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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My Exhaust Setup

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My Exhaust Setup

Post  Johnny Johnny on Mon Oct 05, 2009 7:23 am

Not a question, but thought it was kind of funny. I'm not sure how many of you follow the Rennlist and Pelican forums, but recently a guy put his 944S2-based 968 conversion car up for sale. I was flipping through the pictures and saw this one.

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Ironically, I just bought a Hooker Max Flow muffler and Magnaflow spun steel catalytic converter, both which are on this guy's car, along with the same 3" diameter exhaust pipe. Well, at least I know it fits!

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Re: My Exhaust Setup

Post  Porch on Tue Oct 06, 2009 10:36 am

I'm just sayin', but 4" is just as easy...
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Re: My Exhaust Setup

Post  Admin on Tue Oct 06, 2009 10:49 am

Who's car is really that clean under the rear end area? Shocked

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Re: My Exhaust Setup

Post  948 on Tue Oct 06, 2009 11:41 am

Very clean.
Fitting a 3" system is no problem. A 4" system is also an easy fit, though it would be a little big for any motor putting out less than 475hp....
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Re: My Exhaust Setup

Post  robstah on Tue Oct 06, 2009 3:34 pm

4" is way too big IMO. I've seen turbo cars put out over 600 to the wheels and not even need a 4" exhaust. 3" should work and should be the easiest to deal with, but I am probably going to end up doing true dual 2.5" or 2.25" all the way to the back.

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Re: My Exhaust Setup

Post  Porch on Tue Oct 06, 2009 4:21 pm

Dual 2.5" exhaust doesn't fit under the car as neatly as a single 4", and it's three times as much work.

Just going by area alone, 4" = 12.56, dual 2.5" = 9.817. You could go with a 3.5" if you were worried about too much flow (3.5" single = 9.62). For a 5.7L i don't think i would want a 3" or dual 2.25's...

Anyways, i'm happy with my 4" and it was a piece of cake to put together, but whatever makes you happy Smile

Edit, just for fun:
3" = 7.068
2x 2.25" = 7.952
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Re: My Exhaust Setup

Post  robstah on Tue Oct 06, 2009 4:44 pm

I'd still prefer the true dual setup over a single any day. A true dual setup will have better exhaust scavenging effects as well as a lower chance of drone and higher noise control. My 944, when done, will be more on the sleeper side compared to the "Hey look! I have an LS1" side.

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Re: My Exhaust Setup

Post  Porch on Tue Oct 06, 2009 5:53 pm

I'd actually be a little surprised if a dual setup had better scavenging. If you can prove it (find me a link!), i'll believe it. The passing exhaust gasses from the other cylinder bank, in my mind, would help to draw out the gases from the other bank.

As far as lower drone/noise control, you're actually better off with a single exhaust. The exhaust noises from each side cancel each other out and make for less noise. My car is actually a little "too" quiet for my tastes with 2x high-flow cats and a magnaflow muffler (dual 2.5" in and out). If it weren't for the cam, nobody would look twice. Even if you went dual 2.5" you would want a crossover of some sort ("H" or "X") for noise cancellation and increased tq/hp.

And really, "too much flow"? No concern there... I'm sure i lost some bottom end and picked up a tiny little bit of top end, but i really don't care about low-end torque (if anything, i'd rather lose some to keep my transmission and CV's happy).

I worked at a shop that specialized in high performance exhaust systems/headers/general fabrication for a little over a year. It doesn't quite make me an expert, but i've seen and heard more exhaust systems on more than my fair share of cars.
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Re: My Exhaust Setup

Post  948 on Tue Oct 06, 2009 7:43 pm

Those skilled in the art of exhaust design, for NA motors, will tell you the headers and collectors have the most impact on power and torque; specifically the shaping of the pipes into the collectors. They will also tell you that Turbo exhaust systems are a completely different animal, since most of the action occurs before the exhaust impeller....so a 4" system would not have a massive impact on the low mid range of a turbo engine.

