Muffler replacement question, 2003 M45

[M45]

I am planning to replace the 3 OEM mufflers (rear and 2 side-by-side in front of rear) with MagnaFlow mufflers, but have a couple of question:

1. Is there a negative performance impact of changing the three mufflers with a higher flow product? Specifically, does the ECU get impacted by this in any way? The oxygen sensors are way up front, and I am not planning to change anything from cat to front.

2. There is a valve that can be found behind the left side-by-side muffler and in front of the rear muffler. I guess, at full throttle, this valve can close to redirect the flow through the right muffler to the rear muffler, to increase back pressure. Is that valve electronically or mechanically triggered? If I were to replace the three mufflers (the valve, of course stays), will there be any change in valve behavior, i.e. when or if it gets triggered?

Has anyone done an aftermarket exhaust on an M45?

Thanks

M45, Melbourne, FL

[elwesso]

1. not aynthing I can think of... As long as theres some back pressure (IE you still have some back pressure for EGR and o2 sensors) youll be fine..... You have emissions so you cant get rid of the cats.....

2. Not sure what this valve does, but I dont know if Id want to keep it.....

[M45]

Thanks for the reply.

On 2) I'd love to lose that valve, but I am wondering if it comes to use during a full throttle take-off, compared to kick-down while the vehicle is moving. I don't want to lose any performance by taking it off... thoughts?

Should I post this question in another section, as well?

[elwesso]

I really dont konw what to tell you... If youd like, I can have moderator move this into INFINITI general, as to not waste another post.....

What I would do is, unplug the valve sometime and drive for a little bit (around the block) and see if you get any check engine lights or what. I wonder if the owners manual would have any info on this. Unless im getting a bad mental image on where its located, i dont think it needs ot be there.....

I doubt you will lose any low end power by doing this mod, thus im not sure about this valve.....

[M45]

Went to Infiniti of Melbourne, FL, today, and found out a couple of more things.

The valve is a restrictor which is closed by default and opens the left path behind the valve of the exhaust under the following conditions:- accelerator paddle position below half in no load: valve opens above 4830 rpm- accelerator paddle position above half of load: valve opens above 475 rpm

The tech I talked to said that he believes that the backpressure is taken care off by the cat's, but was not sure (common message here). Therefore, I plan to retain the piping after the two middle mufflers, which includes the valve, replace all three mufflers with MagnaFlow's, and see what I get. Should work and look pretty clean. MagnaFlow has some very high quality tips as well, and I picked two to look like stock/similar to the dual ovals that are stock, stainless steel. Diameter on the new will be 3 in, while the old one's are 2.5, so I think it will look pretty good.

BTW, this exhaust is identical to the Q45, I was told. Maybe you want to add this to the knowledgebase...

[Q451990]

BTW, this exhaust is identical to the Q45, I was told. Maybe you want to add this to the knowledgebase...

If that's the case you might want to download one of the service manuals here for the Q45 to read up on the system. Not sure how much is there but it's worth a try...

http://www.iposer.com/TBO/Niss...0FSMs/

Heath

[M45]

Thanks for the links. I downloaded the 2003 Q45 manual and looked at the engineering drawings, and the exhaust and suspension components look, interestingly, identical, from what I can tell. The RPM range where the exhaust valve gets triggered is different though; the Q doesn't open it under full throttle until around 2800 rpm. Below half of accelerator position it looks the same.

So the question of the day remains as this: what happens if that valve is not there? The ECU will trigger the actuator unit, which will attempt to open/close the valve through a cable if the conditions are met. No codes should be thrown, as the sytem is intact, just the cable to the valve and the valve itself would be missing.

My only unknown with the approach to eliminte the valve is if backpressure is needed to a) support the emissions system for some reason and/or b) to keep the engine running smoothly (or maintain the torque) at below half of accelerator pedal position, at low acceleration. Where are the engineers when you needs one? :-)

[maxnix]

Where are the engineers when you needs one? :-)

In Japan! The valve is there to reduce back pressure at high rpm. Don't monkey with it unless you know more than Nissan and have the dynomometer research to prove it.

