Look here for help first!Not saying that I'll find any...but will log the attempt.
There are some commercial products you can buy that are supposed to improve MPG, but they can be expensive relative to the MPG gained (if very much)....with a long payback period. Some people on the MPG lists buy various kinds of commercial devices and try to get MPG gains...expensive to do...others are doing some basic & "exotic" R&D and might get patents for what they find.
Basic impression is that the older the car...the easier it will be to modify and be able to increase MPG. Later model cars with FI and O2 sensors will run leaner and be more difficult to improve very much??? The Tercel gets good MPG for a carbed car and might be difficult to improve if you are currently getting good MPG.
Keeping this simple, here is what I've done & found so far:
* Did a decarboning at least 2Xs and advanced the dist timing on the road** to try and increase power.
** This is done by putting the throttle to 3/4s position (engine hot) at around 25-30 MPH in 5th gear (manual trans) and listening for pinging up thru maybe 40-45 MPH...slight amount expected at start...then tapering off. Max RPM where you should be hearing any pinging should be around 1700 RPM...probably a good bit lower? Any pinging at an RPM you usually use indicates that you are defeating the purpose of advancing the timing...pinging robs power...though you will have some a lower RPMs.
You DO NOT just set your timing at a certain number of degrees advanced...you road test according to to your engines conditions ONLY.
PINGING in this car actually sounds like TICKING...might try listening for it with windows open or closed. Don't confuse it with an exhaust leak or valves....
<a href='http://www.lubedev.com/articles/octane.htm' target='_blank'>http://www.lubedev.com/articles/octane.htm</a>
"A lot of cars come from the factory with ridiculously late timing. These cars really improve with 5 to 10 degrees more spark advance. This comment is aimed at SUV and off-road vehicles. The power gain obtained is often phenomenal--30 to 50 HP in some cases. But it must happen with the right testing, starting with good basic gasoline stocks and diligent checks of your daily mileage.
In general, the lowest octane in your area delivers the best mileage. Best mileage and best power go together rather automatically."
** Have since installed NGK V-Power plugs...which reduced the pinging a lot vs the Bosch single plats....which run hotter. Timing is now adjusted to keep the pinging down to a lower RPM...maybe 1200?
* Added heated fuel....this involves routing the fuel being sent to the carb around the top rad hose several times using a copper line to heat the fuel before it enters the carb. Haven't been able to measure the fuel temp, but the copper line gets so hot when ambient temps are above 70F, that you can't leave your hand on the line...should stay around 180F or above.
* Added heated water injection...using the same method with the top rad hose and using about a 1 to 20 ratio of water to gas.
* Installed a PCV jar that is supposed to increase MPG.
* Using an air bleed...allowing a minor amount of extra air into the PCV line. This will also be used at high altitudes to increase combustion air. Eventually will control this so it will admit air only above idle. Found that the air bleed as used by Toyota on some Tercels likely reduces gas flow by injecting air into carb's gas jets rather than adding significant extra air to the intake.
* Timing was readjusted to max possible without pinging after each mod.
The theory & purpose of these mods?
Heating the fuel is supposed to allow it to vaporize easier and also the expanded volume of the fuel might cause the carb to flow less gas...maybe increasing MPG. Better vaporized fuel should result in better burning and more power.
"The thermal coefficient of expansion of gasoline is .095% per degree
celsius."
So IF gas is at 80F normally* and I heat it to 180F...how much
greater is it's volume?
* fuel system normally circulates gas to tank all the time, so it
should be near ambient temps...gas to carb normally goes thru insulated line...
except for some slight added engine heat.
80F = 26.7C & 180F = 82.2C
82.2C - 26.7C = 55.5C
55.5C X .095% = 5.27% ...so 1 gallon might expand to 1.052 gallons?
But I might be getting a 12% increase in MPG...so part of that comes
from better fuel vaporization?
Found that fuel temps are more in the range of 124F to 132F in most situations...so most MPG gains are from better fuel vaporization.
Injecting and heating the water is supposed to reduce the burning temps, allow advancing the timing, and increased torque.
<a href='http://www.teknett.com/pwp/drmayf/injchem.htm' target='_blank'>http://www.teknett.com/pwp/drmayf/injchem.htm</a>
The PCV jar is supposed to condense the heavier vapors from the crankcase fumes allowing a cleaner burn. Also allows monitoring the water injection & oil condition to some extent....meaning that I get to watch tarry stuff & water collect.
