Master list of 65+ proven mods for increasing MPG

[Intrigued]

There's a few things you can do, but only if you do a total "basjoos" to your car's body (look up his name and car) will you gain more than plain old smart driving. You can't do much real 'adjusting' to the engine itself, other than synthetic oil, unless you have a good friend who has a car computer programmer that knows what he's doing. (Other modders insert arguments here... ) Otherwise it would be forever getting the money involved back out of it. A couple of starter things to do are keep the tire pressures up at the max on the sidewall, narrower tires when you replace them, keeping all of the extra junk (weight!) out of the back seat and trunk, and then the simple aero mods that most of us can do. I bought some .060 Lexan on eBay, and blocked off my bumper holes, since most of the air to the radiator channels in from the air dam under the front of my Intrigue. If your Acura still has a functional opening above the bumper, you could do a similar thing below the bumper. For the bumper block I started by cutting out cardboard to get the right size, and then cut the .060 (1/16) Lexan with tin snips. 4 screws held it down, see the first pic. Then I used the rest of the piece (a 4 foot by 8 inch to start out), cut it in two, and extended my air dam out to the edge of the fenders. I heated and bent the last inch over to screw it to the inner fender mount in front the tire. (second pic. Never mind the poor quality...) I used Wal-Mart Krylon flat black to spray the extensions to the air dam, and left the bumper block clear.

That same sized piece might just work under the bumper of your Acura, with just a little trimming.

With (and beyond) that, you'll just about have to read what others have done, and see if it's something you can do or not to your car. Mileage improvements vary greatly with these. You'll need to average a few tanks fills after each modding, since there's too many other variables involved to know for sure right off how much it helped.

[whatjigg]

what about filling tires with Nitrogen - it's said to result in a 4% on avg increase in fuel economy (not sure how true this may be). Not only that, it's cheap to do, costs $5 per tire typically and results in more stable tire pressure (when heat builds from driving and changes in temperature). This one's fairly controversial in terms of its effectiveness but so are some of the other items on the list. Oxygen has an atomic weight of 16 while nitrogen of 14. Doesn't look like a big difference, but it is a 12.5% decrease from oxygen which may not mean a whole lot at the end of the day when it comes to a potential approx 10% drop of the weight of the volume of pressurized gas in your tire. Have i tried it? Not yet but I plan to soon.

[Intrigued]

Yeah, I'm running Nitrogen in my tires. I'm doing it more for the tire life itself - Nitrogen has larger molecules, and won't leak out as fast, and also it is an inert gas, that will help the tires from becoming weatherchecked with age - or at least that's what "they" say when trying to sell it.

Whether or not it helps fuel mileage, I dunno...

EDIT: Oh, and I always get tickled when the comparisons are done with Oxygen and Nitrogen. The air we breathe is already 78 percent Nitrogen and 20 percent Oxygen, so I'm not sure why comparing with Oxygen is the way to go: I sure wouldn't put pure Oxygen in my tires!!!

[whatjigg]

You notice any fuel economy changes? I too am doubtful of what 'they' say. I mean, a tire at 32 psi of air/nitrogen is still going to be 32psi. And yes I just meant compressed air not pure O2 which nullifies some of the comparison.

[Intrigued]

Yeah, I wasn't really picking on you, I just see on the ads for nitrogen filling how it compares to Oxygen. I'm not even sure if they are realizing what they are saying!

I wasn't really able to tell any difference in fuel mileage, since mine has dropped some for the winter just like it does every year. Just in my opinion the main gain is in tire life itself. With tires being one of the more costly and difficult items to recycle, (and being such the "mosquito motel" as they are when piled up outside) there will be an eco-gain there somewhere.

[Andyman]

I thought of another modification that can be added to the "Drivetrain mods" section. Use a tight or low slippage torque converter. This could also be called a low stall speed torque converter. Stall speed is the engine RPM when the automatic transmission is in gear with the brakes on to keep the car stopped and throttle opened completely. This shouldn't be done for more than a few seconds since it creates a lot of heat in the transmission. It's also important that there is nothing to hit in front of your car in case your brakes fail during the test.