[marksport]

So any updates on how the exhaust worked out? And any info on the piping?

[maxnix]

I downloaded the 2003 Q45 manual and looked at the engineering drawings, and the exhaust and suspension components look, interestingly, identical, from what I can tell.

Maybe not on topic, but the F50 front McPherson strut suspension is quite different from the Y50 dual A arm type.

[marksport]

Bump......I'm looking to replace the rear muffler on my F50 Q45. Any more info on the exhaust setup?

[elwesso]

Ive been doing some reading, and those butterfly valves are used to meet the regulations for drive by noise (so they are real quiet at low RPM where it doesnt really matter if you have a super free flowing exhaust) and then they open up, like the above was stated, at 4850RPM.. Thats way too high, IMHO. Id rip that crap out of there and pipe up something nice.. maybe the first thing id try is to rig the valve to open all the time...

[maxnix]

Ive been doing some reading, and those butterfly valves are used to meet the regulations for drive by noise (so they are real quiet at low RPM where it doesnt really matter if you have a super free flowing exhaust) and then they open up, like the above was stated, at 4850RPM.. Thats way too high, IMHO. Id rip that crap out of there and pipe up something nice.. maybe the first thing id try is to rig the valve to open all the time...

Of course, this is all WRONG! The valve has to do with regulating the back pressure at specific RPM for optimal performance.
Modified by maxnix at 9:25 PM 3/12/2006

[M45]

Correct. I am not touching the valve, as it provides backpressure at every day driving and opens it up under performance. My research shows that the exhaust on the 03M45 is already high-flow, so I decided to not modify it. I don't want to take the risk of losing torque just to gain noise... I like the stealth effect... :-)

BTW, on the 2003 M45 the valve activates at a certain throttle position (I think > 3/4) above 875rpm, according to spec and ECU documentation. That is different from the same year Q, which open the valve only > 2850rpm. So for the M it's pedal to the metal at idle and the valve goes open, and you got all the pipes flowing. Works for me. No complaints here...

[NISTECH]

This valve used to be internal to the muffler. It is now external and controlled by the ECM. This valve is there for noise reduction. It reduces the amount of noise from the exhuast. Back pressure will play a part ,but a very small part. These things dont need back pressure for egr any more as they either use an electricaly controled EGR or no EGR at all. Having the exhuast slightly restricted at Idle reduces idle "rumble" and "popping" It is mearly a comfort part much like the electronicly controled motor mounts.

[Nismo_Freak]

Just to dull the Infiniti love fest going on in here I thought I'd throw this in.

1. You will not lose torque by replacing mufflers with higher flowing units. You stand to only gain torque by reducing backpressure.

2. Backpressure is bad in any situation for performance and engine operation (with the exception of EGR functionality in older cars -- See Nistechs previous post).

3. Your car would sound awesome with Magnaflow mufflers.

4. Did I mention your car would sound awesome with Magnaflow mufflers? Did I also mention you would get better gas milage from the reduced weight, and the reduced backpressure.

Then again you can ask Weasel and he'd tell you my M45 would be stripped to the bare chassis, riding on suspension that resembles a covered wagon, and would rival 747's in terms of outputted decibles

[maxnix]

Many untuned exhaust systems, some by "reputable" aftermarket manufacturers, have been demonstrated to actually lessen engine performance, even though they were a lot less restrictive than stock (and oh so much louder!).

As far as "pops" at idle being controlled by an external valve, I am more than sceptical. The fact seems to be that engines equipped with these valved exhaust systems always had more high end horsepower (increased torque) at the same revolution than non-valved exhaust sytems that preceded them. If back pressure at low rpm was not a concern, why any valve at all if it could not increase performance over a moreopen system, i.e. - when the valve is shunted to the most free flowing configuration?

[Nismo_Freak]

Many untuned exhaust systems, some by "reputable" aftermarket manufacturers, have been demonstrated to actually lessen engine performance, even though they were a lot less restrictive than stock (and oh so much louder!)

