Flow question HFC vs gutted cat?
 

How do the flow characteristics of these differ? Sound?

Thanks.

Well a high flow cat still has all cat qualities to filter the exhaust to help pass emissions. A gutted cat has all the internals pounded out.. a form of "resonated midpipe" almost but not really. So I would imagine a gutted cat would flow better and be louder.

given my current mods.Could I gut my cat out for the time being without blowing my engine?

Stock cat is barely over 2" and welded from the inside. Good aftermarket cats are 80mm=3.15" and are 15-20 lbs lighter.

It's safe to gut your cat as long as your boost doesn't go above 11 psi with stock ecu. Every car is different.

considering the fact that my boost is not going any higher than 7 psi for whatever reason I think I may be alright.Generally it seems that boost is raised about 2 psi across the board when running a straight through exhaust.

I can't believe you guys. I wasn't going to click on this thread b/c I saw so many replies and figured it was a 'gimme.'

Gutting the car is similar to running a midpipe, in that you are removing the main exhaust restriction. Therefore, you will have a very high chance of experiencing boost creep, and blowing your motor to smithereens.

Also, from what I have been told, you are not getting optimal performace due to poor flow characteristics from gutting the cat---you can see how there would be more turbulence vs a straight pipe.

It could be that your cat is clogged, and that is why you are seeing 7 psi. Gutting it could raise your boost to 27 psi via creep. You'll be fast as hell, for about .3 seconds, lol.

I would recommend going with a quality high flow cat. They can be had for around $300. If your wastegate is ported, you may want to look into a midpipe, but not if it is still stock.

That is not true. There are many variables at work, so an overarching statement like that can't be made.

I will tell you that when I installed my midpipe way back when (and w/an untouched wastegate) I was creeping to about 15 psi, and this was with the boost controller off (so 7 psi) *and* on a hot texas summer day.

Each FD is different, but being as how it is winter, I would be very careful. If you gut your cat and your turbo system is working properly, you are going to see a whole lot more than 9 psi.

Just trying to help you save your apex seals :)

Rich

Thanks..

i guess gutting the cat is outta the question then.LOL
Damn.I really dont wanna burn 300 to 500 bucks on anew cat when im eventually going to run the midpipe I already have.Decisions decisions.

Anytime :bigthumb:

Do a search for the Home Depot boost controller. It will allow you to keep boost under 11psi and adjust out the transition spike. It will not stop boost creep if your exhaust is too open. However, I would expect a 2" restriction of a gutted cat and a muffler would be enough restiction to avoid boost creep (I may be wrong too!). I would fix your low boost problem first. Read up on everything you can about boost creep, boost spike amd boost increase or find someone local to help you. You can't undo gutting the cat so make sure that's what you want to do. I still think you can probably get away with gutting the cat if that's how you want to go and you know what your doing. A PFC may be a good investment now if your going to run a mid pipe later and don't want to buy a HF cat (still need wastegate ported for mid pipe). A list of your mods would be helpfull.

Gutted Cat=No restriction=boost creep. Be careful, that needle climbs awfully quick at higher rpms, and I am not talking about the tachometer :)

ask and you shall receive.

I disagree. It depends on other mods. I very much doubt that a gutted main cat with everything else stock will cause boost creep. It will likely cause a boost increase. There is a big difference between a stock gutted cat and an aftermarket 80mm mid pipe (about 1" and less turbulance). Someone had a downpipe, midpipe, RB dual catback and no wastegate porting and had no boost creep. Just because it's straight thru doesn't mean there is not restriction. How open the intake is also matters as it's the overall intake/exhaust restriction.

I do agree with the be careful part and creeping boost at high rpm is especially dangerous on the stock ECU. A near stock car looses boost at high RPM because restriction is too high.

Im at a point where im not sure what to do. I want to run a midpipe but I dont have an apex power fc to compensate for the extra airflow.Nor do I have a ported wastegate. Running a highflow cat could still lead to disaster. Buying a new main cat is outta the question.Im a bit confused as to what to do.

Anyone know of a place that sells a 3way cat that doesnt need air injection to work properly?

you see my airpump has been dead for over a year.I figured that the main cat would clogg eventually.