Another blown expy coming soon!

[toms89]

I just averaged 15.25 mpg!! No BS... lol.

Got some hwy miles on her cruising at about 75mph (2100 rpm). Not really hyper mile-ing but not going w.o.t. either. If I really tried to conserve fuel I know it could do even better.

 

[1997SCEBFEX]

impressive!

i'd go back to the same gas station for another refill as i've noticed stations around town [here] that receive fuel more often.

forgot to ask, and don't remember [yeah the age thing] did you change the computer to go along w/ the Lightning powerplant & are you running Premium?

 

[Jeff532003]

Damn Tom way to go! Your doing better than my stock 4.6 at the moment. Hoping once I finish this tune up I'll be able to get above 15.
All this tuning your doing makes me curious to see what you pull at the track this year. I give you a lot of credit. It sounds like your getting up to the fast and furious level of tuning with an expedition haha. I've only ever built carbureted, distributor engines. Much much easier to dial in as I'm sure you know.

 

[toms89]

Having weird issue..

Its not new but has been getting progressively worse. There are harsh vibrations that can be felt in the gas pedal and floor. Its more like a resonance and not rhythmic in nature. It also seem to be worse when its colder outside regardless of engine temps. This had me considering harmonic balancer or exhaust. The harmonic balancer should not be effected by outside temps once the engine temp is up because it will heat up with motor. The exhaust would make sense to me because it is effectively cooled by the outside air and the air temp could have a dramatic effect on it.

It has been progressing slowly over long period of time. It is also worse at low rpms.. specifically between 1,000-2,000 rpm which is also where "exhaust drone" is at its worse. My guess is the large dual 3" exhaust is causing the exhaust to resonate internally at low exhaust flow. But my concern is why has it been getting progressively worse. Everything feels solid and no sign of rattles with solid hits to it. I did do a pressure test at the O2 sensor location several months back and no pressure. Actually the needle fluctuated rapidly between slight pressure and vacuum but pulled more vacuum if anything.

The resonance is not felt at the motor via hand or heard with stethoscope. When you feel the exhaust any where past the collectors it is pronounced. Fairly certain its not in the motor due to the type of resonance and not being rhythmic in nature.

Trying to figure out where to go from here..

Want to get it taken care of but really need to know what exactly is the cause. Can get expensive just throwing money at it.

Considered having 1/4 wave resonators installed and / or installing larger convertors in hopes of increasing back pressure.

The motor runs fine otherwise.

 

[toms89]

Took my expy to the exhaust shop earlier this week.

The exhaust specialist said he is not convinced it is the exhaust but could not say for sure. He did say the muffler packing has "blown out" but he has never heard of that happening in just a few years. When you hit it hard it sounds more like a tin can type echo vs a dull thud. I got to compare to new muffler and there was a difference.

This to me would explain why the exhaust is vibrating/resonating more over time. I do have resonators post muffler so it would still help quiet it down before it exits the exhaust completely.

Still up in the air on what I am going to do....


What I do know is the exhaust is what is vibrating/resonating and that is whats felt in the vehicle. I cannot feel it at the motor. Easily felt in the exhaust tubing. Now whether the motor could be transmitting this vibration through to the exhaust due to some other misc issue other than normal operation I cannot say for sure....

I changed the oil today and cut open the oil filter to have a look. No foreign material.. just oil.

Gut feeling says its the exhaust!!