Mods for better gas mileage

Why would I want to give myself vapor lock?

-DanD

This may have help with gasoline vaporation for carburated engines in cool climates. It is not going to do anything for engines with port tyope fuel injection.

Years ago I can rember a magazine article that compared various gas saving devices. Most effective device was a wooden block installed under the accelerator pedal. Bet that still works.

Ed

Worst thing about using a fuel pre-heater on an injected vehicle is that a good portion of the fuel in the distribution rail does not go to the injectors, but rather is returned to the tank. Having hot fuel in the rail is one thing. Hot fuel in the tank is just asking for problems with evaporation or worse.

Heh - I remember when I was a kid (I think it was a Plymouth Fury Wagon?) but it had a red needle on the speedometer that you could set, and it would set off an alarm/buzzer when you reached that speed....I'm pretty sure my Dad had the alarm needle pinned and buried at 135... :)

Scott

A better thread would be "Tips for better gas mileage"

A few mods that make horsepower would also improve MPG like a free flowing air cleaner and exhaust, skinnyer tires, a manual transmission, weight reduction, don't use the air conditioner or better yet remove it, remove your rear spoiler (it only increases drag) ect... but the single biggest gain you will see is in the way you drive, limit your accelerator use.

That may be changing as well. I get significantly better mileage during long highway drives at 85 mph than at 65 - 70 mph (with all other factors being equal). I'm sure it depends a lot on the car - aerodynamics of the body, powerband of the motor, gearing, etc.

Lane [ lane (at) evilplastic.com ]

Many performance mods do give you better fuel mileage if you stay out of the pedal. The power addiction tends to defeat that, of course. Cooler and more free air flow helps combustion efficiency, lighter weight/smaller pulleys and flywheels reduce initial lag, less restricted exhaust reduces heat and back pressure, hotter or more successive firing from your plugs increases ignition efficiency, good/balanced air pressure in the tires reduces road friction, clean/smooth/uncluttered body and lower ride height reduce air drag, synthetic lubricants reduce friction, lighter weight equals less fuel use, etc. Try early or "short" shifting when the oppurtunity presents itself (provided you have a manual.) Coast to stops whenever possible. Use defrost and air as little as necessary. Increasing mileage/efficiency/vehicle life and reducing emissions go hand-in-hand with a well-tuned car, performance mods, and good driving technique.

Preheating fuel to an electronically controlled fuel/air mixture will likely reduce your efficiency. This would be a radical variable that your ECM wouldn't be taking into consideration. In extreme cases, this could be volatile. Results may be a backfire.

Try:

- Overinflate the tire by a few PSI. Saturn recommends 26PSI, I use

32PSI.

- Shift at the Saturn recommended speeds (ie. appx 2000RPM)

- Do not use more than 1/3 of the gas pedal travel.

- Remove seats, carpeting, spare tire etc. to save weight.

- D>There's plenty of stuff to get more horsepower out there. What is

snipped-for-privacy@NOSPAMevilplastic.com Newsgroups: rec.autos.makers.saturn Sent: Tuesday, March 29, 2005 5:50 PM Subject: Re: Mods for better gas mileage

This is not believable if "all other factors" are truly equal. It would take an incredibly poorly geared/designed vehicle with a badly tuned engine to get better gas mileage at 85 than at 65. The aerodynamic drag increases by 65% as you increase the speed from 65 to 85. If your car requires 20 hp to go 65 mph, it will required at least 30 hp to go 85. Do you honestly believe that your vehicle is so poorly designed that it is so much more efficient with he engine running at 2000 rpm vs. 1500 rpm, that it can make

50% more power for less fuel? I think if you do a very careful comparison where all other factors truly are equal, you will find that the vehicle gets significantly better gas mileage at 65 than at 85.

Ed

I believe volumetric efficiency has something to do with it. When an engine reaches a certain RPM it can be running more effeciantly at 2000 rpm than at 1500rpm. IIRC the EPA's highway test speed is done at 47mph. My cars EPA rating is at 28mpg highway however I still get that on a cold day doing 75mph (2100rpm). It has nothing to do with bad designing on part of the engine. It has to do with the engine reaching its best range to flow air and get the most out of it while traversing more terrain. Cars can often take advantage of higher speeds and gain mpg. Larger vehicles usually cannot however.