Yes, your exhaust piping can be too big and one will see a loss of mid and low end power; mostly due to reduced exhaust gas velocity, pressure, and temperature and increased gas density.

A true single 3" exhaust, with a well designed header system, will flow enough for ~375hp.

An "X" pipe will increase mid power but will usually create a buzzing resonance, not counter it.

A single exhaust is normally quieter than a comparable dual system.

I have spoken to quite a few exhaust experts and have learned that I still have much to learn.
Luckily it is all out on the net, one just has to look for it......
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Re: My Exhaust Setup

Post  Admin on Tue Oct 06, 2009 8:31 pm

I have dual 2.5" all the way back, it's loud and it draws attention any where I go. And I like it! Twisted Evil Twisted Evil

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Re: My Exhaust Setup

Post  Porch on Wed Oct 07, 2009 11:06 am

Yes, if you have a completely (quality) mandrel-bent 3" exhaust with no seams, a great muffler, and all the latest exhaust theory incorporated, theoretically it's just fine for 375hp. Then again, we live in the real world and a 3.5" exhaust might make 380hp with a few bends and some seams, while only losing a little bit of torque.

There's a lot of info on the net, but i wouldn't say i trust any of it. Everyone has their secrets, and no secrets worth knowing ever get shared on the internet. That's not to say that what i know is right either. There's only two things i can say for sure:

1. I'll always be upgrading my car
2. If i only build one exhaust, i'd rather it be "too big" than "too small".
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Re: My Exhaust Setup

Post  948 on Wed Oct 07, 2009 5:55 pm

When I said experts, I was not talking about "experts" at an over priced muffler shop.
75% of what you need to know about exhaust flow can be had in a few semesters of fluid dynamics.

The information I refer to, from the experts, is out there for anyone to see.
[You must be registered and logged in to see this link.]
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I am hoping to schedule a business trip around March time so I can attend this...just for fun.
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My field of work has allowed me to meet many great minds from the OEM automotive and aerospace industry. When I am presented with the opportunity to pick their brains, I do.

I would prefer that my exhaust is sized just right....

Respectfully,
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Re: My Exhaust Setup

Post  944ls on Thu Oct 08, 2009 10:42 am

There are 3 formulas that I am very interested in. Primary length, Primary d and single exhaust pipe d. Can anybody help me find these? I am also interested in exploring a tri y setup using merge collectors primarily because 2 pipes per side would be easyer to get around the bellhousing than 4. I realize that the tri y setup will louse a little at higher rpm. But it may be an advantage when you compare to a 4 tube set up that is too short, particularly when considering packaging advantages. I have no idea how to size the tri y set up and a cut and try approach is not workable for me either (very limited dyno time). Thanks Guys

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Re: My Exhaust Setup

Post  Porch on Thu Oct 08, 2009 11:34 am

Oh my! Well i certainly don't care about my exhaust enough to take a class in fluid dynamics...you win! Embarassed

Anyways, considering that our headers are certainly less than optimal (whether RH, Sanderson, or the ones being modified in the other thread), and you said yourself that the headers and collectors are the most important part of the equation, what are you really expecting with a "just right" sized exhaust? Our collectors aren't even close to optimally sized, and the immediate 35* turn they make isn't helping...

Theory is nice, but reality is even better...and the reality is that i like my 4" exhaust, and my car makes great power with it! (see below) Smile

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Note: Dyno'd at 5700ft elevation, thus the correction factor. Land & Sea dyno (don't read as high as the dynojets), minimally tuned, and a huge air restriction on the intake (so it dead-ends at 5700rpm). Point being...look at my torque curve.
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Re: My Exhaust Setup

Post  948 on Thu Oct 08, 2009 1:23 pm

Porch wrote:considering that our headers are certainly less than optimal....Our collectors aren't even close to optimally sized, and the immediate 35* turn they make isn't helping...my 4" exhaust.... minimally tuned, and a huge air restriction on the intake..look at my torque curve.
Rolling Eyes imagine how much better it could be if you fixed all the above problems you mentioned....
The torque numbers look like a 5.7L LT4 set-up...what engine do you have?
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Re: My Exhaust Setup

Post  Porch on Thu Oct 08, 2009 2:22 pm

It's not really a max-effort race car to me (just a fun daily driver), so i don't really have an itch to build a set of equal-length headers with longer collectors and another complete exhaust system just to squeeze the last 5 horsepower out of it. Much easier to slap on a power-adder or a better set of cylinder heads on if i get an itch for more power! (and i've got the exhaust to handle it!) There are guys hitting mid 400 horsepower on LS1Tech with just bolt-ons!

