Hey, Through all my reading I have seen performance gains in terms of torque and horsepower when aftermarket intakes and exhausts are added. Assuming that someone still does the, don't crack the eggs, style driving would mpgs also improve? Or is there a point where added power will consistently have a negative effect on gas mileage? Any ideas on this?

 

I done intake and exhaust only before and beleive me.. when i say there was NO difference in gas consumption when i was driving 100 mile trips with only intake and exhaust upgrades.

BUT

when you start doing like compression differences, or adding force induction. then you wouldn't even realize how bad the gas gets. If you think about it.. it SHOULD waste more gas... force induction means A LOT more air... a lot more airs means bigger injectors must be installed to throw in more gas to burn up all that extra air.

 

I would imagine that the Fit engine is relatively efficient. But if the intake and exhaust modifications make the engine more efficient it could improve the fuel mileage. It seems my Fit gets its best fuel mileage about 3000 rpm in 5th gear. If the intake/exhaust modifications improve efficiency in the upper rpm range there probably is little benefit for overall fuel mileage. However you are benefiting the aftermarket industry.

 

Assuming the car is tuned properly, at least in a forced induction setup, cruising MPG's should remain the same.

 

Assuming the car's fuel injection is working according to design (all sensors functioning), adding an aftermarket CAI or cat-back won't improve mpg. They might hurt if you have a heavy foot.

Even a dirty air filter (reduced air flow) won't hurt mpg; might improve it if you have a heavy foot.

the car's FI meters fuel according to how much air enters and how well it burns so you get the ideal mix minimizing waste no matter what.

Forced induction is interesting as it can derive more power from less weight. If you have a light foot this can mean better mpg compared to a car with a larger displacement (heavier engine). But the tendency is to push it negating any benefit this might have.

I'd be interested in seeing any 3rd party dyno runs showing better performance with any aftermarket CAI or cat-back. I'm doubtful about seller/manufacturer claims over what Honda's engineers can do.

 

I realized that if i only had my exhaust, i lose a lot of low end torque, and as a result I felt that I had to constantly give it gas to maintain speed, which could lower ur mpg.

After adding the SR intake, the lost of low end torque is offsetted and i've been on this set up for a while and there is no adverse effect to my MPG.

With a light foot, I get over 600km a tank. With a really light foot (once), I got 670+ km out of the tank.

 

What do you have for an SRI and exhaust?

 

PRM SRI intake and HKS Hi power exhaust

 

I have a Magnaflow muffler and K&N typhoon intake and my mileage hasn't really changed one bit, infact after I added these parts along with wider wheels/tires my mileage to Detroit has gone up from 38 mpg to 39 mpg. The coming home mileage is anywhere from 41.2 mpg to 43 mpg going the same 70 mph. These are must do mods for someone looking to give the Fit a bit more power and tude

 

I've had my K&N typhoon on since the car had 6,800 miles (now has over 20k) and have made about 4 trips back home to Detroit, a couple trips out on route 66 and a 1,750 mile trip to Deal's Gap and the intake and Magnaflow muffler didn't hurt the mileage one bit, no CEL's either, so no worries there.

Once spring comes around I'm going to fill up with 93 and check the mileage again going home. Its kinda funny, the car gets better highway mileage when its hot and the a/c is on then when I have the heater on and its cold out. I understand the fuel blend now and dense air, but its gone down about 3-4 mpg on the freeway.

The intake I have is dyno proven to give you 4.53 whp, you can feel it for sure and when combined with the universal Magnaflow I have (#11132) it makes the little Fit sound so good, w/o sounding like rice

 

As long as your car runs in closed loop at stoichiometric ratio, the mileage will not change.

 

Its been mentioned to me that since I've got a CAI the cold, dense air gives the engine more power and that REAL cold air affects the mileage, but by how much I don't know but its not enough to not get one IMO though.

