EdwardNorth

Hi all,

I just purchased my FD and will be performing the reliability mods over the next few months. It's a 94 Touring completely stock except for a custom straight-pipe catback exhaust and boost & air/fuel gauges.

My immediate plans -

K&N air filter
Downpipe
MAYBE the stock airbox mod.

My questions (which I haven't found good answers to by searching the forum):

1) With a straight-pipe catback, will installing the downpipe make the exhaust obnoxiously loud? It sounds pretty good (and quiet) with the setup it has now, but I don't want it to get much louder.

2) Will having a K&N filter, downpipe, and this type of catback all at once be too much for the stock ECU? The car runs pretty rich right now as is.

3) Would doing the stock airbox mod with a K&N filter constitute an actual Intake upgrade, and be too much for the stock ECU with the DP and CB?

It will be awhile before I can afford to upgrade the ECU, so I want to make sure the car can handle it with boost and whatnot.

Can anyone take a guess what kind of HP and Torque I might put out if I get this done?

Thanks for your opinions and help!

rynberg

Well, you didn't search very hard if you couldn't find the answers to these questions but....:

1. The downpipe will increase the noise level a noticeable amount. Whether you consider it to be loud and obnoxious, would be hard to say. Usually, cars with stock main cats don't fall into the loud and obnoxious category.

2 and 3. You can run those mods on the stock ecu with no problems. You will have to buy a boost controller if your boost rises above stock levels of 10 psi on the secondary turbo. BTW, opening the stock box flows as well as any aftermarket intake.

You should make roughly 250 rwhp or so at 10 psi with those mods, maybe slightly more. I made 240 rwhp with downpipe and cat-back.

EdwardNorth

Thanks for the reply.

I had found some info doing searches, yes, but the one thing that people haven't said much about is a Straight Pipe Catback.

From what I've read, I am under the impression that a fabricated straight pipe CB flows better than most aftermarket CBs. Therefore I don't know how this affects the whole equation of mods prior to ECU upgrade.

So these questions revolve around that factor, which isn't addressed with anything I've turned up in my searches.

jpandes

Here's an economical way to control boost($30)http://www.rx7turboturbo.com/robrobi...controller.htm

As for an ECU, Search for a used re-chipped ecu in the parts section. You can easily buy a used M2 Stage 3 ECU for $400-500. Better safe than sorry... BTW, I dynoed around 310rwhp(dynojet dyno) or 273rwhp(mustang dyno) running this ECU at 13 psi with all the bolt-ons.

rynberg

I got ya.

I'm not convinced though that a straight pipe CB flows better than aftermarket CBs. My Racing Beat, typically known as the quietest and "most restrictive" is straight-through 3" piping until the muffler where it y-branches into two slightly smaller straight-through pipes. I'm guessing your exhaust doesn't flow that much more and probably flows the same or less than something like the Apexi GT exhaust.