Blowing cats but don't want test pipes? Move them down
 

Started finally making some changes with the exhaust set up. I'm running Topgunz A-A kit with a motordyne tdx on my 07 HR. I blew through a couple HFC sets and tossed the OEM ones for a while until I discovered I am getting knock from high temps after a while with the stock cats. Here is what I am going for:

I'll be running resonated FI test pipes with a modified motordyne Y section with HFC cells. Wanted to get some input if moving them to this area would help with cat temps to prevent these things from blowing all the time. Mind the "saggy-ness" they are held on by tape for pics


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Yes, it'll definitely help. That's where I have my 100 cell cats and Fast Intentions puts them in their lead pipes in pretty much the same location

I was on the fence on the cell count I wanted. In the photos, those are 400 cel. Supposed to be higher flow than stock. Wondering if I should go 200 cel with the supercharger set up. I'm trying to be at that mid point in terms of flow and sound.

The motordyne with HFC's was too loud for my taste. The sound was almost perfect with the stock cats, but generates a lot of heat with all that back pressure at 12psi.

I ordered 200 cell ones... I think 400 is factory?

Yep, if I remember right, oem are 400 cell. 200 should be good.

Just curious, are u running catalytic converters to pass emission tests?


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Not sure about NissanTracker but I'm running them to keep the exhaust smell down a little bit

Yes and No. This is a HPDE/street car so I want to be able to pass emissions, but I don't mind using o2 extenders. They are mainly to keep the smell and sound down and to relax the inner tree hugger inside of me. ;-)

I have been running the GESI hi-flow cats in my down pipes for years now. No cel and will pass CT emission with ease.

They are rated for 600hp ea. & 1400deg F - EGTs

Those GESI's are great. A little expensive but the best. I went with Mil Spec. A little cheaper

Some high $$ rolling right there. Haha, I went with Magnaflow 200 cels.

If I had a TT kit, I'd probably invest the money for GESI's/Mil Spec for higher horsepower. The Magnaflow's I got are geared towards V8 exhaust setups and should handle. I'm only at 475 on an v3 SCI 12psi. May upgrade to a V3 SI blower for that extra 100 CFM and see if I can squeeze past 500.

Blowing cats but don't want test pipes? Move them down
 

Part of me wants to have some high flow cats welded in to part of my exhaust too. It’s getting harder and harder to get cars without emissions equipment inspected. A Firestone wouldn’t inspect my G35 because it has an aftermarket magnaflow muffler on it. That’s the only mod to the engine/exhaust….

Plus, I have a bit of that tree hugger inside of me too that feels a little bad for having a street car without cats.


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Got my appointment with the TIG'er for next week. I'll post when completed.

So update on this. Did get the cells Tig welded. Came out great. Like before with HFC's, i did lose some low end power due to the more open flowing exhaust with the supercharger (SCI). I did put a 370z VLSD into my HR nismo and did gain a bit of response due to the final drive. Not as much as I hoped to make up for the exhaust changes.

(VLSD change was really to get rid of the bearing noise that started after playing around with launch control on Uprev and thought why not go for the 370z with a high FD.... )

These superchargers apparently love back pressure in lower rpms. I'm in the middle of a fuel return install, but I'm thinking of adding a boost activated exhaust valve to one bank of the output of the Motordyne muffler.

Going to have it partially open in vacuum and try to set it up to open completely at around 4-5 psi.