My yearly test is coming up on Friday.  I have been working hard to figure out how much fuel I can throw at the truck without causing visible smoke.  

 

I am allowed %20 opacity on lug down tests at 40, 50, 60 mph.   

 

This will be the first year I have run the Quadzilla during the test.  I have my tune nailed down pretty well.  starting % of 76 seems to be where there is next to 0 visible smoke in any situtation.  Last year with the smarty on %50 power mode I ended up at %7 opacity, so I am guessing I am going to at in the 10%-15% range in the test.  I can turn down the fuel more, but I want to try and pass with as much fuel as possible.  It is also worth noting that I am runnning 900 us of wiretap as well, ramping up once boost hits 6 psi.

 

Next comes timing. 

 

1500 rpm: 16*

2000 rpm: 18*

2500 rpm: 22*

3000 rpm: 24*

Max: 26*

 

Timing reduction: 5* ( max timing to pull if at WOT and 0 psi, linear ramp up as boost comes up / TPS decreases) 

Fuel load timing: 2* ( how much timing to pull at 0% load, timing will reach the rpm limit if duration is at %100)

light throttle timing: 2* ( not really considered during the lug down test as they go WOT)

 

 

So questions,

 

the theory is you pull timing to reduce smoke offidle?  I have to say I ran 5 different tunes that were exactly the same other than timing reduction value, I honestly couldn't see any differences between WOT offilde at 11* of timing vs 16 * of timing.  little confused by that.  

 

Anyone have any insight in regards to what to do with timing to maximize fueling without increasing smoke?

retarding timing will move the flame front later into the stroke, this will cause more heat energy to be pushed out the exhaust valve and into the turbo.  it will result in less downward force on the piston however.  

I think we're splitting hair if we only talking about few degrees of timing but at same time I'm stuck on stupid lol, plus I don't get enough beauty sleep for my brain to function properly. 

Anyways after compression stroke where both valves are closed comes power stroke where both valves are still closed, it's not till exhaust stroke when that energy leaves cylinder. So in my mind time we benefit when we get more complete burn so we're not losing energy and it forces other pistons harder to push exhaust gas out and forget what I was going to say. Oh its Friday. 

Retarding timing forces the burn to happen in the manifold/turbine housing. Why egts go up when retarding timing. It physically moves the burn around. Advancing timing keeps the burn in the cylinder providing more work to act on the piston.

Advancing timing puts more power to the crank, but retarded timing makes for a cleaner burn. It's less efficient but cleaner.  It's much easier to see the effects with a pilot injection. Too much timing and the CRs smoke easily and sometimes the difference is really just a degree or two. 

 

Around 1000 rpms advancing timing should reduce black smoke, as the crank speed is slow, but it doesn't take much to go too far. So from idle to 1200 a little advanced it good, but by 1600-1800 advancing timing will increase black smoke. 

 

With different injectors it can also alter the normal reaction. I've had to retarded timing to clean up idle - 1200 low load black smoke. 

 

 

The chart on this page is a good general rule of thumb. 

 

http://dodgeram.org/tech/dsl/FAQ/timing.htm

Edited August 11, 20177 yr by AH64ID

@AH64ID

 

Since you are tuner guru of Smarty what would be the optimal timing for cruising state? (Of course 24v engine)

The CR ecm tuning is just worlds more complex than the vp stuff.  I drool over the CR stuff lol

20 minutes ago, Mopar1973Man said:

@AH64ID

 

Since you are tuner guru of Smarty what would be the optimal timing for cruising state? (Of course 24v engine)

 

With the pilot injection, pressure differences, and differences in the delay from start of injection to start of ignition it's difficult to correlate the CR to a VP. This is the main reason I don't tune VP trucks. If I had one local I could drive for a couple weeks and learn the setup that would be different.  

 

I rarely use more than 8° of main injection timing at 2000 rpms on a CR. 

Darn... Thanks for the try though... I was hoping to find some information on the timing yet...