Jump to content
Ecoboost Owner Forums
Sign in to follow this  
switch527

Power Loss After Catback

Recommended Posts

Hey guys,

Just got back from the dyno after my magnaflow catback was installed and I lost 20hp and 25lbft. Before this I had the catted downpipes, 3 bar, and the livernois tune and it mad 390hp and 450tq. After the catback I'm at 370 and 425....anyone have any ideas on this? I'm not sure where I went wrong here.

Share this post


Link to post
Share on other sites

Apparently you reduced back pressure with the catback and this caused a loss of power. I had the same thing happen with my 98 F-150. Never knew the newer engines required a certain amount of back pressure to perform correctly.  It also may be you just need the tune to be customize to take in the catback.

Share this post


Link to post
Share on other sites

I suppose the backpressure thing is possible, but from what I have read on the forums it shouldn't have had any negative effect. Lots of people have full exhaust including downpipes and it doesn't rob any power. I'm going to attempt to reflash the tune and see if that helps while I try and find a place for custom dyno tuning in Denver.

Share this post


Link to post
Share on other sites

I’m going to disagree about the reduced back pressure causing power loss.  Turbo engines don’t really need back pressure after the turbos as it becomes a restriction. There are too many variables that could be causing your power loss and the fact that you didn’t do it on the same day as the factory exhaust, I wouldn’t read into it too much.

Share this post


Link to post
Share on other sites

I believe you are incorrect about not needing back pressure. We have heard too many times that the modern engines and computers need back pressure to work correctly.  Not sure I understand it, but seems to hold true. There has been too many times that people have reduced back pressure in several different engines and have seen performance decrease.

Kinda like that none of the aftermarket CAIs work to improve performance. The best track times always come with the stock air box.....

Share this post


Link to post
Share on other sites

strange, all i know is when i put my borla cbacks on it had no effect on power & really not a lot of change in sound. tough to make a 6 sound like an 8 unless you start removing resonators or other exhaust parts. as when i was looking, now ages again neither magnaflow or borla had an atak version for the sho like they had for other cars.

Share this post


Link to post
Share on other sites

It's not back pressure - it is scavenging. When you change the exhaust you often affect the scavenging effect which means you are not getting the spend gasses out of the cylinder properly. Back pressure is bad for an engine, and it is often a mis-use of the terms when what you are really after is the scavenging effect. Back pressure means you have a restriction in the flow.

Think of it like a garden hose that is now attached to a fire hose. You can't get the fluid out of the garden hose fast enough to fill the firehose, but that isn't a back pressure problem it is a problem that you can't scavenge the fluid out of the garden hose quick enough.

Now attach the garden hose to a straw. That is back pressure due to the restriction --- and eventually the garden hose will rupture from the back pressure.

Share this post


Link to post
Share on other sites

You have to balance the exhaust system - changing the pipes can alter the scavenging. So a performance shop that understands how it all works and can determine the proper size pipe and mufflers can help balance it.

 

What all was changed OP to  your system?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×