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Location:
Brisbane
Registered:
November 2002
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2", 2½" or 3" exhaust?
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Sat, 05 June 2004 02:15
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Hi guys.
Car is in the exhaust shop shortly, and I had wanted a 3" exhaust. Having owned a turbo six with an auto gearbox and a 3" exhaust previously, the idea pains me a little as the one I had previously droned a bit (when I put the manual box in it was fine).
I also heard an auto JZZ30 with a 3" exhaust the other day and it sounded pretty ordinary. A mate has a manual JZA70 with a full 3" system and it sounds rather spoogeworthy (albeit too loud), so it's a fairly hard decision. I'm funning a differnt turbo (CT26) instead of the twins, so it's a bit of a gamble because I don't know how it will sound in the end.
I also have a few issues with clearance around my steering box, and am considering getting a 3" dump made, but then reducing down to a 2½ or maybe even 2" exhaust. In either situation the exhaust would be mandrel bent, running a cat and probably running two mufflers (up to the exhaust shop, really).
The car is a bit of a sleeper and I'm not after anything spectacularly fast, just wondering if it might be worth the performance hit to reduce the noise and the cost/difficulty of the ehxuast system.
Has anyone had any experience with this?
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Location:
sunny coast, qld
Registered:
October 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 02:30
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as you said, the different turbo makes things a bit different. My 1jz with an auto had the stock Y pipe with 3" mandrel all the way with a high flow cat and 3" muffler and it was VERY quiet. Not droney at all.
You are referring to the VL turbo you owned right? RB30's especially seem to bring out the drone somehow. I didn't think the turbo ones did it as much but the NA ones certainly do! Also, my mates NA RB20 has 2.5" exhaust and it is so loud and droney it gives you a headache in there.
Personally, I would just get 3" all the way 
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Location:
Brisbane
Registered:
November 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 02:39
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Nah, my VL Turbo was a 5 speed.
Was referring to my 7M Supra.
Well, as mentioned, 3" all the way isn't possible due to steering issues. So it would have to be a 3" dump, reduce to about 2" past the steering, and then back to 3"... which seems a bit rough to me.
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 02:49
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Ovalise the pipe near the steering box so it has the same X sectional area. Any half decent exhaust place will do this.
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 03:15
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what dave said.
if you're worried about drone, go back to a 2.5" system after the cat. that way you ge max power for minimal noise.
although I absolutely adore the way my 1jz sounds with a 3" exhaust and no cat
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Registered:
August 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 05:40
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Draven's car does sound awesome!
But you get what you pay for!
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 06:14
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if you want a video of it at the dyno, I can send it to you, or it may still be hosted somewhere on the web.
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Location:
On your mum!
Registered:
May 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 06:45
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| gianttomato wrote on Sat, 05 June 2004 12:49 |
Ovalise the pipe near the steering box so it has the same X sectional area. Any half decent exhaust place will do this.
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GT - when you ovalise a pipe you do indeed lose cross-sectional area (if you keep going - it will end up with no flow area).
This is a point we hit on trying to get 3" pipes over the diff on a V8. 2 x 2" pipes has over 90% of the flow area of a 3".
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 08:43
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Yello, absolutely  . Maximal "ovalisation" leads to a flat crushed tube and zero X sectional area!
They need to use a pipe of larger diameter to attain the same X sectional area when ovalising. If Leigh wants to run a 3" dump, it may be that the shop will need to ovalise a 4" pipe (or larger depending on what the short axis of the oval is) to fit in the space. It's potentially quite a bit of extra work, particularly getting the round to meet the oval smoothly in a cofined space, but I'd dare say it's an awful lot cheaper than a rack and pinion conversion, which was his other alternative.
I'm not much of a turbo guy but IIRC the CT26 has a rather oval or elongated exhaust housing outlet. It may be possible for the exhaust shop to continue this elongated profile till the dump is past the steering box.
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Location:
Melbourne
Registered:
May 2002
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Re: 2", 2½" or 3" exhaust?
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Sat, 05 June 2004 23:54
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3.5inch is almost perfect for the CT-26
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Location:
Brisbane
Registered:
November 2002
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Re: 2", 2½" or 3" exhaust?
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Sun, 06 June 2004 00:19
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Well ladies, thanks for the advice, but it seems to be all sorted now. Had a guy around last night to look at the steering, and seems that a rack & pinion conversion can be done rather cheaply.
I was very impressed that he mentioned "geometry" and "bump steer" during our conversation. Will be calling the exhaust shop on Monday to put off the job and getting the steering done straight away. Feel a bit silly stuffing them around, but there's no point getting the exhaust done, then having to re-do it before the car even sees the road!!
The only issue with the steering conversion is going to be the sump, hopefully that doesn't provide too many headaches.
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Location:
Melbourne
Registered:
May 2002
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Re: 2", 2½" or 3" exhaust?
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Sun, 06 June 2004 00:28
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| 7M-Brisbane wrote on Sun, 06 June 2004 10:19 |
Well ladies, thanks for the advice, but it seems to be all sorted now. Had a guy around last night to look at the steering, and seems that a rack & pinion conversion can be done rather cheaply.
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DANGER DANGER!!! stearing and cheap in same sentance!!!!
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Location:
Brisbane
Registered:
November 2002
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Re: 2", 2½" or 3" exhaust?
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Sun, 06 June 2004 03:21
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Haha, thanks for the warning Allan, but it's all good. By 'rather cheaply' I mean considerably cheaper than my original quote of almost five grand.
The guy does R&P conversions for a living, and mentioned both bump steer and steering geometry in our conversation, so I'm fairly confident that he knows what he's talking about
Now, I'm still left with the decision regarding what size exhaust to use. But, it's pretty straightforward system now so I don't have the heat issues, and I'll just have to live with the drone if it happens.
The final bonus is that with the steering box removed I *might* be able to fit the standard twins on... which is (a) better than a CT26 and (b) will be considerably cheaper.
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