When I went from single to true dual exhaust (cat back) with the H pipe my mph went down four miles per gallon. Anyone else have this experience converting from single to dual exhaust? Do I need to re-program the computer?

Thanks in advance,

Rick

 

Lots of talk these days about "true duals" -- Because someone decided that an H-Pipe connected the pipes, and thus they were not "true" duals.
Hogwash !!
4 mpg drop !?? -- sounds like you may have installed a pair of FlowMasters -- backwards.
Lemme know when you find that problem.

 

You can confuse the PCM wen you do this. All the O2 sensors in place? Looks like you have a massive air leak in the exhaust. The PCM is trying to compensate for what it thinks is a lean mixture. Take it to another professional exhaust shop for a 2nd opinion. Sounds like a FUBAR install.

 

'95 MERC at Flaming Gorge, UTAH
YEP. Somebody messed up. A 2nd opinion is in order.

 

A single-to-dual exhaust system is a modification made to a vehicle's exhaust system that replaces the single exhaust pipe with two separate exhaust pipes. This modification is designed to improve the performance of the vehicle by increasing the exhaust flow and reducing backpressure. The increased exhaust flow can result in increased horsepower and torque and improved fuel economy. However, depending on the vehicle, the installation of a dual exhaust system can also cause a decrease in fuel economy of up to 4 miles per gallon.