Cat back for FX45?

A forum for lovers of Infiniti's hot-rod crossover, the FX! In 2014, all FX models will be named Infiniti QX70, in line with Infiniti's new naming structure.
2manycarz
Posts: 2
Joined: Fri Jun 06, 2003 4:05 pm

Cat back for FX45?

Postby 2manycarz » Sat Jun 07, 2003 6:34 pm

Is anyone working on an aftermarket muffler for the FX45. The stock muffler is one in, two out, and looks huge. I would like just a single exhaust, DTM style tip and gains in hp and torque. So far, no joy from B&B or Stillen. I find Borla (if they are working on one) usually too quiet.

Also, any chip work in planning?

Thx, 2


Q45tech
Moderator
Posts: 14365
Joined: Tue Apr 30, 2002 3:19 am
Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl

Postby Q45tech » Sat Jun 07, 2003 6:34 pm

OBD2 engines can't be chipped [simply like older pre 96 units] as there is no single chip [memory look up table for WOT]. Not to say that an expert cannot rewrite and recompile the tens of thousands of lines of code to remove some off the built in factory safety margins on fuel leanness and ignition advance.

By the time 100,000 are sold there should be enough demand to sell a few dozen.

If Borla is too quiet maybe a straight pipe with a TUBA flair would work for you.

Usually hard to improve on factory much [but they do meet noise standards to protect small animals and human hearing] so I'm sure you can find 1-1.5% if loudness is not a factor.

2manycarz
Posts: 2
Joined: Fri Jun 06, 2003 4:05 pm

Good humor, good answers ...more

Postby 2manycarz » Sat Jun 07, 2003 6:34 pm

OBD II mystery and legend continue, although it seems that companies such as Dinan, and the guy in Salt Lake whose name escapes me, but refered to as Shark chips, have done a good job with BMWs with OBD II. You are probably right about the numbers being low for FXs, especially 45s. There will be more available for the 6 cylinders because of the Z and G35 market.

I wish Nismo had something like Dinan that would permit retaining the factory warranty.

On the exhaust question, I am not looking for something obnoxious, just richer, mellower in sound (all very subjective). The problem is that unless it is engineered correctly, one may gain hp. and lose torque (usually too little back-pressure). The modified Lexus I ran in One Lap a few year's ago had the resonators in place, no mufflers, and Borla carbon fiber (mufflets I will call them) tips and had a very sweet sound. Perhaps a company wanting to create a special FX for SEMA would be interested.

2

Q45tech
Moderator
Posts: 14365
Joined: Tue Apr 30, 2002 3:19 am
Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl

Postby Q45tech » Sat Jun 07, 2003 6:34 pm

"one may gain hp. and lose torque (usually too little back-pressure). "

OLD WIVES TALE!!!!!!!!! created by those that we unhappy with expected gains ........................some what true on old syle [60-70's American engines with a wide exhaust overlap but emissions ruled this out --- illegal by 1990.Since HP is nothing but torque multiplied by RPM/5252.

There is NO back pressure at low rpms to begin with, measure it [after the last cats] and see. In fact most oem exhaust are designed to have only a 1% restriction at the torque peak rpm ..........rising progressively to less than 3% at what ever rpm the imaginary HP peak occurs.

Q45tech
Moderator
Posts: 14365
Joined: Tue Apr 30, 2002 3:19 am
Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl

Postby Q45tech » Sat Jun 07, 2003 6:34 pm

THIS forum [unlike the others] expects you to present your case with real engineering data not some jepped up Joe Smoe dyno runs.I consider Stillen or any person selling custom exhausts system to sometimes be less than 100% reliable in presenting 100% accurate data.

Very few manufactures of exhaust have accurate repeatable REAL dynos and use outside chassis dyno data to try and persuade.

And the time to change exhaust systems back and forth dozens of times [on the same day] make it difficult to keep the chassis dyno and air and fluid temperatures constant and the atmospheric correction tables and adjustments are the sources of many such portrayed GAINS.

Q45tech
Moderator
Posts: 14365
Joined: Tue Apr 30, 2002 3:19 am
Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl

Postby Q45tech » Sat Jun 07, 2003 6:34 pm

Didn't say you couldn't redesign OBD2 just that it takes more skills, time, and therefore needs a wider base of customers to pay the cost of the effort..........or cost more than $600 for custom work.

Every bit of software from every car manufacturer has some built in safety factors............Nissan designed for a 300k possible engine life if you change the oil often [every 90 days] and don't mess with the air filtration system.......at least they did so prior to the current engine designs.......where they seemed to squeeze a little more out ...........when you see more than 75 lb/ft per normally aspirated liter you know that less than 5-10% remains for a street engine

NASCAR uses a 600 mile life, for the right amount of money you can chose any failure point mileage you chose.

In theory and under proper conditions [fuel quality] it is easy to gain more than 20% from most OBD2 engines if you will accept a much shorter life and increase emissions.

Most of the people who buy BMW and pay Dinan for extra power are not concerned with 250k life.

The older Q got 10% more torque from 2700 -5,000 rpms via a simple reprogram and still has a 10% safety factor since the cooling system couldn't control the EXTRA heat [rad size and coolant amount 10 quarts] and gasoline quality wouldn't allow more than 28 degrees peak power advance...........as modified at WOT the mixture was still too rich to cool the chambers down diminishing power.


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