Ok, for anyone who doesn't know, hypermilers are people who are OBSESSED with getting the most gas mileage possible out of their vehicles. The "king" of the hypermilers lives near me, and routinely gets 105+ mpg out of his Honda hybrid. I've been talking to him lately, and believe some of his techniques make sense. Others are crazy.

Now, we're clearly about performance here, but, with many of us using our third gens as daily drivers, anything that will improve economy is welcome, especially if it doesn't compromise performance. So, I've been trying to learn from hypermilers. I'd like to discuss what I've learned, and see what others might think or have experienced.

Aside from basic maintenance (air pressure in tires, etc.), I've been focusing on hypermiling driving techniques, and have seen some pretty big gains. I haven't been trying it on my Firebird yet, it's down waiting for parts, but, I have been on my Jeep Cherokee, which gets worse mileage than my Firebird.

I bought it new in 1996, and have put 81,000 miles on it, so far. It gets 15-16 mpg in town, and 16-17 mpg on the highway (cruising between 70 and 80 mph), and always has.

The first hypermiling technique is simple: slow down. I decided to start putting it to the test this morning. I laid out an all-highway course of just under 200 miles. It starts and ends at the same gas station. I even used the same pump.

The idea is to run the course at 50, 55, 60, 65, 70 and 75, using the cruise control to negate driver technique as much as possible, and see the results. This morning, I ran the 50 mph leg, and got 25.21 mpg. That's an improvement of 8-9 mpg over my normal 16-17.

Now, nice as that may be, nothing will drive you crazier than cruising down a highway at 50 mph. I've had more fun watching paint dry. It's also not safe. At 50, EVERYBODY is passing you; many going much faster than you are, and many cutting the margins pretty close. You've never known fear until you've looked in your rearview mirror to see an Excursion barrelling up on you at 75 with the driver talking on her cellphone while she puts on her mascara (true story). Clearly, slowing to 50 is not the answer.

Remember, though, this is just the first controlled test. The plan is to run that course at the other speeds and compare the differences; finding the best compromise between speed and mpg.

I've been learning how to apply some hypermiling techniques during my normal driving over the past few weeks, and have seen an improvement in my mpg. I drive 30 miles a day, four days a week, to and from work. 28 of those miles are on the highway. I normally drive 70 on the highway (60-65 mph speed limit); I've slowed it down to 60. It was hard at first, but, I've gotten used to it.

Now, when you talk to people about slowing down, one thing you hear a lot is "Yeah, but, what about my time? That's worth a lot to me." I travel (one way) 14 highway miles on my way to work. At 70 mph, that portion of my trip takes 12 minutes. Slowing to 60 makes the highway portion of my daily commute take 14 minutes. 2 minutes ain't much.

Ok, what about on longer trips? At 70 mph, it takes 1 hour, 26 minutes to travel 100 miles. At 60 mph, it takes 1 hour, 40 minutes; 14 minutes longer. Before I moved back here, I used to drive from Atlanta to Tulsa and back several times a year. Right at 800 miles, one way. At 75 mph, it takes 10 hours, 40 minutes (not counting stops) to make the trip. At 65 mph, it takes 12 hours, 18 minutes; 1 hour and 28 minutes more. I've made that trip a number of times. I have to stop for gas twice, and I'll usually make at least one stop at a rest stop to stretch out, as well. I honestly don't think adding an hour and a half to the trip is that big of a deal. In my Jeep, I'd normally use 47.6 gallons of gas on that trip. If slowing down 10 mph netted me a 3 mpg gain, I'd use 40 gallons; 7.6 less. At 3.00 per gallon, that's a savings of 22.80. That's a free steak dinner at the end of my trip.

Back to the savings on my daily commute. Over the course of a year, driving 28 highway miles per day on my commute, four days per week, the highway portion of my commute represents 5824 miles. If slowing from 70 to 60 on that portion of my trip gets me 3 more miles per gallon, look at the difference:

5824 / 17 mpg = 342.6 gallons used per year

5824 / 20 mpg = 291.2 gallons used per year

That's a savings of 51.4 gallons per year. At 3.00 per gallon, that saves me 154.20 per year, on my daily commute alone, assuming I drive no other highway miles, and that I don't find ways to save on my in-town driving (I have). All I have to do is leave home 2 minutes early every day to save a hundred and fifty bucks a year (more, if gas goes higher). That seems worth it.