----- Original Message ----- From: "blah blah" Newsgroups: rec.autos.makers.saturn Sent: Wednesday, March 30, 2005 11:53 AM Subject: Re: Mods for better gas mileage

If you are talking about gas mileage differences at 35 and 45 mph, I can believe you get better mileage at 45 than 35. However, once you get past 60 mph, aerodynamic drag is the major factor influencing fuel economy. For any modern car or truck in a good state of tune, it is simply not believable that the mileage is better at 85 than at 65 if all other factors are truly equal. How are you even measuring your fuel economy at a steady 85? Or 65 for that matter. If you are doing 85, you have to be in an almost traffic free environment, which is one factor that is probably not equal. I have had this very discussion with a good friend over a beer. He makes the same claim. Of course his high speed runs are across multiple sates on weekends and late at night. His lower speed runs are in stop and go traffic on the way to work, but never mind little things like that....

My 2003 Expedition (a huge box on wheels) has a rudimentary fuel computer. It is hideously inaccurate. However, I have tried to check the indicated mileage at various speeds from 55 to 75 (I won't drive 85). I have one weekly trip of 140 miles on a lightly traveled road with various speed limits, 55 /60 / 65 / 70.Several times for the different segments, I have reset the fuel computer and checked it after ten miles of steady state driving (mostly flat roads). The difference is always exactly as expected. As the speed goes up, the fuel economy goes down. 75 (my personal max) is about 3 mpg worse than 55 (15 versus 18). I know others with the same truck who swear that thy get much better fuel economy at 80 that at 60. I say hogwash. I believe it is poor data gathering, combined with a huge dose of wishful thinking, sprinkled with just a little self delusion, and a lot of grasping for an excuse to drive faster.

Ed

Sorry, but I don't think that I will. I've owned the car for 12 years, and put 130k+ miles on it to date. Gallons to fill, and miles traveled get written down with every tank. And yes, that adds up to quite a bit of gas. I pay particular attention to long trips. Over all those years, this behavior has been consistently observed.

Doesn't matter much to me if you believe it personally, but I put it forth here because that is what I have witnessed with my '94 SC2. No faith, belief, or speculation. Observation based on 12 years of fact. I do not attempt to generalize and apply this to any other cars. Each owner and vehicle are different.

And as they say, "your mileage may vary". :) Quite fitting in this case.

Lane [ lane (at) evilplastic.com ]

I also use 32 psi and have nice even wear over face of tire tread and have obtained over 140k km on stock Firestone tires.

hoosier_drifter wrote Try early or "short" shifting when the

the long version follows IMHO

The Saturn S1 series single cam engine is tuned to produce its maximum advertized torque at 2400 rpm. This max torque point is lower than most similar vehicles and for me was the main reason I purchased these cars. The max torque speed is usually the net speed for maximum volumetric efficiency. Operation faster or slower will produce less HP/unitfuel. The Saturn S1 single cam will cruise at 110km/hr @ 2400 rpm.

The best fuel economy will be achieved by driving to minimize HP required. Drag, (both aerodynamic and frictional) increases with the square of velocity. Driving slower than optimal VE will reduce HP/unit fuel but will require less HP due to reduced drag. Driving faster will reduce HP/unit fuel AND will require MORE HP due to increased drag.

2400 rpm /65mph(110km/hr) is the sweet spot, and we want to accelerate up to this speed in highest gear possible. Slightly slower will give greater economy due to reduced drag.

The best way I know to limit both drag and HP required is to use the technique the truckers call progressive shifting. In an automotive application it requires that the vehicle be started in the lowest gear available to minimize starting torque required and to maximize clutch life. Use the minumum throttle required to obtain a smooth clutch engagement and shift to second gear AS SOON AS the car is rolling.

