91stang

the theory behind that is that by retarding your timing all the fuel is burned up before it leaves out the pipes... the higher the timing the higher the temp and the quicker the exhaust leaves

5.0_faithful

I always thought that by bumping the timing the engine is more efficient since it helps give a little more power by allowing for a more complete combustion cycle.

91stang

bumping the timing changes when the plugs ignite... the idea is to ignite at TDC (top dead center) but stock timing doesn't do this. when retarding it ignites before and the gases burn for longer before let out

5.0_faithful

10* ,9*, ??? What do you recommend?

91stang

i have no idea .. i just know the tech part

but i'd say as low as you can go and still be able to drive it to the emissions place. but try asking someone else before you try that

88BlueGT

I would just put it back to stock at 10* They are going to have fun with your car! When I brought my stang there they sat there on the emissions part for 10 mintues just revving the **** out of my car. When I got it back it was ready to overheat. They wanted to fail me because of my SLP's bc they had no muffleres... just resonators (basically a straight pipe). But it passed and Im in the clear for two years! LOL

ZachW04Stang

I would take the car as is for now and see if you pass. Then if you don't it will be easier to tell what needs to be changed so you don't throw away money you don't have to.

vristang

Are ALL emissions systems on the car and operating correctly?
Are any engine diagnostic codes coming up?
This should be the first thing that is done when preparing for emissions testing.



Set the timing to 10 degrees. My experience with taking my 2.3 through emissions makes me think that emissions levels will be minimally affected by timing.

Advancing the ignition timing will ignite the mixture slightly before TDC. Our cars came from the factory with 10 degrees of Advance.

The idea is to get the combustion process started before TDC so that full combustion pressure is exerted very near TDC. Advancing the ignition timing too far will hurt efficiency, due to combustion gasses expanding quickly against the piston as it is still rising on the compression stroke.


When the mixture enters and leaves the combustion chamber is set by the cam timing. We don't have the ability to change when the spent exhaust gasses leave the chamber.

hope that made sense.

jason

91stang

i wish it was 2 years... here in NC it's 1 year

WhiteFoxGT

Anyone ever passed emissions with an o/r h pipe?