What's more, I believe slowing from 70 to 60 represents more than a 3 mpg increase. I've checked the mileage twice on mixed driving since I got interested in this. I got 18.9 mpg on the first test, and 19.8 on the second. That's up significantly from the 16-17 I normally get, and I'm not very good at the hypermiling driving techniques I'm trying to emply yet. I'll know for sure once i get the controlled testing done. It'll take a couple of weeks. Once I get the rearend done on my Firebird, I'll start doing testing on it, too, but, it doesn't have cruise, so, it'll be a lot harder to get controlled results.

Aside from simply slowing down, there are a lot of hypermiling driving techniques that can make a pretty big difference. Cutting out the jack rabbit starts, anticapating red lights and stop signs, shutting it off at idle, etc. can make a pretty big difference. I'll go into them in other topics, if there's any interest.

 

LO3 camaro's and firebirds are the perfect vehicle to squeeze mileage out of. Most came with 2.73's, they have a relatively good drag coeficent and the motors are built for low....low rpm grunt.

Once you have the driving techniques down, which is over 75% of the equation when it comes to gas mileage. Here are some things I've found that noticably help gas mileage.

First is simply running the tallest gears you can stand but still keep the engine in it's power band. With an LO3 it's about impossible to get the rev's too low. On a hotter motor I found I actually got better mileage with 3.50's than with 3.25's just because my motor made no power at around 2000 rpm's.

The second is to dive into the tune and start playing with the highway mode, you can run AFR's way into the high 16's and low 17's. This of course will reduce power, but when you only need 5-15 hp to pull the car down the road you are trying to find the most efficent way to make those 5-15 hp. Also timing plays a big role in how fuel is needed and the engine will react when you start to pull a hill. Also trimming up your pump shot so there is no excess fuel when you have to move the gas quickly will also effect fuel mileage quite a bit, especialy in stop and go city driving.

Although I've never experimented with this, I would imagine anything you do to decrease aero drag would help mileage. Lowering the car, removing the rear spoiler and driving with the windows up will all help to reduce drag. Most people don't realize how big of deal aero is. Just look at the newer vette's, with a double OD and really good aero they can pull down 30 mpg and still have over 350 hp.

 

Another thing that could really help would be to raise the CR to increase the burn speed and run around 18-20:1 AFR. If you could find a good way to limit the maximum MAP the engine sees to around 60 kPa, youd have yourself a leanburn engine that would get great fuel economy.

 

My Firebird, with 3.42 gearing, gets 17 or so in town, and 23-24 on the highway, cruising at 70-80 mph. The problem I'll have slowing down in the bird is no cruise control. I've had my Jeep for 10 years, and, with it's 3.55 gearing, it cruises at around 2000-2200 rpm at 70-75, which is where I drove if until recently. When I drive my Firebird, I find myself settling i=on around 2200 rpm, which is about 80 mph. I have to watch the speedo constantly to go slower.

Swapping gears will usually mean better mileage, but, you have to consider how that affects your performance goals for the car. Is it worth losing a couple of 10ths in the quarter mile? Also, you have to consider the cost of making the change. If I drive my Firebird 8000 miles a year, and swapping gears takes me from 17 to 20 combined average mpg, that'll save me 220.00 per year, given an average gas price of 3.00 per gallon. That's great, but, it'd cost me between 400.00 and 600.00 to swap gears. It'd be 1 1/2 - 3 years before I realized any savings.

It's even more complicated with automatics. I am going to have to go into the rearend on my Jeep, and have thought about just swapping out the 3.55 front and rear diffs for ones with 3.08s. There are guys on the Jeep board I participate in who swear they're getting mileage with 4.56 gears and 32 inch tall tires that's as good as, or better than stock, and that my mileage will go down if I swap to a lower numerical gear. I initially called BS, but, the more I think about it, the more I wonder. My converter locks up at around 42 mph. If I go to a 3.08 gear, I'll be locking that converter up a lot less in around town driving, and an automatic gets much worse mileage when the converter isn't locked up. The Jeep PCM is not easy to tune, but, I believe you can control converter lockup in ours, can't you?

As far as tuning is concerned, here's another reason for doing it. Ideally, I think you'd want an actual switch in the cockpit, so you can easily go from economy/highway mode to economy/city, and performance mode.
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Wouldn't a vacuum gauge do that? Also, with EBL's ability to contol warning lights, could you set one to go off that way?

