The hiss, I am pretty certain, is due to the design of the head and exhaust cam timing. That lip is probably for alignment or to prevent blowing the seal out.

 

Could be to smooth exhaust flow who knows. It'd keep misalignment from happening.

I did get a longer drive in the rain this afternoon but I didn't get much of a chance to do anything but part throttle up to about 5K. Definitely smoothed out the acceleration and sounds pretty damn good with the stock IPL dual exhaust. Doesn't look like I'll get a chance to really open the car up until Friday due to rain. I didn't hear any deceleration hiss at all but there was a ton of noise from the rain and water on the road.

I was actually surprised at how well the installation went. I was petrified I'd screw something up or the wrong bolt would snap. I'm sure it helped not being in the rust belt and not having that many miles on the car. And of course a good dose of the acetone/brake fluid sure helped. I did an application last night and let it soak til I tackled things this morning.

The driver's demon bolt. That Snap-on 14mm swivel came in handy. Theoretically, and according to the Fast Intentions instructions (I read them AFTER the installation, LOL), you're supposed to unbolt the bottom of the steering column and push it aside. I could get it without doing that but just barely. You could probably damage it if something slipped the wrong way. Anyway, I got it on the bolt, hammered the end of the extension with a rubber mallet, slapped on a breaker bar and then slid half of my jack's aluminum handle on the end of that. Pushed hard and I heard a snap. I thought maybe it'd slipped off (it had). So I put the socket back on the nut and started to push up on the bar again and it turned, much to my surprise. Literally the first try. The passenger's side top bolt snapped on the first try so I don't get a perfect score. O2's came out easily too. Honestly, the biggest pain is not having a lift and working in cramped spaces under the car. I had all four corners on stands to give me a bit more room.

I'd rate the difficulty at about 4 out of 10. I actually found installing coilovers a bit more difficult but there's some precision involved. Took me about four hours total, taking my time and stopping to eat breakfast.

 

You know, I was looking under my car and I'm wondering if I'm missing a bracket or something. There are two rubber blocks bolted to the middle section of the exhaust but they're not attached to anything. Literally the next attachment point is at the rear of the car. It almost looks like there should be some sort of bracket on the mid pipe but I did not see any screw holes that'd been used for a bracket or hangers.

I do get a noticeable increase in vibration at idle. I can feel it through the seat, steering wheel and shifter.

 

It wasn't raining on the way into work so I was able to get on it while entering the freeway. Honestly, the car felt slower. Will do some logging of the air/fuel to see what's going on. No engine lights.

 

Yeah there was a brace that connects the stock heavy AF cats to the transmission that you wont use anymore, rip that ish out..

Something is off man, reset your ECU. I noticed an IMMEDIATE jump in the butt dyno. Most obvious at shifts, it really puts you back on each upshift.

 

I've tried multiple times to do the reset via the instructions for inside the car using accelerator with no luck. I've pulled the negative terminal in the past but didn't do it this time. The 02 sensors should compensate. I've been rich since I installed the Nismo intakes.

 

Oh I just realized they were high flow cats and not test pipes. With test pipes there was an obvious jump in power, I couldn't tell you about HFC, I'm sure there's more airflow now so it only makes sense to get more power.

 

There was definitely a boost but I felt it went a bit flat at the upper end of the rpm range. Sure enough, the air/fuel ratios were in the low 10's from about 5K on up (see chart). At part throttle, there's a pretty big difference and it revs more quickly. But going to WOT doesn't produce the gains throughout the rpm range I was expecting. It did lean it out ever so slightly. I'll probably see a 25-30hp jump with a tune.

 

Not sure on the coupes, but the sedans do have rubber hangars toward the back of the midpipes, here's a pic of a stock setup and you can see one of the hangars still hanging on one of the prongs. https://www.myg37.com/forums/g37-sed...ml#post4065731

 

Yeah there are hangers for both the sedan and coupe on the mid pipe, but I think he was referring to the mount to the transmission with the stock cats and that brace that gets removed.

 

It doesn't appear that I have hangers on my midpipe. I have an IPL so it's a true dual. Right now it appears that the only hangers I have are just behind the midpipe section and actually on the rear section. So holding my exhaust up, you go from the header to cylinder head bolts all the way back to the rear section before you encounter a bracket. That's of course with the stock car to tranny bracket removed.

 

They are a bit of a pain. Driver side was pretty annoying. Even with the intakes off it's kinda hard to get to.