Engine/Transmission (1994 - 1998) straight pipes and fuel mileage

[bnelson]

Finally lost the muffler. I replaced it with a single 5" cab stack on my '97 BR3500 flatbed. First impression, the Mrs. told me I could not drive with her window open to hear it. Second, there appears to be about a 2 mpg increase in fuel mileage. My friend Troy noted the same results on his '93. Mine has the TST # 11 plate, Troy's is stock. Question: Is the increase in mileage due to the straight pipe or driving techinque? Mine sounds soooo

nice at lower RPM's and about 1/4 throttle. It cackles just like an 18-wheeler sans muffler.

 

[RHARVEY]

Less back pressure... it lets the motor breathe easier. .



Rick

 

[Got Smoke?]

Can we get a picture?

 

[drees1]

The driving style

I noticed the same thing when I went straight pipe and drive it at low rpm to listen to it.



Before I bombed, I tried driving by up shifting just as the turbo spooled up. Made for slow acceleration but 22+ mpg combined driving empty.



If you have the AFC set for low smoke, it just won't give it fuel until it spools up, and it won't spool up at low rpm. So the mileage goes up.



Opening up the exhaust will help mostly with power production at the midrange and high end like for towing. The stock exhaust is not that restrictive at lower power cruising with low EGT.