If the torque converter slips less, it wastes less energy making heat in the torque converter. This should help improve mileage in slow local driving. On the highway, most torque converters engage a clutch to eliminate slippage. This happens at 35 - 50 MPH on most cars. On my car, it's close to 50 MPH. I get a lot of slippage when I climb hills at lower speeds. I estimate that I'm losing about 1/3 of my engine power in the torque converter when I climb a typical hill at about 32 MPH. My engine runs at 2000 RPM in this condition, but if the torque converter is locked, my car can go 48 MPH at 2000 RPM. So only 2/3 of the engine speed is passed to the transmission when I climb the hill.

Cars with larger engines and engines that run slower (such as diesels) are likely to have tighter torque converters. This would require some research to figure out which torque converters are available for your car and which ones are tighter. Keep in mind that a tight torque converter is likely to reduce your acceleration from a stop because the engine may not be able to get to the speed of maximum torque immediately.

[Formula413]

Originally Posted by Andyman

I thought of another modification that can be added to the "Drivetrain mods" section. Use a tight or low slippage torque converter. This could also be called a low stall speed torque converter. Stall speed is the engine RPM when the automatic transmission is in gear with the brakes on to keep the car stopped and throttle opened completely. This shouldn't be done for more than a few seconds since it creates a lot of heat in the transmission. It's also important that there is nothing to hit in front of your car in case your brakes fail during the test.

If the torque converter slips less, it wastes less energy making heat in the torque converter. This should help improve mileage in slow local driving. On the highway, most torque converters engage a clutch to eliminate slippage. This happens at 35 - 50 MPH on most cars. On my car, it's close to 50 MPH. I get a lot of slippage when I climb hills at lower speeds. I estimate that I'm losing about 1/3 of my engine power in the torque converter when I climb a typical hill at about 32 MPH. My engine runs at 2000 RPM in this condition, but if the torque converter is locked, my car can go 48 MPH at 2000 RPM. So only 2/3 of the engine speed is passed to the transmission when I climb the hill.

Cars with larger engines and engines that run slower (such as diesels) are likely to have tighter torque converters. This would require some research to figure out which torque converters are available for your car and which ones are tighter. Keep in mind that a tight torque converter is likely to reduce your acceleration from a stop because the engine may not be able to get to the speed of maximum torque immediately.

Interesting to hear it put this way. Torque converters with a higher stall speed are a common performance modification for muscle cars with automatic trannys. In my Formula for example, the stock stall speed is 1800 rpm, many people (and perhaps me eventually) replace it with an aftermarket unit with a stall speed around 3000 rpm, even higher for cars used primarily for drag racing. The improvement in acceleration is very large, although of course there is a mpg hit at lower speeds when the converter is unlocked.

On my Escort I can program an X Gauge that shows the ratio of output shaft speed to input shaft speed, so I can see torque converter efficiency expressed as a percentage. Sometimes when climbing steep hills it gets down around 60%, which is somewhat in line with what you are describing (which car btw?). This is also when I see the highest trans fluid temps, between 200-215*.

[Christ]

is there any way to modify a torque converter so that it has a lower stall rating?

not big on autos here, so i'm not sure.. I know you can modify autos so they don't shift automatically anymore, and I know you can make them shift almost as hard as you could want.

[Andyman]

To Formula413: The car I was writing about was my Accord LXi. That's interesting that you can measure torque converter efficiency on a gauge. The other way is to divide the car's speed by the speed you would have if there were no slip. In my case, I know that my car goes 24 MPH for each 1000 RPM in high gear if there is no slip. I would multiply the engine RPM by 0.024 to calculate the speed of the car without slippage.

32 MPH/(2000 RPM * 0.024 MPH/RPM)
=32/48
=0.666
=66.6% torque converter efficiency

Modifying a torque converter would not be an easy thing to do. They are welded shut, so to modify one you would have to cut it apart, do your modifications to the internal parts and then weld it back together. Then you would have to balance it to make sure you don't get vibrations. I don't think you can get a rebuilding kit for a torque converter.

[Christ]

=0.666
=66.6% torque converter efficiency

Why... oh why... can't we round numbers???

LOL.

I'm not all about cutting one in half.. I wouldn't call that something within the caliber of the average enthusiast.