Adding A Muffler

[cherring]

So my R32 Gtst has a 3" Exhaust with just a varex cannon on it, and whilst that is great for shutting the car up, not great for when I want to give it a bit of what for, so I'd like to be able to do that with my car a bit quieter, so the obvious route is, get a mid muffler added to the car. Now I have only just started looking at what is around, started with ebay as it's easy to look, and found,

http://www.ebay.com.au/itm/Magnaflow-3-0-3-0-out-Universal-Race-Series-Stainless-Steel-Muffler-14219-/300700179046?pt=AU_Car_Parts_Accessories&hash=item4603209a66#ht_2925wt_1140

I have heard people mention Magnaflow before so I assume this is good quality item, but I am wondering if adding this muffler will hurt performance very much.

The car has a highflow turbo, FMIC, Z32, 555cc Nismo injectors, and Jez tuned it and got 201rwkw out of it on 20psi, pretty happy with that. I know I will need to get my car back on the dyno if I change the exhaust, but for a muffler like this, is it urgent? and would I see a significant performance drop, also has anyone used one of these mufflers, would the drop in noise even be worth the potential lower performance?

Thanks guys.

[scotty nm35]

I would be looking around for a Jasma spec exhaust if you want good flow with a quiet system. See if there is a second hand one around.

Failing that, I find my 3.5 inch Varex fairly quiet with an xforce 5 inch body mid muffler. It won't pass noise emissions without it being closed but it isn't noisy on the road in the open position.

[AngryRB]

i have a second hand fujitsubo muffler if your interested, its 3 1/2inch with 2.5inch silencer, the guys at the exhaust shop were amazed at how quiet it was, has a nice muffled sound thats angy on full throttle..

the muffler in that pic looks bit small to be very quiet, looks almost like a cannon.

Edited July 31, 2012 by SliverS2

[TiTAN]

big straight through mufflers wont drop your performance.

with only 200kw out of a 3" exhaust you arent even close to pushing the limits of that size exhaust.

get rid of the varex, put on a 16x11x6 muffler at the rear and if your car has a hotdog already fitted it should be very close to legal noise wise.

[cherring]

Yeah I'm not expecting to get it under 90db when the exhaust is open, but it would be nice to get it a little bit closer, and would also eliminate the need to ever have it fully closed hopefully, and without even a hotdog on it, (when I bought it it didn't even have a muffler), I figure putting in a mid muffler is the way to go noise wise.

[cherring]

So I've had a look under my car, and from the look of it I'm assuming previous owner (in his infinite wisdom) had a muffler removed from the exhaust??

How much would people think it would cost/effort it would take to have one put back in there?

[GTSBoy]

Cost of muffler + flanges + 1 hour labour?

Edited August 3, 2012 by GTSBoy

[cherring]

Sweet, I have no idea about welding etc so wasn't sure about labour

[discopotato03]

I'm going to suggest (for a 210 kw 2L six) a mid muffler and consider going down to 2.5" at the back . Most here won't agree but the "signature" 3" exhaust is not the be all and end all because different apps are different .

I've no idea what size exhaust an RB20 gets std and I think 33/34 RB25s were a metric 2.5" , and GTts made 206 kw ?

3"' at the front where the gasses are hottest and wanting to expand should be Ok but as they cool and shrink the only way to keep the velocity up is to reduce the pipe size . In a perfect world 2 3/4 (70mm) tube and mufflers would still be available but the cap on backwards brigade wouldn't be told 3"s too big in some circumstances . The do know better smarter exhaust fitters gave up on 70mm because they couldn't sell it even though it can be better in some apps .

A .

[GTSBoy]

Why would you want to "keep velocity up"? More velocity = more friction = more pressure drop = more back pressure. If this was an NA exhaust and we were talking about the primaries and secondaries and collectors, I would agree that maintaining velocity is important. But there is no sound argument for maintaining velocity in the back half of a turbo exhaust. None.

[discopotato03]

Yes there are good reasons and they mostly come back to the fact that engines are designed and built to suit many different applications .

The one that trips many people up is the old adage "the best exhaust behind a turbocharger is no exhaust" and that would be fine if noise was not an issue and the engine ran in a boosted state all the time .

Noise is an issue and turbo road cars can't be loaded up all the time for obvious reasons . They have to be able to get around at part throttle and light loads and normal speeds - particularly in built up areas .

All the things that apply with too much exhaust on a road NA engine also to a surprising degree apply to a production based turbo road engine .

For the millionth time everyone please delete all notions of backpressure is good because its BS , the value in passages/pipes that carry exhaust is to maintain adequate gas velocity to ensure the engine scavanges properly in the valve overlap phase . A turbo engine is just as vulnerable to reversion as an NA engine is if not more so - most likely because exhaust manifolds are short and the turbine housing and turbine form a restriction NA engines don't have . Plus often the static CR is lower but that is changing nowdays .

Back to the tube size vs velocity . We know tha as hot gas cools it contracts/shrinks/increases in density . If the pipe size is constant the gas will slow down and there no benefit in that . If this was a race engine that never used less than 4000 revs sure maximum flow is everything but we are talking about a road car engine . Road car engines can't be driven flat out everywhere and more often than not they run around at part throttle and low to no boost .

To have an idea what an engine that is loaded most of the time is like look at semi trailer truck engines . Forget that its a four stroke low reving diesel for a minute and note that they run on boost most of the time . Everything including the exhaust is sized for the specific engine running in a full power full boost mode . By comparison road cars are very overpowered and don't need their full output just to drag themselves around - meaning lots of off boost light load running .