Pickle jar converted to PCV jar (PCV gases go in the center tube, thru a small can with copper mesh in it, down and then out the one at the top on the side):
3500 miles of goop (water has all evaporated since warm weather):
Results so far:
Was testing the Tercel on a rough grass covered bank with a 15 degree slope and could run the wagon up this bank in EL at about 1200 RPMs...noticed an increase of torque at low speeds. Normally, especially in warm weather (+75F), I'd need to keep the RPMS up a good bit to prevent a stall on this slope.
On the road I have increased power when running up thru the gears...similar to the improvement in power seen when the temps get below 50F...but probably a little more power than that is seen. Not seeing the typical reduction in power when warm weather hits.
Haven't recorded an increase in MPG yet...might be due to colder weather...could be related to the much advanced timing...might be because I'm always testing the increase in power.....might not find any.
It's possible that some parts of this mod are working against the other...possibly the timing could be set back to standard as a test? Air bleed or water injection might be causing lower MPG? Need to vary inputs...takes time to get results.
Having some doubts about what I'm doing...there are some details to be looked after...keep the water container filled, and some concerns about what the heated fuel & water injection will do to the carb over time. Intend to do a carb rebuild sometime in the future at any rate.
Keeping a continual record of MPG over time...still getting around 30 MPG at this point. Car is drivable...starts OK...no vapor lock so far...one instance of dieseling though. EGR needs cleaning?
4/22/04 Got 33.7 MPG thru the last tank with everything working right...ambient temps from 60F to 85F. This was with driving ranging from easy cruise at 45 MPH...faster & harder drivng up to 60 MPH...lots of stop signs and some offroad driving. This is about a 12% increase from 30 MPG which I consider my base MPG figure. Consistant weather above 70F might show some improvement.
Tried advancing the timing more, but couldn't without pinging.
Next tank will be tested with the air bleed off...all else the same.
* I consider 3 tankfuls as a minimum test of accurate MPG for any one setup due to all the variables....so time will tell.
4/25/04 Am very impressed with the increase in power under some conditions with these mods...stilll changing inputs to see what variables work best.
Not sure about the water injection...seems to give surprisingly increased torque at times...punched it in 1st trying to get into traffic and had to back it off cause I was moving TOO fast.
But too much water or too low ambient temps causes a loss of power (?)...having problems keeping the flow down near 1 to 20.
4/29/04 Got 33.4 MPG with last tank. Air bleed seems to cause a rough idle more than anything else....so it's out. Water injection stopped working due to pinched line. Need to recalibrate it. It's off for next tank.
5/9/04 Got 31 MPG for last tank. It was fairly cold some of the time and I ran it pretty hard some of the time. That, or the air bleed being off made a difference. Still good power & runs smoother without air bleed.
5/10/04 On an 85F day I have been seeing a kind of dieseling when shutting it off 3Xs...actually runs backwards before it stops. Running hot? Need to get the water injection going again. Will wait for the next tank?
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Real world testing using the 5th gear 25 to 60 MPH test:
On an 85-86F day and using the exact same stretch of road....I tested several variables as far as engine adjustments and so forth....ALL tests run with hot fuel setup being used.
TIMING > EGR/water injection/air filter = YES
Advanced at 15 degrees BTDC > 43 secs
Set at spec of 5 degrees BTDC > 55 secs
EGR > Timing advanced/water injection/air filter = YES
EGR working = 43 secs
EGR not working = 41 secs
WATER INJECTION at 2%* > Timing advanced/air filter = YES
WI working = 43 secs
WI not working = 38 secs
*2% = 1.6 pints water to every 10 G gas used.
AIR FILTER > Timing advanced/EGR = YES
AF in = 38 secs
AF out = 39 secs
Conclusions:
Obviously ALL variations were not tested...I was lucky to do 5 tests without being messed around by my secret friends.
Advanced timing probably results in around a 28% increase in power under the conditions tested...noticable for sure.
EGR probably results in around a 5% loss in power under the conditions tested....probably will keep EGR going due to new cat converter.
Water Injection probably results in around a 13% loss in power under the conditions tested....water injection isn't looking so good...especially if there is no gain in MPG.
Air Filter probably results in around a 2.5% gain in power under the conditions tested....probably due to the extra air turbulence from the lack of a filter.
Best power combination? When using heated fuel at least...advanced timing with no EGR and a free flow air filter & exhaust. Forget the water injection.
Keeping the intake air cooler would result in more power...MAYBE an 8% increase for each 10F reduction (extrapolating from previous test at 35 secs on 75F vs current 85F day)??? This is probably hard to believe......and might not be true.
