Thread: Neutral Coast Not So Great for Fuel Economy

Correct guys. But greenless is right also. On the newer cars they still pulse the injectors every couple of cycles in order to keep the cat up to temp. But it is very little fuel used and should be less than the fuel used to keep a stable idle.

But still this is why we don't have a cat and tune the ECU to not do that

I believe in the Outside of US emissions testing more, they focus more on CO2, and you have less CO2 if your engine is more efficient (and gas efficient).

In US its more of NOX, for which we have a CAT for, but the cat needs to be hot to work well, thus extra fuel needs to be dumped in order to keep the cat hot...

I have a spreadsheet with tons of data since I bought it with 44k back in 1998, now 179,5xx.

Just installed a warm air intake today. Not the typical WAI, put tubing around cone filter, across headers, so intake air is heated. Makes a significant difference in mpg for cold weather. Will be interesting to compare results over the whole WI winter vs. previous years.
High of 40F today, and still avg'd 36.5mpg on a 130 mile round trip with 10-20 mph crosswind.
Over the last ~7 years, my early Nov avg was 31.26 mpg mixed city/hwy.
So far, it looks promising...

The problem with WAI's is, the maf might be tuning for less fuel but warmer air has more chance of detonating, aka killing the engine, plus it doesn't give as good of a burn.

Not as good of a burn means your engine is not running as efficiently, thus getting worse gas mileage hehe

I disagree. I have data over the last 10 years, 130k+ miles, that shows in a cold weather climate, fuel economy drops 5mpg, summer vs. winter.
Winter blend fuel also has an effect on the mpg.

Heating the intake air a bit should be closer to the intake temps in the summer.
Running JWT ECU, with 93 octane. Should be fine, no detonation so far.
I could be wrong, we'll see what the data says collected over the winter.

I have noticed a decrease in my gas milage as well. Is it because the air is cooler therefore causing the car to dump more fuel? I was a little annoyed when I started calculating my gas milage and saw it decreasing as the weather got cooler.

It has to do with the car taking longer to warm up/ or not warming up all together. A cold motor runs rich.

Yes. Colder air is more dense so more oxygen is coming in. In order to maintain proper air/fuel ratio, the ecu adds more fuel.




The longer warm up time is also a factor, much more of an affect for shorter trips. The solution to that is a block heater. Now that gas prices have fallen way off, it might cost more in electricity for a block heater than just warming the car up normally.

I used to think the same, until I saw someone take foil and wrap it around the intake, take a pipe to the header, then back to the intake. He saw MPG increase of about 0.25 MPG...

I'm not saying it's possible, I'm saying that taking advantage of colder air to get more efficient burn can render you with higher MPG's.

I drove with a WAI with pop charger for almost a year, usually getting 22mpg city. The first fuel up that I installed AEM CAI i got 26MPG and trust me I stepped on the gas.



That's more like it, esp since CAT has to warm up more.

I am also running no cat how is this affecting gas mileage?