How do "Performance Mods" effect a car's economy???
 

I accidentally stumbled upon this site and have become very intrigued with different ideas to improve my efficiency. I would like a car that can get good gas mileage but can still be pretty quick when needed. I would like to know if anybody has any insight as to how adding things like intake, headers, and/or exhaust to a car would impact its efficiency? Im looking to have a car make decent power while still maintaining the stock fuel injectors and fuel pump. Thanks in advance!

...it "takes" a certain amount of power to drive 55mph due to aero+rolling losses, so ANY improvements in power (HP) "making" ability--if bi-lateral--can likewise (usually) yield improvement in fuel economy (MPG).

NOTE -- by "bi-lateral" I mean something that's NOT just a "oneway" change, such as changing from smaller diameter carburetor jets (good for MPG) up to larger diameter jets (good for HP, but kills MPG).

...headers are a "give & take" situation--they "give" you power at the engine speeds where they "tune" but also "take" power at intermediate engine speeds...kinda like childrens' "teeter-totter" where one end is UP while the other end is DOWN but the 'middle' (pivot) location never changes...the process of "tuning" is a proverbial "...rob Peter to pay Paul..." situation.

Check out Autospeed's website, they have a few articles on setting up cars for both performance and fuel economy
Browser Warning

The simplest ways to get better power and economy are to reduce parasitic power loss. This includes things like manual steering conversions, AC deletion, use thinner grade motor oil, reduce exhaust backpressure, as well as non-engine work like weight reductions. Reducing weight could be as simple as cleaning out your car or replacing a spare tire with a can of Fix-a-Flat to more expensive measures like fiberglass/carbon fiber hoods.

Power and economy can work hand in hand, but if one is going for maximum fuel mileage, power must be sacrificed.

Better efficiency on today's gasolines?
 

Have you ever wondered what this "gasoline" actually contains (or doesn't contain) per unit volume? I'm not looking to start a firestorm here, but has anyone smelled this "stuff" as you pump it into your gas tank? Smells oily to me.... Gasoline used to smell sharp! Comments?

Performance mods can help FE. Some, such as roller rockers, free up parasitic power loss, which helps both power and mpg. Others, such as exhaust, reduce pumping losses. If you get a set of headers well tuned for low end and midrange, you'll gain low end torque, and possibly FE. You can also tune the computer for good performance when you put your foot down, and be efficient at part throttle (more timing = more power and FE, but needs higher octane).

As a rule anything that moves the powerband up will hurt FE, this includes but is not limited to headers, cams, intakes.
Any reductions in parasitic loss will help, but keep in mind where they save x hp.

Whoah WHOOOAH DUde I'm all for performance parts Everyone knows that but i found one HUUUGE gap in your logic *Reduce Exhaust backpressure*
Yes it can be good to an extent but you also have to add in how much torque you may lose from different exhaust mods, Which may add horsepower however if you reduce your torque then you have to give the car MORE gas to make it perform the same in bottom end from lights and such, So you can't just put out things like that without backing Trust me i know

One performance gain i've never heard of hurting FE is Advance your timing with running Higher octane fuel, I do it in my el camino i run 91 octane with advanced timing and it saves exactly 1 MPG

reduced exaust backpressure will not help
2 reasons
1) the increased flow will be directly ofdfset with decreased throttle position.
2) reduced scavenging will bring the power band up.