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Location:
Canberra
Registered:
May 2002
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3" exhaust makes a hell of a difference!
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Sun, 09 June 2002 12:57
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I just finished making my 3" mandrel bent exhaust for the 3TGTE today (previously press bent 2 1/4") and it makes a hell of a difference! No more restriction up top, it screams like a demon posessed right to 7 grand, where it used to taper off a lot after 5500rpm.
Cant wait to get to the dragstrip.......
Phil
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Location:
up yours!
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Sun, 09 June 2002 13:11
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the best thing about straight though 3in is the flames!!!!
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Sun, 09 June 2002 23:22
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3" is the best, but apparently there's nothing to be gained over that. was chatting to some guys from the exhaust centre, and their project car (some 10 second monster) only runs a 3" .. they reckon with almost all engines it's all you need, anyhting else is just extra weight.
and as an aside, I badly want a car that spits flames
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Location:
Perth, WA
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 00:37
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I know a bloke that has a GTR that makes 400hp at the rear wheels. That runs a 80mm (3.2") straight through stainless system with one big ass straight through muffler.
When dynoed using that system, and then running a 80mm side pipe exiting just under the passengers door, the car gained 80hp at the wheels using the side pipe, on the same dyno!
With full system the car ran 11.5 at 200kmh.
Cheers
Mike
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Location:
Western Sydney
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 03:59
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My car shoots flames.... out the carby 
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Location:
Canberra
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 04:33
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Hey phil, how's the new inlet manifold going? Do you notice much of a difference, or is it too hard to tell with the other changes you've made at the same time? Chris.
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Location:
Sydney
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 06:56
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Phil, the 3in gives the 3TGTEU a mighty increase in top end!!
I am looking into putting a 4in piece of pipe just after my 3in dump then back to 3in. It only has to be about 10-15cm long and big power gains are to be had. If you look at any of the newly built Rigolli cars (and a few other companies) they are doing it on them. Apparently gains in the order of 15% are to be had from such a simple mod.
Ill keep you informed.
Jamie.
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Location:
Brisbane, QLD, Australia
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 09:21
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| MRTA22 wrote on Mon, 10 June 2002 4:56 PM |
Phil, the 3in gives the 3TGTEU a mighty increase in top end!!
I am looking into putting a 4in piece of pipe just after my 3in dump then back to 3in. It only has to be about 10-15cm long and big power gains are to be had. If you look at any of the newly built Rigolli cars (and a few other companies) they are doing it on them. Apparently gains in the order of 15% are to be had from such a simple mod.
Ill keep you informed.
Jamie.
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So just after the dump pipe after the extractors (where the pipe starts to go horizontal?) you put a larger bit 3-4" long? How does that increase power?
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I supported Toymods
Location:
Perth WA
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 09:29
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Would this sudden pipe diameter change lead to turbulence etc? Size matters, but so does flow streamlining. You don't really see the little-big-little pipe combo on race cars, or aftermarket Jap exhausts (who supposedly spend megabucks on development).
They might all be wrong though - if you can find a dyno to prove it!
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Location:
Canberra
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 11:34
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YOGI: flames??? how? seems i'm missing out on something here! maybe i should use the antilag on the haltech, then i'm sure i'll get flames!
CHRIPH: the manifold is on, and all is working well, but its hard to guage the gains of this mod alone since i have changed so many other things at the same time.
MRTA22: definately keep me posted on the 4" section thing, sounds really interesting!
Cheers
Phil
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Location:
Newcastle
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 11:37
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i would say that the part about putting in a 4 inch section on a 3 inch system would gain some power. take a look at an expansion chamber on a 2 stroke motocross bike, has all different shapes on it, there has also been a system brought out for 4 stroke motocross bikes with a larger section in them to increase the power and modify the powerband,
with adding the different section you may find that it takes power away from one area and gives it to another, and to me a 15 percent power gain sounds a bit optimistic.
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Location:
Brisbane, QLD, Australia
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Mon, 10 June 2002 12:00
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I'm extremly interested in the theory behind how it works. Did I get the location correct?
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Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Tue, 11 June 2002 08:06
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Remember though that 2-strokes are completely different engines...expansion chambers alter the acoustics of the exhaust they are supposedly very precise. my nsr makes twice the power with the less-than-1-inch ehhaust and expansion chambers than with a dump pipe. I don't believe the 2-stroke style expansion chambers will have any effect on a 4-stroke engine.
In a 2-stroke the "intake" (there isn't really an intake port) and the exhaust port are open at the same time so the reverberation within the expansion chambers stops the mixture from running through the exhaust and increases compression...
So there should be no use on a 4-stroke.
Tim
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Banned member
Location:
Brisbane
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Tue, 11 June 2002 09:05
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are you talking about where a resonator should go and replacing where it should be with the 4 inch pipe, i can see how that would work, though 4 inch would only would for big hp applications other cars would be different
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Location:
Perth, WA
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Tue, 11 June 2002 10:52
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dont forget that on a 2stroke, high back pressure makes more power, but makes the motor run hotter and closer to melt down mode 
Cheers
Mike
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Location:
Newcastle
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Tue, 11 June 2002 11:53
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Ra28
A company Called FMF have done a lot of research into the small expansion chamber system on a modern 4 stroke bike.
granted these bikes come with a 5 valve head and the valves are made of titanium and such but they have made 2 different headers with mini exansion chambers for the YZ250 400 and 426 four stroke race bikes called the power bomb headers. i would say they they had spent a few million on researching the design and they came out with 2 headers, one for supercross which is basicly all low revs work and one for motocross which is more top end.
here is a pic of one
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Location:
Sydney
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Tue, 11 June 2002 12:43
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Hi all,I dont see how the hell Yogi gets flames (im not saying you dont!) unless the car is running mega rich and the heat of the exhaust pipe or valves is igniting it. Would be cool though.
Apollo the 4in section goes about 6in after where the pipe bolts onto the dump. So 3in for 6in then say 8in of 4in and then back to 3in before the pipe exits under the firewall.
I have heard this off a few people i know who own very modified quick cars and i agree the 15% is very optimistic but even 5% is great for next to no outlay!!
I was told it had something to do with slowing the air speed momentarily when the pipe expands to 4in then when it goes back to 3in the air speed increases and helps to extract the exhaust gases from the engine as it speeds up.
I have been stuffing with my exhaust system all day trying to get it to fit under a car 50mm off the ground and i have almost got it done,then ill put the 4in bit in. I cant see it affecting power in a bad way so it will either gain or do nothing so it wont hurt to try it out.
Just thought i would share it with everyone as some people might be interested in doing it.
Jamie.
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Location:
Brisbane, QLD, Australia
Registered:
May 2002
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Re: 3" exhaust makes a hell of a difference!
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Tue, 11 June 2002 23:58
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Next we'll have forced exhausts. 
I'm still a little sceptical. Do a dyno of before/after and monitor engine temps.
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