Bolt-ons = less restrictive, Better MPG???

spearfish25

So if bolt-ons are less restrictive and in turn allow the engine to produce more horsepower, do they lead to better fuel economy under conservative driving habits?

frost

Can't speak for the 370, but I've had a lot of bolt ons for my other cars, and there is a small improvement. Nothing that you can use to justify buying parts to the wife though

kannibul

Not really true.

The engine is an air pump...

The more air that goes through it, the more fuel that also goes through it to maintain the air-fuel ratio.

Fuel economy is more or less (these days) a function of efficency of the engine and drivetrain (how well heat is translated to movement) and aerodynamics and weight.

frost

There is some potential gain (1-2 mpg in my experience).
If we were to say there was NO gain to be had by an engine breathing better, we would also be saying that it doesnt matter how filthy an air filter gets, it won't affect your gas mileage.

kannibul

RE: dirty air filter / MPG

I think it's more of a case of the ECU having to compensate with using more fuel for less air (at speed), to prevent a lean (and potential detonation) condition.



The only way to get more power, is to increase the amount of air going through the engine. The only way to make that air to burn and produce power, is to add fuel. Fuel-to-air, is a fixed ratio (relatively speaking, theres only a slight variance...). Therefore, no matter how much air you can get through the engine, with fuel-air ratio and total efficency of the engine's ability to convert fuel-air into real power...your MPG will NOT increase.

dad

Yes.

__________________

We can do without any article of luxury we have never had; but once obtained, it is not in human nature to surrender it voluntary.

RCZ

There was a thread before where this was extensively covered. Theoretically the answer is no because the AFR stays the same. In practice, bolt-ons lean out the car which you could argue means less fuel usage.

Phimosis

In practice, I have all the bolt-ons offered for the 370z and I average around 13 mpg according to my trip computer.

I'm quite happy that my $3,500 in bolt-ons are saving me gas every day, otherwise the difference in my fuel bill would make me go broke because I drive at least 600 miles a month in my Z.

dad

Headers alone(nothing else, no CAI), won't increase MPG?

__________________

We can do without any article of luxury we have never had; but once obtained, it is not in human nature to surrender it voluntary.

RCZ

dad - unless headers somehow tap into free-energy, no.

dad

I've read and have been told the less restriction of the exhaust would increase MPG!-not arguing, just stating.

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We can do without any article of luxury we have never had; but once obtained, it is not in human nature to surrender it voluntary.

regisbou

Guarantee you it will increase MPG if you drive conservatively.

Shifting at lower than normal RPM (since you now have the same amount of power at 2.5k rpm than you used to at 2.7k. As long as you do not BOG your engine or go WOT at low RPM the car should get better MPG.

So this means not driving 70mph on a 55 anymore...go 65mph or 60mph.

CAI in my car upped MPG by like 3 on the highway but it sucked in the city because flooring just felt/sounded soo much better.

Engine braking (fuel shuts off after about 1 second at most when gas pedal is released) your way to stop lights will increase MPG as well. Add 3-5 psi in your tires for less rolling resistance, short ram intakes instead of cold.

Double clutching helps, but rev match seems the better option!
Clutch catching will help MPG...instead of squeezing the meat on your clutch when you shift, have the clutch catch before adding the throttle.

Hard at first but helps alot in the city!

Just my .02cents,

Regis

Diversion

The real gain in gas mileage tends to be involved with a freer flowing intake, which typically leans out the engine a hair. More intake gains are based on leaning fuel out versus actual air velocity going into the engine. Leaning the fuel out will allow for same throttle position to net more miles per gallon then the stock intake provided.

A lot of us are seeing 18 or so WHP from intakes alone, makes you wonder if the engine really needed the extra air or if a stock 370Z is really really rich..

__________________
09 370Z Touring + Sport + Nav (Status Elite Intakes) (Berk HFCs) (Invidia Q300 CBE) (Nismo Swaybars)
99 Civic Si (Daily Driver, completely unmolested stock rarity)

regisbou

Hmmm thanks for the fuel lesson! seems quite simple once explained.

maybe the extra air from the intakes is misting/making the fuel leaner?
Maybe pushing the fuel at a higher velocity? That or the ECU is adjusting for the change in air velocity...

makes ya think huh

Solus

Well speaking from my experience... I took a road trip in the z before I did anything to it. I got about 25.5-26 mpg... I took the same trip, on the same roads driving the same way I always do, after jwt intakes and berk test pipes.. and averaged 28...