Motor is an '01 LS1 with a mild single-pattern 224/.575 @ 113 cam. A tune and a better intake are coming as soon as it starts running again (i spent quite a few months waiting on Constantine's TT bearings...).
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Re: My Exhaust Setup

Post  Johnny Johnny on Thu Oct 08, 2009 4:39 pm

944ls wrote:There are 3 formulas that I am very interested in. Primary length, Primary d and single exhaust pipe d. Can anybody help me find these? I am also interested in exploring a tri y setup using merge collectors primarily because 2 pipes per side would be easyer to get around the bellhousing than 4. I realize that the tri y setup will louse a little at higher rpm. But it may be an advantage when you compare to a 4 tube set up that is too short, particularly when considering packaging advantages. I have no idea how to size the tri y set up and a cut and try approach is not workable for me either (very limited dyno time). Thanks Guys

Porch wrote:Anyways, considering that our headers are certainly less than optimal (whether RH, Sanderson, or the ones being modified in the other thread), and you said yourself that the headers and collectors are the most important part of the equation, what are you really expecting with a "just right" sized exhaust? Our collectors aren't even close to optimally sized, and the immediate 35* turn they make isn't helping...

I've been working on an alternative method of modifying the Hooker short-tubes, but have stopped working on them - they are bothering me too much. They'll certainly work fine, and you can't beat the price, but there's got to be a better solution. Especially for those with 5.3l, where we need to squeeze out every bit of HP, an optimized header design is very important. I'm 99% positive that a 180deg design won't fit unless we use a very shallow dry sump pan, so it's either 4-1 or tri-y. I've got the supplies together, so I'm going back to the drawing board and pulling out the tools again to see what I can come up with.

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Re: My Exhaust Setup

Post  Porch on Fri Oct 09, 2009 11:27 am

The 5.3's make pretty decent power with a good cam, from what i've heard? The cylinder heads are almost the same as the LS6 heads--they're better than the LS1 heads at least.
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Re: My Exhaust Setup

Post  gt1scca on Fri Oct 09, 2009 12:33 pm

440 HP Trailbazer...

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Re: My Exhaust Setup

Post  Johnny Johnny on Fri Oct 09, 2009 3:53 pm

Porch wrote:The 5.3's make pretty decent power with a good cam, from what i've heard? The cylinder heads are almost the same as the LS6 heads--they're better than the LS1 heads at least.

(the L33 HO variant) - Oh yeah Laughing

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Re: My Exhaust Setup

Post  Johnny Johnny on Fri Oct 09, 2009 3:54 pm

gt1scca wrote:440 HP Trailbazer...

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LS2

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Re: My Exhaust Setup

Post  gt1scca on Fri Oct 09, 2009 6:48 pm

OOps...memory goin' South.
Razz

This is what I was looking for...
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Re: My Exhaust Setup

Post  B.Rudy on Tue Nov 10, 2009 9:38 am

Johnny Johnny wrote:

I've been working on an alternative method of modifying the Hooker short-tubes, but have stopped working on them - they are bothering me too much. They'll certainly work fine, and you can't beat the price, but there's got to be a better solution. Especially for those with 5.3l, where we need to squeeze out every bit of HP, an optimized header design is very important. I'm 99% positive that a 180deg design won't fit unless we use a very shallow dry sump pan, so it's either 4-1 or tri-y. I've got the supplies together, so I'm going back to the drawing board and pulling out the tools again to see what I can come up with.

And you just keep on keep'n on with those headers. Were all looking forward to what you come up with. cheers

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