Exhaust mods

[RobertsnewQ]

Has anyone tried removing the rear suitcase/muffler and replacing it with a straight pipe on a G50? I'm looking at the size and weight of that thing and thinking that a bit more noise would be nice...

[Flagship-Q]

I was just thinking on the same line but I'd like to do a dual exhaust on each side with dynomax or something. I know that they would have to snake the tubing around the spare tire but it looks like it can be done.

[ejXa q45]

Has anyone tried removing the rear suitcase/muffler and replacing it with a straight pipe on a G50? I'm looking at the size and weight of that thing and thinking that a bit more noise would be nice...

i was thinking that to but i was just going to make them.maybe,i'll have someone bend some pipes for me.

[PopPop]

Robert I have already done the MOD's you spoke of! Removed the tank of a muffler and ran 57.15mm approximate pipe size since its a metric size pipe from resonators on back. Did not weigh rear muffler but, sounds a lot louder than stock. Do you still have your stock resonators, Cat's and pre-Cat's on your car. Be careful with exhaust mod's and back pressure loss!Everything you do to improve performance doesn't always work out for the best and somethings are irreversible.

[Jeff Williams]

Be careful with exhaust mod's and back pressure loss!Everything you do to improve performance doesn't always work out for the best and somethings are irreversible.

Well said.

I would first measure the diferential pressure of the stock system, and try to match it with the new system at RPM's of 1,000 throught about 4,000. Then try to remove all pressure above that.

Start out with about $20,000 and 10 different combinations of mufflers, pipe sizes, and cats. Do at least 3 chassis dyno pulls with each system, post your results here so we can just go out and by the best system.

Or, just do a search to see what others have done, and do the same.

[Flagship-Q]

Jeff, that looks VERY nice. So that doesn't have any pre-cats or cats? Could you post a pic of the very back of it (axle to rear od car) so I can see the whole thing? How's it sound? Thanks alot!!

[rsiwicki]

That pics looks very familar Jeff ;-)

here are the sound clips....checkout my signature for all the details on the exhaust stuff. Call around and find a really good mandrell bending shop. Cost was $850 and all mandrell bent very high quality and sounds great. When cruising no more noise than stock...but a lot louder when I hammer the throttle.

http://q45.spilky.com/rob/Moroso.asf

http://q45.spilky.com/rob/Q45%202.asf

http://q45.spilky.com/rob/Q45%202.asf

http://q45.spilky.com/rob/Q45%203.asx

[RobertsnewQ]

Well I live in CA so I have to keep the cats at least. Precats I can probably get away without, depending on which smog shop I hit.

I was thinking of leaving everything else and just ditching the big one in back. That's what the Porsche 928 guys do, which is where I got the idea.

[elwesso]

well it looks like you can just unbolt it.. See how you like the sound... if its too loud, bolt in a dual in dual out setup..

[Jeff Williams]

Here's a picture of Rob's A$$

[jamesmost]

roberti have a cat back 2.5" stillen setup removed the lower catsgutted the pre catsremoved the resonators ( 2 cans under car)and the rear can is a ss walker dynomax 5" inlet split 5" outputit sounds like a 68 mustang or camaro

[redmanfx]

Rob,... are those you actual headers? I wondered what they looked like. Sounds nice!

red

[qsiguy]

Seems like everyone's put some sort of muffler at the tail end. I, like Robert, have been thinking of just deleting the giant muffler on the back and using straight pipes there. There are a few clips labeled "Q45 with exhaust removed 1&2" on q45.org. How much of the exhaust was removed for those clips? Was it just the rear muffler or all the way to the header, or somewhere in between?

There's a few other clips of "Todd's Q45" that says "Free-Flowing Exhaust". Has this one just had the rear muffler removed or the whole exhaust changed?

If there's already a clip of what it sounds like with the rear muffler removed I'd like to hear that and save me the trouble of removing the muffler and risking breaking the rusted bolts on the exhaust just to hear it.

[maxnix]

Might want to read the previous posts of Q45tech on this type of modification, what he did, what power he gained, and why he went back to stock.

Probably archived.

[elwesso]

He just didnt like it loud..... Which is what some of us want...

[INFINITI Q45]

He just didnt like it loud..... Which is what some of us want...

I understand some people dont like their exaust loud, but did the Q45tech report horse power gains through out the rpm range, as far as I know less back pressure (no muffler no cats) will give low end gain but often less power as the R's go up..

[Q45tech]

How is it possible to have gains low when there is no measurable back pressure low.Just like intakes [MAF/air box/filter]......the components don't start to be measurable until the torque peak rpms [>4000 rpm].

300 scfm just isn't much intake/exhaust flow for 32 valves and dual exhausts[274/2 x 4000 ] / 12c12x12= 317 x VE = scfm

Compared to old style large displacement V8.

Stillens best loudest system only yielded much less than 10 HP above 6,000and nothing until 4,000.

Unlikely a loud system will lose much power at any rpm since the 2 cats isolate the reflected waves.

Above 4600 rpm the VVT overlap is almost nonexistent [8 degrees] so no reversion to worry about.....even the 28 from 1500-4600 is so small compared to 2 valve V8.

What ever loudness you can stand.

[maxnix]

He just didnt like it loud..... Which is what some of us want...

Nope, you misread them if that is what you think.

Try NVH, where the H is Harmonics.

[louiegz]

Try NVH, where the H is Harmonics.

Doesn't the H stand for harshness?

[Meaux]

What the heck is a "precat"?

All I see in the picture from the FSM is:

Pipe from header, to cat converter, to small (resonator?) muffler, then on to the big muffler.

Thats all my stock 94 has......This mystery "precat" stuff is confusing....

[elwesso]

its a cat. mounted in the exhaust manifold

[Ozzie]

Video (with sound)coming soon of my Q, with the rear muffler removed.It's all converted, ready to go.Just need Wes or Jesda to host it for me... same as the skyline videoonce one of them is awake!

My rear wasn't a stock one, but no matter....Video soon (next 24 hours)

[elwesso]

IM me ozzie!

[Ozzie]

here it is.

a 10 minute video, with a drive by, and in car driving, with no rear muffler box.

http://www.q45.org/Q/OzzieQ45.wmv

Enjoy!

[Ozzie]

i hope this helped in any decision you make in regards to your rear "suitcase" muffler

[one ton garage]

there's usually a bit to be gained by dumping (or if you are so inclined, replacing) the precats and cats also cuz, at this age, a lot of them may already be clogged up and aged beyond optimal usefulness. A G50 Q with no cats and a good, straight-through exhaust sounds reminiscent of a chevy V8... a chevy V8 that keeps revving past 5000, that is

[qsiguy]

That video is a great example of what it'll sound like, thank you! That will save me the trouble of trying it myself. I like it. Not too loud, but sounds "macho". I think I'm gonna scrap the suitcase muffler and go straight out. I didn't hear any but was there any annoying resonation at cruising speeds, say 40-70mph?

P.S. Someone put your steering wheel on the wrong side! ....oh, and if you get motion sickness don't watch the video, just listen to it, someone get that ozzie a camera with a motion stabilizer feature,

Thanks for going to the trouble to make that, the mystery is solved!

[Ozzie]

No probs.

And i need to get some pipes made up to come out to the bumper now.No resonance at cruising... only at idle. But i think thats because the pipes finish just after the diff now.

With longer pipes... the note will get deeper, and resonance will disappear.

I REALLY like the sound now.Now I just need to get the pipes made