Suitable Exhaust For 350rwkw

[Shaun]

Hi,

I recently posted a question about finding a non restrictive exhaust that will support 350 plus Kw and be quiet at the same time. Those in the know told me the answer was the custom route, so i started my research. Im letting you all know this because i know that there are alot of people out there who could benefit from this info.

I previously had a jap brand 3.5 inch exhaust that was over 100db @ 5000rpm, and it bought out all the rattles in the car and droned like a bitch. Very non restrictive, but a bit to loud for me. I should mention that this is on a single turbo RB26 with large (1.06ar) turbine housing, so for those of you with twins, it will be much much easier to control excessive noise, and the above exhaust would probably be fine.

Anyway, i discovered a great exhaust bloke at Gosford and we set about designing this system. I got Hi-Tech in Bathurst to make my centre muffler which is about 5x8x12 inches, and is offset in/centre out in design. It uses 3.5 inch perforated tube through the guts. It was $360 custom made in stainless.

The rear muffler is a Magnaflow Race Series item, and is a 5x8 oval and 12 inches long. Its centre in/centre out and uses 3.5 inch perforated tube straight through. The product code is 14151 on the Magnaflow website. Its awesome quality and was about $330.

We used 3.5 inch stainless piping and the sound supression is amazing; no drone, deep thoaty sound; cops wouldnt even notice you. It would definately be legal, although i havent had it tested yet. For $950 cat back, im stoked. Ive got a Metal cat 4 inch catilytic converter and the screamer plumbed into the exhaust. Ive got another front pipe though which allows the screamer to be vented to atmosphere.

I can confirm no loss in power compared to the jap system, as i had the final tune yesterday and, with no changes except the exhaust, the car gained 5rwkw and 76Nm of torque. Actually, the tuner probably added a bit of timing which would mix things up a bit, but the exhaust certainly didnt restrict things.

Anyway, just thought id let those who care know that it is possible to build a non restrictive, free flowing exhaust. Ive added some pics and before and after dyno sheets. Ive gotta put a polished 4 inch stainless tip on the rear muffler yet, but ill do that this week. I suppose its not a DIRECT comparison due to those possible timing changes and boost control set up, but i still think its pretty good.

Sorry for the long post,

Shaun.

Edited August 23, 2008 by Shaun

[swanny180]

Great looking exhaust mate, looks very nicely made.

Like you've said, wouldn't read much into the power change if timing was changed too. Would be interesting to see completely back to back tests of your new and old exhaust.

[NYTSKY]

Top stuff mate. With 2 big arse mufflers like that, no wonder its quiet. Good to see no drop in power.

Maybe you exhaust bloke should market these as a quiet alternative for a high performance exhaust upgrade.

[GTR1993]

Is the reason you got the custom made muffler because magnaflow only offer a center in and out item?

[Roy]

Any idea what the system weighs?

[Shaun]

Is the reason you got the custom made muffler because magnaflow only offer a center in and out item?

Thats right. I was originally going to go with two of the magnaflow mufflers, but i really wanted to have maximum noise supression, and the slight offset of the perforated tube in the centre muffler is apparently the best way to achieve this without loss of power.

Roy,

I didnt weigh it, as im not concerned about weight at all.

Shaun.

[GTR1993]

The custom muffler price is less then i thought it would be, i'm definitely looking into this for my skyline and other cars.

[STATUS]

i reckon you will still be over legal Db, but they did a fantastic job.

[Shaun]

i reckon you will still be over legal Db, but they did a fantastic job.

Im interested to know that as well. Ill get it tested and see how it goes.

Whats legal again? 92db @ 75% of engine redline rpm. Is that right?

Shaun.

[T88 ON BOARD]

Thats a great looking custom job...

Whats the ground clearance like?

[saliya]

Im interested to know that as well. Ill get it tested and see how it goes.

Whats legal again? 92db @ 75% of engine redline rpm. Is that right?

Shaun.

ADR28 (don't think you need ADR83) says max of 90dB @ 75% of the RPM at which the engine makes maximum power.

I think they go off the stock specification for 'max power' (6800RPM for the RB26?)

otherwise you'd just show up with a dyno sheet showing max @ 1000RPM

So I think you're aiming for 90dB @ 5100RPM... will be interested to see the result.

Regards,

Saliya

[Shaun]

Thats a great looking custom job...

Whats the ground clearance like?

Ground clearance is about 110mm.

[STRYKR 33]

What jap exhaust did you previously have?

I'm still deciding on custom or not. Where abouts in Gosford did you get the exhaust made?

[Shaun]

What jap exhaust did you previously have?

I'm still deciding on custom or not. Where abouts in Gosford did you get the exhaust made?

It was a trust exhaust. Its for sale if you want it! Lol.