 

Using a governor would be a good way to do it. You can limit the max MAP with a PID routine as well as limit how fast the throttle could open. Youd have to govern the engine carefully to keep it out of detonation. Probably would also be a good idea to use numerically higher gears so the engine isnt as heavily loaded during acceleration. Something like 3.23s and a low stall converter would be ideal for that sort of setup.

 

My dad did courier for a while, so he developed a few techniques of his own. First and fore most, regular maintenance, like oil changes, air filter etc is invaluable to saving gas.

Tire pressure as well as correct type of tire, ie: no winters in the summer help too.

BUT this is the big one, he nearly doubled his gas mileage because of this little trick. First of all, this works best on the highway.
You go the lowest revs you can sustain at the highest gear, most cars that equates to 80 km/h or 50 mph, but again thats not helpful on the highway so just go 100/60 km/mph.
This is the trick, and only really works in automatics. You hold the gas for 2-3 seconds, and you release for 2-3 seconds. Hit the gas for 2-3 seconds and release for 2-3 seconds. The time you hit and release will vary depending on if youre going up hill, down or flat. DONT romp on the gas, just hit it normally as if you were cruising. the speed this works best is also a factor, in my van it works best at 120, any slower, and i will slow down too much on the lift. But at 120 it maintains its speed very well +/- 2-3 km/h.

For city driving, the best trick is acceleration and watching signals. Watch the pedestrian crossing in the same direction, if its blinking to stop, itll probably go red soon. If this happens, dont bother trying to race the yellow/red. Just move your foot to the brake, and if u coast through you coast through.

Next, and this is a HARD one, really really hard! DO NOT RACE EVERY ONE OFF THE LINE!!!!! I know im very guilty of this one, but its very difficult to watch someone pass you while ure behind the wheel of one of these cars. Just accelerate slowly, drive like a granny. You'll save a ton of gas, i promise.

 

This brings up a very good point and I see people do it all the time. When gas prices shot up everyone looked to dump their huge SUV's and no one wanted to buy. I saw people get half of blue book prices and raise their monthly payments by 200-300$ trying to get into smaller more efficent cars. They pretty much ate up any savings they gained in gas mileage in their car payments. You do have to be carefull that you don't shoot yourself in the foot monetarily trying to increase mileage.

The TCC is completely controlled by the ECM and there are quite a few parameters that you can change. You could easily get the TCC to lock up right after leaving from a stop and stay locked untill you needed to accelerate briskly. You could have it set up to unlock at anything past 10% or 15% throttle, but stay locked under all conditions under that particular TPS reading. You would feel the shifts a bit more but under light throttle but it's not that big of a deal.

The idea of having 2 or 3 tunes seems like it makes sense, but in reality there is no reason to have more than 1 tune unless different fuels are going to be used. (gasoline, ethanol, ect.) The way the fuel tables are set up and the way highway mode is enabled you can pretty much hit any AFR you want and any amount of timing you want under any condition. Economy mode is simply less than 15 or 20% throttle, performance mode is 75-100% and anything in between is "normal mode". If you wanted to get really fancy you could run open loop (no O2 sensor) and run the leanest AFR you can under all conditions. Basically the less the load the leaner you can run....very basically.

You have to keep in mind that this is harder on the engine, and playing on the edge of too lean and too much timing can lead to detonation and melted pistons.

 

Theres a better solution to all of this... not easier, better... Its the route I'm attempting.

Make more money.

save 150 a year? by driving differently? Thats not worthy my effort, or time. Thats like 4 hours of work over the course of a year!

I filled up my truck last night for 78 dollars. Premium for the supercharger, when i floor it, MPG goes to 0 on the overhead display!... it gets 12mpg average.I live less than 10 miles from work but I drive about 300 miles a week so I have to fill up at least once a week.

I dont even know how much I paid but probably 3.37 a gallon. Even if gas was 50 cents cheaper - thats 11 dollars saved. I went out last night, bought 6 or 7 beers for myself and a few for friends and tipped the waitress everyround at least a buck - she was cute... I pissed out more than 11 bucks last night. That 11 dollars at the gas station? over 300 miles? 3 cents a mile difference?

 

For whatever reason, it seems if I let my tank run lower the more gas it uses. I can top off at around 3/4 of a tank and figure up my mielage and it wll usually be around 20-21, if I fill up below half a tank it usually is like 18-19.

I once had a 1978 plymouth fury with a 2bbl lean burn equipped 318 and a lockup convertor trans. Super highway gears, something like 2.56. I got 26 mpg on the highway in that car on several occasions.

