WRX Brussels Posted October 29, 2010 Posted October 29, 2010 I pretty much run a straight pipe exhaust for my WR125x and haven't noticed any decrease in power except for some backfiring sounds when I downshift. Will I fould up the engine because I have lost backpressure? Thanks!
Paulwhite Posted October 29, 2010 Posted October 29, 2010 has the carb and filter been adjusted for the straight through exhaust? if you put a new exhaust on and its straight through then the engine will run lean so a re-jet would need to be done to compensate.
WRX Brussels Posted October 29, 2010 Author Posted October 29, 2010 has the carb and filter been adjusted for the straight through exhaust? if you put a new exhaust on and its straight through then the engine will run lean so a re-jet would need to be done to compensate.
WRX Brussels Posted October 29, 2010 Author Posted October 29, 2010 I put on the pipe and left out a perforated capped cylinder that fits in between the muffer and tailpipe connection. I also removed the DB killer. I do have the muffler, so I guess it is not a "pure" straight pipe. Will the configuration I have drop the compression? I smell gasoline from the exhaust. The compression is supposed to run at 11.5:1
WRX Brussels Posted October 29, 2010 Author Posted October 29, 2010 Paulwhite, Here's the diagram showing the peforated part I removed. Part Tappo #40 My link
Paulwhite Posted October 29, 2010 Posted October 29, 2010 it shouldnt lower compression no. but the reason why you can smell petrol is because there is a tiney point where both valves are open and because there is no back pressure in the exhaust some of the air/fuel mix is escaping the cylinder and entering the exhaust, this is where the back pressure would kick in and push the air/fuel mixture back into the cylinder. and this is why you need to re-jet when putting on a performance exhaust/ straight through pipe on. just do a spark plug check and adjust the jet needle accordingly then you will need a slightly bigger main jet to help out the top end. should sort it out oh and that perforated metal bit you took out would be the baffle which would keep the back pressure in check. so you could always pop the baffle back in and then compare the spark plugs (saves stripping the carb) and would probably give you a little more top end (say 2-3mph)
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