Cam Timing

[jpowel29]

What affect will advanced cam timing have on a turbo diesel engine (in reference to a dedicated drag race build)? I have a pretty good understanding of what it does on a naturally aspirated gas motor.

Looking at the cam card on a new grind and trying to wrap my head around what I could expect by advancing the cam.

Anyone making adjustable cam gears for the DMax?

 

[Stingpuller]

Cam

You can use a offset keyway and do the same thing and a lot cheaper. You can advance 2* to make up for slack in the gears but don't expect much change. I'm surprised a company gave you a cam card! Most act like it's top secret. Not sure why when others will just put it in a cam doctor and get all the numbers. Jeff

 

[jpowel29]

You can use a offset keyway and do the same thing and a lot cheaper. You can advance 2* to make up for slack in the gears but don't expect much change. I'm surprised a company gave you a cam card! Most act like it's top secret. Not sure why when others will just put it in a cam doctor and get all the numbers. Jeff

Thanks Jeff.

 

[SmokeShow]

Mine came with card.

 

[ZeroGravity58]

I dont know about aftermarket duramax cams but most off the shelf gas cams are ground 4 degrees in advance already. When i dynoed my one gas motor i made one pull with the cam 4 degrees retarded, then striaght up, and then 4 degrees in advance. I lost power when it was retarded. But all that happened when i advanced it was the power was almost the same it just moved the peak tq/hp up a few hundred RPMS. That was the only time i messed with it on that one SBC because i had a 3 piece timing cover

 

[S Phinney]

I dont know about aftermarket duramax cams but most off the shelf gas cams are ground 4 degrees in advance already. When i dynoed my one gas motor i made one pull with the cam 4 degrees retarded, then striaght up, and then 4 degrees in advance. I lost power when it was retarded. But all that happened when i advanced it was the power was almost the same it just moved the peak tq/hp up a few hundred RPMS. That was the only time i messed with it on that one SBC because i had a 3 piece timing cover

Thats exactly what advancing the cam will do. It changes when or what rpm's it makes it power at. You have to change centerline, lift and duration to affect operating needs.

 

[jpowel29]

Would advanced cam timing help or hurt spool characteristics?

 

[S Phinney]

Changing the centerline would help by increasing the number. A stock cam is ground on 108 degree centerline. I used a cam ground on 113 degree centerline. It will help spool your turbo better and sounds a bit different also. My truck sound more like a gasser at the exhaust.

 

[dmaxfireman]

how many teeth on the cam gear? maybe setting it one tooth advanced could be a cheaper/easier shortcut?

 

[S Phinney]

That would be a lot of degrees! Wouldn't work very good at all. John if you want your power sooner advancing it will help. If the parts are available going 4 degrees advanced would bring down operational ranges around 200 or so rpms. Remember in doing that it also brings down wot operational ranges.

 

[jpowel29]

I am mainly just thinking out loud with the advanced timing - although I would like to gain every advantage that will help my truck spool. It has been the achilles heel since day one. I am stubborn and don't want to backtrack on gear selection or turbo size so I am looking at all other possibilities.

Thanks for the feedback

 

[SmokeShow]

What rpm does it light at? What EGT does it seem to start to light?

 

[jpowel29]

With the previous cam it would come to life at 2800rpm

 

[bullfrogjohnson]

Who's tuning?

 

[dmaxfireman]

ok i have a serious concussion so my counting may be off but i count 85 teeth on the cam gear (approximately) so one tooth with be advancing or retarding 4 to 5 degrees

 

[jpowel29]

Who's tuning?

Mine at this point

 

[bullfrogjohnson]

Tuning can make a huge difference in how a charger lights. I am lighting the same size turbine wheel with a BIG housing at 2000rpms with the same gears.

 

[dmaxfireman]

ok i have a serious concussion so my counting may be off but i count 85 teeth on the cam gear (approximately) so one tooth with be advancing or retarding 4 to 5 degrees

or would it be 2 -2.5 degrees per tooth since the cam only one half rev for each rev of the crank? my brain is not working right now lol

 

[Mike_S]

Moving the camshaft 4 degrees via moving it one tooth would effectively be moving the cam timing 8 degrees relative to the crankshaft. The crankshaft revolves 2 degrees for every 1 of the camshaft, therefore the changes made to the camshaft double relative to the crankshaft.

Or I could be way off base on that...but it makes sense in my head.

 

[S Phinney]

Moving the camshaft 4 degrees via moving it one tooth would effectively be moving the cam timing 8 degrees relative to the crankshaft. The crankshaft revolves 2 degrees for every 1 of the camshaft, therefore the changes made to the camshaft double relative to the crankshaft.

Or I could be way off base on that...but it makes sense in my head.

You are correct. That is why it takes offset bushings and altered key ways to accomplish those kind of adjustments.