For best distance/unitfuel always use the highest gear possible and minimize the TIME spent in lower gears. Because of the torque multiplication, lower gears do not require the full available torque to provide acceptable acceleration and allow slower engine operation speeds. Shift through the gears picking progressively higher shift points required due to the increased drag at higher speeds. You want the resulting engine speed to be UNDER 2400 rpm AFTER shifting to next higher gear. The exact shift points will vary according to the load, the grade and the desired rate of acceleration. If you are on a downgrade or are lighter you can use a lower shift point, and higher loads and/or steep upgrade will require a shift point above 2400 so that the AFTER shift rpm will be at or slightly above

2400 rpm max torque speed.

Gas engines are not built to survive long at high load/low speed operation, in other words they do not like excesive lugging. The S1 series pulls quite well above 1500 rpm or lower depending on load or grade. Minimizing engine speed minimizes frictional drag and lowers piston speed resulting in lower ring and cylinder wear provided that the temperature is kept up and the oil changed as required. Short trips kill engines.

In my experience I seldom if ever need to exceed 3000 rpm and normally shift around or well below 2000 rpm. It is important to be smooth and to take advantage of rolling terrain to preserve your momentum. Ease off on the throttle going up a hill and allow the vehicle to slow going over the top. You will easilly regain your speed on the downgrade and will have a net fuel saving.

ANY brake use wears the brakes and tires and wastes fuel Anticipating required stops can allow a coasting stop or a rolling slowdown which is even better. Watch how heavy truckers roll slowly rather than make a complete stop at traffic lights.

Lighter is good but seats (removing rear seat lower cushion is easy and will alow flat floor in SW) and carpet don't weigh much. Spare tire is a gamble. VERY IMPORTANT remove unused roof racks and boxes when not required and keep windows closed if possible.

YMMV snip

-The Saturn S1 series single cam engine is tuned to produce its maximum

-advertized torque at 2400 rpm. This max torque point is lower than most

-similar vehicles and for me was the main reason I purchased these cars. The

-max torque speed is usually the net speed for maximum volumetric efficiency.

-Operation faster or slower will produce less HP/unitfuel. The Saturn S1

-single cam will cruise at 110km/hr @ 2400 rpm.

Interesting and ironic that two of my three Saturns are in fact SOHCs. And, yes early shifting does benefit economy in these vehicles. Relying on low end torque with minimal accelerator useage is something I learned to get me by when driving a service truck on long distance trips, and not being near enough to a service station that accepted my company's gas card. Sometimes you have to stretch out that last bit of fuel to make it home. I don't recommend doing this to any excess either in frequency or at extremely low revs, but it does work.

I think we are agreed that low speed lugging is to be avoided, but that above lugging, low end torque is where the SOHC engine really shines. I have not experienced any of the oil consumption problems reported here and always wonder if these problems are mainly found in DOHC engines (or SOHC engines) driven in shall we say a more spirited manner. I think that low speed operation also benefits timing chain and alternator and accessory belt idler bearing wear, and that clutches and transmission syncros also last longer when shifting at a lower than common speed.

I have found by experience and oil analysis that 6000 km seems to be a good oil & filter change interval in our useage which is mainly highway. Oil consumption seems to be more related to the quality of oil used and as I normally use what ever is on sale have noticed some variability. Oil seems to burn more as it ages in use so normally I just wait until the oil is down to the add mark and then change it all. Our oldest car now has 235,000 km. so is just getting to the age that our driving style will I hope be returning the benifit of longer life before overhaul.

I have kept close track of every gas fill and have achieved a consistant 6.8 lt/100km (42m/imp gal) in mixed/city mainly mountain (3,5-4,500 ft elevation) highway (Canadian winter) usage. My wife can get it down in the high 5 low 6 range 50/mpg(imp)) on the highway but I have a heavier foot and have never done that well.

Happy trails

My friend had an old GMC with a fuel economy gauge. I think it just worked off vacuum. I installed an aftermarket vacuum gauge in my Mazda to help detect some problem peculiar to the RX-7. Manifold vacuum, of course, drops when the throttle is opened. If I watch the guage, my fuel mileage does improve. For those who don't know, a 1.3 liter rotary can get from 10-30 mpg, depending on intake type and how you drive.

Chris