Good idea might be to insulate the metal air cleaner housing with thin foam/alum insulation with adhesive backing so that it doesn't pick up so much heat from the engine and engine compartment. I've measured the air behind the air cleaner and in the engine compartment at around 112F on a warmer day.
Using a remote thermometer...I found that, with my car at least, the air temps inside the air cleaner average around 110F after the car is warmed up...taking about 15-20 minutes to reach this temp on a 50F day...& on warmer days just a few minutes.
Since there are other factors involved...such as burning up one's cat converter and harming an engine due to having too advanced timing...it's best not to try and duplicate these results at home without careful setup & testing as you go...not to mention the emissions issues.
Since this is limited testing...results might be off some. I'm assuming that a 10% reduction in the time taken to reach 60 MPH from 25 MPH = a 10% increase in power...I think it's a reasonable assumption...at least...it's close enough.
Use this info at your own risk.
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6/15/04 Haven't been keeping this log up to date. Have fixed the EGR...found that hoses to the EGR & vac modulator were reversed...then had to adjust TP setting front of carb (high idle)...then had the TVSV break (controls the EGR among other things).
Meanwhile found that water injection is probably reducing power by 13% or so, without improving MPG by much if at all...so it is probably a goner. This illustrates the need to test things yourself and not depend too much on what you read on the web..had heard mention of increased torque. Strangely enough under some conditions and %s of injected water, this might be true, but the issues of the water washing oil off the cylinder walls, keeping the water level up and flowing, etc....negate any gains...IMO.
Intend to do a decarboning every 3 months or so if not using water injection.
Advanced timing and heated fuel are increasing power & MPG...."power" by as much as 28%.....MPG by as much as 12%. Though my baseline for MPG might be too high....meaning that I might really be seeing a higher MPG gain. Might end up backing the timing off to around 12-13 BTDC due to a dieseling problem.
Intend to try a do-it-yourself version of the Fuel Atomizer 2000 this summer...parts will be about $35 or so...maybe....but looks do-able since I already have the other needed systems set up (PCV jar).
PCV jar is now NOT collecting water as it had during cold weather (when using water injection)...it is situated behind the radiator and so gets warm air from that...now just has a slight layer of black goo that will slowly run if the jar is tipped.
Have changed the design of the PCV jar to just having line run to the bottom of the jar thru a gas hose that has 3 donut-shaped copper mesh scubbers stacked around it...simpler except for cleaning it. It could also be set up using a pint jar instead of a quart jar for this 1.5L car...at least my car which doesn't burn much oil...so far.
6/24/04 Over the last 4500 miles I've used around 1/2 quart of oil...typical oil use before was around 5-6000 miles per quart. MMOil/water decarboning & water injection was started about 3500 miles ago...meaning that the steam cleaning when injecting fron 25% (not intentional) to 2% water has probably helped reduce oil use. Using 10W30 Havoline synth oil.
<span style='color:red'>* forgot that I also replaced a leaking valve cover gasket...but PART of this improvement in oil use is due to the WI.</span>
7/3/04 Seems that a functioning EGR might cause a loss of 5% in "power" and maybe 10-12% in MPG. This result is from short-term testing (a few tanks) and other changes were made also (new exhaust). You need an EGR to pass emissions.
7/9/04 Installed a fuel atomizer using my current PCV jar and found no gain in MPG. This doesn't mean that the commercially available FA2000 would not work...just that my attempt to make one has apparently failed.
It took around $50 in parts to set it up. I'll probably use the valve & hoses to setup a controllable heated fuel system...where the valve will be used to reduce fuel heat above 85F ambient temps. Also will install a cheapo coolant temp gauge in order to monitor the actual fuel temps.
7/31/04 Checking thru at least 3 tankfuls for each condition, I found that a working EGR costs around -11% in MPG...29 vs 32.7 with no EGR...with my setup. When testing a Nissan V6, I found a LOSS of 10% in MPG with no EGR.
8/9/04 Got 35.2 MPG highway on a trip with a 600 lb total load in the car...85% highway miles.
8/9/04 Put remote thermometer on copper gas line within 6" of the carb...covered with foam/alum insulation:
* ambient temp = 80F
* within 1 mile = 93F
* 129F to 132F on back roads
* sitting 10 minutes = 143F and falling
* drive 1/2 mile = peaks at 147F
* 55 MPH cruise = 124F-127F
Much lower temps than expected....waited this long becasue I expected temps that might damage the thermometer that is rated up to 156F.
