So far. For Q70's. I'm seeing Stillen & Ark. I Like the sound of Motordyne the best. But not seeing Motordyne listed for Q70's yet. But curious if you all might offer opinions on which catback usually gives best results. After researching cat backs. Looks like you lose low end torque & HP but gain it back in mid range & top end. Never mind about cutting things off the stock system. That trick seems to give great sound but make the car lose it's Getty up & go. So for Arguments sake. Without a care in the world for sound. Which catback system delivers best RWHP? Cause at this point. I'm leaning towards an ARK.

I doubt you'll gain any significant amount of RWHP with any of these catbacks. Especially for a V6 and especially for how much they cost.

You can't go wrong with Stillen or ARK. I myself have Stillen and think it sounds f&ckin damn good and performs extremely well. You're not gonna gain anything worthwhile without getting the Uprev tune on these cars. In fact you're absolutely correct about losing power because it happened to me when I first installed it. I just got my car retuned last night and made 312whp on my M37 V6. My baseline was 282 whp before Uprev. I'm running HPS tubes, K & N drop ins with the Stillen cat back. 30 whp gain is pretty damn good for only those mods. To make the exhaust worthwhile for performance u need to have the car tuned. Otherwise, you'll sound good but that's about it in my opinion.

The easy answer is: none. A catback system does not change much other than sound. The factory exhaust from the engine to the cats is still just as restrictive (if at all). Not sure about the prices of the brands you are considering, but Infiniti's sport muffler system sounds brilliant and is about $650 I believe. Should be no trouble to pick up at the dealer and have any shop install. I love my Tanabe Medalion catback but I don'r believe they make one for the Q70.

Here's my question to you all. I'm under the impression that the stock exhaust system is under 2 inches in diameter. Granted. To big a pipe will kill HP too. But with the right diameter. Say... 2, 1/2 inch pipe. Wouldn't that improve rwhp if tuned properly? And I hear you about the cats being restrictive too. So ordered some HFC's to help with that restriction too. But ARK is having fitment issues I think around the Ypipe area/Tranny. And Stillen is an almost catback. which means no Ypipe.

My though is that for any worthwhile increase in performance, the entire exhaust system must be less restrictive (without over-doing it) from the engine to tail pipe. Changing only one small portion along it's path will do relatively nothing. Depending on the budget you have set for this mod, I suggest an up-rev tune, HFCs, and a minimum of cat-back or axle back muffler system with a good, deep throaty sound closer to a bentley then a magnaflow. That will provide a nice level of sound without detracting from the "luxury performance" character of our cars.
I love my Tanabe Medallion cat backs. I wasn't after more HP. I just wanted a throaty but non-mustang sound and Tanabe came closest without going past the loudness level I was looking for. A deep throaty exhaust that invades the cabin without taking over the cabin.

Consider the whole system and what you want the finished product to be. Keep in mind that changing any one part will affect the sound inside and outside the car. The more parts you change, the more dramatic (and louder) the effect. You have to find the middle ground that is best for you between the two extremes: Obnoxiously loud ricer <<<< throaty with performance sound >>>>> Stock low level sound

Check you tube for sound clips of the brand you are after eg: "ARK Inifniti" "BERK Infiniti" etc. below are some examples. These are with G models, but they have nearly the same engines as the M35, M37, and Q70 3.7 models. Our cars are quieter inside than any of the G models, so consider your car will have a slightly less interior presence with exhaust changes but it gives you a good comparison.


Tanabe + HFCs only:
https://youtu.be/ZxfkHIx3MIM

Tanabe + HFCs + Y-pipe:
https://youtu.be/N8FmYwldhbE

Tanabe only - inside sound level:
https://youtu.be/h7mIP3lCFqA

Tanabe + Y-pipe acceleration form inside:
https://youtu.be/yZZkFCAUGTo

I went with this cutback

http://topspeedauto.com/infiniti-m37-se ... evel-tips/

More than impressed. I don't have a HFC on it yet. Something I did notice, which another member stated. I have to go get it tuned. When I am in Sports mode, and hit it, then come off of it. It holds the gear longer than usual..