Within Nissans I have yet to see any case of this.

There have only been very few occassions where I have found this to have merit. Mainly they are within highly tuned factory cars like the Integra Type-R, Ferrari's, and other cars where alot of factory emphasis was on exhaust performance and not on noise restriction as these cars are built for performance enthusiasts. Say what you want about the M series, it's market is not the same as that of the Type-R.

Often times I feel the Infiniti crowd tends to think like the Porsche group. Basically there is alot of talk and alot of overanalyzing something that is seemingly quaint and easily solved.

Nissan engineers are hindered in exhaust design by a number of things:

1. Sound2. Cost3. Longevity4. Factors of Production Other than Cost

I can guarantee you an aftermarket exhaust system that is properly designed will net gains.

Oh and any exhaust that produces backpressure will always produce less power than one that one that has no backpressure. The classic confusion is when people assume backpressure and velocity are hand in hand when they are not.

Maintaining the factory piping diameter will provide ample velocity similar to stock, and reducing the flow restriction through the mufflers will aid in reducing backpressure. From a flow standpoint there is zero factorization that would lead me to believe that such a mod would not increase the engine's efficiency.

Essentially the motor operates on a mass flow basis in relation to three forms of efficiency, mechanical, volumetric, and thermal.

[NISTECH]

The FX when it first came out was getting overwhelming amounts of complaints of exhuast noise both at idle and at cruise speeds. People thought there should be more sound deadening mating in the car. Thats expensive in production terms. Valving the exhuast to cut back on sound is a much more cost effective means of doing that. Hence the controlled valve was added to the M as it is a high class vehicle.

The valve is simply to reduce noise or complaints. How ever you want to look at it.

[maxnix]

Within Nissans I have yet to see any case of this.

Need to check out some of the 350Z tuner cars. Stillen comes to mind. Cars producing more horsepower some how being the same or slower on acceleration.

There have only been very few occassions where I have found this to have merit. Mainly they are within highly tuned factory cars like the Integra Type-R, Ferrari's, and other cars where alot of factory emphasis was on exhaust performance and not on noise restriction as these cars are built for performance enthusiasts. Say what you want about the M series, it's market is not the same as that of the Type-R.

Markets? Say what? Not sure this is even relevant nor is it germane.

Often times I feel the Infiniti crowd tends to think like the Porsche group. Basically there is alot of talk and alot of overanalyzing something that is seemingly quaint and easily solved.

Yeah, they produce some of the slowest 3L - 3.8L flat sixes I have seen over the last fifteen years. Those broken down turbos littering the highways are expecially annoying!

Maybe we should all buy Toyotas! They don't seem to sweat the engine details quite so much (the new 3.5L V6 excepted). But the best would be Chevy, large pushrod V8, 2 valve heads, iffy build quality. Don't sweat the details, just throw more cubic inches in it! Or heck, that exemplary piece of finesse engineering, the Viper? Got cubes?

Nissan engineers are hindered in exhaust design by a number of things:

1. Sound2. Cost3. Longevity4. Factors of Production Other than Cost

1.) It is a proven fact that louder exhausts on the VH45DE with less back pressure produce an insignificant increase in horsepower over stock system by Q45tech.

2.) That's why Nissan uses a stainless steel muffler on the VH45DE?

3.) Ditto. Stock systems on VH45DE are known to last 150K+ when not in the rust belt.

4.) Time? That's part of cost. Materials? Ditto. Durability? See 2.) and 3.) above.

I can guarantee you an aftermarket exhaust system that is properly designed will net gains.

Yes, but if it is less than 10%, it is not noticeable. If the OEM system is designed well, such as the VH45DE, it will be lucky to get a 5% improvement.

Oh and any exhaust that produces backpressure will always produce less power than one that one that has no backpressure. The classic confusion is when people assume backpressure and velocity are hand in hand when they are not.

