ppritchard

Is there an easy way to tell on a '93 FD if the precat has been replaced or if its still in place? I have most of the service records for the car, but didn't see anything for exhaust changes.

Thanks for any help,

Phil

bajaman

Yes, the pre-cat is a large ungainly looking unit, as opposed to a downpipe which is just a smooth 3" diameter piece of pipe.

dgeesaman

iTrader: (7)

The precat is also covered with goofy-looking heat shields and has an pipe size equal to the pipe on the main cat. Aftermarket downpipes clearly have a bigger pipe than the stock main cat.

Dave

jeff p

be happy if it has replaced! its nothing but a blow tourch for your motor and turbos. it will eat up all your under hood plastic parts over time.

Jeff

ppritchard

So, replacing the downpipe w/precat is a "welding" type job?

I have a downpipe that was never installed (previous owner), just trying to figure out how big of a job it is.

thanks!

dgeesaman

iTrader: (7)

Just 6 bolts. No welding or cutting. Trouble is, they can be mf'ers. Start soaking them in PB Blaster for a day or two, or pay an exhaust shop to do it for you. You'll probably never see manifold bolts exposed to such temperatures anywhere else.

Dave

ppritchard

Any idea of what a muffler shop would charge to remove the old pre-cat downpipe and install the new one (already have)???

thanks

alexdimen

iTrader: (13)

Some downpipes even need allen bolts to replace the studs/nuts at the turbos because of the way they are shaped. I have an old school PFS pipe and even needed to modify one of the allen bolts to have a conical head to fit.

I'd be scared shitless about taking my FD to the corner exhaust shop... maybe you fancy yankees have better exhaust monkeys up there.

SLOASFK

iTrader: (5)

No, we have mennonites in this area. I have no idea why Dave would say that, I'd never let those guys touch my FD.

I once had a car where the rear downpipe had rusted through and broken off of the rear header(it was a FWD V6), and they swore up and down there was no exhaust leak

silverflash2

iTrader: (2)

Check the SE section, i believe there's a list of Florida shops that you can pick from.

dgeesaman

iTrader: (7)

Compared to not getting the job done at all, it's not a crazy idea. The trick is that they don't have any idea of what they're getting into, and agree to a fixed price in advance.

In this case, I'd rather have a corner shop work on it than have a precat on the car...

Dave

Lawman_AUT

Hmm, i heared some bad rumors about dismounting the precat. Rumors like to much boost then, ECU cant handle the "free flowing" mod or so.

Is it true or just some urban legends?
Andi

4CN A1R

iTrader: (6)

urban legend...i have no mods and stock ecu and i replaced mine with a 3" downpipe. i dont know wat results anyone else got, but i only noticed my car only running a little richer.

i'm guessing a 8-10hp increase cause of flow. my boost pattern did change to 10-9-10 unless i'm reading it wrong?

dgeesaman

iTrader: (7)

What you are reciting is not true.

However it may be that you're confusing this (changing the usdm pre-cat to a straight downpipe) with changing the stock main cat to a straight-thru midpipe. On a car with a full exhaust, your boost can go beyond reasonable levels because the flow overwhelms the wastegate. And it's a wastegate sizing problem, not an ECU problem.

In any case, the important fact to always remember is 1) have a boost gauge installed to do a boost test before and after installing the flow mod 2) know the boost level that your setup can handle. People who ignore those facts are the ones who get in trouble.

Dave

ppritchard

Dave,

So, by just replacing the precat downpipe with a straight thru downpipe will that
be enough of a change to cause risk with the boost?

Everything is stock, just looking at the precat changeout as a reliability mod (heat), but if it causes more risk (boost) then it might not be worth it.

thanks,

dgeesaman

iTrader: (7)

Changing the downpipe alone is almost never enough to raise the boost. Boost went up for me after I added an efini y-pipe and racing beat cat-back.

But you should install a boost gauge anyway. You're flying absolutely blind without it.

Lawman_AUT

Thx for your reply, Dave.
I asked my japanese friend before i had to drive to my nightshift, he told me exactly what you wrote - but of course he meant changing the pre-cat to a straight downpipe.
Since i found a hose for a boostgauge allready installed near my gas pedal, there is no reason why i should not hook it up with an boost gauge.

Andi