I also have a CAI on it.

It is a noticeable difference.

Hey Larz. Are you a tanabe salesman? Damn. LOL. Got to admit. Tanabe sounds awesome.

Darthswan. Affordable. But not a fan of the sound. Little blah for me. But thank you much for the suggestion.

in regards to exhaust system. Agreed. I have HFC's. Now it's time for a nice smooth sounding 2.5 inch catback system. Hopefully with enough scavenging effect to help improve overall HP and not hurt it. Along with a nice exhaust note I can tolerate.

Which Ypipe fits our Q70? Cause it's even been suggested to buy a G37 sedan exhaust. Take it to a muffler shop and have them do the tweaks to have it fit right. Things I've noticed. Q70 is approx. 194 inches long. G37 sedan approx 187-188 inches long. With the q50 at approx 189 inches long. So if anything. I should order a Q50 catback exhaust and tweak that. But... The Ypipe still worries me. So... Any suggestions on which system is best to tweak? Or get a Ypipe first?

A member on here lost performance changing out the y pipe due to that scavenging effect so I would think twice about doing it. There was nice write up about it if you search the forum. Also,the Stillen near cat back was R&D'd properly and they decided to leave the stock y pipe for reason. If u plan on doing it though I've heard the motordyne xyz from a 370z would work on our M/Q70's.

Awesome. Thank you DKASM37. I'll research it further. I hear you on the Ypipe and scavenging. By no means am I looking to lose power. But on the contrary to maintain or hopefully surpass.

No problem. U might also wanna look into the HPS Intake tubes for the G37 as they're not ribbed on the bends like the stock intakes are. Which theoretically will have a smoother air flow and not cause turbulence like the ribbed stock ones, thus creating more power. Those will fit our cars with a slight modification (pair of 90' elbows). With the removal of the stock resonator boxes attached to the stock intakes it gives the HPS Intake a slightly deeper sound. HPS claims it will give gains of up to 6.77 whp. I gained 6whp from my last tune after installing them this past week. That gain could also be attributed to having a clogged cat replaced by the dealer and retuning with the new one. Maybe a combination of both for all I know. Just thought I'd let u know before u start thinking of buying a new Intake to complement your exhaust mod. BTW my tuner said it's best to leave the stock Intake boxes and just run them with K&N drop ins for performance. I had Takeda SRI's n removed them earlier this year. Just an FYI since u might start getting the modding bug after the exhaust. Lol.

DKASM37 wrote:No problem. U might also wanna look into the HPS Intake tubes for the G37 as they're not ribbed on the bends like the stock intakes are. Which theoretically will have a smoother air flow and not cause turbulence like the ribbed stock ones, thus creating more power. Those will fit our cars with a slight modification (pair of 90' elbows). With the removal of the stock resonator boxes attached to the stock intakes it gives the HPS Intake a slightly deeper sound. HPS claims it will give gains of up to 6.77 whp. I gained 6whp from my last tune after installing them this past week. That gain could also be attributed to having a clogged cat replaced by the dealer and retuning with the new one. Maybe a combination of both for all I know. Just thought I'd let u know before u start thinking of buying a new Intake to complement your exhaust mod. BTW my tuner said it's best to leave the stock Intake boxes and just run them with K&N drop ins for performance. I had Takeda SRI's n removed them earlier this year. Just an FYI since u might start getting the modding bug after the exhaust. Lol.

I do have a question for those who are running the HPS intake hoses...I know that the ribbed part of the OEM hose allows you to flex the motor half of the stock intake box away from the other half, to allow easier removal of the air filter..with the HPS intake hoses, how hard is it to change the air filters since the hoses are tied in hard?

