Newbie '02 Corolla queries - coasting and chips
 

Hi,

Recently bought a '02 used Corolla CE and was wondering about some mods and driving changes.

I am guessing not, but does the Corolla's fuel system cut-off fuel to the engine when you take the foot off the gas when it is in "D"? Better to coast in "N" or "D" when the engine is on?

I saw MPG and BHP enhancing chips for sale. Do they really work for the Corollas?

What about K&N filters? Do these filters help with better fuel combustion?

Thanks!!

Avoid ebay "chips" they are a scam. Most newer vehicles will shut of fuel while coasting in drive, but you should probly test it both ways.

Invest in a scangauge II, will provide the most help to your fuel economy for the money since you can watch your mpg in real time.

K&N filters are usually for performance, and have nothing to do with combustion. They are more open than your stock filter allowing more air (and dust) into the motor. Most will agree a stock filter is best.

If you havent already, check out the 100+ driving tips, and bump up the air pressure in your tires to sidewall max. Both free and should help get you off to a good start! Good luck!

Filters aside, I think the theory about the aftermarket air in-take kits is that they allow more air in-take that brings in more oxygen into the combustion chamber. More oxygen allows for a higher percentage of the fuel to be burnt giving you more power and better gas mileage.

All this is assuming that the unburnt fuel left behind by the current fuel-air mixture is significant enough so that when the extra oxygen helps it burn, you see a measurable difference in MPG/BHP.

I think broader air in-take and exhaust have always been used by performance modders to improve fuel combustion. Better fuel combustion should also improve MPG.

Not sure how all this plays out with modern car electronics.

I used to think that also but, it has been brought to my attention recently, if you have more oxygen the ecu just adds more fuel to maintain the correct A/F ratio. A larger filter would allow the engine to breathe better through the reduction of the restriction of air flow.

In the carburetor world it may work but not the electronic fuel injected one.

Thanks for explaining that bit of car *intelligence* to me :)

No known mods to manually tweak fuel-air mixture ratio that the ECU operates on?

The atmospheric or barometric pressure sensor. If you put a 25k pot switch on it, you turn it down until the idle speed lowers. There are no funky lights or warnings to contend with. You are simply telling the ecu you are driving at a higher altitude than you really are.

They are usually three wire, ground, 12v, and one thats around 2-5v. The lower voltage one is the one you want to put the switch on.

The oxygen sensor will still override the map sensor (if your engine even has a map sensor) and return the air/fuel ratios to stoimetric. Plus, altering map sensor voltage will alter timing as well as fueling.