Anyway I think its enough to say that an exhaust thats beyond making good power for an engines state of tune achieves noting other than more noise more bulk more weight . I reckon if a real good 3" exhaust is good for 270 odd Kw on an RB25 or 30 its overkill on a 210 Kw RB20 .

I remember years ago a GTST coming into a workshop I used to use lots and it had a Jap metric 3" exhaust (more like 80mm) and it was silly loud and drony . That shop basically changed the rear section to 2 1/2 inch and the car was much quieter and lost zero performance .

A rear exhaust change doesn't have to reduce in size right behind the cat and if anything you need to keep it up a little way behind the "cooker" because of the temperature rise . I honestly can't remember where the last joint is in a Skyline but if its down around the axle somewhere its not difficult to experiment with a smaller size from that joint to the last muffler . If that muffler flows real well for its size and the transition is gradual you might be surprised at how much performance id doesn't lose .

Something else very few people think about is how much a big bore exhaust rings like a bell . The larger diameter tends to make the tube a LOT more rigid and at times they transmit a lot of mechanical and combustion noise into the body/cabin . If you can get them those spring loaded carbon ring flex joints they can help isolate the engine roar from the exhaust and if fitted possibly in the exhaust behind the gearbox hanger it takes the car length "engine steady" part out of the exhaust and can at times reduce the echo chamber effect .

Your calls , I'd just be a little conservative with exhausts and play around with the rearmost section .

A .

[GTRNUR]

I purchased an aluminum muffler recently and I've got to say its pretty impressive. The quality was flawless, and its surprisingly quiet considering its a straight through. 1.1kg as well, which was a factor for me as I was trying to keep the weight of the exhaust down to a minimum, and full titanium mufflers aren't generally available for this kind of money.

http://www.ebay.com.au/itm/Aluminum-Race-muffler-3-3-out-al-/270590975652?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f007a9ea4

I used a magnaflow in the same car with a different engine setup once before. Stainless steel quality is good, but they are very heavy by comparison.

[GTSBoy]

Yes there are good reasons ....

...

Your calls , I'd just be a little conservative with exhausts and play around with the rearmost section .

A .

Yes, but whilst noise and weight are valid reasons for not going bigger than you have to, gas velocity (or more to the point, the benefit of keeping it ihgh) plays no part in your last post as a good reason.

[zebra]

Disco, the theory usually never plays out

At leat in my case, I had a 3.9L falcon, with good headers and a 2 1/4" exhaust, changed that to a 3" and it picks up power everywhere, most notably part thottle, was also quieter

Same for the v6 commodore I had, went from 2 1/4 to 2 1/2, again power everywhere

Rx7 was the same

Skyline was the same

My soarer picked up heaps with a dual 2 1/2 in system with crap mufflers over standard

All of the pulled more vacuum at cruise, with a bigger exhaust

From what I understand, no matter the pipe size, the exhaust gas rushed down the pipes at or above Mach 1 hit the static atmosphere at the end of the pipe and bounces back up the pipe to the exhaust ports or a turbo, in the case of our cars

So scavenging in the case of a turbo car is more or less nom existent apart from maybe potentially creating slightly less +ve pressure at the turbine outlet

Also and I'm sure you have probably read it, the scientific design of exhaust and intake systems stats, in basic terms, that any forced induction engine including supercharged motors ruins any chance of tuning your engine via exhaust lengths/size shape etc

Too small will limit power, but the is basically no such thing as too big, in practice, having 2 1/2" primary pipes in a turbo manifold is silly on a streeter rb25, but after the turbo anything goes

[zebra]

^^ Was on my phone there, so sorry if it came off as if I was trying to discredit you, not my intention

But to add, a turbo engine effectivly has 2 seperate exhausts, pre turbo, and post turbo, so exhaust waves bounce back from the tail pipe, but can only go as far as the turbine wheel, not the exhaust ports, so scavenging the cy;inders doesnt apply, you can scavange the turbo a bit better, but given that most street exhausts have mufflers, all scavanging ablity is lost, due to the mufflers doing weird shit to exhaust pulses, so In practice, disregard any thoughts of scavenging effects.

All r&d I can find for turbo/supercharged exhausts is that bigger is better, and if its too loud then get better mufflers.

I love this stuff!

Can you tell haha

Now...i need to hurry up and get my 3 1/2" hooker super comp muffler on the Supra haha

[Rolls]

Something to remember is the turbo rear housing size makes a massive impact to exhaust volume, eg a GT3076 will be much louder than a stock/highflowed stock housing.

[cherring]

That's good to know, currently have the high flow so I guess it's as restricted/quiet as it's going to get in that regard.

[battery]

Im after a new mid muffler, needs to be 3" into 2x 2.5" out... can get this http://www.magnaflow.com/02product/displayapplications.asp?partnumber=12198 around $200 shipped..

Any other suggestions? I have never used a magnaflow before, not sure if there any good.

[TiTAN]

Im after a new mid muffler, needs to be 3" into 2x 2.5" out... can get this http://www.magnaflow...artnumber=12198 around $200 shipped..

Any other suggestions? I have never used a magnaflow before, not sure if there any good.

14" long and 5" high is going to be a problem for a middle muffler.

you want to stick around 3-4" high if you want to avoid bashing it on the ground/driveways and 12" long with single exit or less if you want twin pipes out of it or you have to mount it stupidly low. have you measured what size you can fit under there?

why not simply make the rear muffler larger instead as there is a lot more room to play with there and height isnt an issue

[battery]

14" long and 5" high is going to be a problem for a middle muffler.

have you measured what size you can fit under there?

Yeh the one i have in there is the same size, I don't think the height will be an issue...