The truth about open headers...
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From: From the Bowels of Hell!!! You want some of me bitch?!?!?!
Re: The truth about open headers... Sure, on non-emmisioned cars(no O2's), it makes a good bit of difference.
On a car w/O2's, plain and simple, it sucks. Now, yes you can play with collector length to help out, but just taking the exhaust off, nope sorry, I have to agree with Colonel and I have tried it myself. The low end power was not there. It sucked BAD. SOME backpressure IS necessary.
Tim
On a car w/O2's, plain and simple, it sucks. Now, yes you can play with collector length to help out, but just taking the exhaust off, nope sorry, I have to agree with Colonel and I have tried it myself. The low end power was not there. It sucked BAD. SOME backpressure IS necessary.
Tim
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Launching!
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From: St. Paul, MN
Re: The truth about open headers... Well, I was the original poster and I must say that ChrisB seems to be the only one to convince me. This is very interesting. It makes perfect since that tuned correctly open headers is the best (i.e. cars at the dragstip!!!) I realize that I'll need some pipe afterwards for the o2's...but not much!
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From: From the Bowels of Hell!!! You want some of me bitch?!?!?!
Re: The truth about open headers... [quote]Originally posted by Jacobi:
<strong>Well, I was the original poster and I must say that ChrisB seems to be the only one to convince me. This is very interesting. It makes perfect since that tuned correctly open headers is the best (i.e. cars at the dragstip!!!) I realize that I'll need some pipe afterwards for the o2's...but not much!</strong><hr></blockquote>
Go for it. Post your results whether good or bad.
Tim
<strong>Well, I was the original poster and I must say that ChrisB seems to be the only one to convince me. This is very interesting. It makes perfect since that tuned correctly open headers is the best (i.e. cars at the dragstip!!!) I realize that I'll need some pipe afterwards for the o2's...but not much!</strong><hr></blockquote>
Go for it. Post your results whether good or bad.
Tim
Re: The truth about open headers... ChrisB is correct however, what is not talked about is exhaust scavenging. The pulse of air flow created in the tubes that sucks the "bad" air out of the cylinder. Proper tuning of the exhaust is needed to enhance or amplify the pulses which is why X (or balance) pipes work well (mid range torque). With open headers, properly tuning the collector length accomplishes this. A while back, I tested some SBC (with EFI) Hooker headers with open headers, closed full duals and X pipes and found the most power when we tuned the collectors length and ran open tubes. Without the header collector extensions we DID see a loss in low end power over the full duals with the balance tube.
Just my view <img src="images/icons/wink.gif" border="0">
Mikey
[ November 26, 2001: Message edited by: Rapid Motorsports ]</p>
Just my view <img src="images/icons/wink.gif" border="0">
Mikey
[ November 26, 2001: Message edited by: Rapid Motorsports ]</p>
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From: College Station, Tx
Re: The truth about open headers... [quote]Originally posted by Tim98TA:
[QB]Sure, on non-emmisioned cars(no O2's), it makes a good bit of difference.
On a car w/O2's, plain and simple, it sucks.<hr></blockquote>[/b]
Well then it follows that it isn't the backpressure, or anything else - it is the a/f ratio (tuning) that is causing you to loose powers - otherwise it wouldn't make a difference if you had O2's or not. So instead of saying it doesn't work, I am saying you have to take this into account - you can go open loop (what I did), run extensions, etc. - but the point is it's not Open Headers (low backpressure) that's bad, it's problems with your fueling system.
[quote] Now, yes you can play with collector length to help out, but just taking the exhaust off, nope sorry
[...]
The low end power was not there. It sucked BAD. SOME backpressure IS necessary.
Tim<hr></blockquote>
I agree - you can't just take them off - when I qualified my statement I said you need to keep the timing and fueling optimal - as well as possibly adjust the collector length for your rpm.
But no, backpressure is NOT necessary. There is no model of a 4 stroke engine that requires backpressure to perform - it is at it's simplest just parasitic loss.
