HOW TO DO AN ADVANCED SEARCH.

Mon Jul 08, 2013 3:56 pm by Admin


For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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Single 3" exhaust vs 2.25" duals?

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Single 3" exhaust vs 2.25" duals?

Post  eclou on Wed Feb 10, 2010 7:50 am

I am wondering what the consensus is on adequate plumbing. I run a 3" on the 951 and saw that lots of folks take the headers to a Y pipe and tie into the single exhaust. A single 3" has about 12% less cross sectional area/flow than a true 2.25" dual setup, but I was not sure what was needed to support 400whp.
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Re: Single 3" exhaust vs 2.25" duals?

Post  944v8inDFW on Wed Feb 10, 2010 9:47 am

About the best unbiased source / calculator there is out there is

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Please note that all HP ratings are in BPH (normally flywheel)

What is not usually accounted for is the quality of the bends when sizing your exhaust. The standard wrinkle bent pipes can reduce the flow as much as 15 to 20%. What really kills the v8’s power is the reuse of a 20 year old cat.

Be aware that most exhaust tubing is sized by the outside diameter not inside.

All that said, I think a good quality mandrel bent 3 inch would serve 400 hp well. One important component in a 2 into 1 exhaust is the quality of the transition from 2 to 1. Do yourself a favor and spend the $40 on the Flowmaster merged Y. I have seen plenty of guys spend thousands on headers , intake and even heads and have a scabbed together Y and cant figure out why they only picked up a very few horsepower.

My personal favorite setup is to bring the head pipes run separately to just past the front seats then use the merged Y and finish it off with a single tail pipe. Definitely gives that more exotic sound to it. Easiest way to do it is to stack the head pipes in the tunnel rather than run side by side.


Last edited by 944v8inDFW on Wed Feb 10, 2010 10:01 am; edited 1 time in total
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Re: Single 3" exhaust vs 2.25" duals?

Post  eclou on Wed Feb 10, 2010 9:55 am

that's a great link. Thanks!
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Re: Single 3" exhaust vs 2.25" duals?

Post  944v8inDFW on Wed Feb 10, 2010 9:57 am

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Re: Single 3" exhaust vs 2.25" duals?

Post  Porch on Wed Feb 10, 2010 10:28 am

We've had this argument before, but i'll state my opinion again Smile

I think 2.25 is a little small. Dual 2.5" is more reasonable. It may not be required, but it isn't hurting anything.

If you're going single (which i think fits a lot better) then 3.5" is more reasonable. I personally run a 4". Everyone on the site tells me that's way too big and it'll kill my torque, and yet the dyno doesn't agree. So take that FWIW....
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Re: Single 3" exhaust vs 2.25" duals?

Post  Dawgz83948 on Wed Feb 10, 2010 10:38 am

My exhaust consists of 2x 2.5" pipe 1 X-pipe 2 cats (now illegal to replace in California IDIOTS) dual 2.5" to a welded dynomax muffler (2 inlet 1 out although it's supposed to be the other way around) single 3" to the tip.
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Re: Single 3" exhaust vs 2.25" duals?

Post  eclou on Wed Feb 10, 2010 10:44 am

Summit carries this which should work with less restriction - dual 3" inlet merging to a 3.5" outlet

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I think I am going to go with a single 3.5" outlet with a 6" round 3.5/3.5 in/out Magnaflow
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Re: Single 3" exhaust vs 2.25" duals?

Post  944v8inDFW on Wed Feb 10, 2010 10:49 am

The major reason i said that a 3 inch would be ok for his projected HP is that it is already there. If you are hunting for HP I would definatly do 2 1/2 head pipes and 3 1/2 tail. All mandrel bends.
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Re: Single 3" exhaust vs 2.25" duals?

Post  eclou on Wed Feb 10, 2010 11:08 am

I figure if I build it with a single 3.5" instead of 3" I have "room to grow" if I put some $$ into the heads and cam
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Re: Single 3" exhaust vs 2.25" duals?

Post  Porch on Wed Feb 10, 2010 12:21 pm

Preeeee-cisely.
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Re: Single 3" exhaust vs 2.25" duals?

Post  944-LT1 on Wed Feb 10, 2010 2:53 pm

Uh... News to me. I was planning a 3" exhaust but the calculator tells me I need 3.5". Rick, you saved me a bit of pain. I was just about to order 3" pipes and two 3" collectors! Neutral

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LS Exhaust

Post  Max Energy on Wed Feb 10, 2010 2:59 pm

Gene,
I am planning to use 2- 3" pipes from my collectors to a spade 2 into 1 4" Oval Merge collector. Then run 4" oval tubing to a magaflow 4" SS muffler. Check out Burns Stainless.
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Re: Single 3" exhaust vs 2.25" duals?