 

They way I see it, if you want good gas mileage, then why are you driving a V8. If you want really good gas mileage, buy a honda as a beater and the money you will save will pay for it.

 

It's not that simple.

First, beaters that get good mpg aren't that cheap anymore. Second, there are other costs involved. I already have a "beater" in my Jeep, so I have some experience with that.

I've been looking at old Honda CRXs. A decent one will run you 2 grand.

My Firebird gets 17 mpg combined. A CRX will get up to 40. I drive about 8000 miles a year.

At 17 mpg, my Firebird uses 471 gallons of gas a year. At 3.00 per gallon, that's a yearly fuel cost of 1413.18.

At 40 mpg, a CRX would use 200 gallons of gas a year. At 3.00 per gallon, that's a yearly gas cost of 600.60.

I'd save 812.58 per year. Yay! Oops, wait a minute. The CRX cost me two grand, so it'll be 2 1/2 years before I save any money.

Oops, wait a minute. It'll cost me at least a hundred bucks a year to insure it, and, here in Oklahoma, about 50 to tag it. So, 150.00 off of my 812.58 per year in gas savings means my net savings will be 662.58, so it'll actually be 3 years and 3 months before I recoup the cost of the car.

Oh, wait, what about tires, oil changes, spark plugs, filters, etc for the CRX? Figure 100 bucks a year in maintenance costs for the CRX (VERY reasonable). That leaves my yearly fuel savings at 562.68, so, it's almost 4 years now before I recoup my acquisition costs and see any real savings, and that's only if nothing goes wrong with the CRX in that time (starter, battery, alternator, fuel pump, shocks, etc.

The fact is, buying a beater JUST to save on gas only makes sense if you drive A LOT of miles.

There's nothing wrong with trying to find reasonable ways to make any car fuel efficient. The "go buy a more fuel efficient car" virus that's going around right now has car dealers laughing all the way to the bank. People are taking a huge beating on trade-ins on their old cars, and paying a premium for their new gas misers, and any gas savings will be more than offset by their losses on the old car and the aquirement cost of the new one.

 

cool thread. DIY tuning rocks

 

See, there you go, you are looking at a 2000 dollar CRX, you can get a civic for under 1000 easily. You are going for looking or something perfect, I consider a beater something not so great looking and not too desired, but all that matters is MPG. I am glad that you are not driving an import though.

 

say the crx was free and you didnt have to pay for anything else.. 800 a year = $15.38 a week saved. Hopefully you make 15 bucks in an hour. So 1 more hour a week is spent to allow you to drive whatever the hell you want however you want. A small price to pay. You pay more than that A DAY!!! in taxes.

BUT... if you want savings. Instead of getting that CRX, get a 2.73 rear end and only put the other in for the track...

 

If you spend a thousand bucks on a hoopdie that breaks down after 3000 miles, you've just thrown the thousand bucks away.

I am the king of hoopdies; from the rolled 68 Nova I bought for a hundred bucks and had the firemen cut the crushed roof off with the chain saw-rotary saw and drove for three years, to the 69 mustang I paid 125.00 for and drove for a year with no rear shocks, there's nothing I love more than a cheap car that runs forever.

The thing is, you're not going to find deals like that as easily today, especially when you're talking about cars that get good gas mileage in an energy crunch, and cars are more complicated today. It takes more to keep them running.

But, let's say you're right, and we can pick up a hoopdie Civic for a grand. I'm still going to have to spend at least a hundred a year in insurance on it, and it's still going to have to pay 50 bucks a year to tag it, and the 100 bucks a year in maintenance costs is now an even more generous figure. That means I'll save a little over 600 a year after operating expenses, so, it'll be a year and 8 months before I see any savings, and then only if I don't have to put any additional money in the hoopdie.

You bet, if I fall into a deal for a hoopdie for 500 bucks, I'll gobble it up and take my chances. Those deals are harder and harder to come by, though. Right now, a 10 year old Civic with over 150,000 miles on the clock is still worth 5-6 grand, unless it has rust holes you can put your fist through, etc. The better the mileage it gets, the more the hoopdie is worth.

