put a set of ceramic coated headers on my buddies 04 seirra 5.3 and now its really sluggish until it warms completely up. exhaust is long tubes with off road Y and 3 in all the way back with a magna flow muffler. heard of people putting corvette O2's in them and that helps. can i get some imput here on what we should do to it?

 

did you retune it and turn off the rear 02 sensors?

 

no retune but we did shut off the rear O2's with HP tuners

 

You should not be running the truck hard untill it is def up to op temps. Not good on parts.. LT's will usually result in a slugish or slower low end, but make up on the mid and top end.. A retune would take that feeling away..

 

Ill have to tell him all of that. Thanks Guys

 

That's normal after a header swap as mentioned early. Funny as it may sound it is too free flowing and hurts your low end torque it does not have enough back pressure. There is a fine line to walk and once you start playing with it there are some inherent sacrifices you'll find along the way.

BUT: A tune definitely needs to be done. Headers completely change the airflow characteristics and aggarvates the stock tune.

 

Long tubes by nature make better low end and short tubes make better upper...

Obviously a re-tune would be needed if either is added but the long / short relation to lower end torque hasn't changed.

 

Obviously a re-tune would be needed if either is added but the long / short relation to lower end torque hasn't changed.[/QUOTE]

since when?

 

since when?[/QUOTE]

Long tubes have always made better low end torque on NA applications.

Did it change recently? I am certainly not an expert but any vehicle i have had always makes better low end with long tubes. Both my carbed and FI vehicles.

I am not sure about upper rpm HP though.

 

LS1 Header Test - Evaluation and Dyno Numbers - Car Craft Magazine

Some decent info with tests...