AUM

Today I decided to install my Pettit downpipe, my first real mod on the car that I have done. After I jacked up the car I saw that the catalytic converter was missing. The previous owner told me when I bought the car that he had replaced the cat because the original was clogged. At that time I assumed he meant he replace it with another cat.

This is what I found, it looks to me that instead of replacing the cat he just had them remove it all together. Who ever did the work reconnected the air pump tube to the piece they installed.

After finding this I did not install my downpipe. So my question is what should I replace this so-called cat with. I don't have an upgraded ECU and don't really plan on doing this for a while. I was planning on just running a downpipe and my current drop in K&N as the only performance mods right now. I definitely don't want to run a downpipe/midpipe combo and basically from what I can see I have a midpipe on my car right now. How safe would it be to run a K&N, downpipe and high flow cat?

rx7twin

iTrader: (1)

*removed

my bad

rynberg

Perfectly safe to run a hi-flow cat with those mods, you will need a boost controller (manual or electronic). You could also put a stock cat back on -- people frequently sell them for next to nothing, although shipping's probably a bit pricey.

AUM

Thanks for the info; I guess I will buy a hi-flow cat as well as a boost controller.

I am having secondary boost problems and I am sure it is because of the pre-cat so I would like to get the downpipe on to see if this resolves my boost problems.

What would be a good hi-flow cat?

AUM

Well I haven't installed the pettit downpipe or bought a hi-flow cat and boost controller yet. I know that my stock pre-cat is partly clogged and now one of the heat shields on it is rattling bad so putting the downpipe on is needed. The stock main cat is replaced with a piece of exhaust piping with the air pump hooked up to it. The thing is the piping is the same diameter as the stock exhaust piping, 2.5". Basically it is a 2.5" midpipe so if I left this on the car and installed the downpipe how much would it affect my boost as opposed to a 3" downpipe/midpipe combo?

I am assuming this is similar to installing an exhaust restrictor plate in a 3” exhaust system. Rynberg suggested that I install a high-flo cat and a boost controller, good advice, but I was wondering if I just left the 2.5” midpipe and installed the downpipe and boost controller would I have problems?

Also instead of a boost controller I am thinking about purchasing a PFS PMC since the car is an automatic and this seams to be the best ecu for an automatic. Would this be a better move over buying a boost controller?

poss

iTrader: (5)

What's that heat shield in the back for?

AUM

Do you mean the heat sheild in the picture at the end of the what was the main cat? If so the is just what is remaining at that end from when the cut the cat out of the middle. The sheild that is rattling is one attached to the pre-cat.

poss

iTrader: (5)

I haven't ever had a stock cat so I didn't know that there was a shield on the piping after the cat.

AUM

The previous owner had the cat removed. I either want to get a used stock cat, hi-flow cat or even keep this for now if it won't cause boost and fuel problems due to its diameter, and get the downpipe on so I can drive the car without it sounding like a junker rattling away. It's so embarrassing pulling up to a red light, people looking at the car and then the rattle starting once the car idles.

POS7

Clogged precat is bad, I'd say its even worse than the dp midpipe combo.

Basically what you can do is swap the dp, and work on gettting a boost controller or ecu + hiflow cat asap. Just do your best to stay off the boost if you absoutely must drive your car. At least you have the stock exhaust to provide some restriction. Also, the midpipe is only 2.5", which also helps.

You may be able to get away with the dp, 2.5" mp, stock exhaust, boost controller. I would be wary of creeping though.

mkiv98

iTrader: (5)

similar question...

if I have an HKS catback and get intake, dp/mp there would be some problems with boost right? would it be safe just to use a boost controller or later on an apexi PFC?

POS7

I would say no, because there would be no exhaust restriction and you would experience boost creep. Stick with a high flow or the stock cat with those mods and a boost controller and pfc.

FLA94FD

I would say go for the PFC and a high flow cat. You wont need the boost controler with that setup. It's only money...