i've installed a 2,5" simons exhaust from the original header and back, no cat. Engine is B230FB (na 940 gl man m47)
Performance increase can be felt, but also mpg seems to be worse. With stock exhaust i used to get around 22-23 mpg. but now i get around
20-21 mpg. My driving style is the same freeway and some town but I suspect driving around i 2nd gear sometimes for 15-25 min every day trying to find a parking space might have a bad impact on fuel economy? I found a crack in the join where the two secondary pipes of the original header connects but i got that welded now. Theres is a small leak about 80 cm behind the lamda sond. Can this fool the lamda? I find it hard to believe that air can get sucked in there upstream of the exhaust flow? I have changed to studded winter tyres about the same time as i changed the exhaust. Also temperature here is down to 14 deg F (-10 C) in the night and morning. About 32- 41 in the day. Can this be the reason for the higher fuel consumption? I quess it really isn't that bad for a volvo? I recently bought the car from my father and he usually got around 24 mpg combined and 30 mpg highway. My average speed is proabably 15-20 kmh faster than him. I will get a unitek 4-2-1 header soon and also have all the joints in the exhaust welded up. It also appears that when i upshift at around 2K engine seem to "hang around" at that rpm for a split second, but i not sure if this came wiht the new exhaust. There are on error codes.(LH-2.4)
Is there something wrong or is there nothing to worry about?