 

Ok Here you go my wife has a 02 toyota solara "sports car". 34 to 36 if you keep you foot out of it 4cyl, my daily driver has a 3.8 s.c and can get 26 to 28 if i keep my foot out of it not aero at all. Then my toy gets around 16 to 17 if I take it easy who does that? I work hard enough to take my toy out which is a 305 and give it pure hell. The rest of the week drive my olds and still eat em up if the need arises. Best bet buy a beater and drive it it will pay you back or like me have the best of both worlds and drive a grandma car with a S.C works for me

 

I just got over the idea of buying a beater last week. Put the pencil to it and the type of car I would allow myself to be seen in would take 5 years to pay for itself in fuel savings and thats not counting tag, insurance and maintenance which would add who knows what. Right now my truck gets around 15mpg in the city, not sure what on the highway. Its paid for and I do not like the idea of starting a payment to "save" money. I have adjusted my driving habits and am working on a better fuel saving tune. Getting the majority of the public to adjust their driving habits will definitely be a task and actually seems impossible.

Climbing on to soapbox....

Driving style and planning smarter trips is one of the many best ways to save. With all this gas savings in mind, just stop and watch a traffic intersection for a couple of light revolutions, it will disappoint you. At least here in the Oklahoma City area and probably most elsewhere people still drive like fuel is cheap. Cat starts, revving motors, oh and lets not forget those BIG bad diesels that "must" stay running while some yeehaw goes in 7/11 to buy more cancer sticks. Last I remember crude oil is used to make diesel too.

Electric will be the way to go in the upcoming future. Buy stock in battery companies now!

Stepping off of soapbox......

Brian

 

Lets look at it this way.

I paid 350 bucks for my gas guzzling pickup. I drive the hell outta it, maybe 90 mph on the highway. I get into the throttle a little at nearly every take off. It gets about 10-12 mpg. How long would I have untill the extra fuel costs offset the initial buying price?

Wait.... I dont even know what I was asking.... But basically I paid 350 bucks for it, I can drive it like a maniac and still come out less than if was a fancy vehicle that got 20 mpg that I had to pay several grand for... at least for a few years anyway.

 

You know...it drives me crazy to think of all the people that can modify their cars to increase fuel economy but don't.

I have done everything I can think of to increase my gas economy. I have installed underdrive pulleys, free flow exhaust, an electric fan and a hotter coil. I routinely get about 16-17mpg on city driving and 26mpg on the interstate in my Caprice...It would probably be better if I had a real good CAI.

Two of my friends have Dodge Ram Trucks with Hemi's and they get like 8 or 10 MPG City tops...which royally sux. I realize that a lot of it has to do with 4WD and Drivetrain loss but man...how can people go on paying for gas?

I have recommended that they each look into get CAI's and free flow exhaust systems to start with...then maybe a hand held programmer...just for the sake of gaining a few HP and making it a bit more efficient. They always say "I don't have time for that"...or "That stuff is expensive" but they are losing out. I mean...either way they HAVE to keep buying gas...why not spend some money and get a few things that not only improve driveability but increase fuel economy. Its a no brain'r.

 

What kinda gears you running in that caprice? Im only getting 20-21mpg with mostly highway driving.

 

We are talking about personally saving money at the gas pump. Also consider the savings if everyone uses less gas both the foreign oil angle and the environmental angle. I like my 125,000 mile 305 with TPI CAI and 2.73 gears. 18 -19 in town and 22-24 highway. And i am not the king of maintenance.

 

In my 305 TBI, I get ~17-18 around town, and 26-28 (65-70mph)on the highway- so long as I keep my foot out of it. I attribute around town to not jumping lights and taking my time with most of everywhere I go. Call BS all you like, but I drive like a grandpa and there are plenty of people who hate me for being a slow poke.

Also, like the OP, if I leave with an extra 2-5 minutes early to my destination, I save myself cash just because I changed habits. Best of all, because I leave that little bit early, I'm not stressed to rush somewhere.

Its hard to keep the foot out of the pedal, but I manage by concentrating on getting that perfect bassy exhaust note from my pipes.

 

when bill owned my car he'd get 250 miles or more per tank... while tuning... i've been getting 160 miles per tank maybe. LOL all that AE adjusting and testing.

 

Great thread.. Ill add my .02

Hypermiling - never heard that term before, but very familiar with the concept Im my DD, I 'try' to slow and coast where i can, and keep the speeds down, drive as fluidly as possible and to use as little gas pedal as possible to move the vehicle...