Scott at Gosford performance exhausts and intercoolers made the exhaust. I think he's just closed the business, but he's still doing mobile stuff and has a factory by in Gosford. Not sure what he calls himself now; something to do with race cars. If your interested, i can certainly arrange details to be traded.

Shaun.

[STRYKR 33]

If you could pm me the details that would be much appreciated.

At the moment I have a custom 3 1/2 inch front / dump and flows to a 4 inch cat back exhaust. I'm trying to get rid of the droning noise from the vehicle so I'm still deciding if I should just change the rear muffler or go for the kakimoto regu 06&r exhaust. Any suggestions to reduce noise level?

Thanks in advance.

[Shaun]

Its the centre muffler that makes the difference, and custom is the only way to go if you want to maintain the 3.5 or 4 inch diameter. Scott put the rear magnaflow on first (with my old exhaust's centre section), and he said that it did make a big difference , but the centre muffler really quietened it down the most.

The Kakimoto is in 3 inch only, so i suppose youve gotta decide on size. It depends on how much power youve got.

[«Cyph3r»]

First thing, system looks great, i really like the lack of a cannon or straight pipe.

Secondly, i think this mainly applies to rb26s as i have heard many rb25s making in the 300-350rwkw bracket and remaining quiet without drone, i think quite a few jap systems with centre mufflers seem to work ok on the 25 (apexi is one).

Regarding the cat:

Fwiw i had a metal core magnaflow cat in my s15, the insides let go on the track and blocked my muffler and caused my turbo damage when this happened.

I contacted magnaflow and they didn't want to know about it, talked about how their products are designed for race cars blah blah pr bullshit, then go on to say if the car is not running a standard ecu its not warranty'd as the afrs could be lean or rich which will void warranty. This is the email they sent me:

One of the key components to understanding how a catalytic converter functions is knowing how air/fuel ratios effect their operation and survivability. Like any other devise in powertrain of the car they have operating conditions which can be exceeded. A simple over rich condition can cause numerous problems ranging form excessive cooling and light off failure, to combustion of fuel in the catalyst causing catastrophic failure of the substrate. Excessive EGTs will melt down any converter. In properly controlled environments (Emissions calibrated PCMs) even our standard ceramic cats survive in vehicles such as new 3 Series 300 HP BMW twin-turbos, the 505 HP Corvette Z06, or the 500 HP Ford Shelby GT500 with supercharger. Our metallic performance cats have an even higher threshold for exposure temperature however they are not indestructible.

Often times, custom application turbos are calibrated or dyno tuned for Wide Open Throttle conditions to make maximum power. The vehicle’s PCM fuel and spark map is however nearly left stock for cruising, idle and all other conditions. If these conditions are NOT tuned in addition with the WOT conditions, any catalyst will fail and no amount of design will be able to prevent that.

All of our catalysts are extensively tested in fully calibrated applications and have no issues with survivability or functionality in the application they are designed for. When our cats are used in application for which they are not certified, additional variables are introduced and PCM calibrations do not meet emissions protocols we cannot be held accountable for any subsequent issues as the causation of the failure cannot be solely attributed to the design of the catalyst and variable of the condition it was exposed need to be considered.

xxxxxx xxxxxxx

Engineering Director

Car Sound Exhaust / MagnaFlow Performance Exhaust

Funny thing is in the 33 i had ignition cut and a standard jap metal substrate cat (i never knew about ignition cut+cats being a no no back then) and it never failed after much limiter bashing.

I wouldn't touch magnaflow cats again, inferior quality and not willing to back their products with a worthwhile warranty. Hope their mufflers are of a better quality, although with the design of the mufflers at least no packing can get past the mesh lining the center.

Cheers

Jamie

Edited August 25, 2008 by «Cyph3r»

[«Cyph3r»]

If you could pm me the details that would be much appreciated.

At the moment I have a custom 3 1/2 inch front / dump and flows to a 4 inch cat back exhaust. I'm trying to get rid of the droning noise from the vehicle so I'm still deciding if I should just change the rear muffler or go for the kakimoto regu 06&r exhaust. Any suggestions to reduce noise level?

Thanks in advance.

If you have no centre muffler, i would recommend putting one in, i had really bad drone in one of cars, so i had a large centre muffler put in, this got rid of all the drone but didn't lose the exhaust note.

[R31Nismoid]

Looks like a great setup mate

It'll still be over legal, but quiet enough not to draw massive attention, i went through a bit defect station here in Vic the other day, cops didnt even blink an eye for a welcome change

Did he add timing because now he could add more? Ie, less restriction etc perhaps?

[Shaun]

I actually dont know if he added timing at all; im just assuming that he did, as the other tune was to run the brand new engine in and i suppose it would be a conservative tune.

Looking at how straight my other exhaust is, i dont really think there would have been restriction in that either!

Shaun.

Edited August 25, 2008 by Shaun