New cat reduced low end torque

[cp2295]

I put a flow master hi flow cat in and it seems to have lowered low end torque, I was thinking though what if my intake is now reducing flow? I have a square air filter, and I figured maybe if I switched to one of those aftermarket cone filters it might increase power?

Or do I need a bigger camshaft? I've been thinking about doing one of the comp cams, either the 410 or 422. I read with the 422 you have to have dual valve springs made sounds like a pita haha.

Or do I need a tuner, and if so what would be a good one?

 

[RonD]

Yes, changes in exhaust system can change power band, stock system is tuned for mid-band, most headers lower the power band.
All exhaust systems are tuned nowadays.

What a tuned exhaust does is to create a vacuum(lower pressure) at the exhaust ports, the 'myth" of back pressure is just that.....a myth.

Exhaust systems can create between 4 and 7 inches of vacuum at the exhaust ports, the higher the vacuum the better, as this also helps pull in new air/fuel mix when intake valve opens.
Where the highest vacuum occurs in the RPM range is what is "tuned" by the sizes and lengths of the pipes.

Cone filters are "eye candy", nothing wrong with that so are nice wheels, but like nice wheels they won't improve the power, for sure.

Until you change the cam, there is nothing to "tune", Ford already did the tuning for the stock engine, they set it up for best MPG and power, why wouldn't they, lol.
"We have crappy MPG and low power, please buy our trucks, Ford"
And another "myth" is that automakers de-tune engines, why on God's green earth would they do that?????

 

[cp2295]

Okay yeah I figured nothing much will happen until you change the mechanical operation

 

[cp2295]

What if I put a neck down flange in between the cat and muffler? Like the stock setup would it return power to normal?

 

[adsm08]

You would need several inches of neck down to produce the effect, and it would still not be as good as before. Also, cats need heat to work, and so they need to be close to the engine. The farther away they are the less effective they are. Too far and you may as well not have it.

You aren't going to get back to stock performance as long as you have a snake-oil cat in there. The "High Flow" portion is wider holes in the catalyst material, which effectively makes it a bigger section of pipe, reducing the ability to the exhaust pulses to pull each other along. This makes the engine work harder until you are pushing enough gas to get the effect back. High flow cats are great when you have a ported, polished, blown engine with a huge cam. You don't, so you don't need, nor can you support the extra volume at low RPM. All you have really done is move the power band up really high.

 

[cp2295]

I just did it for the sound... I understand what it does, just sounds much better now is all, but okay.

 

[adsm08]

Did you ever consider changing the muffler instead?

 

[cp2295]

No I like the sound of the flowmaster 40, I considered putting a 2" pipe between the cat and muffler though, since it's sitting at 2.5"