Diesel Place banner

1 - 5 of 5 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter #1
My truck changes the tune of the diesel at roughyl 2800 rpms.. Is it goona be ok?.. has 3200 miles on it.. btw.. I used to own a 2001 PSD climbing a bill mountain in KY the psd would take me with camper and jeep on the trailer over the top at 40,,, tops.. The 2004 DA dually will take same load plus.. at 53.. I am impressed
 

·
Registered
Joined
·
112 Posts
It seems to me that the sound change you are hearing may be due to the pilot injection cutting off. This is a normal function, and nothing to worry about. I have had to explain this to passengers before as it is quite obvious at times. --SS
 

·
Registered
Joined
·
12,262 Posts
As above , pilot Injection shutoff point ...In case you wanted a second opinion ...

Mac
 

·
Registered
Joined
·
23 Posts
Discussion Starter #4
Thanks .. I appreciate all replies.. I was coming down "big Hill" and the tranny downshifted and it went all the way to 3700 rpms.. had me worried but it gradually came under redline. sure beats wearing out the brakes
 

·
Registered
Joined
·
3,291 Posts
Here’s a description of Pilot Injection, copied from Overdrive Lockout Info at :

http://dieselplace.com/forum/forum_posts.asp?TID=754&PN=1



Diesel engine fuel injection systems that use a common rail system, as the Duramax™ diesel does, may or may not have what is referred to as pilot fuel injection at the lower engine speeds. Pilot fuel injection is defined as a pre-injection of a small quantity of fuel 5 to 20 crankshaft degrees before the main fuel injection. This pre-injection softens the main injection pressure rise and reduces combustion noise. At engine speeds above 2600 RPM, and a fuel quantity supply greater than 35 cu mm, it is necessary to eliminate pilot injection to meet emission requirements. When driving at or above these speeds, main injection combustion noise may be noticeable. It is normal and not harmful to the engine.


When traveling in 5th gear, the pilot injection to main injection transition is typically in the 136 km/h (85 mph) range, however it may also be heard under heavy acceleration and when pulling loads up a hill during shifts at or above 2600 RPM. Customers that install the fifth gear inhibit switch may encounter the fuel knocking of main fuel injection at speeds around 107 km/h (67 mph) in fourth gear between 2600 and 2700 RPM. This sound is considered normal and is to be expected.
 
1 - 5 of 5 Posts
Top