5.4l Help
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Joined: Feb 2003
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5.4l Help
hi all,
i have a '99 Lariat SCab with the 5.4L and about 110,000 miles. i took it off my brother's hands b/c the gas bill was hurting him in the wallet, and i have a question concerning that. he had true dual exhaust put on it some time ago, with delta 40 series flowmaster mufflers. i was looking underneath it, and noticed whoever did the work cut the crossmember, and sent each exhaust pipe straight back. that would be fine, but as i am sure many of you know the right pipe goes straight back while the left exhaust pipe snakes through the truck. there is no x-pipe configuration, and that is my question. is this hurting the gas mileage, or overall performance? i am pretty sure the o2 sensors in front and behind of the cats are not the issue, but maybe the egr valve? sorry for the long post, any help would be appreciated.
i have a '99 Lariat SCab with the 5.4L and about 110,000 miles. i took it off my brother's hands b/c the gas bill was hurting him in the wallet, and i have a question concerning that. he had true dual exhaust put on it some time ago, with delta 40 series flowmaster mufflers. i was looking underneath it, and noticed whoever did the work cut the crossmember, and sent each exhaust pipe straight back. that would be fine, but as i am sure many of you know the right pipe goes straight back while the left exhaust pipe snakes through the truck. there is no x-pipe configuration, and that is my question. is this hurting the gas mileage, or overall performance? i am pretty sure the o2 sensors in front and behind of the cats are not the issue, but maybe the egr valve? sorry for the long post, any help would be appreciated.
Technical Article Contributor
Joined: Dec 1997
Posts: 9,417
Likes: 11
From: Windsor,Ontario,Canada
Unless you have an x pipe or some sort of balance "H" pipe you are hurting power. The firing order is 1-3-7-2-6-5-4-8 so the passenger bank fires 1-3-skip-2-skip-skip-4 and the driver bank fires 7-skip-6-5-skip-8. This is not condusive to proper cylinder scavenging. Adding some sort of pipe to connect both banks together will help balance out the skips in the firing order.
JMC
JMC
Technical Article Contributor
Joined: Dec 1997
Posts: 9,417
Likes: 11
From: Windsor,Ontario,Canada
You are correct they don't have a "crossover tube" but they use a common muffler which accomplishes the same thing. read the section on Cross Overs and balance pipes. http://www.popularhotrodding.com/eng...xh/index1.html
JMC
JMC
Senior Member
Joined: Jul 2004
Posts: 6,200
Likes: 39
From: Easton, Pa.
This is exactly why when most put aftermarket exhaust on it loses power in the lower pulling rpm.
I think only Magnaflow has done a proper job of designing a system that keeps at least the factory performance level.
The factory system is very good because they are trying to get all the power that is practical out of these small engines.
4.6L = 281 cu/in.
5.4L = 330 cu/in.
Just because after market = power in the past, doesnot mean it, in this case, for regular non-performance use.
I think only Magnaflow has done a proper job of designing a system that keeps at least the factory performance level.
The factory system is very good because they are trying to get all the power that is practical out of these small engines.
4.6L = 281 cu/in.
5.4L = 330 cu/in.
Just because after market = power in the past, doesnot mean it, in this case, for regular non-performance use.