Hi everyone,


Just a question that I've always wondered about...

How does changing the intakes, air filters, and exhaust affect the following?

- MPG/fuel consumption
- engine life

I am considering of modifying/upgrading these parts, but since I commute at least 80 miles per day, I just want to know how it will affect my car in the long run.

 

ur good

 

I commute daily 100 miles round trip.

Ever since I installed my Nismo and Berk HFC, I noticed that my gas mileage has been the same, maybe slightly higher. On the way to college, I have a 22 mile straight-stretch that I usually test out what kind of highway mileage I am getting. Before I had my exhaust parts installed, on that stretch I averaged 27-28mpg. After installing exhaust parts I averaged 28-29mpg.

Engine life is negligible because most likely you are not going to be keeping your car long enough to know how it performs in the latter part of it's life.

 

On gas mileage, the intakes and air filters are not likely to make a significant difference. On the exhaust, if you improve scavenging, you can improve gas mileage. High flow cats, test pipes, X pipes, and headers can help, depending on the design. Of course, more than anything else, gas mileage depends on how you drive you vehicle. Low rpm's equals better mileage, while high rpm's reduce mileage.
On longevity, that's largely dependant on three factors: 1) how often you change your oil, 2) how often you start your car, especially in cold weather (put another way, short trips are harder on cars then long trips), and 3) how hard you drive your car. Intakes and exhaust don't really affect these factors, though they can lead to more of item 3....
I'm with gsingh, in that my mileage has increased slightly after modifications, but I think most of my increase came from weight reduction versus modifications.
On my 89 Mustang, my cam cost me 1.5 mpg, my Trick Flow heads gained me 1.5 mpg, my 3.73 rear gears cost me 6mpg on the highway but nothing in town, and all other modifications (intake, throttle body, mass air flow sensor, headers, cats, X pipe, exhaust) were essentially neutral to my gas mileage.

 

You would have a garage filled with OEM parts that no one wants.

 

That's not entirely true, people going back to stock might need the spare parts.

To the OP: In my experience, the mods that get you get the most improvement in power also give you the best improvements in fuel economy... that is, if you can keep your lead-foot in check. My reasoning behind this logic is that a performance part reduces the amount of work your engine has to do, both pre- and post-combustion, which leads to higher engine efficiency, giving you both more power and better fuel economy.

Air filters and intakes increase the amount of air your engine can charge into the cylinders, thereby making the air/fuel mixture more combustible. Exhaust systems, particularly high-flow catalytic converters, reduce the amount of work your engine has to do to get rid of left overs. Include the weight savings from a lighter exhaust system and it all adds up to better engine efficiency.

Now if you plant your foot down all the time, you obviously won't see an improvement in your MPG's, but if you pay attention to how you drive, then you should see at least some marginal improvement in fuel economy ~ 1-2 MPG. Another thing to consider is tuning your ECU to take advantage of your mods. A re-tuned ECU will maximize your engines ability to take advantage of your power mods.

Also consider your fuel savings: at 80 miles per day, if you get 25 MPG and see a 2 MPG improvement, that's an extra 6*5*4= 120 miles per month, or about 4.5 gallons of gas.

As for engine longevity: I wouldn't worry about it, the 3.5-liter engine in your Z is pretty stout. And like gsingh said, you probably won't own the car long enough to find out about any negative impacts the mods have on your ride.

If you end up modding your Z, check out this place, it's where I get most of my auto parts: http://www.autoanything.com/

 

Thanks for the info. You guys are awesome!
I've been talking to several friends of mine, and their feedback is pretty much aligned with all of yours.

Currently, I am interested in getting the Fujitsubo Legalis R. I know that it is not Ti, but it should do with the current budget I have. Anyone have the Fujitsubo Legalis and recommend the best setup for it? I've done a search and I've been getting inconsistent results.

 

^

what do you mean "recommend the best setup for it"?

are you asking whether it sounds good with stock cats or hfc's or test pipes?? i recommend some good metallic cats..

Berk or Fast Intentions

 

How do you like your Berk HFCs gsingh?

Any JDM HFCs you would recommend?