I have a completely stock FD and am going to put the HKS racing titanium exhaust on. This exhaust removes my main cat. Will anything bad happen if I just daily drive it. Shifting between 3 and 5 grand.

http://www.hksusa.com/images/?id=2240

 

If that is going to be your only mod you dont need a 4inch exhaust. but if you keep your stock downpipe with precat its probably gonna boost spike a tad so i would watch your guage if you have one.

 

I was just curious, is thier any negatives to a 4 inch cb? I have dp intake and custom 4" apexi gt spex exhaust, never knew their were ill effects of 4 in. pipe.

 

It's not going to matter what your RPM's are. It's the load and on the engine and the boost you'll be making.

 

Ok, you have a DP and you're going to a full 4" exhaust from there back. The main cat and/or pre-cat does a significant job of keeping the stock boost control system working - once removed you will need to watch the boost levels carefully to ensure you don't overboost your fuel supply. 4" is even less restriction than the typical aftermarket, so it's more likely you'll have boost issues - IMO it's total overkill and more headache than it's worth. It makes much more sense to install a high-flow cat and manual boost controller if this is street driven and you won't be trying to take advantage of the extra flow.

Unless you have already ported your wastegate, you can see boost creep and maybe also boost spikes. Your boost will probably increase, so you'll need to get re-tuned for the higher boost or install a boost controller to keep it at current levels. Run a search for midpipe, boost creep, boost spike, boost controller and you should get a lot of info.

Dave

 

so no thoughts on a 4" catback, I have a regular hks dp and soon to be a high flow cat, would the 4in catback be at a disadvantage?

 

Nothing wrong with 4", but it won't really increase HP compared to standard 3" or 3.5" piping unless you get to really high power levels.

 

I have read in some japanese magzine that suggest using stock gaskets with the high flow exhaust system. In this case, the setting will increase the flow character of the exhaust on low end but provide some back pressure for stock waste gate at high rpm. I do not have anything to back up this statement but it might be helpful to look into.