jfandl

I have a 93 AT w/90K miles that has performance issues that I suspect may be the precat. I get almost 10 psi boost on the primary turbo, then it struggles a little during the changeover to the secondary and boost drops to 4-5 psi. Petit recommended downpipe saying that these 7's pre-cat's don't last beyond 50K.

It seems when the car is hot and on hot days the car really looses performance and runs weak! Now that it just dropped to 50 degrees outside, it feels like I just got it back from the shop with some serious mods b'cuz the car runs very strong now. It al changed again when the day got hotter (up to 80 degrees) and the car started running weaker again.

So how do I actually know that the precat is bad? I don't want to drop 300 bucks for a downpipe to findout it doesn't make a difference. Has there been any success with just hollowing out the precat either?

Any help appreciated. (Since I didn't find any threads about how to actually check the precat)

Rated R1

You could buy a gutted precat. I have one for sale make me an offer.

Turbonut

iTrader: (1)

Either put an eliminator pipe in there, which is a dp, or replace with a hollowed out cat. Either purchase one or beat the heck out of yours. I personally would keep the original and put a hollowed out cat on. That way if it isn't the cat, you haven't screwed yours up. Never know when you'll need it.

P'cola FD

Get the downpipe regardless. Beyond the power improvements, it makes the car run cooler, not have to work as hard, sound better (hear those turbos), and it makes the car, in general, happier. The 300 bucks will not be wasted, no matter the condition of your precat.
The reason your car feels faster when it's cold, is because the cool air makes your intercooler more efficient.

GoodfellaFD3S

iTrader: (213)

Yeah, what he said . The stock precat is an evil device. I know of a downpipe for quite a bit cheaper than 300 bones. PM me if you're interested...

RX7 RAGE

iTrader: (22)

Get a downpipe asap.

Mahjik

iTrader: (1)

I agree with the others on getting the downpipe, however it still sounds like you might have another problem still.

With your secondary boost being that low, I don't think the downpipe is going to solve that. Put the downpipe on and see if your secondary boost is still low, if so, Pettit is one of the best places to take your car to have it diagnosed.

RX7SpiritR

iTrader: (1)

Definately get a downpipe. I got a Stainless steel direct bolt on (don't know of any that aren't) with a 2 year warrenty on it for $203 including insurance and shipping. Check e-bay out and then check some other places, you don't have to shell out $300 bucks, just shop around and you'll get some good deals. Whatever you do don't get a mild steel one, they'll rust in like 6 months. Just go with a nice stainless steel one, cause those precat's have many problems, number one being they are huge uneccissary ugly beasts that may do more bad than good, that's why downpipe's were made, =). It's a good investment and would be well worth the money even if it doesn't help your boost problem. Hope you get your problem fixed.

Drifter93

Get the down pipe and save your precat because you never know.

Scorcher

i'm having the same problem. it's great to know i'm not alone... not that i'm happy your car's not running well. I had decided that i would get the dp, but now i'm worried about overboost. I already have a catback and a K&N filter, so i'm worried that getting the dp will cause me to run lean. I don't have an air/fuel gage or a boost controler. Does any one have my set up without running lean?

Alien7

iTrader: (1)

I had a 10-5-8 pattern after I got the car with 54k miles last year, and after putting on a downpipe I finally saw the 10-8-10 pattern, so my problem was the clogged precat.

Now I'm back to the old pattern, so I'm thinking that my main cat is clogged. argh!

13brv3

Congratulations, you've pushed me over the edge

I've been asking this same question about how to tell if a cat was plugged, but never saw a clear answer. Perhaps I still haven't. The usual reply is always install a DP, but you're the first person I've found that said it actually changed their boost pattern.

I picked up an 83K mile R1 a couple months ago, and have worked through a number of boost issues, but I still have 10-6-(10 falling to 7 by redline). After seeing your post, I got on the phone with the RX-7 Store, and ordered a DP with an extra bung for a future wideband sensor.

Thanks for the info.

PS- No Danny, I don't have a wideband yet. You'll have to wait to borrow it

Benjaminaco

hang on to your precat, never know ......

-Ben

jfandl

I noticed quite a few people say to hang onto the precat. Why in the world would you do that unless you sell the car and want to keep it for your next Rx? Seems if you upgrade to a downpipe, no need to ever have the precat around.

Mahjik

iTrader: (1)

I'm not sure why... Even people in Cali pass emissions with downpipes, so I would see no reason you would ever want to switch back. Now, keeping the main cat would be a different story...

Just FYI, my pre-cat went the way of the Do-Do bird.