I drive a beater car I got 4-5 years ago (i dont remember) it gets a solid 30mpg. even with 145k on it (suzuki sidekick) and I expect it to go another 50k. In this case my 'toy' is my tow rig/truck that pulls my trailer with my jeep on it.. While I could drive it and eat the MPG, it allows me to have an older tow rig, thats better suited to towing vs DD.

I drive ~50mile a day round trip w/ mixed driving. The biggest issues i see with the topic is, its NOT the best solution for everyone. At current gas prices you'd need to drive at least 30miles and get good (25+)mpg (best guess) to see any pay back, depending on the cost of your beater car. If you can't wrench yourself you will NEVER see any gains as you will have paid to much in even simple repairs to offset any MPG gains.. You need

Acetone - i've run small amounts of ACE in my car off/on for the last 3 years with GOOD results. The theory is that it lowers the surface tension of the fuel and allows it to attomize better for more complete burn. On my DD, i feel the suzuki did a good job as it is desigining the engine (alum. head/alum block, etc) and the controls to basically do as good as it could.. So not to debate the theory part. I belive the gains come in from the cleansing aspect of the fuel system allowing it to run as good as it possibly can. I ran it continually for over 6 months and saw immediate 2mpg gains (up to 32mpg) and even after I stopped continued use. So I add it every few months. The ammount is very small 2-3oz per 10gal. NO MORE..

The other thing not factored in anywhere above is the overall cost to drive a vehicle. Using my truck as an example, i need load rated tires, change fluids/routine maintenance, etc.. All of which I can do some simple math and break do into a cost/mile to move the truck. ADD fuel costs on top..

With my beater car, I run low end 40k tires, 4qt oil changes, cheep(er) filter, 2gal cooling system, etc all contributing to a much lower cost/mile to operate that ALSO adds to the MPG gains i see with it..

ALSO I drive over 10k per year just in work milage. If you project out any major repairs on your vehicle say 10years/100k like engine work, transmission work, etc.. I'd rather put those miles on a disposable car. (or somthign i'll happily use junk yard parts on) If you run a $300 junk yard motor well ok then.. But I suspect many don't..

All this really means is it's a very individual thing.. I like knowing that I can save some MPG and help out. Its also a personal challenge to see how good I can do. Especially since I drive 45min, each way everyday.. These little things really help pass the time. And I find driving slower is way more relaxing than going faster. I really don't have to worry about every passing anyone. My car 'looks' slow so I don't feel like people are surprised when I 'am' going slow.. It would help if more people went slower. I know when I finally catch up to a line of cars (2 lane state rd) on the way home, I feel better im not the only one holding up traffic for a short while.. Even though im doing the 55 limit, some people almost crash just to pass, only to have me pull up behind them at a light 5min down the road.. They showed me

I look forward to the milage reports.. Good topic..

 

I don't know about this, you are invoking the AE routine (acceleration enrichment) every time you do a delta tps like that. On most cars this will probably waste more gas than just staying on the pedal all the time.

I would rather pay the extra $$ than drive slow, I just can't do it!!!! That's the way it's gonna be.

 

haha, same here. I should be getting around 16 mpg in the city with a modded 350. but It isn't running right and I am running about 9 mpg. I will fix it very soon though. 4 months of 9 MPG and 91 octane doesn't add up very well.

 

I just thought I would speak of some experience on the L03/TBI mileage thing.

The TBI 4.3/305/350 has its sweet spot between 1,800 and 2,400 rpm with 2,100 rpm being ideal. You want the gearing to go as fast as possible and stay in that RPM range without comprimising acceleration too bad. I can tell you that my G20 Van has 3.08 gears. At 60 MPH in OD with the converter locked the engine is lugging @ 1,500 rpm. Doing 75 mph in OD with the converter locked, the engine is turning about 1,800 rpm. I consistantly get better mileage doing 75-80 mph than I do at 55-65 mph, despite the aerodynamics of a brick. Around 1,800 rpm the volumetric efficiency of the engine picks up and you can actually let up ALOT on the go pedal and still hold the same speed.

My experience building a L03 for mileage resulted in a pretty nice engine. 310 FWHP (240 RWHP), 375 FWTQ (340 RWTQ), and 23 mpg highway with the cruise set at 75-80 mph.