8/10/04 Retarded timing some to around 12 degrees BTDC...worried about pinging & possible dieseling in towns from light to light.
8/31/04 Have come to the conclusion that for the most part...a PCV jar isn't worth installing on an engine in good condition that doesn't use oil...only exception might be when using water injection. Found that what a PCV jar collects is mainly oil mist that acts as a top lube if allowed to enter the manifold as is.
10/22/04 Installed NGK plugs...this reduced pinging problem found with advanced ignition. Have relunctantly arrived at the conclusion that my cleaned EGR....new $30 O2 sensor....partially fixed EVAP system (charcoal canister) are doing nothing to improve MPG...so I should have left things alone?
11/28/04 Tested a tank with the O2 sensor disconnected and got around a -12% loss in MPG...since I saw no difference when putting in the new O2 sensor...my guess is the old crappy looking one still worked OK...reconnected the new one. *this was only one tank...and conditions were changing...tire pressures were low also.
11/29/04 Have added another fuel atomizer and air bleed to the car....won't be able to test this much over winter due to snow and cold.
12/1/02 Getting NO MPG gain with the Torco oil/extra addtives...so far.
4/10/05 added bypass valve to heated fuel line...and did a power test:
* on a 60F day (ambient)...(2) 30 to 55 MPH tests show that it takes 8% LESS time to cover this distance in 5th gear with heated fuel.
no heat = 27.7 secs
heat = 26.4 secs
Fuel temp during this test was 123-124F....radiator was partially blocked.
During warmer weather I would expect the fuel temps to be adjusted to peak at around 150F....maybe the temp at 55 MPH cruise would be around 130-135F....making for maybe a 10% gain....maybe about the same gain in "power" as in mileage.
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Looks like the 3AC engine runs OK and gets good MPG without most of the EXTRAS (except for O2). And as far as I know...it might pass emissions testing with a good converter. Forget the expensive Weber carb?
So I have a car that could LIKELY do an overall city/highway avg of 38-39 MPG with the former oversized tires & heated fuel....and with non-functioning EXTRAS.
Things that seem to work to improve MPG are...heated fuel & oversized tires...O2 sensor...the NGK plugs reduce pinging with advanced ignition.
Acetone would work, but probably is a no-no when using heated fuel...it basically duplicates what heated fuel does...increases fuel atomization.
Things that didn't work are the PCV jar, water injection, and the EXTRAS....except for the O2 sensor?
Now testing Torco oil & additives. Will eventually try an FA2000 fuel vaporizer.
Next tires will be oversized 195-70-14". Might get past 40 MPG.
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Inflation pressures...use this at your own risk.....
"I used to inflate the tires on my Isuzu Impulse 10 lbs over - this was *in the owners manual* under "continuous high-speed operation instructions". I got better MPG, the tires wore like iron, and I didn't notice a loss of traction (except perhaps in rain, but it was always a twitchy beast).
Everything I own gets 10lbs over *what's on the tire* now! Been 7 years and 4 vehicles, so far so good!"
"I use a little bit different method....rather, I USED to do it as follows:
1)Set cold inflation pressure to sidewall indication.
2)Drive at LEAST 25 miles (or 40km) at whatever your normal driving speed is.
3)Check "hot" tire pressure immediately upon stopping.
4)If "hot" tire pressure is 10% or more above "cold" pressure then adjust cold pressure up to the highest hot pressure reading you observed.
Now. The reason I don't do it that way anymore is that I almost always ended up inflating my tires 10%-13% higher than the sidewall said.
Now I just inflate all my tires 10% (+/-) over sidewall and call it done.
Just to double-check, I then do the "chalk test". For that, I put a chalk mark on each tire, from the edge of the tread/sidewall transition to just past the edge of the "sidewall tread" as I call it, and slam the thing through a few hard corners.
If any of the chalk marks get scrubbed off more than halfway down the "sidewall tread", then I add 5psi to both tires on that end (front or rear). The added pressure seems to keep the tire from "rolling over" in turns and improves handling."
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Not sure how these mods might affect emissions testing..........
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Easiest way to increase MPG is to put 175/80/13" tires on the original wheels. These should be the inexpensive type...about all you'll find in this size. I was running these at around 32 PSI. Maybe a 5 MPG gain?
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Note: Above info is mostly unedited from original posts...conclusions change as time goes by...and I get more and more confused. :unsure:
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