GTM Performance Engineering: MHI Twin Turbo Official Release

SPOHN

I'm definitely getting rid of the resonators. The crossover pipe is right there but not in the way. But as mentioned having equal pressure is the question. Is that is a issue I wonder why the crossover is a little more than half way back. I assume it doesn't matter as long as it happens before exit.

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mikey1600

I'm running an Invidia system with Berk HFC, going to keep the cats in just due to regulations here if we get reemed and have to drive over the pits and them check the underbody, massive fines for no cats. (doubt it will happen, haven't even been pulled over for my car yet in 2 years)

I remember looking through all the exhausts years ago, the ones without any crossover seemed to have more rasp and tinnyness to them, pretty sure the x-over pipes and resonators helped with negating this a little.

Alkatraz

Just do what im planning Mickey. Leave the HFC's on to get it engineered and then whack TP's on once you have the paperwork sorted. No cop is going to be able to see your cats on the road or even by sticking his head underneath. As long as it is not obnoxiously loud, you'll be fine.

The HFC's will be blown to pieces within a month or so and probably resemble TP's on the inside anyway lol.

COSMO

Spohn I just had my stillen exhaust 75% redone. Let me explain, with the stillen the exhaust diameter varied in size from joint to joint so what I did was start from the gtm test pipes and go back with a True 2.5 OD piping for each side. I also had the shop weld back in the resonators and the sound is like no other. It sounds like a Porsche but a bit louder and yes the turbo's do in fact spool up a lot faster. I know to most that might sound crazy but I liked the sound of the stillen before going FI and took a gamble on the modification but it paid off. Now I have an exhaust that I know one has and it sounds GREAT. When I go for my tune this Monday at z1 I will snap a few pics...

SPOHN

Yeah I have the same issue. The Greddy is mostly 2.75" but where it's connects to the TP's or in my case it will be the 3" downpipes Greddy hads is reduce down to what I believe is 2.5" to a flange. I assume so it would mount to most setups.

So that being said I have to remove the Greddy reducer ( the hole section of 2.5") then add another reducer from 3" (with 3" flange to mount to the the downpipe) to 2.75" to weld back into the Greddy. So right there is about $80 in parts. Then buying pipe to remove the resonators is another $80 then what ever it may cost to Tig weld all this.

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Alstann

Yeah, IIRC, the crossover is near the middle, but more towards the rear on the Ti-C exhaust.

Exhaust scavenging is a tricky game. It's something you can actually calculate, but at the end of the day, the best way is to just experiment with different setups. All in all, I would keep the crossover. Like another poster said, the cross over also helps reduce unwanted frequencies and raspiness, since the two sides will collide and create a standing wave for that particular resonance frequency.

Another thing to note - since we have a v6, our exhaust pulses are in thirds for each bank, and that makes pressure wave propagation a bastard to figure out, especially when you remove the balancing aspect of a crossover.

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1slow370

Must be nice if the Australian popo's dont have exhaust sniffers in their cars like the ones here in the peoples republic of California

I think it would be neat if someone did a run with straight dumps so we could see what the theoretical best exhaust would do vs some common ones like a fast intentions or gtm3inch that way you could ask yourself if having it too loud would be worth it.

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Alkatraz

Actually the laws are really strict over here, its just a matter of being a little bit clever to get away with things.

The cops here can pull you over and put a 'yellow sticker' (defect notice) on your car simply based on their opinion that something on the car may be illegal. They don't really need emissions testers, if they think its smells, yellow sticker for you! Even if you have all of the paper work to prove that everything is legal, you will still have to take time out of your day and pay $80+ to get the yellow sticker removed. Unfortunately we don't have a bill of rights to protect us over here. Silly laws come in all of the time.

That being said, if you drive like a moron and act rude to the cops, then you will have more troubles than if you don't. The cars that get picked on here are highly modified Australian V8's and anything that looks JDM. Thankfully the 370z and G37 look more European so they don't get picked on.

Anyone have any pictures of a 370z with side pipes??? :P

mikey1600

Haha not a bad idea, although I know the cats will be blown to bits, won't be to bad to just leave them as is

I dunno if you are running a non-standard exhaust yet, but mine is fkn loud at full revs already, don't think I'd want it any louder especially as it's my daily, moreso my girlfriend can hear me coming home from over a km away if I get into it anywhere home lol.

Alkatraz

I'm running the Fast Intentions cat back with 12" resonators and non-resonated HFCs in my 370GT and its reasonably loud but not too bad. Ive had cops behind me at the lights before and they haven't blinked. It would obviously be a different story if I was at wot but with normal cruising its not too loud.

TP's will obviously make it a little louder but the turbos will quieten it down as well, so hopefully it doesnt change too much because i love the sound right now. I went to a skid pan day last weekend and everyone was commenting on how awesome the car sounds. Had the same comments from a bunch of V8's at the drags a month or so ago which is a pretty big compliment. Nothing sounds as good as a big, worked V8 but they liked the sounds of the little V6 enough to come and ask me about it.

SAM@GTM

Update: the BLM technician came in today and got started on setting up the machine.

SPOHN

Party time. Get the beer.

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09nismo498

One step closer!

DEpointfive0

Fixed

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7AT_Z

I knew you would never go FI. Everyone knew you were all talk lol