That didn't even cross my mind while installing them but nevertheless a valid concern. I'll post back on that later today n let u know.

DKASM37 wrote:That didn't even cross my mind while installing them but nevertheless a valid concern. I'll post back on that later today n let u know.

Cool thanks...just looking at a picture of the installation, it looks like you'll have to remove the engine cover and hose. No big deal, just curious. It's not like you're changing the filter all the time anyway.

Just checked, no issues removing the filters. Same as having stock Intake tubes. It's a cool lil mod, I found it on Amazon for $49 a couple of weeks ago so I snatched it up. Now they're going for like $120 for the G37 version.

DKASM37, before I get the mod bug? LOL!!! Let's see. Ordered HFC's. Motordyne xyz Ypipe w/ resonator. That'll be my exhaust mods for the moment. Probably go with Stillen after thanksgiving. Have Injen CAI's for G37 sedan. So I know modding will be needed with those. Z1 Motorsports intake manifold, plenum & 70mm TB's. That's it for the moment. Just trying to extract every last N/A HP I can get from her. And if I didn't live in the people's republic of Kalifornia. I would've opted for LTH's too. And I will get UPRev once everything is installed.

PostalsQ wrote:DKASM37, before I get the mod bug? LOL!!! Let's see. Ordered HFC's. Motordyne xyz Ypipe w/ resonator. That'll be my exhaust mods for the moment. Probably go with Stillen after thanksgiving. Have Injen CAI's for G37 sedan. So I know modding will be needed with those. Z1 Motorsports intake manifold, plenum & 70mm TB's. That's it for the moment. Just trying to extract every last N/A HP I can get from her. And if I didn't live in the people's republic of Kalifornia. I would've opted for LTH's too. And I will get UPRev once everything is installed.

Sounds like ur going all out. U might as well get that Stillen supercharger or a Turbo while ur at it! Lol. One thing to take into account when getting Uprev'd, make sure u go to someone reputable n who has a lot of experience using the software. The tuner is the one who makes all the difference...

Copy that. Well. Neighbor races his Honda Civic in 1/4 mile. 9 second car. Crazy set up. And no longer street able. He'll help me with install. Then his friend. Who I've never met does a lot of tuning for guys in the area. So his reputation with me is in question. But his reputation with my neighbor is not. But I will say this. Some guys know how to tune race cars. But don't know how to properly tune street cars. And vice a versa. First hand experience in that with my prior American muscle cars. Turbo would be nice. But I'm not into monitoring her all the time for conditions. Just N/A HP is all I'm after. So porting and polishing heads with bigger valves. LOL.

No doubt, PostalsQ. Let us know how u make out on ur build. Interested to see how different that Motordyne xyz pipe performs over the stock y pipe. I came close to pulling the trigger on one of those earlier this year.

Well. Money being the way it is. Not going to Dyno before or after. Going to hopefully tune with the guy next to me. I guess like data logging in person. I know UPrev should be able to read rich & lean conditions. And there's a certain perimeter your suppose to be in. Then adjust all RPMs for that. So I would be able to tell you if the ole butt Dyno feels any difference. But you know how reliable the ole butt Dyno is. LOL. But there's a great Z mechanic and tuner about an hour away from me. Once I install the stillen I can have him retune it on the Dyno. But that may be a couple months from now. I figure save money & get stillen exhaust after thanksgiving.

I drove an hour and a half away to get my M tuned after I made the mistake of going to a local tuner first who tuned mostly Subaru's but said he did Uprev too. What a F'N waste of $$$. Long story short, take the hour long trip n get it done right the first time. When our cars (V6's) are plugged into the Uprev software they read as a 370z. They tune just like them so if this guy does good tuning on 370z's, u should be in good hands. Data logging is cool but nothing beats getting it tuned on the dyno in real time. Save ur self the headache and MONEY!!!

All valid points sir. I may rethink the friend tuning and take it to the reputable Dyno tuning guy