A/F and Exhaust

[nadzerin]

So my "friend" says just putting on a 3 inch TBE (DP+TP+Cat-back) (everything else left alone/left stock including stock O2 housing) will cause the car to run rich. He claims rich enough to the point where flames could shoot out the back. He claims it will run this way until you get tuned. I'm skeptical of this statement.

So thinking about it, I suppose there'd be the possibility that if you put on a test pipe (removed the cat, and essentially the secondary O2 sensor as well) the portion of fuel trim feedback dictated by the secondary O2 sensor would be eliminated and/or "messed up", which could maybe cause the A/F to be slightly off from stock levels. But I wouldn't think it would "mess it up" to the point where flames would be shooting out the back. I'm not really sure how much the secondary O2 contributes to A/F control on the evo if at all. Other than this issue with the SO2 sensor and the cat I don't see how A/F could become altered by the simple addition of a larger diameter exhaust pipe. Is there something else I'm missing? Or is my "friend" full of EvoM heresay and BS?

Thanks for the help, guys.

[turbolarry]

Originally Posted by nadzerin

... is my "friend" full of EvoM heresay and BS?

Yes he is.

Our cars run very rich, stock, from the factory. Adding the exhaust components you mentioned will not make it run any richer. If anything it adds air (leans it out) by improving the airflow throught the motor.
The second O2 sensor is only there to make sure the cat is working. All fuel adjustments for idle and partial throttle crusing are based on the front (first) O2 sensor.
Get an exhaust. You'll be happy you did.

[rammsteinmatt]

Originally Posted by nadzerin

He claims rich enough to the point where flames could shoot out the back. He claims it will run this way until you get tuned.

hahahahahahahahahha!!!!!!!!!!!!!!!!!!!!

right answer, very wrong reason. the car shoots flames on throttle dumps because unburnt fuel is combusting when it hits hot exhaust components and igniting down the exhaust. since there is a test pipe, and therefore no cat, there is nothing to stop the flames from shooting out the back. no cat = flames out the exhaust

Originally Posted by nadzerin

I'm skeptical of this statement.

damn right you should be. good thing your smart enough to not take everything as truth, and confirm or deny something if you think it might be complete nonesense

ever wonder why there seems to be a large number of people on evom that have bent connecting arms or other internal damage? because someone says run x parts with y AFR, and everyone does it, do they know what they are doing. probably not, they just know that their car feels slightly faster than stock

[turbolarry]

Originally Posted by rammsteinmatt

... [do] not take everything as truth, and confirm or deny something if you think it might be complete nonesense

This idea can't be stressed enough. Don't even believe me sometimes . Through proper logging and monitoring you can see first hand how cetain mods really effect the motor.

[rammsteinmatt]

Originally Posted by turbolarry

This idea can't be stress this enough. Don't even believe me sometimes

sweet jesus. graduate of, goku's school of english mastery for those who can't post good


are you going to sell all the parts on your car, only to buy replacements for them all?

[turbolarry]

Originally Posted by rammsteinmatt

sweet jesus. graduate of, goku's school of english mastery for those who can't post good

Oh man that's bad. It was late when I wrote that.

[Fourdoor]

Originally Posted by rammsteinmatt

hahahahahahahahahha!!!!!!!!!!!!!!!!!!!!

right answer, very wrong reason. the car shoots flames on throttle dumps because unburnt fuel is combusting when it hits hot exhaust components and igniting down the exhaust. since there is a test pipe, and therefore no cat, there is nothing to stop the flames from shooting out the back. no cat = flames out the exhaust

One thing to add, this only really happens when you have a vented bov rather than a recircing bov. Having the BOV vented causes a very rich condition when the throttle is shut quickly and having no cat allows the flames out the tailpipe effect.

Keith

[nadzerin]

OK, yeah that all makes sense to me. I was pretty sure he was smoking something when he said that. I just wanted to bring it to The High Court of Evo Knowledge for the final word. Thanks guys.