Question About Diesel startup?
Thread Starter
|
Post Fiend
Joined: Jul 2005
Posts: 14,582
Likes: 12
From: 21791
Question About Diesel startup?
i have been meaning to post this question, just have never remembered it to post it when im on here. when starting gas engines, they all seem to crank over, fire, and rev up to about 1500 rpm (at least both of my dad's 6.8L's do) and then fall back to a normal 700-900 rpm idle. but diesels dont do that. they crank over, and most of the time the 6.0 sputters and slowly climbs to about 625, where it idles. my truck cranks over for about two seconds and then just jumps to 700 rpm real fast. what i want to know is what is different in the gas/diesels that make this happen? thanks.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,112
From: Rio Rico, AZ.
Some smaller diesels use a fast idle to speed warmup time. An example is VW's Eco-diesel. There is a timing advance **** that you pull when cold starting to advance the injection timing a couple of degrees and add a couple hundred RPM's to the mix.
Thread Starter
|
Post Fiend
Joined: Jul 2005
Posts: 14,582
Likes: 12
From: 21791
initial startup- i was talking about the first 1-2 seconds on start up. the gassers turn over, fire, and spin to about 1700 for one second, and then it falls back to a normal idle within seconds. why doesnt a diesel do this?
Trending Topics
Former Vendor
Joined: Mar 2004
Posts: 4,362
Likes: 3
From: Hendersonville, NC
Being a larger mechanical device, the IAC on a gas engine has a much slower control loop gain and correspondingly won't drop idle to a commanded speed as quickly due to response time. The injection system on a diesel responds almost instanatenously, with a fairly high PID gain to match- so it takes essentially no time to find the commanded engine speed once started.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Rezvani's Latest Post-Apocalytic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,112
From: Rio Rico, AZ.
Originally Posted by thematkave
that's strange...when I cold start my 90 7.3 , my rpm go's to 1000, then after about 5 or 10 minites it drops down to 500 
Matt...
Matt...
