[JohnInNH]

CBE= Cat Back Exhaust. So.. thats from all the cats BACK.
You can get Full Downpipes (catted or "Race", w/o any cat, or Lower Downpipes, which retain the OEM primary cats but eliminate the SECONDARY cats. We have 4 OEM cats.

The secondary cats are the biggest restriction of the OEM exhaust system.

Full down pipes are a PITA to install in comparison to the LDP's. The performance gain between the full vs LDP is not "that" much and is why many do not get the full DP. (Or they want to do an easier install.)

Catted vs race DP .. big $ difference BUT is 48 state CARB legal (nothing is in CA now).

I opted for catted full DP's. Little to no difference between the two, but according to FI they got a couple of tics better with the catted downpipes. But I wanted cats and be legal. You also don't get the funny smell the non catted downpipes have.

Really should get LDP's at a minimum with the CBE. If you are going to tune and want as much umph as your tune will get you, get full downpipes.

I really don't see the point of spending the $ on a FI CBE w/o getting downpipes of some kind to go with it.

Forgot to add: Full downpipes are a bunch louder and you should get the resonated X-pipe with them unless you want LOUD.

 

[JohnInNH]

Your pic is misleading. Calling the 1st (primary cat) the "second", and secondary cat the "third". Just saying ? Unless there is something I'm missing.

 

[JohnInNH]

What about emissions with LDPs? Will it pass? In CT they hook up the ObD port and run tests through that. I'm assuming that the readings will come back as fail from the levels since the second cat is missing. Rather not have to switch out every time I need to test.

Since you have the big primary cat you will/should be OK as no ECU codes are popped with just LDP's .. Your O2 sensors are still in.

 

[JohnInNH]

Correct, 100% stock exhaust with only lower down pipes. They are 2.5" I believe and bolt right up to the existing exhaust. Sorry, I don't have a sound clip but honestly, it's not much different than stock, if different at all. I got the idea of doing only lower DPs from watching that youtube video of that silver AMS Q50 beating that Ferrari and other cars in the quarter with the only exhaust mod being lower DPs.

It would be interesting to know the HP gains on lower DPs only, catback only, and DPs + catback.

Injectors, high pressure injector pump, intank pump, & E85 mix. IIRC - Nordstrom car.

I must have watched that video 20+ times.

 

[JohnInNH]

Yup, good video. Let me repeat what I said though.... only exhaust mod was lower DPs.

Yep, I read that. Just making sure others knew this was a heavily modified motor. Easy to skim over and just read LDP. It verifies my repeatedly saying "The secondary cats are the biggest choke point in the OEM exhaust."

Still one of the best Q50/60 videos.

A stock Q50 Red Sport on the Atlanta Motorsports Park track: https://youtu.be/1-3zRgt9QG4

 

[JohnInNH]

"Core capacity exceed." Well, at least mine is!?