Just to let everyone know. I built my own custom exhaust and an intake midpipe (similar to the 350z tube, but metal). I used a 22" Magnaflow 10436 resonator and a 14830 dual tip magnaflow muffler with 2.5" crush bent pipe. I made sure there was only 30 degree max bends and all joints were perfectly welded/joined.

Ok, results, quarter mile stock at 1200 ft altitude NHRA track (firebird) 2.3 60' times yielded a 14.4 at 97 mph repeatedly 100 degrees

with the mods, 2.4 60' time yielded a 14.6 at 98 mph repeatedly at 60 degrees.

so little to no gain in hp, possibly a half mph in trap speed
lost torque on the low end by my 1/8 mile time worsened from 9.4 to 9.55

again these are repeated tests taking into account temperature difference. The 60' times are poor as I wanted repeatable "street style" launches. I have run better 60' but can't seem to break 14.4 due to operator error.

I spoke to technosquare and they are finding the same problem with the 6MT. With the stock muffler, they find no gain with their adjustments. The extra fuel don't show until an aftermarket muffler is place on the car (this is a guess, they are testing it currently.) So increase catback air flow does not help much until you have better a/f programs.

Better Life thru Chemistry
Black on Black 03.5 Sedan 6MT - Custom Catback, Custom Intake Tube, HyperGround Kit

 

Looks like the G is so well tuned from OEM that the only changes should keep to better flow thru pre-muffler, Intake, Crowford but leave the rear muffler alone. Unless you want to go with full blown mods.

~ GT-R the Ultimate Driving Machine ~
- 2004 G35 Ivory Pearl/Black Leather
- Auto/Nav/Premium/Sports/Aero
- 6 wire grounding kit

 

You said that you replaced your stock muffler with a magnaflow muffler and your quarter times were slower, then you say that technosquare says that they find no gain with their adjustments with a stock exhaust. Which is better? What are a/f programs?

Are you encouraging people to get exhausts or are you saying that it is not worth it?

Sincere questions. Thanks for any response 3point5SE_Auto.

 

Man I gotta get my setup dyno'd. I got significant gains from my custom exhaust. But in fairness it's more involved than yours. I fully believe Stillens claim that their system will net 22hp at the flywheel based on my own experience.

Also, lets not forget that part of the power gains enjoyed by the coupe, come from the fact that it gets a performace muffler vs the sedans variable capacity setup.

"i, for one, am not a fan of glory hounds."

Dang straight, it's all about the glory of helping. Who have you helped today?

 

i recommend you get a custom exhaust IF you plan on doing other mods, such as headers, plenum, ECU etc. Otherwise stick with the stock exhaust.

From my experience with other cars, the ECU MUST be ready to accept and take advantage of other mods. Quite frankly the Nissan OBDII ECU is NOT good for this.

I knew going in that an exhaust requres infinite tuning to get it just right. I have no problem getting some more pipe, removing some bends and trying again. This is fun for me. Now that I have invested in a resonator and muffler, the rest of the costs are 5 and 10 dollars at a time so I can make MANY variations before I get to the cost of a Magnaflow.

Better Life thru Chemistry
Black on Black 03.5 Sedan 6MT - Custom Catback, Custom Intake Tube, HyperGround Kit

 

You should really look into a mandrel bent exhaust, rather than a crush bent exhaust, that could be why your exhaust isn't gaining much (if any) power over stock. Mandrel bent exhausts provide a smoother flowing exhaust and don't cause any restriction through the system. Even if it doesn't look too crimped up, it does make a difference. Your car gained the mph probably from the cooler/ more dense air, rather than the exhaust. That is if your 60ft times were the same between the two runs.
Your magnaflow resonator is not restrictive (I actually have the same one on the midpipe on my G20 heh) so that shouldn't be an issue at all. FWIW, mandrel bends also create a smoother sounding exhaust than crush bends do for some reason. I got some custom work done at Scottsdale Muffler here in Phoenix (I'm assuming you live here, since you mentioned Firebird) and they did some nice custom mandrel bends for me.
The best way I've heard it expressed is "the best exhaust setup is one that reduces backpressure while keeping exhaust velocity as high as possible"

Also, the Nissan ECU's are very good at compensating for changing factors. They have the ability to compensate for different intake/exhaust efficiency, slight changes in injector size, air temp, density, etc.. They're not tuned right on the edge by any means, but they also don't want people blowing up their motors either. JWT offers some kick *** remapped ECU's, but haven't released anything for the new line of Nissan's yet. I think they're expecting to have all the tuning done in the first part of '04.

Justin McClanahan
Heavily Modified 95 Infiniti G20
www.InfinitiPartsUSA.com

 

Yup, Justin P10 is right you need mandrel bent pipes...if there is no place that have a mandrel pipe bender....considering the machine itself cost $50k......then you can go to JC whitney and order a specific bend...they can get just about any angle....and in any size...from 180 degrees to a U joint. Try cutting where you had the crush bends and reweld those bends with mandrel bent pipes....You also don't want to get to big of a pipe cuz you will lose backpressure....lose to much backpressure = you lose torque.

Also since you used an intake....you will lose torque.....until you free up your exhaust system......with those crush bent pipes you might of restricted your exhaust system even more than it was originally.....if the pipe was 2 1/2in in diameter in the inner side, those bends could of made the inner diameter of the pipe as small as 1 1/2....where as if you had 2 1/2in pipe that was mandrel bent then you would still keep the 2 1/2in diameter thru the bend.

Shift_DEZ' NUTS
www.midnightimpulse.com

 

I have had good luck with crush bent as long as I keep an eye on the individual bends. I still am playing around a little and I enjoy this. I am not using an "intake" just a midpipe with the stock airbox.

thank you for the advice. I will consider it as I consider the next revision.

Better Life thru Chemistry
Black on Black 03.5 Sedan 6MT - Custom Catback, Custom Intake Tube, HyperGround Kit