Test Pipes and plenum spacer saving mpg?
 

Hello my main question is that i'm trying to help my 2007 g35 coupe to achieve better mpg due to the need to be traveling quite far distances due to some circumstances. I was wondering as a steady daily driver if I were to install some test pipes and a plenum spacer would it increase my mpg? Note I do already have after market exhaust HKS replica m2 performance. Also a Stillen intake. Anyway if there are any other performance upgrades/mods I'd greatly appreciate it Thanks.

The only way you can achieve more mpg is by making the engine more efficient for the given amount of fuel injected at any certain time.

Breather mods allow more air into and out of the engine, allowing for more fuel to be dumped in, therefore making more power.

Installing those mods without a tune will make you run dangerously lean, which may be more fuel economic, but is dangerous for your motor.

Edit: However, our ECU is adaptive. It will try to compensate for mods until it hits it operating limitations, which is set in a tune.

Your best bet would be to get a tune for more fuel effiency, IE reducing the amount of fuel dumped in.

You will loose power.

With our cars, it is extremely difficult to get better mpg unless you drive extremely slow or at the bare minimum. If you wanted better mpg, should have stuck with a civic or corolla.

more air = more fuel = less mpg

To some extent, it may work - less losses to inefficient parts, like a restrictive catalytic converter, results in more usable power from the same amount of fuel/air. However, especially with the catalytic converter, there's the downstream O2 sensors that will probably end up completely screwing up the fuel/air mixture from an efficient mix to a "safe" mix. Since rich is almost always safer than lean, that's the way it'll go.

Plenum spacer may allow for more flow, but since there's the mass air flow sensor, the engine will still give the same fuel/air mixture, you'll just be capable of a higher amount of air and fuel to be mixed - and again, the computer erring on the side of safety, will likely give higher fuel to air as the airflow increases, so it will be either unchanged while you're in the same airflow zone as before, and lower MPG when you exceed it. Additionally the computer will probably see higher flow for a known % of throttle opening, and probably increase the fuel as a safety measure while it re-learns the throttle position vs. airflow.

The easiest way to increase your MPG with a test pipe is to take a small section of that test-pipe, and weld it to the underside of the accelerator.

Oh jeez in for the twenty follow on threads by this guy

This thread's a joke. Don't buy performance parts if you want higher MPG's. Go back to stock and get and get a tune with an "economic" map. Even then, you'll barely gain much from it. Our car's simply don't get good gas mileage.

If you need to travel long distances, get yourself a beater car.

But this doesn't make sense, since a tune is going to cost upwards of $500. Even if it added 5 MPG, which is unlikely, with gas at $4.00/gallon, you wouldn't recover that $500 until you'd driven almost 19,000 miles.

Assuming stock 25 MPG highway, + 5 MPG = 100 extra miles per tank, or $16 in gas. $500/$16 = 31.25 tanks of gas. 31.25 tanks with the new and improved 30 MPG = 31.25 * 20 (tank size) * 30 MPG = 18,750 miles before you break even. That's assuming you can even get a 5 MPG improvement, which would only be on the top end anyway. Stock is about 17/25, but you won't get 22/30 with a tune. You'd be lucky if you got 20/28, which means even more miles before you recovered your investment.

Bottom line, don't drive a G35 if you want good gas mileage.

You bought the wrong car, deal with the price of gas, get a gas efficient beater, or sell the car. Tough love, but you aren't going to make your g35 get 40mpg

I get 28.7 mpg on I-70 from Grand Junction to Denver, its mostly 80 mph driving with elevation varying 10,500 ft down to 5,000 ft. Check my garage and progress thread for my mods, and look through the market place for those parts, they sell cheap at the market place. The G is not fuel efficient, but you can make the most of what it can get. Your biggest gas saver is your foot, try to use cruise control as much as you can. You need to develop good driving habits, that is the best way to save on gas.

That might be the funniest thing you have ever posted on here. :bowrofl::bowrofl::bowrofl:


OP I'm afraid our mileage is what it is. I've found that any performance mods I have done to my car make my gas mileage worse, especially at first, because my foot gets heavier enjoying the new additions. :biggthumpup:

Perfect, and the very best answer I've seen in regards to increasing mpg....ever!
Gary

I got 30 mpg driving to and from school 2 weeks ago. I averaged about 63-65 mph and it was 100% highway

OK thanks guys I greatly appreciate it but I do have one more concern would a matter of weight reduction help? Considering like racing seats etc?

Weight will help but marginally, racing seats would hardly be worth it unless you didn't mind losing your side airbags and also wanted racing seats. Removing your spare and stuff like that could remove a decent amount of weight but then you don't have a spare on hand...

You can make minor changes to get a bit more gas mileage but you really aren't going to get much more doing weight reduction or other mods, this car simply isn't designed for that purpose. If it truly is this big of a deal to you, you may actually want to consider getting a beater car or trading cars.