The LS1 swap has begun
09-13-2010, 09:04 AM
#213
The set of headers I have are longer than those just becaues the collectors are welded to the tubes . I think long tube headers are just a space issue. I have seen one set someone made but they were not in a car.
09-13-2010, 10:02 AM
#214
Rennlist Member
Thread Starter
I haven't seen the collectors yet Tony. I assume they bolt to the primaries and neck down to then bolt to the cats.
Yep, I have to run all the emissions stuff in my state, that's why I have the smog pump fittings on them. These are as long tube as I can run and still fit everything properly.
They are the S&P headers, fit very well!
The oil pan has finally arrived, so hopefully everything is going into the car and it will fire soon!
Oh and Greg, it'll definitely fit!
Yep, I have to run all the emissions stuff in my state, that's why I have the smog pump fittings on them. These are as long tube as I can run and still fit everything properly.
They are the S&P headers, fit very well!
The oil pan has finally arrived, so hopefully everything is going into the car and it will fire soon!
Oh and Greg, it'll definitely fit!
09-13-2010, 05:54 PM
#218
Burning Brakes
agreed. If you were going for just maximum raw horsepower, i'd definitely suggest LT and true duals. Some guy on ls1tech did a comparison on his h/c car and i think he gained something ~15 HP with true duals and dumping the exhaust by the axle. but again, i don't know if the effect will be as drastic with the 944 since there's less bends... and no over axle bend.
also, you said you're trying to stay within 380 so you're probably fine as is.
DVC, what headers are those? and how'd you get them to come together like that?
also, you said you're trying to stay within 380 so you're probably fine as is.
DVC, what headers are those? and how'd you get them to come together like that?
09-14-2010, 11:23 AM
#219
Burning Brakes
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agreed. If you were going for just maximum raw horsepower, i'd definitely suggest LT and true duals. Some guy on ls1tech did a comparison on his h/c car and i think he gained something ~15 HP with true duals and dumping the exhaust by the axle. but again, i don't know if the effect will be as drastic with the 944 since there's less bends... and no over axle bend.
Here's the link in the picture, has some nifty calculators:
http://www.engineeringtoolbox.com/da...ion-d_646.html
On a v8, the only reason i would go with duals is for sound...but then, i also have no complaints about the sound from my single 3.5"
09-14-2010, 05:34 PM
#221
Burning Brakes
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Area (pi x r^2):
3" single: 1.5^2 x 3.1415926.. = 7.0685...
2.5" duals: 1.25^2 x 3.1415926.. x 2 = 9.81747...
3.5" single: 1.75^2 x 3.1415926.. = 9.6211...
So my point is, duals aren't necessarily better than a single--and on paper at least, they have a decreased velocity, which would negatively affect scavenging.
In the end though, who cares. These are street motors, not F1 engines.
09-14-2010, 06:42 PM
#222
Rennlist Junkie Forever
And the 2.5" duals still have a greater area than a single 3.5" (even if only by a little bit).
But the deal was the engine felt "flat" on top with the single 3". The duals added the power where it needed to be.
The other thing that help the top end was eliminating the sharp 90 degree bend in the intake (to clear the hood latch). But cutting out the hood latch and going straight from the throttle body to the MAF & Air filter I picked up another 7+RWHP ish... All up top.
Plus... it gave me an excuse to use a glass hood which saved a TON of weight (up high weight).
TonyG
But the deal was the engine felt "flat" on top with the single 3". The duals added the power where it needed to be.
The other thing that help the top end was eliminating the sharp 90 degree bend in the intake (to clear the hood latch). But cutting out the hood latch and going straight from the throttle body to the MAF & Air filter I picked up another 7+RWHP ish... All up top.
Plus... it gave me an excuse to use a glass hood which saved a TON of weight (up high weight).
TonyG
Right, but again that's going from a smaller exhaust to a bigger exhaust:
Area (pi x r^2):
3" single: 1.5^2 x 3.1415926.. = 7.0685...
2.5" duals: 1.25^2 x 3.1415926.. x 2 = 9.81747...
3.5" single: 1.75^2 x 3.1415926.. = 9.6211...
So my point is, duals aren't necessarily better than a single--and on paper at least, they have a decreased velocity, which would negatively affect scavenging.
In the end though, who cares. These are street motors, not F1 engines.
Area (pi x r^2):
3" single: 1.5^2 x 3.1415926.. = 7.0685...
2.5" duals: 1.25^2 x 3.1415926.. x 2 = 9.81747...
3.5" single: 1.75^2 x 3.1415926.. = 9.6211...
So my point is, duals aren't necessarily better than a single--and on paper at least, they have a decreased velocity, which would negatively affect scavenging.
In the end though, who cares. These are street motors, not F1 engines.
