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broken exhaust and its effect on fuel consumption
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mike hammer
User
Mar 17, 2007, 7:31 PM
Post #1 of 2
(6330 views)
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broken exhaust and its effect on fuel consumption
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While driving over a dirt road that was heavily rutted and refrozen in to rock hard ridges i bottomed out my 94 cavalier. The exhaust broke at a joint that is roughly between the two front seats the exhaust i think is reparable and not a great concern to me bbut after having cobbled the exhaust back together with a piece of pipe inserted where the broken joint was and no small amount of wire i took the car home which is a trip of about 125 kilometers. The car was pretty loud but not illegal and it held until i was at home with slightly more tools and resources. The problem is that my fuel consumption doubled on the return trip. is it possible for a broken exhaust to make such a difference or have i broken a gas line or punctured the tank. The car smells a little of gas but my nose cannot tell the difference between straight gas or exhaust after having passed through an incomplete or altered exhaust.
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DanD
Veteran
/ Moderator
Mar 18, 2007, 5:23 AM
Post #2 of 2
(6325 views)
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Re: broken exhaust and its effect on fuel consumption
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Yes; the lack of back pressure in the exhaust could cause the fuel consumption to go up
The air/fuel mixture could be leaving the combustion chamber so quickly that it’s not being completely burnt. This is kind of a double edge sword, not only is un-burnt fuel leaving the combustion chamber but also un-burnt oxygen. The O2 sensor(s) sees this oxygen; the computer thinks the engine is running lean and in turn adds more fuel; in an attempt to get the O2 to toggle rich.
The next thing that maybe happening is that if the exhaust leak is close enough to the O2 sensor, outside air might be getting to it; causing the same effect as what I mentioned above. Believe it or not there is a small amount of vacuum that develops in the exhaust between cylinder firing; this vacum will suck in fresh air/oxygen.
As for a possible leak in the fuel system; you tell us, get out there and have a look for any moisture on the lines or tank? At over a buck a litre you want to make sure that all of it is at least making to the inside of the engine. LOL
Dan.
Canadian "EH"
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