Crappy Exhaust Brake??

#1
I have two FG84's. On the older 2014 model (done only 15,000km) the exhaust brake is strong. On the brand new 2017 one with half that mileage on the clock the exhaust brake is rubbish.

I have had the dealer look at it and "adjust" it but it made no difference.

What can be done?
 
#2
Question: Should the butterfly flap be fully closed when exhaust brake in on?


I had to replace the vacuum diaphragm in my truck to get the exhaust brake working and I "adjusted" the butterfly flap to be fully closed when the exhaust brake is on. Mine works ok, but this is the first truck I've driven so I have nothing to compare.


Sean
 
#3
Mine has worked fine the entire time I have owned the thing. If anything I have to hit the skinny pedal to make it look like I am keeping up with the traffic on the back side of a pass.
The truck drivers like me as I blend into the stream of trucks over there in that lane. Like I can pass anything in a MF unless it is stopped on the side of the road?
 
#4
Hitting the skinny pedal on my truck makes no difference it is always bloody slow LOL

But I do like to save the brakes with the use of the exhaust brake.

I will look into the vacuum diaphragm. Should all be under warranty on a brand new truck I should imagine.... or it is going to be!
 
#5
As I have said to many friends that give me crap, I'm on vacation." I get there when I get there". They all have big fancy campers and I ask them about fuel mileage. OK, abut same as I get.
They can just drive a bit faster.
 

SkiFreak

Expedition Leader
#6
Question: Should the butterfly flap be fully closed when exhaust brake in on?
No.

As per the workshop manual...
Average of top and bottom clearances between butterfly valve and body with valve fully closed (with power chamber vacuum of 87 to 93 kPa {650 to 700 mmHg} or above) = 0.10mm to 0.25mm
 
#7
To the OP,

Any chance you have taller gearing and/or bigger tires on that 2017 than on the 2014?

RPM means everything with exhaust brakes, and the higher the RPM (regardless of speed) the more effective they are.
 
#8
No.

As per the workshop manual...
Average of top and bottom clearances between butterfly valve and body with valve fully closed (with power chamber vacuum of 87 to 93 kPa {650 to 700 mmHg} or above) = 0.10mm to 0.25mm
Thanks,

I guess with the carbon and crud in there my "fully closed" will have the required 0.10mm to 0.25mm gap !


Sean
 
#9
To the OP,

Any chance you have taller gearing and/or bigger tires on that 2017 than on the 2014?
Bugger could this be the problem? Yes I have changed the diff ratio on the newer truck for longer legs indeed. I took delivery of it with the diff conversion done by the dealer so never drove it with the O.E. gearing.

The older truck has standard gearing.
 
#10
Yep, that's probably it then.

Next time you use it, drop a gear first to get RPMs up.


When I pushed from 4:10s to 3:55s in our old 7.3 Powerstroke, the exhaust brake I have became near useless.

Gained a solid 2 MPG loaded, but now have to use the brakes more.