Depends on the rpm range and the factory ECM/valvetrain/cylinder MEP tuning. Again begs the question on why the VQ35DE with the valve in the system had more HP than the system without? Don't think Nissan was lying. Don't think they threw it in there because they had extra units lying around and couldn't figure how else to move them out the door.

Maintaining the factory piping diameter will provide ample velocity similar to stock, and reducing the flow restriction through the mufflers will aid in reducing backpressure. From a flow standpoint there is zero factorization that would lead me to believe that such a mod would not increase the engine's efficiency.

Essentially the motor operates on a mass flow basis in relation to three forms of efficiency, mechanical, volumetric, and thermal.

But if there is little restriction to start with, there are little gains to be had. If the main gain is noise and low frequency harmonics attentuation (see Q45tech) and power gain is insignificant, why bother?

One can make a chassis stronger by gluing strategically placed toothpicks to it, but is it worth it?

[elwesso]

I feel like we're beating a dead horse... Let me point out a couple of things...

1. The factory exhaust is HEAVY on the Q... Im talking at LEAST 100lbs... That rear can alone has to weigh about 40lbs.... So if you dont do it for the HP, do it for the weight reduction...

2. Lets take a look at the HP gains that Rob posted since hes the only person who is naturally aspirtated that has posted dyno numbers. His average HP before any mods were done was 226RWHP..... AFTER mods was 286.7 HP.... Total gain of 60HP... You cant think that ALL the HP gains were due to the headers alone.....!!!

Depends on the rpm range and the factory ECM/valvetrain/cylinder MEP tuning. Again begs the question on why the VQ35DE with the valve in the system had more HP than the system without? Don't think Nissan was lying. Don't think they threw it in there because they had extra units lying around and couldn't figure how else to move them out the door.

What are you referring to?

Basically in that long post that you made, you have proven one thing.. That the G50 Q doesnt have much gains in exhaust.. I agree with that... Still, has nothing to do with the valve thing (which its function is already known).. I think the fatal flaw is that you cant assume that all exhaust systems (even on the newer infinitis [M45, Q45, G35, etc]) were as well designed as the one on the old Q... So while an aftermarket system may provide only 5HP or so on the old Q, it can easily make 15HP on another car, even within the brand!

Still has nothing to do with the M.. People will whine if the exhaust isnt quiet enough...

m45,I still say, just weld in some nice dynomax, magnaflows, borla, or whatever you like mufflers into the factory tubing and youll have a (most importantly) nice sounding car and you WILL have some HP gains...

[Nismo_Freak]

Need to check out some of the 350Z tuner cars. Stillen comes to mind. Cars producing more horsepower some how being the same or slower on acceleration.

You can't produce more overall horsepower and reduce acceleration unless traction is a limiting factor.

Yeah, they produce some of the slowest 3L - 3.8L flat sixes I have seen over the last fifteen years. Those broken down turbos littering the highways are expecially annoying!

I don't think any Q45 owner is in a position to make this comment with any real weight behind it considering you'd have trouble outrunning even a 60's 911 on the track.

Perhaps you should think further into the whole commentary you just made, considering N/a 911's could decimate anything Nissan built up to and including the GTR on a road course. To me it's the greater measure of a car than straight line acceleration.

I also find it funny you debate the legitimacy of part of my arguement then in the next paragraph decide to attempt a mockery of it.

Maybe we should all buy Toyotas! They don't seem to sweat the engine details quite so much (the new 3.5L V6 excepted). But the best would be Chevy, large pushrod V8, 2 valve heads, iffy build quality. Don't sweat the details, just throw more cubic inches in it! Or heck, that exemplary piece of finesse engineering, the Viper? Got cubes?

More lame mockery.

1.) It is a proven fact that louder exhausts on the VH45DE with less back pressure produce an insignificant increase in horsepower over stock system by Q45tech.

Unless you are going to provide evidence that directly counter-argues my opinion then you are going no where with this. The meer fact that you mention "insignificant" eludes to the fact that the car did in fact gain power.

Perhaps you should read and understand my statements.

