Contour Enthusiasts Group Archives Forums Modifications Duratec Performance More Power? Lean the A/F or Richen it?

I am confused. I have a Ford Racing Y-pipe ( Made by Some performance guy at ford) Anyway it flows just like the SHO-SHOP. People say that this leans out the A/F ratio. I have the Precats gone....No Cat (Replacment Sprial type of muffler instead) and anothey dynomax Bullit muffler and nothing in the back as far as mufflers go. I have a dirty K&N cone and thats about it as far as performance goes. I was driving on front of my friend the other night and when I did a big downshift he said he saw small flames come out of the tail pipes! Wouldnt that mean that I was running rich? I thought the y-pipe would make me run lean. I am super ocnfused on whats better for Hp (up high/ and down low) I just ordered a SAFC today. I am hoping this will help out the flame thing...Should I feel a difference in Power?
Thanks,
Joe

Hmph! i WISH flames would shoot out of my exhaust pipe and your complainin?!

Wouldn't a wideband O2 scan be a better idea than just buying an afc? There could be anything going on with your car. Find out your air/fuel ratio at a dyno and let us know.

I will have aussie look at the Mixture...I will let you know...And the flame thing is cool but, I dont think its good for performance...my car is trying to tell me soemthing

A wideband O2 sensor is priced in the thousands aren't they?

I didn't mean buy one. A good dyno will have one available.

Oh, I guess I thought too deep into the situation...there is a guy here at work with a last gen RX7 that is looking into one for himself....more money than brains....

this is what i know from other motors not my 98 tour se on dynos.....lean gives u hp to a point until the motor gets hot on motor dynos and chassis dynos....but rich will give u a cooler motor and my top end hp....with a deeper sounding idle....this is with our dirt and asphalt race car...but when I did my pre gutting I noticed that if I left of the O2 sensor it ran and smelled richer with alot better torquey feeling....but the flames would come from a rich mix....our race car does it all the time....be cause we run it very fat....but we dont think about gas mileage either

in theory the leanes gasoline will burn is 18:1. the richest it will burn is 6:1

there are two different mixtures on either side of the centerline. The centerline is where there is exactly the ammount of fuel needed to completely burn with the ammount of fuel. The mixture is 15:1. It is refered to as the stoicheometric number. This is a mixture to be avoided since it is the mixture that produces the greatest ammount of heat. You can tell when at this mixture becasue the fire burns with a brilliant blue/white flame.

Now if you go leaner than stoicheometric you run into whats called best power lean which is around 16-16.5:1. But as we all know lean is bad becasue of its higher tendency to detonation.

If you go richer than stoicheometric you run into best power rich. This is about 11:1. This mixture yeilds more power than best power lean, and burns cooler, and is less likely to detonate, but under low throttle settings will cause carbon buildup inside the combustion chamber.

the idea is to find a happy medium in pipe sizes.

Small pipes = good low end power, poor top end
large pipes = poor low end, good top end