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Old 02-22-2013, 11:40 AM   #1
mike27408
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Stepped headers....

Anyone in here seen a car's HP/TQ increase or E.T. go down from switching to a stepped header in an NA application?? I could see if I was SC or Turbo'd needing an 1-7/8"x2" stepped header...

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Old 02-22-2013, 11:48 AM   #2
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My SOTP feeling is I lost torque with my Kooks SS headers. No dyno graph to back it up, just my impression. Hopefully will get the car dynotuned in a month or two, so we'll where I'm at then.
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Old 02-22-2013, 12:33 PM   #3
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Stepped headers attempt to combine the higher exhaust velocity of a smaller primary tube with the reduced pumping losses of a larger one. Actually, it would help very little with a properly cammed F/I engine, as the scavenging improvement sought by the higher velocity portion would be lost on a low overlap cam setup. Whether it improves or degrades performance in a given setup is meaningless without knowing a lot more about the cam and head specifics. Sorry interwebz racers, stroke, head, cam, and exhaust are inexorably intertwined.
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Old 02-23-2013, 07:43 AM   #4
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I was noodling with the idea but shot it down...im not going to make a $1500.00 gamble and risk worse ET/less perfrmance... 1-7/8" is enough for a built BBC
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Old 02-23-2013, 12:18 PM   #5
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Stepped headers are all about keeping the exhaust gas moving faster. Your exhaust port in your head is less than 1 5/8". When you put a 1 7/8" header on, there is a loss in exhaust pressure and velocity because the port is so big. The stepped header adds a 6" section of 1 3/4" piping to keep exhaust velocity up. There is no way really you can lose low end TQ in this scenario..and it should increase it. In very simple terms, I always remind people how if you slightly pinch a garden hose, the water moves faster. Save idea with a stepped header.

I pay attention every time someone posts a stepped header dyne sheet...and for the application, the power numbers are always at the very high end of what you would expect.
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Old 02-25-2013, 07:30 PM   #6
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Mine were installed when the Kooks SS header's first came out. The dyno runs at Carolina Auto Masters were higher than any other car with a similar set-up (other than headers obviously) as mine at that time there. 349 rwhp and 361 torque on a naturally aspirated '04. Only other mods were a K&N fipk, SLP MAF and Loudmouth II exhaust. I didn't go with the catless mids.

I haven't changed anything else since then and have no desires of doing anything else. I am very pleased.

Last edited by bandit12; 02-25-2013 at 07:37 PM.
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Old 02-26-2013, 06:39 AM   #7
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Cool info, bandit. My car has similar mods to yours, albeit WITHOUT a proper dyno tune and 85mm MAF. Hoping that the dyno tune is my missing element (which it likely is) to bring out the full power of my Kooks SS. My SOTP results are just that, SOTP results, so they've not been "normalized" with a dyno tune to put them on the same playing field as other folks with Kooks SS, nor do I have any dynographs to "prove" anything.
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Old 02-26-2013, 10:58 AM   #8
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I don't have exact comparison numbers but I know my car added some good torque when I changed to stepped heads along with a few other small things.
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Old 02-26-2013, 01:55 PM   #9
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Stepped headers will add power no matter if it is n.a or power added. Its always best to run a stepped header if possible.
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Old 02-26-2013, 02:54 PM   #10
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I bought the stepped headers for the increased power under the curve. I remember when Marylandspeed first introduced them, the comparison dyno showed something like an additional 5-10 ft/lbs or so under the curve.
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Old 02-26-2013, 03:25 PM   #11
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I was looking into 1-7/8"-2" stepped headers but I figured when i switch to trick flows they cut the exhaust port and valvejob it to where it works like i have a 1-7/8"-2" stepped set...
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Old 02-26-2013, 03:59 PM   #12
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Quote:
Originally Posted by tech73x...View Post
Stepped headers will add power no matter if it is n.a or power added. Its always best to run a stepped header if possible.

Try it with a cam with no overlap and get back to me.
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Old 02-26-2013, 07:02 PM   #13
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Steped headers work GREAT! i had KooKs make me the first set about 6 yrs ago.The gain is seen with OPEN headers ,once you bolt the rest of the sytem up you lose your gain... If you run open headers it will help
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Old 02-28-2013, 05:01 AM   #14
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Quote:
Originally Posted by mistermike...View Post
Try it with a cam with no overlap and get back to me.

