SeaFoam write-up under repair guides.

I honestly can't tell you specifically why she does so well. She needs new bearings, better tranny and diff lube, better tires, new coils and front struts.... She needs a good bit of love.

takza · Post by **takza** » Sun Mar 11, 2007 7:09 am

A few stupid observations....

First of all...I guessing those high mileage tanks were with the previous retarded cam timing?

Could be that the 4-6* retarded cam timing might be the way they designed it to run...so the original cam timing is EXPECTED to run a bit retarded from how it is originally set?

"I have all of my vacuum hoo-hah detached from the VSV and the TVSV, distributor aside. Whatever sources into the side of the carb is still there. Hoses are plugged and fitting capped where needed. Dist bypasses the HACV and utilizes the ported vacuum source above the 2ndary in the side of the air horn above the butterfly valves."

This might be the key rather than cam timing?

Your rpms at 70 to 90 mph might be ~3700 to 4700 rpms? Try not to over rev it!

You are running ATF in the trans?

The MYSTERY remains....

Typrus · Post by **Typrus** » Sun Mar 11, 2007 10:28 am

No........ 80W90 I believe.
Then fix it. It seems to be running damned good for me.
4700? Errrr... I don't think its that high.... Could be though I suppose.

xirdneh · Post by **xirdneh** » Mon Mar 12, 2007 12:13 pm

takza wrote:A few stupid observations....

First of all...I guessing those high mileage tanks were with the previous retarded cam timing?

Could be that the 4-6* retarded cam timing might be the way they designed it to run...so the original cam timing is EXPECTED to run a bit retarded from how it is originally set?

"I have all of my vacuum hoo-hah detached from the VSV and the TVSV, distributor aside. Whatever sources into the side of the carb is still there. Hoses are plugged and fitting capped where needed. Dist bypasses the HACV and utilizes the ported vacuum source above the 2ndary in the side of the air horn above the butterfly valves."

This might be the key rather than cam timing?

Your rpms at 70 to 90 mph might be ~3700 to 4700 rpms? Try not to over rev it!

You are running ATF in the trans?

The MYSTERY remains....

i do not know about all that.
my 40 mpg tercel is all basic stuff.
recently reringed with old parts and timing is set to factory standards.
i drive in a normal manner

takza · Post by **takza** » Tue Mar 13, 2007 5:59 am

Typrus wrote:No........ 80W90 I believe.
Then fix it. It seems to be running damned good for me.
4700? Errrr... I don't think its that high.... Could be though I suppose.

My '83 runs about 2800-3000 ~ 60 mph in 5th. So your later model with the 10% higher ratio should run ~ 3200 at 60? Add 50% at 90 mph...you get 4800 rpm?

Bottom line...if it runs...drive it?

I've topped mine out at 5K now and then...engine was still smooth. Cruising up in that area...not so sure. Around here they'd probably take your ass out with a Predator and a Hellfire missile if you tried this espec with a Tercel.

Post by **ARCHINSTL** » Tue Mar 13, 2007 12:09 pm

takza wrote:My '83 runs about 2800-3000 ~ 60 mph in 5th. So your later model with the 10% higher ratio should run ~ 3200 at 60?.....Around here they'd probably take your ass out with a Predator and a Hellfire missile if you tried this espec with a Tercel.

Yup - although maybe 3150, depending on the tach's accuracy.

Where is the Tibetan Plateau - near Area 51?

Tom M.

Typrus · Post by **Typrus** » Tue Mar 13, 2007 6:53 pm

lol.
I have an 84. Same ratios as you takza.

Around here, you're likely to HIT a Predator and CREATE a ball of Hellfire. lol.

keith · Post by **keith** » Tue Mar 13, 2007 8:07 pm

Kill a predator in Colorado and face a $million fine. A utility there was fined that much when an eagle landed on a transformer with unprotected HV bushings (no birdguards).

takza · Post by **takza** » Wed Mar 14, 2007 2:57 am

ARCHINSTL wrote:Where is the Tibetan Plateau - near Area 51? Tom M.

Actually near where they first developed the Predator...far as I know. In due time...you'll likely see a few in the sky...or maybe their cousins or progeny. Then again maybe you won't see them.

hberdan · Post by **hberdan** » Fri Mar 16, 2007 5:45 pm

I'm driving a stock '87 deluxe wagon right now, and as I mentioned a year ago, I do lots of mountain driving; it's a 3400' climb in 17 miles from my house to work. Driving with dedicated,but not studded, agressive snow tires, and a ski roof rack, I get about 27-28 mpg. If I have to drive in heavy snow-on-the-road conditions, in very cold weather, the mileage drops, esp. if I have to drive the whole distance in 4wd. This winter that has happened quite a bit.
In the summer, with all seasons and no roof rack, mileage goes up to 31-32 mpg.
Vehicle now has over 275,000 miles and is still going strong, no major body damage, just some small door dings, and NO rust.
Replaced the spark plugs today, do that every six months, really helps the mileage.
I think the only way to really compute your actual mileage is to chart at least ten-fifteen or more full tanks of gas, let's say 135-200 gallons, and then figure an average based on that. Doing it by the tank lends itself to many statistical errors.