I know that there are similar threads to this, but I wasn't able to get an exact confirmation while going over the posts. Please excuse me for the slight repetition, but I want to get a very clear confirmation. I have a 5AT coupe and I very rarely drive over 3.5k RPMs in my day-to-day. My setup is the Fast Intentions CF CBE and HFC's. So, after digging around some threads, I'm under the impression that I'm actually loosing torque/power in the low RPMs, which is below 3k, I assume. Can anybody clearly explain or confirm this? Would I actually be putting out more low-end power (below 3k) if I switch back to the stock cats? My best interest is for increased power precisely in the low-end. What should I do?

 

You won't know for sure unless you dyno the car the same day stock and with the mods. But generally speaking, whenever you open up restrictions ( intake or exhaust) you do trade some low end torque for high end power.

 

So, for example, if I don't really care about the high-end power and remove my HFCs, will my car actually be a bit more powerful below 3.2k range or so? I felt the power gain in the low-end RPMs right away after installing both the exhaust and the HFC's, but now I'm thinking that it'll actually be better with just the exhaust on its own... ?

If anybody has experience with this, please share!

 

unfortunately, with breather mods, you open up the exhaust system, typically. with higher flow of gases out the exhaust manifold, the less back pressure you have (some say this isn't true though). less bottlenecking (from restrictive oe parts) gives better flow and shifts your torque curve upwards (torque comes from bottlenecking effect). i'm not entirely sure of this, but a tune could help restore some torque...but again, i'm not sure where exactly the torque would be placed in your power-band. you COULD do gears to lower your torque curve, but it's a modification that members seldom do (the cost doesn't really justify the gain, but it IS indeed a good mod to have). if you replace your oe cats, you WILL see a regain in your more torque at lower rpms in your power curve.

does that help some?

 

I'm not entirely sure where to draw the line between restriction versus breather mods, but in theory...you SHOULD see a regain of TORQUE at lower rpms (you'll lose top end power though - more towards the top of 3rd/4th). The first modification I did were Injen Cold Air Intakes. I certainly thought THAT upped the torque at lower rpms. Only with the addition of my non-res TP's did I notice a significant loss in low end torque (makes sense since the OE cats are the MOST restrictive in the oe exhaust).

 

That does help, yes. And see, I wouldn't mind doing the whole ECU tuning stuff, but from my place, I don't know where in the world that would be possible, and I can't really get the time to invest into ECU tuning. But you're theoretically proving what I'm assuming, which is more power at the low-end with the OEM cats instead of the HFCs... Great, lol! I should've thought about that before buying the cats, but I'm no expert on this, so I would've never guessed.

I appreciate the inputs, guys! If anyone else has confirmations or facts, please share! I'm on the verge of deciding to get rid of the HFCs now.

 

Just tune. Then you will stop freaking out

 

And thanks for your help, eksigned! I want to see what more people will say, but I'm thinking that you're spot on with my dilemma. Much appreciated.

 

I would love to tune and make the better of the problem, but a tune isn't a possibility for me anytime soon. That's why I'm considering to just take them off.

 

HAHAHA hell no don't go back to those weak stock cats. Your car is plenty fast already haha. Don't worry over like a few lbft of torque.

 

Hmmm... I guess that's true, too. When I saw the stock cats compared to the FI HFCs, my thoughts were "dang, the stocks look like garbage, lol." But still, I wouldn't mind getting rid of the HFC added drone, either, so this is debatable for me. While though again, I don't mind the drone so much as to going through the trouble and money of going back to OEM cats. Ehh...

 

You're very welcome!
How long have you had them on for? It could just be your car adjusting to more air flow. I honestly wouldn't take them off. You spent good money for those man! Think of it as a gateway drug...er...modification for future modifications down the road. You'll get there eventually (tune).

LOL

 

LOL get an invidia and get test pipes! Perfect sound haha

 

@eksigned: Haha, yes, I think you're right. I've had them on for a little over a month, but I've managed to put on over 800 miles in the meantime. And so far, the setup seems to be feeling better every time I drive. So what would you guys recommend for future mods in terms of low-end power additions? I'm guessing the Gen. 3 intakes will only actually screw my low-end power, so is there anything other than that which would be worth it performance-wise?

 

@ipitythefoo: Don't the test-pipes usually give you a CEL? Because that would kill it for selling the car down the road.