Post  robstah on Wed Feb 10, 2010 4:40 pm

4" is still way too big and I have never heard of this "room to grow theory". Unless you are aiming for 1000whp, 3" and or dual 2.25" is perfectly fine.

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Re: Single 3" exhaust vs 2.25" duals?

Post  HandofTron on Wed Feb 10, 2010 4:58 pm

My personal favorite setup is to bring the head pipes run separately to just past the front seats then use the merged Y and finish it off with a single tail pipe. Definitely gives that more exotic sound to it.

I don't know if I've ever heard one like that.. Any examples to how it sounds?

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Re: Single 3" exhaust vs 2.25" duals?

Post  Porch on Wed Feb 10, 2010 5:13 pm

Yeah yeah, 4" is too big. Why don't you argue with my dyno sheet...

2.25" duals or 3" single is too small in the real world with a modified motor, i don't care what "theory" says.
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Re: Single 3" exhaust vs 2.25" duals?

Post  gt1scca on Wed Feb 10, 2010 10:17 pm

Porch wrote:Why don't you argue with my dyno sheet...
Rolling Eyes

The end-all of all other opinions.
The "Dyno Sheet".

I have another one for ya...
The "Telephone Pole".

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Re: Single 3" exhaust vs 2.25" duals?

Post  Porch on Wed Feb 10, 2010 10:33 pm

I went with 4" because it was about the same price, it fits just as easily under the car, and it's way easier to cram 2x 2.5" pipes into an oval 4" pipe than an oval 3.5" pipe. My exhaust goes 2.5" dual to 4" single to 2.5" dual, through a 2.5" dual-in dual-out muffler and two tips. You can guess where the restriction is.

Is it overkill? Sure. Did it affect my power at all? No.

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Suck on that, exhaust theory!
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Re: Single 3" exhaust vs 2.25" duals?

Post  gt1scca on Wed Feb 10, 2010 10:37 pm

That was a joke, BTW.

Seriously,

Most of the opinions here are correct to an extent.
Low to mid-range torque is tunable with exhaust routing and sizing. Peak torque can be moved up or down the RPM range by varying tubing size and collector design and location.

High RPM horsepower benefits greatly from larger, free-flowing exhaust.
The "defined crossover point" is also affected by cam profile and cylinder head design.
Factor in volumetric efficiency while your at it.

Unless you have a flow bench, you're taking an educated guess at it.

No arguement.
Just the way I see it...

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Re: Single 3" exhaust vs 2.25" duals?

Post  modenas on Thu Feb 11, 2010 11:04 am

i dont understand why you guys are getting mad over losing torque. you should be happy, if you didnt lose torque then you snap the tranny, lose several hundred dollars all cause you waned to keep your stupid torque
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Re: Single 3" exhaust vs 2.25" duals?

Post  Admin on Thu Feb 11, 2010 11:09 am

Torque is what move your car, not HP.

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Re: Single 3" exhaust vs 2.25" duals?

Post  948 on Thu Feb 11, 2010 11:21 am

Why don't you argue with my dyno sheet...

Porch,
How does this compare to your dyno numbers when you ran the 2.5" down pipes and 3" exhaust?....
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Re: Single 3" exhaust vs 2.25" duals?

Post  Wild Bill on Thu Feb 11, 2010 11:48 am

I was thinking of continuing 3" from my collectors to a merged Y into 3 1/2" to the back. Band clamp the Y pipe to the collectors, Short resonator/glasspack? in the middle and 17" X 9" oval at the back. I have some 5" exhaust pipe, figured I would just fab something up?


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Re: Single 3" exhaust vs 2.25" duals?

Post  Porch on Thu Feb 11, 2010 5:18 pm

I know you were joking, gt1scca... Smile

I never had a 3" exhaust, this is the only exhaust i've had on the car.
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Re: Single 3" exhaust vs 2.25" duals?

Post  stuart f. wright on Thu Feb 11, 2010 6:29 pm

i have 4 inch exsaust in stock location routed to a big chrome fart can mufler in stock location and it seems to work just fine .sounds good not to loud till you get on it.i put the fart can on it just to screw with the import guys.nothing like the sound of a well tuned v8 .if your dumping a lot of fuel and moving a bunch air then you need a lot more.my rule of thumb is volumetric efficency.depending on your cam heads intake size compresion ratio affects what size of exsaust that you need.dual chrome tips dont make it any faster.
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need to pull the trigger

Post  xschop on Mon Mar 08, 2010 7:46 pm

What are the suggestions for the modded 2312 headers. I looked and the stock 944 muffler looks in good shape, but I can get a flowmaster if need be. Can the stock half of the exhaust including the muffler be reused since I'm only running a 5.3?
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