Seriously? If you have ever had a motor not make more horsepower with stepped headers something was way wrong. Ask any major performance engine builder.
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Old 02-28-2013, 05:02 AM   #15
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Reminds me of the post that vacuum pumps don't help with making horsepower on here not to long ago, jeez the internet
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Old 02-28-2013, 06:01 AM   #16
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Quote:
Originally Posted by mistermike...View Post
Stepped headers attempt to combine the higher exhaust velocity of a smaller primary tube with the reduced pumping losses of a larger one. Actually, it would help very little with a properly cammed F/I engine, as the scavenging improvement sought by the higher velocity portion would be lost on a low overlap cam setup. Whether it improves or degrades performance in a given setup is meaningless without knowing a lot more about the cam and head specifics. Sorry interwebz racers, stroke, head, cam, and exhaust are inexorably intertwined.

As far as exhaust scavenging is concerned, a supercharged motor will behave almost like an N/A motor, as the exhaust still has the same flow path/pressure differentials/characteristics, and the intake side just has air that's at 25 PSIa instead of 14.7 PSIa. It results in less of a gain, but how much less is directly dependent upon how much boost you're running, since it's about pressure ratios. Increasing boost will increase the pressure differential, making the gain in pressure wave tuning only worth 14.7/(14.7+X boost)% of what it would be on an N/A motor.

At least, this is my understanding. *hoping EdC doesn't come in and make me look like a retard, lol*

Quote:
Originally Posted by mistermike...View Post
Try it with a cam with no overlap and get back to me.

I think he's right mike. Most of the effects would be gone, since the main benefit is during overlap, but the design itself helps prevent reversion and will see SOME kind of gain...definitely not a loss (when comparing 1.75x1.875 to 1.875 the whole length. It might not be significant, but it won't make less power, unless i suppose if the 1.75" section is choking the exhaust, but you need to be pushing some good power first
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Old 03-04-2013, 01:54 PM   #17
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Quote:
Originally Posted by paulsz28...View Post
Cool info, bandit. My car has similar mods to yours, albeit WITHOUT a proper dyno tune and 85mm MAF. Hoping that the dyno tune is my missing element (which it likely is) to bring out the full power of my Kooks SS. My SOTP results are just that, SOTP results, so they've not been "normalized" with a dyno tune to put them on the same playing field as other folks with Kooks SS, nor do I have any dynographs to "prove" anything.

You are going to want that tune....

1st run before tune: hpr - 311.5, trq - 319.9
4th run after tune: hpr - 349.1, trq - 361.6
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Old 03-04-2013, 02:07 PM   #18
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The gain is seen with OPEN headers ,once you bolt the rest of the sytem up you lose your gain... If you run open headers it will help[/QUOTE]

^Before deciding on stepped or not I consulted American Racing Headers
they stated this exactly.
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Old 03-04-2013, 02:12 PM   #19
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Quote:
Originally Posted by HunterKiller89...View Post
As far as exhaust scavenging is concerned, a supercharged motor will behave almost like an N/A motor, as the exhaust still has the same flow path/pressure differentials/characteristics, and the intake side just has air that's at 25 PSIa instead of 14.7 PSIa. It results in less of a gain, but how much less is directly dependent upon how much boost you're running, since it's about pressure ratios. Increasing boost will increase the pressure differential, making the gain in pressure wave tuning only worth 14.7/(14.7+X boost)% of what it would be on an N/A motor.

At least, this is my understanding. *hoping EdC doesn't come in and make me look like a retard, lol*



I think he's right mike. Most of the effects would be gone, since the main benefit is during overlap, but the design itself helps prevent reversion and will see SOME kind of gain...definitely not a loss (when comparing 1.75x1.875 to 1.875 the whole length. It might not be significant, but it won't make less power, unless i suppose if the 1.75" section is choking the exhaust, but you need to be pushing some good power first

Yeah, pretty much. Scavenging, at least in the sense of outgoing exhaust pulling more fuel/air into the combustion chamber requiring intake and exhaust valves to be open simultaneously, will allow a volumetric efficiency > 100% over the RPM range when the phasing of the intake and exhaust pressure waves is favorable. I certainly don't think that throwing stepped headers at a engine with a blower cam would be deleterious, but without the additional scavenging you'd see with a cam with lots of overlap, certainly no better than a set of straight 1 7/8 under those circumstances. The reduced diameter at the end closer to the head would have minimal effect on pumping losses, because the exhaust gasses are so hot at that point, the density is not going to allow a pressure bottleneck until the power levels are ridiculous. As the gasses cool, the primary diameter has an increasing resistive component.
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