How much power loss from running open headers?
Thread Starter
Melting Slicks
Joined: Jan 2003
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From: What did the 5 fingers say to the face? SLAP!!
How much power loss from running open headers?
I just got done bolting on the headers so I did what anyone else would do. I went for a drive before hooking up the rest of the exhaust. I was surprised to find out that I had no power thrpoughout the range. I know I'll get the power back when I put the rest of the exhaust back on tomorrow, but THIS much?! What experience did you guys have?
Melting Slicks
Joined: Mar 2002
Posts: 3,108
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From: S.L.C. UT
Re: How much power loss from running open headers? (flyersfan1088)
You probably leaned out your air fuel mixture. If you were going to run with open headers, you would want to add fuel to correct your air fuel mixture.
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
Re: How much power loss from running open headers? (tpi 421 vette)
Unless you tune the fuel for reduced back pressure you will lean out. That's the usual reason people say the need back pressure; of course the other reason is too "big" of a cam so that the intake charge just blows through.
If you had a scan tool you could bump fuel pressure till you got about 890-920 mV at the O2 sensor at WOT.
Race Director
Joined: Dec 2002
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Re: How much power loss from running open headers? (tpi 421 vette)
You don't need 'back pressure' to run strong, but you do need to tune the engine for the change in the exhaust.
If back pressure were required, then the stock exhaust manifolds/pipes would be the 'hot ticket' for power and a single 1" exhaust would be mandatory for those 12 second runs.
A free-flowing exhaust is required for more power because it has LESS back-pressure.
The old wive's tale that you need back pressure for power is a popular one, but false nonetheless.
Keep tunin'.
Larry
code5coupe
If back pressure were required, then the stock exhaust manifolds/pipes would be the 'hot ticket' for power and a single 1" exhaust would be mandatory for those 12 second runs.
A free-flowing exhaust is required for more power because it has LESS back-pressure.
The old wive's tale that you need back pressure for power is a popular one, but false nonetheless.
Keep tunin'.
Larry
code5coupe
Thread Starter
Melting Slicks
Joined: Jan 2003
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From: What did the 5 fingers say to the face? SLAP!!
Re: How much power loss from running open headers? (rocco16)
Keep in mind I don't want to tune for open headers. The rest of the exhaust will go back up in the next few days. I was just kind of surprised at how much it killed my power.
[Modified by flyersfan1088, 8:46 PM 7/5/2004]
[Modified by flyersfan1088, 8:46 PM 7/5/2004]
Race Director
Joined: Dec 2002
Posts: 13,348
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Re: How much power loss from running open headers? (flyersfan1088)
Keep in mind I don't want to tune for open headers.
[QUOTE] I was just kind of surprised at how much it killed my power.
QUOTE]
It shouldn't have been THAT drastic. Are you sure you didn't do something else? Even something by accident? Check around....
Larry
Team Owner
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From: I'm the walkin dude I can see all of the world...
St. Jude Donor '03
Re: How much power loss from running open headers? (flyersfan1088)
Have you installed your O2 sensors yet and are they heated. This would make a big ol difference......
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From: Manassas VA
Re: How much power loss from running open headers? (VictorRussell'92)
I have heard that you have to add about 2 ft of pipe to the end of the headers due to the o2 sensor being out at the end.
