So I'm deciding to move back to a single-pipe exhaust, and my choice right now is between the resonated Z1 Y-Pipe and then either the Z1 Touring Exhaust (Coupe), or a Tanabe/Revel Medallion (tried that before without a resonated Y-Pipe, round 2, baby). I'm leaning towards the Z1 Touring, but I've seen a few install videos where the passenger-side muffler/hanger contacts a splash shield underneath the car (on stock cats both times, as IIRC aftermarket HFC hand a little lower). I know that the Tanabe fits fine from experience, but I heard a G35 with the Z1 and HFC and it was amazing.

Anyways, anyone here that can attest to the Z1 exhaust fitting/not fitting? Seems like a nice exhaust, but would REALLY prefer to not remove that splash shield if I don't need to.

 

So are you asking if the Z1 exhaust hits the shield up by the cats or back by the muffler?

 

Back by the muffler; it's a plastic shield that is located right next the the rear-most, passenger-side exhaust hanger. Multiple install videos I saw showed issues with that shield; can't tell if they just had to remove it for install, or leave it off (as most G35 owners in 2020+ aren't exactly the best videographers.

Granted, all the videos had stock cats and I have aftermarket, so fitment will be a bit different, but I was wondering if it was a known issue (nothing on the reviews for it, but just weird that I've seen it in 2-3 videos so far).

 

I’m not sure why you would think having aftermarket or stock cats would make any difference. Whether AM or stock, the outlets are in the same spot and has no impact on how the rest of the exhaust fits.

That being said, yes, the right side muffler is very close to hitting and maybe even hits that shield depending on the car. I slightly bent the shield rearward and have clearance.

 

My FI HFC hangs slightly lower than stock (only a bit, but still noticeable) and might be slightly longer, which could potentially cause fitment issues further down (I guess it would angle the rear of the exhaust up slightly? I know that my HKS collided with a Soul Function brace that was advertised/shown in pics to clear it, and no amount of adjusting could fix it; I chalked that up to my FI HFC modifying how the rest of the exhaust fit.

Still, good to hear that you can simply bend the shield and not have contact; as long as I don't have to completely remove the shield, I'm a happy camper lol. Thanks!

Order is on the, fingers crossed it goes on easy.

 

Figured I'd update; slapped the exhaust on last night. Of note, I have FI RHFC, stock headers. Everything fit up really well; only issues was the heatshield over the evap canister (or whatever it is on the passenger side underneath the trunk). All it took was a minute or two bending the thin heat shield by hand to get a cm of clearance or so, and using a chisel to slightly dent in the more substantial metal shield that interferes with the rear muffler passenger-side mount.

Loosening the midpipe clamp while fiddling gave me a bit of wiggle room, so I probably spent about three minutes total with the heatshield(s) adjustment. Exhaust fits great aside from that, sits noticeably higher (especially at the flex pipes) than my HKS. Have yet to test drive as I'm doing brakes, but this exhaust is pretty legit (even with the asking price). Sounds incredible even when parked.

 

Glad you got it installed with minimal fuss. Curious how it is once you get it rolling. I’ve got mad drone from 50-70.

 

The drone is definitely there; about 1800-2500rpm is the zone, with it being the worst right at 2000rpm. It could be me, but after about a hundred miles (and a few hard-throttle pulls) it seems to drone slightly less severely, but I'll have to wait and see if that continues (my guess is carbon buildup slightly changing the frequency at which it vibrates). It's a fairly aggressive drone, I can feel it in my seat during its peak.

Used a spectrum analyzer and it seems 63-80Hz is the offender, peaking at about 80dB in normal Seattle driving, at the mentioned rpm range. Resonated HFC, resonated Z1 Y-pipe, the exhaust is super deep and "clean" sound, with zero rasp that I can hear from inside; it's a really "pure" tone, if that makes sense. Pretty impressed that even with this exhaust set-up, the loudest I've seen in daily driving is less than 82dB.

It's bearable, but extended times at those rpm would be a bit much for me; might end up trying a few things like attaching rubber pucks with clamps to change the frequency of vibration, or maybe fat-matting the floor (got it on the sides/doors/trunk currently).

 

I had the same problem with the Medalion tannebe on my 04.
I tried sound deadening the trunk . Didn’t help.
I read you can weld in a J pipe right before the exhaust.
There is a formula to calculate the length for the frequency of the resonance.
I too have FI HFlow Cats.
Put the original exhaust back on.
But the sound deadening is nice!

 

I used to have a full Tanabe Medallion as well with these same cats lol; drone was definitely more constrained than with the Z1 exhaust, occurring in a much tighter spread (2000-2400rpm, or tighter, it's been a while) and while it was annoying, it sounded higher-pitched/less boomy than this.

