Free-flowing but quiet exhaust required for track (98db drive-by)

[lockwood77]

Right, I have a Border Racing Burnout 90mm (3.5") full exhaust on at the moment, which is lovely but way too loud to get on most tracks (certainly my local, Donington).

The car is being run-in after a rebuild, so will need a remap when it\'s ready and now seems a good time to change the exhaust to meet noise regs, so that it can be remapped at the same time.

The car is running a "twin single" (non-sequential) Apexi turbo setup, which according to a dyno printout I got with the car, is good for 425bhp. As such, I\'m really after the most free-flowing exhaust I can find that will still be under the noise limits on trackdays.

Assuming the downpipe is 90mm too, which I think it is, is there any point keeping that if the rest of the exhaust is narrower?

Anyone got any ideas what will be best? It has been suggested that getting some extra silencing welded on could do the trick, but judging by the volume now, I don\'t think it will be enough. Would like to avoid a custom job if possible, unless it turns out cheaper than buying off the shelf!?

Oh, and if anyone wants a 90mm Border Racing Burnout exhaust system, there will be one available fairly soon!

[Tedrux]

Hey lockwood77,
I doubt the down pipe is 90mm and if it is, it\'s probably wrong and not getting the best power output. I\'m no expert in exhausts, all theory, (read lots of books) the downpipe should be smaller tuned to the engine with the cat back the largest pipe to reduce back pressure so the exhaust should get bigger towards the back like a tapered funnel.
The best exhaust would probably be designed so that the diameter is the optimum size for the exact pressure required to promote the flow at that point. The taper would therefore not be exponential and not constant which would obviously be too expensive for commercial use. The reason for the varying taper is to move the exhaust gasses along from an area of high pressure to relative low pressure. The low pressure gasses move slower so need more space (diameter) to still shift the same volume of exhaust as the high pressure otherwise you get back pressure.
Not sure on this but the down pipe shouldn\'t be bigger than 2" deppending on mods but you should speak to an exhaust expert. It\'s a bit more complicated to calculate the back pressure point when turbos are stuck in the exhaust path. I could have a look in one of my books! Anyway, back to the subject.
 
I\'ve been enquiring for the same thing. I think my exhaust is an apexi with 3" pipework and a 4.5" tail pipe. It\'s a shame to replace as it\'s in good nick but it\'s just too loud for my neighbors. As a general rule, the less restricted, the more noise and power but with my car being a \'stocker\', it\'s not so much of a problem as the free flowing muffler is a touch large for the power range and may even cause boost spikes. They can be too big which doesn\'t always help the exaust flow for all power ranges. So I\'ve been looking at getting the racing beat 2 pipe. It\'s supposed to be quite free flowing and still fairly unrestrictive, certainly more than having to shove a bung in the end of a free flowing muffler. Trouble is, the racing beat exhaust is £800 for the cat back alone. I did some asking around at Car Planet Racing where I get service and MOT and they can make a custom cat back for arround £500 for the FD. They have lots of options for silencing - 1 or 2 pipe - and different pipe diameters etc.

[lockwood77]

Hmm, I\'m thinking the custom solution would be the way to go. Without removing it, I couldn\'t say if it\'s definitely a 90mm downpipe, probably not from what you say.

[AtomicRex]

I do an exhaust system that would be perfectly suited to your needs!
 
It is so quiet that you can hear a fuel pump over the exhaust note on idle!!
 
The system is fully repackable and comes with a lifetime guarantee.  The system is 3" but I can do a 3.5" if you need the extra size.
 
Give me a ring if it interests you

[skybusr34]

there is a company in brum that do a 4" exhuast system thats ubber quiet. if you want i`ll dig out there number

[lockwood77]

Thanks guys, working on some other issues at the moment, but I\'m sure I\'ll return to this soon - Atomic, what\'s the price on your system?

[AtomicRex]

The 3" system is £480 (£576 inc VAT) for the back box and £450 (£540 inc VAT) for the mid section.  If you want one, I\'m sure I can sort a bit of a deal.  They are super quiet....and I mean very very quiet!  We\'ve fitted 6 of these systems now...and although they are quiet when on test, once you\'ve put your foot down....they sound like the 4 horses from the Apocalypse have just ridden from behind your car!
 
You will not be disappointed!!  Plus its buy, fit and forget!

[SiH]

Personally, I\'d try getting an extra silencer welded in - I purchased a couple and had a mate weld them in - apart from making it sound mellower and bassier, they are sooooooo much quieter it\'s unbeliveable!

If you have a decat at the mo (and I guess you will have with a single?) It\'s certainly something to consider shouldn\'t cost much over £100 either
I\'d guess tha thte system you have now is not just a sinmple 90mm downpipe though dude - I\'d have thought it would be custom for your rather unique setup - I\'d get under there and see how far back the custom work goes - it may run a stock layout system from the mid section back, or it may still be custom at that point and you\'ll need to look at purely cat back.

I\'d imagine it\'s pretty tight for space there, so anything in the downpipe would be an immediate no-no.

98db driveby could be tricky - do you know what sort of distance that\'s measured at?

Also, are the turbos internally gated or externally, and if the latter, do they vent back into the system or run straight to atmosphere?

[lockwood77]

Thanks Atomic, sounds on a par with a lot of other systems for price - the problem for me might be that it sounds loud under load, as Donington\'s 98db drive-by doesn\'t care how quiet it is at idle! The microphones are fairly close to the track I think.

Si - I did that on my DC5, certainly worked a treat as it was borderline until I had a bigger silencer welded on the mid-pipe. If there is room (still haven\'t been underneath!), that\'s probably the easiest answer. Not sure about the turbos, it certainly doesn\'t have a screamer pipe - car is still being run-in, so not sure how loud the venting is yet!

[AtomicRex]

I can promise that the noise will be more than suitable for Donnington!  Our systems have been used at both Castle Combe and Goodwood and they are probably the most strictest of all circuits in the country.
 
Plus if you have blown the wadding out, then we can supply you with spare wadding, so you simply have to unbolt the box, repack it, and try again!

[lockwood77]

Ah, cool - I thought with your racing activities you would probably have come up against such problems yourself!

[PGiljevic]

I supply SMB exhaust to rotary users all over the world. Proven power, best sound, lowest noise, hell they even beat factory emissions standards and still out accelerate "race cars" :rollin:Thumbs-up


Can\'t beat them, tested at Nurburgring 24hr on factory race cars
Won 12hr production "super specials GTP" car races in Australia

Have a listen to a 500bhp 13B-REW running SMB exhaust :3gears-lh http://www.youtube.com/watch?v=OqvaMTJZn8k

This identical exhaust fitted to a non seq twins running 1.2bar+ and setting a lap record that still to this day no one has come close to let alone beaten! very very quiet system!

http://www.riceracing.com.au/rides/SeriesVIII_SpiritR.htm

Video on this page ^

This is full 3.5" with middle muffler and racing grade catalyst. back pressure is lowest of any competitors systems or promises! power is highest, sound quality is best, noise is very low (pass any road side inspection let alone track restrictions)........ Durability is race proven. NOT the cheapest, but its the ONLY system with this much research and proof of ability V\'s promises and no data from others.

[ashc]

racing beat silenced mid-pipe?