The disscussion about header wrap got me to bring up this topic.

Now I am not in favor of any new rules unless it is really needed. But this is something that needs to be addressed.

The exhaust collector is not included in the rules on the header. I would like to see the addition to the rules of having the factory collector being required.

Nobody I know is using a custom piece at this time but it is open to being done. Someone with the time and money could possibly come up with a collector that may alter HP or TQ curve.

May as well get this included before we get too far.

Fully agree.

We can discuss this 2012 rules change period. The easy part on the 1-4 and 2-3 pipes is that they are easily compartmentalized. Meaning it totally bolt/on stuff. No measuring or cutting.

Once you get to the collector it is more complex since this what I call the "cat pipe" since it when stock has collector, cat and runs back another 3 feet or so. These pipes are never stock any more from tip to tip because most of us remove the cat. Now way I did it was to remove the cat right near it weld (actually cat removed itself one day on track )and I had the remaining section re-fabbed. So my collector/cat pipe is still the same length and stock at the front and not at the back. Stock diameter pipe was used however.

So if we rule that the collector must be stock we need dimensions as to how far it needs to be stock. Clearly you are talking about the section from the 2 pipes to one, but how far after they join. 2 inches, 6 inches? One problem I don't want have is guys needing get new parts just because their cat deleted pipe joined the collect or 1" too close for the new rule.

So while the rule change make some sense, practical enforcement is important to think about. So far it has been considered "not worth the hassle", but maybe that needs to change.

I may be wrong on this and only have the experience of owning two cars. First was an 85.5 944 and second was an 88 924s. I have had several spare collectors and all of them seemed to be the same though I did not measure them.
On both of them the collector ( the pipe that goes from the two headers and is a 2-1 arrangement) was a fixed length and had a welded on flange that the rest of the exhaust system bolted to.
Again I do not know if this stock and if this is universal on all 944-924s factory exhaust systems.
If this is not so then I can see the problem you are talking about. It would be too difficult try to get all the collectors to one specification.

Joe is it possible that your car had been altered before you purchased it?

We all know that there is some HP available in the header system if we go to a properly designed header. It stands to reason that the is HP or TQ available in the collector if someone spends the time and money. I doubt it is more than 2-4 but it can cause others to look there.

Can anyone else out there look at your header and see if it has a flange on the back end and measure the distance from end to end?


I am just interested in cleaning up the rules if at all possible with put making any new ones.

Charlie,
My "cat pipe" is show from this Jan 2003 photo. It is stock from header to the middle hanger where cat normally goes. Then has custom section to a stock aft flange. Not a great photo, but this configuration is identical to all of my cars mutiple parts cars. It is the same pipe.




Here is a picture from the factory parts list. Same collector part number for all years, but it shows the Cat as seperate. I alwasy see them welded together.



We could require it to remain stock to the O2 sensor port, but some guys don't use O2 sensors... They may have cut it off before then. So then it will be time to get the tap measure out.

Ok that is what mine looked like. So if we required the 2-1 pipe to remain unaltered until after the o2 sensor bung then that would solve the potential issue.
My guess is that most did not cut it shorter than that.
Let me know what you think.