[quote] Its all just theory until you actually try it and dyno the changes.
For me it was a measured loss. <hr></blockquote>
I agree -it is all theory (the way I was approaching the question). Like mikey points outs tuning is required. Since there isn't an easy way to tune the LS1 computer (yet - LS1 Edit) there is a big difference between saying you need tuning and actually doing it. My LT1 lost power/torque with just open headers - but after setting up the fuel and timing properly it made more power across the board.
Chris
[QB]Sure, on non-emmisioned cars(no O2's), it makes a good bit of difference.
On a car w/O2's, plain and simple, it sucks.<hr></blockquote>[/b]
Well then it follows that it isn't the backpressure, or anything else - it is the a/f ratio (tuning) that is causing you to loose powers - otherwise it wouldn't make a difference if you had O2's or not. So instead of saying it doesn't work, I am saying you have to take this into account - you can go open loop (what I did), run extensions, etc. - but the point is it's not Open Headers (low backpressure) that's bad, it's problems with your fueling system.
[quote] Now, yes you can play with collector length to help out, but just taking the exhaust off, nope sorry
[...]
The low end power was not there. It sucked BAD. SOME backpressure IS necessary.
Tim<hr></blockquote>
I agree - you can't just take them off - when I qualified my statement I said you need to keep the timing and fueling optimal - as well as possibly adjust the collector length for your rpm.
But no, backpressure is NOT necessary. There is no model of a 4 stroke engine that requires backpressure to perform - it is at it's simplest just parasitic loss.
[quote] Its all just theory until you actually try it and dyno the changes.
For me it was a measured loss. <hr></blockquote>
I agree -it is all theory (the way I was approaching the question). Like mikey points outs tuning is required. Since there isn't an easy way to tune the LS1 computer (yet - LS1 Edit) there is a big difference between saying you need tuning and actually doing it. My LT1 lost power/torque with just open headers - but after setting up the fuel and timing properly it made more power across the board.
Chris
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From: Troy, AL
Re: The truth about open headers... For anyone wondering, I do run open headers on my car WITH tubes afterwards (don't know if they are the right length for tuning but they do keep the O2 sensors happy.) Even with my large displacement engine I saw absolutely no increase in performance with open headers over my 3" Y-pipe (this was also confirmed on MTI's dyno.) My running them open is strictly for weight reasons.
So I guess everyone can agree that at least SOME pipe after the headers is necessary (is that still considered "open" headers?)
Try it completely open (no extentions) and then again with an adequate Y-pipe and I'm sure you'll see that completely open doesn't work very well for LS1s.
[ November 26, 2001: Message edited by: Colonel ]</p>
So I guess everyone can agree that at least SOME pipe after the headers is necessary (is that still considered "open" headers?)
Try it completely open (no extentions) and then again with an adequate Y-pipe and I'm sure you'll see that completely open doesn't work very well for LS1s.
[ November 26, 2001: Message edited by: Colonel ]</p>
Re: The truth about open headers... I have experimented at the track, and I have not seen a gain by going open headers, or with 12" pipe bolted on. But I do believe that I may have seen something if that combination was optimized, by ATAP & MAFT. I dont believe that the true potential can be seen with any system, unless you explore all ways of maximizing that system. I'm still learning about ATAP, So when I experimented, I could not go beyond bolting on and hitting the track. Between the open headers, the Y-pipe, & the X, the X-pipe duals produced the best times for me.
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Teching In
Joined: Nov 2001
Posts: 1
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From: OKC
Re: The truth about open headers... Well I have a real nice open headers system with turndowns. It is on my lowered 99 TA and does not have any clearance problems. I picked up +3MPH and .3 quicker in the quarter mile with my setup. I used Dynatech longtubes (FLP's) with Coated Shoenfeld 3" 11"long collectors with 9" long turndowns. Inside the collectors I used Car Chemistry Insert Mufflers. The fit is perfect. Length is perfect so 02's dont go screwey. E-mail me for pics.
