Performance mods that actually give power and economy.
I've always been involved with tuning ...everything from an old civic DX hatchback where we shoved in an Accord motor to a Chevy Diesel work/weekend drag racing truck. With everything the better you get your vehicle to "breathe" and the more fuel you pump, the more power you make.
Has anyone found proven performance mods that have actually given economy bonuses if driven conservatively? ie. adding an air intake, performance headers, free flow cat., exhaust?
For the general public I would suggest finding a forum for your particular car or bike and find out what others do specific for your car.
For me I go to http://www.tdiclub.com/ there are lots of people getting crazy mileage out of there TDI's. Some even go as far as aerodynamic fairings and such.
It comes down to time and money, cost and benefit. I have heard that some guys are putting in Lithium Ion batteries in there Prius and get amazing results but the cost is so high that it would take years to recoup if at all. In the land of the VW TDI there are a number of items out there that actually increase Horsepower and give better mileage IF you can keep your foot from loving the extra power! LOL! If you have messed with your Chevy Diesel you would probably know a bit about that. Not sure about gas cars but with a diesel cars there are after market computer chips that increase power and fuel efficiency? Bigger injectors would help me and I have heard that getting a bigger exhaust helps the Diesels also.
actully don't ever get a after market airfilter for the TDI jetta. They cause problems with Mass Air Sensor. With the TDI only able to get to 4800 RPM there is no need and the stock one filters so much better.
Bigger injectors and chiping would be a good start. I have not done that yet because I am waiting on getting a new clutch first. I heard messing with the exhaust is also good but then again with all of these you just got to watch the right foot as what I am hearing makes the power go way up and you will be spinning some tires pretty fast! LOL! Keep looking on http://www.tdiclub.com/ lots of info there.
I see you have a 03 wagon. I had one till I had to get a mini van. I had a killer tow hitch on mine, 2 inch receiver! And would tow a 1400lb camper with it with no mods except for some Bilstein HD rear shocks. I never did get the milage ouf of it like I do with my 01 sedan. later
Years ago, long before smog laws, I had a VW Super Beetle that I rebuilt to improve performance over the 1300 CC motor that was in it. I put together a 1600 CC engine and put rebuilt heads on. I didn't notice at the time but the rebuilt heads had small intake valves (there are at least 2 standard sizes, maybe more) and the original engine had larger valves. I realized a fair improvement in acceleration (not very hard to do from the 1300 CC engine) and significant increase in fuel economy. The car went from about 26 MPG to over 30 MPG on the freeway. The funny thing here was that I thought I was hot rodding it, with no intention of increasing mileage, that was an accidental and inadvertant side effect of replacing the motor and I didn't realize until months later why it had happened. When I dropped the motor and took off the heads to check the ring break in I saw that I'd put heads on with obviously different valves. After I discovered what I'd done, I started talking to some VW performance enthusiasts and tuners and found out that I was just an idiot, they'd all been doing it for years with their daily street legal drivers for that reason.
On my 1988 Yamaha FZ600 I switched the carb jets for added performance and realized some increased fuel economy at the same time. That time I knew more about what I was doing. I increased the size of the secondary jets but DECREASED the size of the primarys. It seems counter intuitive but by increasing the secondary's you get the fuel delivery that you are after when you roll on a handfull of throttle. Downjetting the primary gives you less delivery at idle and when you aren't on it. That works out to better fuel economy at cruise and steady power settings like on the highway or freeway. The caveat there was that the increase wasn't huge, something like 10 % and was easily off set or even over ridden if I did a lot of light to light hard accelerations which burned fuel at a substanitally higher rate than the stock jets did. But what fun it was to ride that bike around with the added power provided by the jets and a high flow / low resistance tuned exhaust system. 103 Horsepower on a 400 pound bike worked out to mean that the front wheel was only on the ground when I was braking if you know what I mean.
For Hondas you can check out a company called Jackson Racing, they are located in Huntington Beach CA and have an online catalogue. They have some performance products available for sale that may increase fuel economy as well. Be careful of swapping chips as that violates many smog laws and may result in serious fines if you're caught. That being said a buddy had a 1990 Chevy Camaro with a 305 V8 in it and he switched out the main chip to a off highway only chip that gave him marginally better fuel economy but a significant horsepower increase all for a little over $125 and about 20 minutes worth of work to remove the stock chip and replace it with the new one. But with the added power he started replacing his rear tires a lot more frequently as it was a lot easier to light them up after the change.
Just remember guys, performance modifications that create more power and more torque do this almost exclusively by moving more air and more fuel into your cylinders, not by making your combustion more efficient. You may be opening the throttle slightly less to accelerate the same amount, but that doesn't mean that you're using less gas to accelerate the same amount. The only way to make your car more efficient is by reducing parasitic losses like driveline friction and aerodynamic drag, or by making your combustion more efficient. A performance intake and exhaust might (but probably wont) reduce engine pumping losses by a very small amount, but if it actually shows up as a fuel economy difference, I'm sure it would never pay for the cost of the mods.
To add to what rem83 posted about parasitic drivetrain loss;
When I replaced the clutch in my MR2, I decided to go with a lightweight flywheel as well. The stock flywheel weighed in at 16lbs, and I put in a 9lb one with the new clutch. This is considered a performance modification, as it lets the engine revv up faster and gives you better response, etc. However, it also has the added benefit of better fuel economy, as the engine works LESS to give you the same amount of power. I guess the physics term would be rotating mass, and the general idea is you want less of it.
This is also true for rotating mass such as wheels and tires, or even your brakes rotors. Those parts also fall under the term "un-sprung" weight, as they are a part of your car that is not supported by the shocks/springs of the car. Less un-sprung weight is considered ideal in the performance world, and a lot of tuners try to get very light components to go faster. Once again, these mods will also increase fuel economy on a street car, as the engine is going to work less to give you the same amount of power.
If you care to modify your car even more, you could consider lightweight body panels, and lightweight interior components. Realize, however, that these mods often interfere with road safety laws. Your average car seat fitted with all of today's modern technology and luxury weighs a ton. Swapping yours out for a "tuner" style seat can save you a good amount of weight, which computes to better fuel economy.
In my MR2 I removed all of the trunk's carpeting and paneling, as well as the factory spoiler. I then removed the front trunk's (frunk's) carpeting and paneling, as well as the spare tire, brackets, jack and tools, etc. I drive my car in town only, so having a flat is no problem my cell phone can't handle lol. All of the removed hardware turned out to weight over 100lbs combined. And when your car weighs 2400lbs like mine, a 100lb weight reduction is pretty significant. And a note on the MKI MR2 factory spoiler; as far as aerodynamics go, it's a brick wall. It provides virtually no downforce at speed, Toyota really didn't put any R&D into the functionality unfortunately.