This is a must do mod on our cars for sure....GO FOR IT

 

The only way you affect the mileage is if you change the air temperature or the MAP/MAF (I don't know what Fit has yet) sensor or you are running open loop.
Of course your foot affect the mileage a lot!

 

MPG difference for CAI and Exh are usually minimal leaning to the negative side. However psychologically is a different story, your car will sound nicer and promote mental foolishness like revving more, driving more aggressively when you can. Those are what will kill you MPG.

 

I guess im reviving a dead thread here lol
I just put an hps short ram intake on, got rid of that extra tube and installed two breathers instead. Also, a week before that I put the Tanabe catback exhaust on. The mileage with the exhaust stayed the same but its possible i didnt give it enough time for the ecu to adjust.

The intake...is a different story. When it was installed, it was nice and cool outside. I immediately noticed a change in acceleration. In first gear, WITHOUT S mode being on, the car revved all the way to the redline before shifting, so I was satisfied. However, I generally drive 52 miles to work and 52 miles back on the hwy 5 days a week. I live in Florida, on the east coast, and while driving on the hwy at 65, my "avg mpg" display started to decrease.

However, it was hot outside. When night hit, it was nice and cool again. Same thing on the hwy, and the mileage started to increase. Its made me come to the conclusion that either:

A) Warmer air is getting me worse mileage

B) The ECU still hasnt adjusted properly (and i started running 93 at the same time from 87 so im not sure if that has anything to do with it.

C) I haven't done enough to the exhaust?

So at this juncture, I'm inclined to believe the stock airbox is the most effecient. But I guess Ill find out once I do a Fill up test lol

 

more power always uses more gas.
to get more power you must burn more fuel; more power, less mpg.
the theory behind the drive to forced induction of smaller engines is the time the increased power is not used the smaller engine needs less gas so the tests will show higher mpg. but if you use the turbo/super charger power your mpg will fall like a rock dropped in air. In most cases it will not be useful for anything but advertising. the power to move anything over a given path is pretty straightforward the same for anything of a given shape and weight and how quickly you want to do it.
that is the drive for hybrid and electric vehicles
of the three cars one a track car, one a hybrid, and one an elevtric, the electic powered by a solar power station is by far the cheapest but has the shortest range; the hybrid gets 50 mpg and has unlimited range depending on gas stations, andthe track legal on the street gets 28 mpg. naturally the power increases from electric (though not from standing start) to hybrid to track car. the electric has a top speed of 90, the hybrid 105, and the track car with close to the same displacement will reach 122.
the hybrid and track cars have been tracked at such events so they have documented top speeds.

 

So generally speaking, hp is inversely proportional to mpg.

 

absolutely. more hp requires more fuel. gas, diesel, hydrogen, or electricity.
the curve isn't direct and varies with every engine but the more hp the more fuel it takes to generate it.

 

Im not sure if thats necessarilly always true though, at least not with every car. The only examples that come to mind are when I upgraded my spark plugs in my 99 crown vic to platinum tip, my highway mileage increased. It was only by 1.5 mpg but it was an improvement nontheless, plus increased power (i also upgraded the ignition coils to accel supercoils)

That might be a bad example though. The other example would be a 2015 vw gti. Its a turboed engine, has at least 100 more hp, isnt much heavier, motor is a little bigger, but the mileage isnt too different. City mpg is 25, and highway is 36 i believe. Though i dont necessarily go by what the epa ratings are, and me being conservative i could probably get 38 hwy, 34 mixed.

I feel a lot depends on the type of upgrades you do. If said cars motor wasnt turboed, its possible that you might be getting 50 mpg on the highway. This is all speculation of course lol

 

2015 LX CVT.....

Stock intake and exhaust - mpg on highway was between 44-47mpg
44mpg on stock wheels
47mpg on lighter wheels

After installing a custom cold air PRM intake and 2.25" TO 2.5" exhaust (Cats eliminated) mpg went down to 33mpg on average.
This is from driving the same way, on the same highway, the same directions, with similar temps.