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The mkiv Supra Owners Club

Exhaust Restrictions?


Tricky-Ricky

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I want to quieten down my exhaust as its getting on my nerves, so there are stainless absorption silencers available, but the largest size is 2.5" do you think that welding in a section that is 1/2" smaller than my existing pipe, somewhere before the tail pipe will make any real difference? i know that its possible and sometimes advised on some applications to have a tapering exhaust system on some turbo cars, but i am still a little weary, as my baffle that i made for my last exhaust 5Zigan 3.5" dia, lost 50 bhp on the dyno, and it wasn't particularly restrictive, so i have a dilemma.

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me too, I had a big back box made for the 4" and that helped, but did not kill the drone. I heatwrapped the main section under my seat; that helped too, I may do the rest.

 

Michel Lane was talking about fitting an apexi butterfly valve that you can engage for pottering and then free flow for a blast. My old subaru had one of these, and they are widespread on a number of high performance cars as stock, but they are all automatic, from my knowledge the apexi one is manual.

 

and apexi have now gone bust!

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Well i already have an Apexi valve fitted, and although it quietens things down a bit, its also a pain as in time it gets stiff and doesn't open fully, it is also no good if you want to squirt out of a junction quick as it acts like a fuel cut and you suddenly loose lots of power and end up nearly getting hit by the cars your trying to get out in front of in time:(

Robert gave me a link to a US site that seems to have absorption silencers in stainless with 3" in and out that would be just right, and they are $68.95 maybe a group buy is in order, to cut down on shipping charges?

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Well i already have an Apexi valve fitted, and although it quietens things down a bit, its also a pain as in time it gets stiff and doesn't open fully, it is also no good if you want to squirt out of a junction quick as it acts like a fuel cut and you suddenly loose lots of power and end up nearly getting hit by the cars your trying to get out in front of in time:(

 

wow, thanks for sharing that with me. I'm giving up on that one then!

 

The noise is good on mine but it is the resonance in the pipe, the drone at 3-3.6k (80mph on the motorway) that does my head in. At 100 it is silent, at 60 the same.

 

I'm going to wrap the rest of the exhaust as the drone is only coming from the unwrapped section. With a 4" system there is absolutely no room for an additional silencer.

 

I've been thinking about it and it must be the flex in the pipe that causes the resonance, so if you can stiffen or damp that it would cure it. It's even been suggested that a stiffner bar clamped to it would help. Sounds a bit crude though.

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silencers in stainless with 3" in and out that would be just right, and they are $68.95 maybe a group buy is in order, to cut down on shipping charges?[/quote

I`d be up for that

 

yep me to as i'me building my own 3", have you any specs on the ones you have seen, length, oval, round, etc

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Well my favourite so far is this one http://store.summitracing.com/partdetail.asp?autofilter=1&part=MPE%2D14419&N=700+0&autoview=sku

but if anyone can find a better, post it up,

i was thinking this one because of its relatively small overall size, its also straight through, just perforated and glass packed, so no restrictions, and its cheap, since its a bit of an experiment, as we have no idea how well it will silence.

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Forgive me if I'm being stupid, but can't the problem of losing large bhp by putting on a more restrictive exhaust be circumvented by just upping the duty cycle on a boost controller?

 

I lost about 0.3 bar of boost when I switched from my 4" BL to the 3" TRD exhaust (which is extraordinarily quiet). With BC off, it dropped from 0.8 bar (with the old exhaust) to 0.5 bar. With the boost controller on, each channel lost about 0.2 bar.

 

I'm presuming that by upping the boost controller, I'll now be getting the same power, but with EGTs a bit higher.

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Unfortunately no it doesn't quite work like that, although your theory is sound, and you can recover lost boost to a degree by adjusting the boost controller, you are actually shooting yourself in the foot as you are making the turbo work harder to martian boost therefor adding more heat into the equation, which in turn saps power,

Example i added a bung to my old exhaust, can't remember if i needed to adjust my boost controller, but if so it cant have been by much as i would have remembered, but the upshot was that i lost 50BHP for the same boost.

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what about these?

 

http://www.burnsstainless.com/

 

the smallest silencer they do is 6" long, perhaps weld an additional one in.

 

http://www.burnsstainless.com/UltraliteMuffler/SSmuf-7.gif

 

Ultra-Light Stainless Steel Race Mufflers

I.D. O.D. Length Wt. lbs Part Number Each

2" 4-1/2" 14" 2.96 SM-200-450-14 232.05

2-1/2" 3-1/2" 12" 1.87 SM-250-350-12 212.16

2-1/2" 3-1/2" 17-1/8" 2.61 SM-250-350-17 236.59

2-1/2" 4-1/2" 17-1/8" 3.56 SM-250-450-17 247.23

2-1/4" 4-1/2" 14" 2.90 SM-225-450-14 233.47

3" 4-1/2" 12" 2.40 SM-300-450-12 202.32

3" 4-1/2" 17-1/8" 3.53 SM-300-450-17 242.47

3" 6 1/4" 17" 5.00 SM-300-625-17 298.50

3-1/2" 4-1/2" 12" 2.30 SM-350-450-12 234.34

3-1/2" 4-1/2" 17-1/8" 3.23 SM-350-450-17 250.68

3-1/2" 4-1/2" 6" 1.02 SM-350-450-6 226.04

4" 5-1/2" 12" 2.80 SM-400-550-12 243.13

4" 5-1/2" 17-1/8" 4.00 SM-400-550-17 260.16

4" 5-1/2" 6" 1.50 SM-400-550-6 232.16

4" 5-1/2" 9-3/4" 2.24 SM-400-550-9 243.13

4-1/2" 6" 15" 4.39 SM-450-600-15 264.31

4-1/2" 6" 6" 1.46 SM-450-600-6 234.47

4-1/2" 6" 9" 2.57 SM-450-600-9 242.03

5" 6" 12" 3.65 SM-500-600-12 241.42

5" 6" 17" 4.72 SM-500-600-17 269.96

5" 6" 6" 1.50 SM-500-600-6 235.93

5" 6" 9" 2.50 SM-500-600-9 248.99

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