in my reading of this forum ive read that our car runs rich. i have a NA s4 that i drive every day, 50-75 miles a day depending on the day, so i pay a lot of money for gas. i was wondering if anyone knew of a way to lean out the mixture, to help mileage as well as give a little more power, and my car is bone stock. i did a little searching but found nothing. any help is appriciated

 

The only way to alter the mixture is with a fuel computer. Either a piggyback like an S-AFC or a stand-alone EMS (big $.) Both have to be tuned after installation to be effective.


https://www.rx7club.com/showpost.php...7&postcount=40


https://www.rx7club.com/showpost.php...0&postcount=50

 

darn, im looking for a cheap/DIY way to lean it out. i barely have money for exhaust mods and stuff that will also help mileage

 

If you do a lot of low-load, highway cruise type of driving, you are not going to get much better gas mileage.
The closed-loop O2 sensor system allows the engine to run at it's most efficient under those conditions.


-Ted

 

running lean isnt good for your engine in the long run, but thats your call.

 

i keep reading that horsepower could be gained by leaning out the mixture a little. but apparently that can only be done with an extra fuel computer?

 

Yes.

 

Let's not forget to keep tires inflated. This is a simple but often overlooked way to improve gas milage.

 

this is true to a point, in a ideal world, cars would be able to run at 14.7:1 at all times including full throttle... but in the real world anything beyond 12.5:1 on a turbo motor at WOT can and will cause serious engine damage. Durring part throttle on a piston engine the car will run very close to this mixture, but on a rotary it will run more on the line of 13.5-14:1 becasue rotarys need more fuel due to a inefficent combustion chamber design. so basicly, leave it alone

 

you can lean out the mixture without a computer. there is this little screw on top of a s4 n/a's thorttle body called the variable resistor that controls the mixture of fuel, it may be on the turbo model or the s5 but i haven't checked. I thought the renesis rx8 rotary doesn't neccessarily need more fuel. Most 18 wheelers and tractor trailers made today have relatively clear exhaust and inject less fuel, they get better gas milage than the old ones spewing black exhaust (unburnt fuel).

 

Please keep false statements like this out of the forum please.
Strike 1.


-Ted

 

Another one...stop spreading false information.
Strike 2.


-Ted

 

Variable resistor only affects idle, right?

 

Then you should shelve this idea unitl you have more money to do it the right way. Note that if you reduce exhaust restriction the increased volumetric efficiency will result in better fuel economy, assuming you drive in a similar manner afterwards.

There's a big difference between running lean (and running leaner than stock. Most engine's run very conservative (i.e. rich) stock full-load mixtures as a safety net, so there is scope for running a bit leaner to improve combustion efficiency, resulting in more power and as a bonus slightly better average fuel ecomomy.

 

ok well if the variable resistor only affects idle it helps my friends rx7 because while he is delivering for his job he usually leaves the car idling.
strike 3000000000 fool, thats so whack

 

Actually, most people, and even the factory recomend never to mess with the variable resistor. Its pretty risky, but then again its your car.

P.S. Im from IRAN TOO! Chetori?!

 

The idle mixture screw is NOT on the intake manifold.
Strike 3.
GTFOOH.


-Ted