So I'm debating on which would be the ideal setup for someone who does not plan on running without a catalytic converter. Yes the ability to take out the HFC's module and run straight pipes is nice but i don't think I would ever do it unless i were to seriously track my car (which I do not). This is my daily driver and I'm currently on OEM exhaust with a 5/16 spacer and MREV2.

I already have the motordyne XYZ pipe with the resonator module and purchased a single 3" y back section which has not come in yet (exotic speed R1-T). So with that said I want everyone's opinion.

Resonated test pipes + XYZ HFC module
or
HFC's instead of test pipes

 

I like my HFCs but sometimes I wouldnt mind being a little louder...

 

TP with the MD HFC module. You can alwasy drop the HFC module for the straight pipe if you decide that you want to track your car.

 

^I see you are running HFC's with resonated module. have any sounds clips?

 

I say go for the XYZ cat and the MD test pipes.

The MD test pipes will be out soon.

 

My guess is that Tony at MD is probably spot on . . . However, for best results it may be a good idea to get your new y back exhaust on first and then decide whether to keep your resonator module and add HFC or go with TP and swap in the MD cat module.
I'm in a similar situation; I am running the XYZ with straight module on stock cats and a Fujitsubo exhaust. I think I'm going to go with TP and the MD cat module because the Fuji is so quiet. My main issue is that I have to choose between the MD test pipes that aren't out yet or Fast Intentions resonated test pipes. I only have two opportunities to install them between now and Christmas so availability is kind of an issue.
Good luck!

 

If u don't like Tony's idea you should look into Berk or Random Technology HFC's.

 

Well of course you are going to recommend your products Tony! lol I want somebody to help explain the benefits of one single HFC after the Y-pipe over having 2 HFC's before the y-pipe...performance wise.

 

Cost.

Either way the cats perform the same. Both make about 3-4 HP less than regular test pipes, but a single cat on the XYZ costs about 1/2 as much as regular HFC's.

Also, the cat on the XYZ is more durable because the exhaust gas isn't quite as hot when it reaches the cat. Its more than hot enough to do the catalytic conversion but the reduced temperature makes the core much less likely to fail when pushed hard.

 

Well hurry up and release those test pipes!

 

The cost all depends on how much the TPs cost though, as to whether or not there is a savings to just buying one cat. At least, that is my intuition - for his purposes he already has the XYZ pipe + resonator, so if he wants to go to HFCs, he just has to buy the cats. If he replaces the resonator with a HFC, then he has to replace his existing cats with the test pipes, so it's not exactly a "you're buying 1 cat instead of 2" savings.

From a flow perspective though, I always thought the further away from the head the better (for the cat) though I come from predominantly a turbo background, so maybe that is true to the extent that a cat close to the head and consequently the turbo impacts spool up times.

Independent question - how does the ECU function on the G35? Are there not downstream o2 sensors to make sure the cats are functioning? If you switch to the single cat set up, does the XYZ pipe or midpipe come threaded to accept those o2 sensors downstream from the new cat so it doesn't trip any ECU parameters?

 

Depending on what test pipes are used. Generic China made test pipes cost very little. For some people this will be the the option. For others it may not.

And yes, from a flow perspective having the cat(s) further away from the engine is better. And this is why a single cat on the XYZ performs as good as two cats right next to the engine.

The ECU does monitor O2 sensors downstream of the cats. The O2 sensors can simply go on the test pipes with non-fowlers installed.

 

Ahhh yes, I forgot about the non-foulers. Thanks for clearing that up