1983 LE9 305 Shortblock with Flattop pistons (.040" over)
Ported 14022601 casting heads 1.94/1.60 valves, 52cc chambers
10.5:1 compression ratio
Stock GM replacement TBI 350 Truck camshaft (pullout of a zero mile Goodwrench 350 TBI crate) with 1.6:1 rocker arms and a double roller chain. Cam 4* advanced.
Stock 1992 G20 Van TBI intake manifold bored to 2"
Stock 1995 454 TBI unit with 2.8 injectors (36# @ 12 psi) @ 32 psi
1.5" primary headers with 2.5" collectors and dual 2 1/2" exhaust
DIY custom prom tuning optimized for the engine using highway mod (1993 caprice ECM w/ Highway mode & WOT A/C compressor cut-out)
Crane HI6 Multi-Spark Capacitive Discharge setup (.060" plug gaps)
GM S10 2,000 rpm lockup torque converter
700r4, 3.08 gears, P295/50/R17 tires

The end result was 23 mpg over 750 miles averaging close to 75 mph running cruise 90% of the time (nearly 80 miles of the trip were made at 85-90 mph). That was loaded with 6 people and everything needed for a 4 day trip running the A/C full blast on a 100* day.

The trick is a high dynamic compression ratio, properly timed cam, lean air/fuel mixture, proper timing advance, fully heated intake and stock heated air cleaner (vacuum motor connected to the EGR solenoid for heat at part throttle) ducted to cool air(at Idle/WOT), very good fuel atomization, proper shift points, proper TCC settings, properly working EGR, proper .035-.040" quench area, and a very hot ignition setup.

 

That is all fine and good but your data is also very vehicle specific. My truck for example power to speed wise peaks at 70 mph right at 2k rpms. At that speed it is making max torque and actually runs 1 to 2% less throttle then it does at 65 mph. If you are going to slow down and depending on your gearing sometimes dropping to 3rd will actually make your mileage better. For example I ran 32 inch tires and 3.08 gears for 4 months with just a fuel intake mods and full exhaust on a weak 350 TBI. In overdrive it would lay over and die, it just wouldn't pull itself at all at 1400 rpms at 65 mph. In 3rd gear I had usable power and even running in excess of 85 mph on a road trip in 3rd I was able to get almost 16 mpg running nearly 3k rpms at times simply because the engine wasn't lugging, it was running more timing, and less throttle and less fuel. On a bone stock vehicle the hypermiler theory would more then likely work but even in that case you must know your vehicle and how it performs and when it performs its best. Also one easy trick is wax your car. I've heard as much of a .1 second gain in the quarter mile just from waxing a car that had dull oxidized paint. The slicker the surface of the vehicle the easier it cuts through the air.

 

Dude, there's no way you're going to pick up a tenth of a second from waxing a car, unless you're in the 300 mph range.

That's just another silly old wive's tale. You see a ton of 'em when it comes to gas mileage, too.

First, there's the tornado, etc.

Then there's running Acetone, etc.

On the Jeep forum I participate in, there's a guy who insists that replacing the stock fan with an electric fan is worth 1.5-2 mpg. Hogwash. I have no doubt that there will be an improvement from doing so, but no way it's that much.

If that guy had a third gen, he'd be swearing the ultimate TBI mods were worth 5 hp, too.

 

Funny story, I sold a subaru to a friend a few months back. He calls me up a week later and says the car is stalling, getting poor mileage and just plain running crappy. I ask a few basic questions about how it acts, and it sounds like the car is lean. Then he slips in that all he did was put in a tornado.....I ask if it's before the MAF sensor, he says yes. I tell him to pull the pop can out of the intake and call me in the morning. The car has ran fine ever since. The tornado was causing turbulence and messing with the MAF.

 

LOL what a piece of crap

 

"Hypermiling" and "TBI" don't go in the same sentence as far as I'm concerned.

Lose weight, lose weight, lose weight. Rotational, sprung, if it's weight, get rid of it. That's the best way. Why do BRAND NEW cars STILL get 20mpg?? Cause they weigh 6000lbs. It take a minimum energy level to move these tanks, which translates to the maximum on mpg.

Short of making your internal-combustion engine significantly more efficent(another oxymoron), losing weight is about it.

People here who tune the living **** out of their drivetrains looking for every last thread of energy still only achieve 25mpg AT BEST(v8's). If someone with hard numbers wants to claim otherwise, please, chime in.

Buying a seperate beater car for mpg has been shown not profitable. But then again, putting money in f-bodys isn't real profitable either.

In reference to the "tornado" or anything like that...if a simple stamped metal part could increase power AND mpg, wouldn't the factory use one??? Granted factorys do some pretty questionable things, but that would be a no brainer IMO if actually worked. No matter what they try and tell you...pouring water out of a bottle is NOT THE SAME as air rushing into your engine at high velocity.

