[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]
On 23 Jun 99, at 7:08, Steven Ayres wrote: > Assaf=> every time that I'm sliding downhill, I've got backfire. > > I agree, this is caused by a leaky exhaust. I realize that this is the common answer that "everyone" gives, but it is not true. Backfire is caused by overrunning the engine with the throttle closed causing a mixture that is too lean to burn in the chamber to flow out into the muffler. The expansion into the exhaust system cools the mixture allowing some condensation, and richening. When you press down the throttle and get the cylinders to fire again (or when one just randomly manages to fire) the exiting exhaust gases ignite the mixture that is just outside the heads, causing backfire. FI cars overcome this by shutting off the injectors on overrun, while some of the later carbed engines came with various devices to keep the throttle valve from closing all the way. This reduces engine braking but allows the mixture to be rich enough to burn properly. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ----------------------€µÉ¨ ------------------------------------- Too much? Digest! mailto:type3-d-request@vwtype3.org Subj=subscribe