Gonna do some cheap experiments like clamping 5-10 pounds near the mufflers, maybe trying resonated tips (3 inch inlet 4.5 inch outlet resonated tips are impossible to find), or throwing some mass in the backseat to see if it attenuates anything. I don't want to do any permanent modifications like welding if i can avoid it.

I'm still split on if it's strictly drone or is just vibration; the drone does NOT occur when revving in neutral, only when in drive and, well, driving. If it's vibration, then hopefully adding mass helps a bit.

 

I have read some added weight to the muffler body.
The holmhienz)(?) J pipe works the best.
I guess that was why the medallion exhaust was less expensive than the top names.
I still have it in the shed (lol).
Good Luck and let us know if it works.
Oh yea, I have the FI resonated cats. Maybe that’s why mine drowned between 1200 and 2000 rpm.

 

So I clamped two of these bad boys at the flange for the rear muffler assembly (4R3Z-5F240-BA), and drone is substantially down (between 6-8dB at the problem 100-125Hz frequencies), which is 2-3 times reduction. I'm going to get a third and put it upstream where there's room to take the final edge off. Going uphill at 2000 RPM and lugging the engine is now merely a bit loud, as opposed to ear splitting.

It takes some finagling, but you can definitely fit two at that rear flange and clear everything (one is only about a centimeter away from the pipe, so I'll be monitoring if it starts to deform with heat and find a new spot for it if needed; rear of the exhaust vibrated more than the front so I'd prefer it further back, but the main goal is adding mass).

At ~$28 a pop, it ain't bad for a fix. With shipping you're probably at about $100 for three of them, although anywhere from 1-3 would work depending on how bad your drone is/your personal tolerance for it.

One weird thing is that I now hear a very brief metallic rattle at sub 2000 RPM de-acceleration, but I did just clamp metal to metal (or the change in mass is making something else vibrate). Much preferable to my head being split open when driving. Would recommend this for Z1 Touring exhaust, YMMV for other exhausts.

EDIT: After some more extensive testing, it did reduce the drone a bit, but it's come back; either I didn't get the exhaust hot enough (it only drones after a few minutes of driving, it's like I can feel/hear the drone originally from behind the car moving towards my seat as I drive), or the packing has worn in more. It DID reduce vibration though, especially in the steering wheel. Still gonna slap a third on (going with one at year, one off each cat) and see what that does; the more on the car, the more the drone range seems to narrow; with none it was 1700-2400rpm, with two it's really tight at 1800-2100rpm or so. Still not 100% certain if it's drone due to frequency resonation, or simply vibration due to engine load at low RPM (thinking drone as there's zero of the low hum from idle until 1800 where it suddenly appears).

On a related note, I have my old HKS exhaust lying around; unfortunately the shop did a crap job welding new pipe in, so it's kinda hard to sell. I've been thinking; couldn't I cut off one of the rear Helmholtz resonators and weld it onto the Z1 exhaust? From what I remember, those resonators are tuned to engine frequency, i.e. it'll target that ~125hz range that's an issue, no matter what pipe it's attached to. Don't think there's realistically any room, but was curious if that would theoretically work. Would like to do everything possible before cutting metal lol.

 

Random update for those who see this; turns out my FI RHFC had busted on the inside due to contact with speed bumps when lower than it is now. Running Berk HFC now, and there is some rasp when hard accelerating at around 3000rpm VERY briefly, but the stock "warble" of a G35 has returned below that when accelerating more gently. After replacing, the vibration in the steering wheel at idle in drive (with 1x of the above Ford dampers on the rear of each cat and 1x at the rear muffler connection) is practically gone, but the drone is still there (maybe slightly less than my busted FI RFHC? Dunno).

I think the only solution is gonna be helmhotz resonator, clamping a LOT more mass to the pipe, or swapping the (IMO way too small) midpipe resonator with a Vibrant one. Vibrant is probably the best call because Z1 Touring with resonated Y-pipe/Berk cats (and pretty much ever other breather mod) is civil enough when being gentle on the throttle, but a bit of gas is a BIT loud, and I kind of want to be a little quieter. Not sure I want to dump $100 on a resonator and whatever the current labor rate is at my local shops to weld it in, so I might just get one or two more of those dampers and see what it does for the interior.

Still think it's a pretty quality exhaust, minus (a) the passenger-side shield issue and (b) the midpipe resonator should be thicker (there's definitely room for it). Wouldn't mind the rear mufflers being a bit beefier either; there definitely looks like there's room to make them wider/absorb more.

Also someone please point me towards 3 inch inlet/4.5 inch outlet resonated exhaust tips; they just don't appear to exist...