09-14-2010, 06:44 PM
#223
Drifting
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Over a comparably-sized single? I would be really surprised. If he went from a single 3" to dual 2.5" i could see a hp gain (just from a cfm of airflow standpoint), but just having dual pipes isn't an advantage. In fact, it destroys velocity, which affects scavenging:
Here's the link in the picture, has some nifty calculators:
http://www.engineeringtoolbox.com/da...ion-d_646.html
On a v8, the only reason i would go with duals is for sound...but then, i also have no complaints about the sound from my single 3.5"
Here's the link in the picture, has some nifty calculators:
http://www.engineeringtoolbox.com/da...ion-d_646.html
On a v8, the only reason i would go with duals is for sound...but then, i also have no complaints about the sound from my single 3.5"
Definitely worth the effort Doc, is the right way to do it
09-14-2010, 06:55 PM
#224
Burning Brakes
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I don't have a single 3" exhaust, nor was i advocating for a single 3". I'm talking about a single 3.5", which is what i have 
It fits better than duals, it's cheaper than duals, it has a higher exhaust velocity than duals, and in terms of pipe area it's only a tiny bit smaller than 2.5" duals (though if we were to really test them out, i think velocity would more than make up for the size difference).
Edit: by the way, i'm not saying anything bad about duals. I'm just saying that "dual exhaust" isn't necessarily a performance feature. A high flowing exhaust is what matters--whether it has one pipe, two pipes, eight pipes, or 100 pipes.
Edit again, here you go:
1. For avoiding significant restriction from back pressure, the pipe should flow at least 2.2CFM per horsepower produced.
2. A straight pipe will flow ~115CFM per square inch of area (using inside diameter of the pipe)
-(Courtesy of David Vizard)
I'm not going to measure the inside diameter of pipe, but just using the outside pipe diameters:
Dual 2.5" pipes = 9.8 x 115 = 1127 cfm / 2.2 cfm per horsepower = 512 horsepower capable
Single 3.5" pipe = 9.6 x 115 = 1104 cfm / 2.2 cfm per horsepower = 501 horsepower capable
Since we're all talking about 400hp engines here, there is no difference. If you approached the 500hp mark, i would move to a larger exhaust whether i had 2.5" duals or a 3.5" single.
...but don't let me stop you from enjoying the extra 11 horsepower that a 2.5" dual exhaust system could hypothetically handle :P
It fits better than duals, it's cheaper than duals, it has a higher exhaust velocity than duals, and in terms of pipe area it's only a tiny bit smaller than 2.5" duals (though if we were to really test them out, i think velocity would more than make up for the size difference).
Edit: by the way, i'm not saying anything bad about duals. I'm just saying that "dual exhaust" isn't necessarily a performance feature. A high flowing exhaust is what matters--whether it has one pipe, two pipes, eight pipes, or 100 pipes.
Edit again, here you go:
1. For avoiding significant restriction from back pressure, the pipe should flow at least 2.2CFM per horsepower produced.
2. A straight pipe will flow ~115CFM per square inch of area (using inside diameter of the pipe)
-(Courtesy of David Vizard)
I'm not going to measure the inside diameter of pipe, but just using the outside pipe diameters:
Dual 2.5" pipes = 9.8 x 115 = 1127 cfm / 2.2 cfm per horsepower = 512 horsepower capable
Single 3.5" pipe = 9.6 x 115 = 1104 cfm / 2.2 cfm per horsepower = 501 horsepower capable
Since we're all talking about 400hp engines here, there is no difference. If you approached the 500hp mark, i would move to a larger exhaust whether i had 2.5" duals or a 3.5" single.
...but don't let me stop you from enjoying the extra 11 horsepower that a 2.5" dual exhaust system could hypothetically handle :P
09-14-2010, 07:05 PM
#225
Drifting
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I don't have a single 3" exhaust, nor was i advocating for a single 3". I'm talking about a single 3.5", which is what i have
It fits better than duals, it's cheaper than duals, it has a higher exhaust velocity than duals, and in terms of pipe area it's only a tiny bit smaller than 2.5" duals (though if we were to really test them out, i think velocity would more than make up for the size difference).
Edit: by the way, i'm not saying anything bad about duals. I'm just saying that "dual exhaust" isn't necessarily a performance feature. A high flowing exhaust is what matters--whether it has one pipe, two pipes, eight pipes, or 100 pipes.
It fits better than duals, it's cheaper than duals, it has a higher exhaust velocity than duals, and in terms of pipe area it's only a tiny bit smaller than 2.5" duals (though if we were to really test them out, i think velocity would more than make up for the size difference).
Edit: by the way, i'm not saying anything bad about duals. I'm just saying that "dual exhaust" isn't necessarily a performance feature. A high flowing exhaust is what matters--whether it has one pipe, two pipes, eight pipes, or 100 pipes.
Would love to hear/see back to back dyno of two 2.5, vs one 3.5 - would be curious about backpressure/low end/mid range comparisons. I suspect the twin muffler of a dual may have as good mid with a reduced backpressure benefit on top.