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#1
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Single exaust pipe size
Just read in another thread that when going to dual exaust it probably better to go with 2" pipe. What do those who have modified their exaust but kept it a single pipe recommend for pipe diameter? 2.5"? 3"? I don't recall anyone ever saying.
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Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
#2
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Heh...I think I just answered myself. The square surface of two 2" pipes openings is 6.28". A single 2.75" pipe would yield 5.93" and a 3" pipe would yield 7.06".
Anyone used either or both of these in the past and if so, what would you recommend? I like the idea of a single exaust for weight savings.
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Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
#3
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As an aside, a 2 7/8" pipe would yield the closest match with roughly 6.45 inches.
Hey, Earl! Can you relocate this to the mods forum?
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Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
#4
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Exhaust pipe size.
Johnny,
The pipe size should stay the same size as the orignal. It is not a case of total gas flow, it is still one cylinder flowing at a time, no matter how many pipes there are. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#5
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But 2in pipe looks so wussy.
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92 SVX #772 140k 6speed, ECU Tune stage II, Koni/Ground control, 3,270lbs. 91 Legacy Turbo 5spd. FMIC, crappy stock turbo, ACT clutch. 78 BRAT (New toy) (Soon to be EJ22T powered) 90 240 SX. RB25 powered!! DRIFT!!!111!!! (GF's car) To many cars to spend time on teh web! |
#6
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Re: Exhaust pipe size.
Quote:
Aside from that, I had 2 1/4" pipe on my old Horizon with a 1.7 liter engine. It ran way stronger than stock with only a change in air filter to go with it. Gas mileage was pretty poor but it spun the tires hitting 3rd gear. Like Freak said, 2" pipe is just wussy!
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Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
#7
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2" pipe is too big for true duals. 1 3/4" would be better. Stock single is approx. 2 3/8", not 2". 2 1/2" is fine for a single. If you go duals, use a X pipe or it will sound goofy and lose some low end. Believe me, I have tried everything under the sun. I am currently running 2" from o2 sensors joining into center cat with a 2 1/2" 'Y' pipe back to dual 2" and out through dual mufflers. It is awesome.
Stephen
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92 Ebony - Level 10/n2o REAR-ENDED 92 Teal - painted yellow/4.11 5spd/n2o SOLD 92 Claret - 4.44 SOLD 94 Barcelona - FWD SOLD 92 Ebony - 3.90 SOLD 94 Laguna ROLLING w/4.44s/Ecutune ECU +TCU/STI springs/Infiniti M45 rims |
#8
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Some photos in here
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92 Ebony - Level 10/n2o REAR-ENDED 92 Teal - painted yellow/4.11 5spd/n2o SOLD 92 Claret - 4.44 SOLD 94 Barcelona - FWD SOLD 92 Ebony - 3.90 SOLD 94 Laguna ROLLING w/4.44s/Ecutune ECU +TCU/STI springs/Infiniti M45 rims |
#9
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Re: Re: Exhaust pipe size.
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No, there is no need for back pressure. This is a myth Johnny. The main function of the exhaust system is to reduce the pressure that exits the exhaust valve from about 70psi to zero as quickly as possible. This is to reduce the pumping losses that would occur if the piston has to push the gas out. This is why we use an expansion chamber or resonator at the end of the header pipe. The chamber acts like the end of the pipe, as the high pressure gas plug will expand, the same as if it had an open pipe there. After the chamber, the gas pressure has dropped and we just want to be able to flow the gas out without restriction. Header pipe diameter has an effect on cylinder scavenging, by using the inertia effect of the gas plug, to pull a low pressure at the cylinder. The diameter is mainly controlled by the rpm the engine is to run at. The higher the rpm the larger the diameter, time is the reason. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#10
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Thanks for the explaination, Harvey. From anyone else I would definitely question your information. I was always under the impression that you needed back pressure to scavenge the exaust from the cylinders. What you are saying is that it is the headers that do all the limiting and the size of the pipe after that does not matter as long as it is less restrictive than the headers? That is very interesting and definitely improves one's choice of parts when redoing the exaust.
Lets face it though, larger pipes will decrease the velocity of the exaust gases, thereby limiting the potential volume of my WooWooooo tips.
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Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
#11
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Quote:
I think it is a confusion of the inertia effect that I mentioned and the effect of the tuned negative pressure wave that returns to the cylinder, as a " BACK PRESSURE ". Two strokes use a build up of pressure in the expansion chamber to limit the fresh charge spill, out the exhaust port, as both inlet and exhaust ports are open together. The inertia thing is why you hear that "a large diameter pipe will hurt the bottom end torque". They are referring to the amount of inertia that the gas plug will develop as it rushes down the pipe. Smaller pipe, higher velocity, higher inertia but more restriction. Larger pipe, less velocity, less inertia but less restriction. The main objective is to have the lowest pressure from the exhaust valve on. It is all a compromise. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#12
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2.5" from the headers back has always worked very well on the EJ25 motors, but their pulse pattern is significantly different than that of the EG33. The 2.5 doesn't lose a significant amount of low end torque from increasing the pipe diameter (within reason), if anyone has good info on how the 3.3 responds, I'd be interested in hearing it.
Maybe I can get Harry up here to the dealer and we can dyno his car with the stock system and then the Stebro to see what changes, plus maybe mock up a set of 2.5" catless straight pipes and dyno the change again. Sounds like a fun way to spend a Sunday. I love having a 4 wheel Dynapack chassis dyno 30 feet from my office. Last edited by Porter; 08-12-2003 at 05:13 AM. |
#13
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That does sound like a fun way to spend a Sunday!
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Pearl '92 LS-L 179K (Historic 1st 5-speed SVX) Mods: 5-speed, 4.11's, Group-N motor mounts, dual Magnaflows, cone air filter, Kenwood MP-228 CD/Receiver, white-faced gauges, '97 grill, custom window tinting. Ebony Mica '92 LS 80K Oct 2002 - Dec 2004: Victim of theft. She served me well. You can tell the lack of craftsmanship by the wrinkles in the duct tape. |
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