Yes, but if it is less than 10%, it is not noticeable. If the OEM system is designed well, such as the VH45DE, it will be lucky to get a 5% improvement.

5% is still 5%

Depends on the rpm range and the factory ECM/valvetrain/cylinder MEP tuning. Again begs the question on why the VQ35DE with the valve in the system had more HP than the system without? Don't think Nissan was lying. Don't think they threw it in there because they had extra units lying around and couldn't figure how else to move them out the door.

You can't arbitrarily compare systems like that. You have no idea if the timing curves or fuel curves were altered or if the cam timing was phased differently. Without sufficient knowledge making an assumption that additional power is the result of a simplistic device is arbitrary at best.

But if there is little restriction to start with, there are little gains to be had. If the main gain is noise and low frequency harmonics attentuation (see Q45tech) and power gain is insignificant, why bother?

Because some people like it, and some of us want that 5%

If you want to sit and quantify everything then you should never modify a car, as it's not an ideal investment.

[elwesso]

If you want to sit and quantify everything then you should never modify a car, as it's not an ideal investment.

This is the bottom line! and this is why he has 3 stock Q45s and why others have faster Q45s that look and sound better!

[Nismo_Freak]

This is the bottom line! and this is why he has 3 stock Q45s and why others have faster Q45s that look and sound better!

Hell my S13 weighs half what his car does hahah.

Time to go put the motor back in it hahah.

<--- Cheater.

[jamestgk]

many pros and cons here. but, the bottom line is to get the proper setup you need to dyno it with different setups. the bends, the pipe size and the type of mufflers will all make a difference. so if you got the time and money or a friend at the muffler house go for it.

next remember your in a M45 not a monte carlo, you represent the VIP of japan (cedric/gloria). you sould be seen coming and going not heard.

the valve is for emission purposes just like the 4 cats. all cars are by california emission and noise requirements. so, the valve is normally closed. depending on your mileage and ow much full throttle you do. youll notice the valve side piping is not as dark due to less heat from exhaust. you can remove it or tie it open with mechanics wire.

if your still in warranty tie it open but, if you change the exhaust then you know what happen to the warranty. the dealer will probably claim the change screwed up engine function also.

whatever you do make sure you relearn the transmission, shift pattern will change but, for the good.

[Jeff Williams]

My 2000 I30t Sport has the valve internal to the muffler. It basically give the owner (me) the advantage of a nice quiet muffler under normal 1/2 throttle operation, and a performance muffler under aggressive driving situations.

Bottom line, if you want a louder, more aggressive muffler all the time, replace the OEM with Magnaflow. No matter what we say. I have been contemplating replacing my Q's mufflers with Magnaflow, installing an X-pipe, and re-locating the spare tire well, so I can have symetric exhaust tips on each side of the tag. OK, go ahead and flame me now

[maxnix]

If you want to sit and quantify everything then you should never modify a car, as it's not an ideal investment.

Then you must be standing in a boot full of urine because you are pissing upwind.

If it is not quantifiable, then it doesn't matter. You are just putting lipstick on a pig and hoping it actually runs faster.

[maxnix]

This is the bottom line! and this is why he has 3 stock Q45s and why others have faster Q45s that look and sound better!

Depends on how much you like kissing pigs with lipstick! Just be careful to note on which orifice it has been applied.

I'll put any of mine up against any of yours (well, I guess the only one that is still running) for mechanical condition or problem free performance. I know I am not smarter than the Nissan engineers. I know I do not have their resources, and few others outside of Nissan or another OEM can even come close.

For those that know better, go for it. We need more posts on troubled Infiniti's like Wes's in the Infiniti Mechanic Forum.

[Jesda]

PMQ also thinks backpressure can be a good thing.

Brien agrees with Brian!

'nuff said.

[elwesso]

this isnt a competition or anything, come on now! Comparing a stock(ish) Q45 to one with a ton of mods is apples and oranges...

I dont know if you were closet-slamming my Q or what, but I dont really feel that is appropriate to do, YES my Q has seemingly unsolvable issues but that is not likely due to any modificaitons i have.