Pre-cat Only?
Pre-cat Only?
Hello everyone, I just joined the forum today. I bought a 1994 RX-7 last week and I love it! It has 42,000 miles and has been meticulously maintained ( I have known the owner since '96). I have done a lot of reading on this and other RX-7 sites...excellent info! I did a search on this site regarding Pre-cats and could not find an answer to my question. My car has only the Pre-cat with a Peter Farrell 3" midpipe and mufffler. It also has a Peter Farrell Piggyback, Intercooler, Intake, clutch, brakes, spirings and Tokcio shocks. It is tuned to run rich and I run it on the mid setting (13 psi boost). The claimed hp is 370.
Is it ok to leave the Pre-cat only or should I install a downpipe to have a straight thru exhaust? I have read that possible damage can occur due to boost creep if this is done. The car will be driven on the street and not raced. I will run it pretty hard sometimes though. Any advice is appreciated. Thanks.
Is it ok to leave the Pre-cat only or should I install a downpipe to have a straight thru exhaust? I have read that possible damage can occur due to boost creep if this is done. The car will be driven on the street and not raced. I will run it pretty hard sometimes though. Any advice is appreciated. Thanks.
This has been talked about many times before. First of all, if you wuant to have a straight exhaust you need to port your wastegate. If you dont want to, you can by the stand alone ECU (Apexi Power FC) and have it tuned to run a full exhaust. However this will not preent boost creeep or spikes, it will just decrease the risks. The best way to go would be to port the wastegate, because otherwize there is too much air and the wastegate cannot release it quick enough. If you do not want to get the ECU yet, i would keep the pre cat on to creat enough back pressure to prevent boost creep. Also running your turbos on 13 psi daily is pushing it. Any more and you will cook the turbos. Either upgrade to the efini 99 spec ones if you want to run around 13 or 14 or you can go BNR to run even higher boosts.
I would get a downpipe to reduce engine bay temperatures (reliability mod) and either port the wastegates to reduce creep or get a high flow cat. If the car doesnt have a boost gauge then definitely get one to make sure you are not overboosting. Also if youre running that setup with the stock fuel system then that needs to be upgraded. And I doubt it puts down 370 at the wheels with only 13 pounds, the midpipe is worth a lot but not that much. Good luck with the car and welcome to the club, you'll enjoy it!
-Andy
Oh btw, my mechanic doesn't recommend using a midpipe unless you have 3mm apex seals.
-Andy
Oh btw, my mechanic doesn't recommend using a midpipe unless you have 3mm apex seals.
I would seriously consider getting rid of the precat and possibly replacing the mipipe with a high flow cat for backpressure. It also is a pretty good idea to go ahead and buy and install the powerFc. I would install a boost gauge as well as upgrade the stock fuel pump at the least.
On the 3mm apex seals... I think there is good and bad to em. Your housing do wear faster due to the larger seal. How much faster? I dunno. But the newer 2mm seals last a long time so I just stick with those.
I don't see the car putting down 370. But you are definately in the 300 range. Congrats on the new car! It really sounds clean.
On the 3mm apex seals... I think there is good and bad to em. Your housing do wear faster due to the larger seal. How much faster? I dunno. But the newer 2mm seals last a long time so I just stick with those.
I don't see the car putting down 370. But you are definately in the 300 range. Congrats on the new car! It really sounds clean.
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Joined: Dec 2001
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From: San Lorenzo, California
Yep, install a pre-cat and replace the midpipe with a hi-flow cat. Either that or port the wastegate or add a restrictor plate in the exhaust.
A lot of people have run the PFS ecu, but it does have a nickname - the purple motor eater. I would not run more than 13 psi under any circumstances. The stock injectors do not flow enough to run safely rich at 13 psi or above, that's for sure.
When you are ready, I would step up to the PFC and have it tuned by a professional.
A lot of people have run the PFS ecu, but it does have a nickname - the purple motor eater. I would not run more than 13 psi under any circumstances. The stock injectors do not flow enough to run safely rich at 13 psi or above, that's for sure.
When you are ready, I would step up to the PFC and have it tuned by a professional.
Originally Posted by rynberg
Yep, install a pre-cat and replace the midpipe with a hi-flow cat. Either that or port the wastegate or add a restrictor plate in the exhaust.
A lot of people have run the PFS ecu, but it does have a nickname - the purple motor eater. I would not run more than 13 psi under any circumstances. The stock injectors do not flow enough to run safely rich at 13 psi or above, that's for sure.
When you are ready, I would step up to the PFC and have it tuned by a professional.
A lot of people have run the PFS ecu, but it does have a nickname - the purple motor eater. I would not run more than 13 psi under any circumstances. The stock injectors do not flow enough to run safely rich at 13 psi or above, that's for sure.
When you are ready, I would step up to the PFC and have it tuned by a professional.
And another thing, AFR gauge always helps, I'd at least run a dyno and have them check your AFRs, TUNING is very important. But if its supposed to be rich and its been running fine for awhile with that configuration then you're probably fine.
-Andy
Joined: Oct 2003
Posts: 11,576
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From: Morristown, TN (east of Knoxville)
Originally Posted by rynberg
Yep, install a pre-cat and replace the midpipe with a hi-flow cat. Either that or port the wastegate or add a restrictor plate in the exhaust.
A lot of people have run the PFS ecu, but it does have a nickname - the purple motor eater. I would not run more than 13 psi under any circumstances. The stock injectors do not flow enough to run safely rich at 13 psi or above, that's for sure.
When you are ready, I would step up to the PFC and have it tuned by a professional.
A lot of people have run the PFS ecu, but it does have a nickname - the purple motor eater. I would not run more than 13 psi under any circumstances. The stock injectors do not flow enough to run safely rich at 13 psi or above, that's for sure.
When you are ready, I would step up to the PFC and have it tuned by a professional.
While I agree with Rynberg and RR (both experts IMHO) to replace the precat with a dp and pull the midpipe for a cat of some kind, I want to suggest a couple more reasons:
1) Main cats and precats have a limited life due to the extreme heat they see. At 42k, believe it or not, that stock precat may not have a lot of miles left in it before it collapses internally. The main cat tends to operate at lower temperatures than the precat, so it will last longer and be less likely to fail by clogging.
2) Going full exhaust, first, requires wastegate porting and a boost controller. So it's easier (cheaper) overall to put in the high-flow cat. Plus, your car won't stink like ****, you won't stink like ****, the noise levels will be more streetable, the cops will leave you alone more, you won't emit clouds of smoke (which I believe in FL is illegal), etc. So again, it's a lot less hassle in the long run.
Dave
1) Main cats and precats have a limited life due to the extreme heat they see. At 42k, believe it or not, that stock precat may not have a lot of miles left in it before it collapses internally. The main cat tends to operate at lower temperatures than the precat, so it will last longer and be less likely to fail by clogging.
2) Going full exhaust, first, requires wastegate porting and a boost controller. So it's easier (cheaper) overall to put in the high-flow cat. Plus, your car won't stink like ****, you won't stink like ****, the noise levels will be more streetable, the cops will leave you alone more, you won't emit clouds of smoke (which I believe in FL is illegal), etc. So again, it's a lot less hassle in the long run.
Dave
