downpipe question
 

I had bought a stainless steel downpipe for my last FD, now that I have another one, is it necessary to have stainless, or is the mild steel OK. I thought I had heard someone mention that it doesn't make that much of a difference. Also, what is the make preference among you guys.
thanks

The two most prefered are:

- HKS mild steel - Was told it was painted for corosion and not heat coating. Stock location of O2 bunge.
* M2 stainless steel - There is no need for it polished unless you are "not" heat coating it.
* RotaryExtreme - M2 replica's. * No stud removal/replacement necessary.

There is plenty more information, if you "search" the archives for "DP", "downpipe" or "down pipe".

There is also Tri-Point in SoCal and Pettit Racing is SoFla. Mild steel is prolly 10lbs and SS prolly 5lbs (guessing). The stock pre-cat is prolly 40lbs, again guessing.

what do you mean by the stock location of the O2 is bunge?
does heat coating make a significant difference, and does anyone sell one already coated?
thanks

Bunge is the metal outcropping the O2 sensor mounts in. Some DP's have this in the stock location close to the turbos, some have it further back. The further back ones make it hard to use the stock O2 sensor and the wire is not long enough.

On HKS, the O2 sensor is mounted in the same location as the precat (at end of pipe). All others (that I know of) have the mount (bunge) welded further back towards the Cat', which is "closer" to the connector by probaly 3" and some aftermarket O2 sensors will have a shorter wire. Since HKS looks similar to a precat, so it can fool some smog places but you need the longer wire on the O2 sensor.

Yes, 2k degree heat coating makes a signifcant difference in under hood temperatures.

No, no one sells them allready heat coated (that I know of).

If I lived in an evironment like New Orleans, I would be getting an SS downpipe. They're lighter than mild steel pipes anyway. The Bonez (from www.rx7.com), M2, rx7fashion, or rotary extreme's are all good.

I would not call mine to be M2 replica. It's made by their old manufacturer but M2 does not own the jig or anything in that factory. Besides that, I don't advertise my downpipe as "M2 replica" because it's different from their current version. Just want to clear a few things up. Thank you.

Chuck Huang