Noise tube delete air/fuel logs?

[jm1681]

Sounds silly, but anyone run logs after deleting the noise tube?

I've had mine plugged since Tuesday last week, along with the resonator beneath the 90° elbow, and my average MPG has been steadily dropping. Up till the delete I was at 31.8 and climbing, and this morning I was at 30.6 and falling.

I know there was a dyno that showed a small loss by deleting the tube, and was wondering if there may be a correlation between that loss, and a rather large loss in MPG. My driving habits didn't change in a week, so all I can attribute the loss to is the deletes.

Maybe try an ECU reset?

I really like the way the car sounds/feels now, but if I'm going to keep losing MPG, I'll swap it back in a heartbeat.

[gmookher]

silly

[wparsons]

If the temps in NY are anything like they were in Toronto, I would blame the weather long before the sound tube.

Colder air = denser air = more fuel being added.

[jm1681]

Ah, good call, I just didn't think it would have such a profound effect so quickly.

[RedRocket]

Originally Posted by jm1681

Ah, good call, I just didn't think it would have such a profound effect so quickly.

WHAT?

This is the basic idea behind Forced Induction/Nitrious. IT DEFINITLY has an effect.

[jm1681]

Originally Posted by RedRocket

WHAT?

This is the basic idea behind Forced Induction/Nitrious. IT DEFINITLY has an effect.

Yeah... I know air temperature has an effect... thanks.

I just didn't forsee it impacting my mpg by over 1 mpg, before it even starts getting properly cold. Maybe when the temps REALLY dip, but a 1 mpg loss for what, 10°?

It didn't add up to the point that I'd even factor temperature into the equation. At a rate of decline like that, by the time it REALLY gets cold, the average would probably drop by 5 mpg or more.

I've been modding NA and Turbo cars for 12 years and I've NEVER seen a decline like that.

[2point0]

Did you see this in relation to a recent fill-up? Could be that you're now on winter gas, and that'll make a difference.

[jm1681]

I don't believe so. I tend to only put a couple gallons in at a time (Can't really ever afford to fill), always from the same station, same pump.

[wparsons]

I don't even know where to begin... yes 10° can easily effect mileage that much. Honestly, 1 mpg difference could come from anything, that's a very small variance. That's a +/- difference of about 11 miles per tank. When I was still commuting for work (~40km's each way, pure highway) I was averaging anywhere from 7.2L/100km (32.7mpg) to 7.6L/100km (30.9mpg) driving the exact same road, in the exact same conditions driving the same way.

Not sure how the FR-S is going to react to winter, but I know my past cars have dropped about 60-70km's per tank in the colder temps, with winter gas and snow tires. I'm hoping running shell gas (no ethanol) will help keep mileage up a bit, but who knows.

Beyond that, you need to be monitoring miles traveled and fuel added to accurately get mpg. The cluster is close, but not dead on (mine was off by about 0.1-0.2L/100km consistently). If you're not filling up a full tank, it's basically impossible to get close to an accurate reading.

[jm1681]

Originally Posted by wparsons

The cluster is close, but not dead on (mine was off by about 0.1-0.2L/100km consistently).

Fair enough, but, if yours was consistently off, then it's fair to say that it reads consistently, right?

That being the case, my mpg dropped off by what is now 2 mpg, that starts to add up. Maybe this has ALWAYS been the case with all the cars I've driven and owned throughout the years, and I've just never had a car throw the number in my face with a display.

Regardless, I guess I learned something new.

[RedRocket]

How I drive/where I drive impacts my mpg most. Ohhh and what's driving next to me!

[jm1681]

I'd say 7 out of 10 times I'm in my car, I've got my eyes on the instant mpg. Most of the time, I'm just trying to get somewhere, and usually with someone. Those times, all I care about is keeping those numbers as high as I can.

2 out of 10, I'm by myself, and STILL trying to get somewhere. I might have a little more fun those times, but for the most part, I'm still just trying to save gas.

That 1 out of every 10 times that I'm having a great day, not driving to or from work, driving with a passenger, or am otherwise required to have a somewhat responsible driving ethic, can I actually just DRIVE my car.

[2point0]

Originally Posted by jm1681

Fair enough, but, if yours was consistently off, then it's fair to say that it reads consistently, right?

Not necessarily. I've had it be spot on, and I've had it be 1.5-2 mpg off (mine typically reads high). The only way to know for sure is to fill up and do the math yourself. The gauge is handy, but not that reliable.

Now, I'm only guessing here, but my assumption is that it uses IDC to measure fuel used (fuel level gauge is worthless). With differing temps, you've got different densities that could throw it off. Add to that the fact that the speedo/odo is not accurate to begin with and colder weather means less air volume in the tires, etc.

All this being said, I haven't seen 30mpg since I first got the car! CA gas is crap, and I don't drive like an old lady.

[wparsons]

Originally Posted by jm1681

Fair enough, but, if yours was consistently off, then it's fair to say that it reads consistently, right?

That being the case, my mpg dropped off by what is now 2 mpg, that starts to add up. Maybe this has ALWAYS been the case with all the cars I've driven and owned throughout the years, and I've just never had a car throw the number in my face with a display.

Regardless, I guess I learned something new.

Mine was off in different directions, sometimes it read high and sometimes it read low. The only consistent part was that it wasn't correct.