 

you could do what I plan to do and buy a 2005 gsxr600 for 6000. it gets 40+ miles to a gallon and can keep up with the fastest cars around. and you can build your thirdgen to be what you want instead of ruining it. cool thread though.

 

De-screening it can cause this issue as well. It still seems to be a popluar mod, so I thought I'd add that here as de-screening your MAF may very well lower your MPG.

How much is your motorcycle? $6000? more? It'll take at least two years to recoup those savings. And I might not even live that long considering drivers around here couldn't pay less attention to motorcycle riders. And that car seat will be kinda hard to fit with my wife and 5 year old already on there.

The "buy another vehicle" debate has been closed. Not profitable. Barley profitable when the vehicle is free and requires no maintenance.

If you have to spend more than $500 to get 2-3 mpg, your not making a profit.

 

I got 1.6x the mileage by adding a newer 350 long block, blower, 4.10 gears and a giant 4.5" cowl. Figure that one out!

LG4 with CC Qjet = 15mpg
current combo = 24 mpg

same stretch of hiway in the same season with the same driver.

I believe it has alot to do with how "happy" the engine setup is as a whole. Then consider vehicle weight and gear ratio

 

TBI is actually a resonable choice for this as you can get very homogenous fuel mixtures if the intake is set up right. The other ingredients, IMO, would be better gears, low stall TC, high compression, leaner AFRs, weenie little cam, light car, etc. Out here in the real world with real people behind the wheel, even the fruity hybrids can only get into the 40's. If you could get into the 30's around town during normal driving, then IMO, youd have achieved the goal of a high fuel efficiency car.

 

Depending on the terrain and type of driving you do (highway or city) weight may or may not play such a crucial roll. On flat ground once up to speed it, in theory, doesn't take any more power to keep 4000 lb moving as it does to keep 3000 pounds moving. Of course we don't all live in Kansas, and we have to get that 4000 lb's up to speed which does take more power and fuel.

I still stand by observation that at highway speeds aero is THE most important factor as it's the primary force acting on the vehicle. I think you don't see such impressive mileage out of newer cars is that americans like big brick like cars.

 

i don't have a TBI, but i have been following this thread.

seanof30306, if that jeep guy had a heavy duty fan clutch that stayed engaged all of the time, i can see a pick up of a mile or better with an electric fan.
as for waxing the car, i can't say for certain. but it makes sense that a clean waxed car would do better than a dirty unwaxed car. i guess the only way to know for sure is to pull a dirty car into the wind tunnel & see what numbers you get. then wash & wax it & see what the difference is

pizza_guy, from my understanding, TBI can do about the same as TPI as far as gas mileage goes.
my car started out in the 20~22 MPG highway range, i fixed a few minor problems & with a little chip tuning i got to a little over 25.
with more chip tuning on my last trip, i went from Houston to Tyler then over to Ben Wheeler. on the return trip i stopped for gas in Palestine, including a missed turn along the way i clocked 303 miles, 11.2 gallons of gas to top the tank, that comes to 27.0. going by the mile markers on the highways here, my odometer is off by 10%, i hit the reset & driving 10 miles by my odometer puts me at the 11th mile marker. 333 divided by 11.2 = 29.7 MPG.
i was mostly running around 65~70 MPH with around 20 minutes or so at a little over 80, this was with cruise & A/C on. i could have done better without cruise after i hit Lufkin.
i know for certain there is more MPG in the chip
so far, i haven't "tuned the living **** out" of it, i don't have a wide band yet, but its ordered & should be here in a day or 2

 

My brother had an LG4 camaro with a quadrajet and 3.08 gears, that car would easily average 27-29 mpg on the highway. Like I said thirdgen's are relatively aerodynamic, with the right gears and a nice torquey motor high 20's are not a problem.

 

Well, I'm obviously missing something then.

My Lo3 firebird with 700R and 2.73 gears never beat 25mpg. Even on a highway trip over 500 miles.

And the L69 camaro t-5 w/3.73, it's even worse, somehow.

 

Yeah you are, there are so many things that can effect your mileage it's not even funny. Very few people actually have their vehicle running as well it possibly can. Also very few people actually slow down enough to get decent mileage.

Slow down 5-10 mph and you'll break 30mpg.

 

3.08 Posi...I get about 26 MPG on the highway....