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Post Fast Intentions RHFC Install Issue(s) and Concerns
I installed my Fast Intentions Resonated High Flow Cats this afternoon and have run into a few issues that I'd love to get your input on.
First, some pics of the product:
Note: the hardware bag comes with 8 nuts and 8 bolts. I didn't realize two had fallen on the floor at the time of this pic.
A couple of things to note as it relates to my situation:
1. I used Z1 Motorsports full metal exhaust gaskets in place of the composite gaskets that came with the RHFCs.
2. I reused the OEM stud (it doesn't come out) that protrudes from the OEM exhaust manifold flange + the OEM bolt that was on there since the FI nut would not thread on. So on each side, two 14mm nut/bolts are FI and one 14mm nut/bolt is OEM NISSAN.
3. On each side, I was not able to muscle the 14mm nuts as tight as I would've wanted to. I was using a 14mm ratcheting combination wrench, lying on my back, with (a lowered) car on ramps. I can't exactly get a ton of leverage in there - especially with 2 of the 3 nuts on each side rather tricky to get to.
4. I did perform an ECU reset following install. I used the pedal dance method.
Concerns:
1. I've got a PFFFFFTTTT exhaust leak coming from right under my feet (or thereabouts) under hard acceleration and it sounds ghetto AF. I suspect it's the exhaust manifold/RFHC connection at the flange. I can't tell if it's one or both sides. Did I do myself a disservice with the full metal gaskets or is this possible an issue of the bolts not being torqued down enough? If it's the gaskets, then I can swap in the composite ones. If it's lack of torque on the bolts, any suggestions? Clearance is tight in there and I don't have the ability to get this thing on a lift without taking it offsite.
2. Power. Where's this noticeable increase in power? I didn't feel anything in terms of improvement. In fact, I'm wondering if I lost power... Seriously, I felt more of a difference when I added aFe Pro 5R drop in filters and HPS post-MAF intake tubes in one shot. I was super disappointed today. Wondering what the heck is going on.
Thanks in advance for any constructive guidance you can provide
Not sure about the power issue but as for the gaskets there's a couple ways to find the leak. From my own experience, driving by a guard rail will reveal which side the leak is on. The sound will whistle or 'pulse' with the rails. Also, you could sea foam the car. Will pin point exactly where the leak is and quickly. Wouldn't recommend that though with the absence of clearance and you'd have to be under there looking. I've also seen the old trick of stuffing a towel in the tailpipe and see if you can find it.
I'd keep the metal gaskets, they're usually the go to when people have leaks to start with. Combine it with some high temp gasket sealant(?) and go from there.
Give Brad (newt) a shout and see what he used when he did his headers and torque them down. When I had a leak on my Mazda I had a similar issue and switched to Metal gaskets and sealant around the flange and that fixed the problem right away.
This is why I always get pipes that use oem ring gasket. All test pipes reuse some oem hardware as the header is a stud in a couple spots. Gaskets blow on the VQ alot. That's why nissan switched to the ring metal gaskets where they could. Z1 gaskets are okay at best. I've blown those out on my nismo 350z HR as well. Take to a shop to get some torque on the bolts.
So today I unbolted both cats and tried to reposition the Z1 metal gaskets and then used a universal joint and a variety of extensions and a breaker bar to snug everything back up. I felt I was able to torque everything about 2X more vs. the original install.
Well, after letting the car warm up and testing things by revving the engine, there's still a leak on the driver's side cat. I'm still hearing a definite PFFFFTTTT sound. Check out the video. My eyes may be deceiving me, but it seems like you can see a faint about of fumes shooting out.
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Also worth noting, there's definitely a gap between the driver's side FI flange and the OEM exhaust manifold flange. The passenger side doesn't have this problem. Wondering if the composite gaskets will fill this gap better than the Z1 gaskets.
I used high temp RTV sealant on both sides of all gaskets, apply the RTV, just a light snug down on the fasteners, than a few hours later do a full tighten down on all the nuts/bolts, should be good to go assuming there's nothing warped or something that's not causing the mating surfaces to mate flush.
Also, highly recommend copper-based anti-seize on all exhaust bolts, you'll thank me later
When you swap to any HFC/Test pipe on these VHR's, you will definitely hear a kind of whistling noise even on acceleration. However, yours is a little more pronounced though. When you pulled the Z1 metal gaskets, did you see any black spots on the gasket? Mine leaked when I had my first set of test pipes. I'd add the layer of RTV on top of the gaskets like what Brad suggested. Make sure you follow the directions on dry time.
I have ART pipes now but my leak is coincidentally enough between my ART pipe and Y pipe merge. I still have not 100% fixed it but I'm close.
Quick tip: Wrap the lower edge of the aluminum front subframe with painters tape to lessen that sharp edge. It'll slice you if you're not careful. Especially when working in that space and turning wrenches, one slip and you could slice open your wrists. I taped mine off after a small nick.
Here's how the Z1 gaskets look after about 75 miles on them. Driver's side gasket is on the left. Doesn't appear to have had a good seal...on any level.
Z1 gaskets im going to say are crap. They are no where thick enough to create a good seal especially on the tp to header flange. Your Definitely leaking and im doubting silicone will hold up long term there. Id double the gaskets if you can. Id probably go vibrant gaskets and double them up.
PNW_IPL, I'm going to have to agree with you on the Z1 3-hole manifold gaskets. My 2-hole gaskets work flawlessly so far. But after removing the FI RHFCs today and inspecting everything, the Z1 gasket on the driver's side was not sitting flush on the high flow cat flange - nor did the center hole (main) line up. In fact, the gasket seemed bowed slightly. I decided to go ahead and use the composite gaskets that came with cats. They fit perfectly flush against the flanges, lined up perfectly on all the bolt holes, and the center was perfectly aligned with the inlet. I also felt that they were a bit thicker and would flatten where they would need to flatten and fill where they would need fill - more so than the Z1s. After I bolted everything up and took the car for a test drive, the PFFFFTTTT was totally gone and it sounded normal under hard acceleration (drop the hammer) and cruising.
Impressions so far: the car feels like it takes longer to accelerate in the mid-range, but I'm not sure if this is just in my head. I feel like most people would over-rotate the other way like "holy $h!t, this thing feels like I gained 40 hp! Butt dyno FTW!" In this case, I'm of the opinion that the power has taken a hit in noticeable way. In terms of sound, while the exhaust tone is mildly louder, it still doesn't give that beautiful rumble like the stock G37 coupe (or FX35 like I used to have). So for $706, I'd say I'm overall disappointed for now, but we'll see how I feel in a few weeks - maybe the ECU has to "re-learn" as so many people seem to suggest here on the forum (is it really making a determination how many times I bury the throttle?)
Yeah, my Z1 gaskets are holding up OK, but I think I could have ran the thicker (but significantly cheaper) gaskets that came w/ my RTPs, I'd imagine the FI gaskets are a few steps above in quality vs. the ones that came w/ my RTPs.
OP, at least you sound like your pipes are now sealing better, hopefully you'll be happier w/ them as time goes on.
08-22-2017, 11:54 PM
