jwoznica

I have an 09 F150 STX with the 4.6 3V V8 and installed a Super 44 on my truck in July. I did a really simple install by just putting the Flowmaster in the space of the stock muffler with a 30" single turndown. The muffler is a 2.5" in/2.5" out. Since install I have noticed that I definitely have to brake harder, especially when I come to a complete stop, the last 10 or so mph are the worst. With winter coming I don't really want to struggle with braking. Did I do something wrong in the install? Whats the best solution? Thanks in advance for any help!

RajunKajun59

Have you checked your Brake pads?

jwoznica

They have a life left it looks like. Truck has 48,000 miles and I think original brakes but they look great, for a 20 year old I drive like a grandpa most of the time, beside the occasional burn out 😝

jwoznica

I was thinking it was something to do with back pressure but that is something I don't have much knowledge on.

RajunKajun59

Might be a possibility, A friend of mine 200x Stang had similar issues with an xpipe, it would also surge on him when stopped.

ns_redneck

what rpm does your truck idel at. when i installed my magnaflow kit mine dropped a bit, you had to unhook the bettery for 15 min for the computer to reset for the backpreasure changes. but really the muffler shouldn't do anything to your breaking ability.

BlackHD06

back pressure isn't something that anyone wants. they often confuse it with the scavenging effect that a good exhaust system will have. The truck manifolds suck so badly as they are that there will be little to no change in performance after the y pipe as long as you don't cork it off.(sits back and waits for magazine mechanic to "school" us on back pressure)


For your issue you have either damaged an O2 sensor or the 2 are completely unrelated and just coincidence that it happened at the same time.


smart *** answer:
perhaps removing the extra weight of the rear exit tail pipe has thrown off the braking balance.

dcrabby

There is no normal interface between brakes and exhaust. However, check your brake line to see if you crushed it inadvertently while installing your muffler. Don't just look at it, FEEL the line.

When you depress the brake, does it feel "hard", or is it "spongy"

Is the brake line totally clear of the exhaust line. I'm thinking that you may be "cooking" the brake fluid.

BlackHD06

yeah, the brake system is a good place to start(the place to start)...I read it assuming that the engine was doing something that was over coming the brakes as he came to a stop. In my last vehicle it would down shift when you were almost to a stop and nearly make you rear end the person in front of you.

jwoznica

My truck idles around 600 maybe 700 rpms give or take 50 which from what I can remember is the same as before. I also have disconnected the battery twice (once to help with the muffler, another time for a subwoofer install) which did help some. But that's exactly what it does, it surges when I brake, from third to first gear, but it doesn't when I just coast. For an O2 sensor, would that make the engine run a little rougher? The engine runs smooth it's just this braking issue where the rpms spike before I come to a complete stop