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Discussion Starter · #1 ·
I have searched forever, but haven't seen a definitive number. I do know that most of the tunes I've received only have about 6 degrees of timing at cruise areas of 55-75 mph and no load. That seems very low to me from a mileage standpoint, which is the next area of my tune I'm working on.

Does anyone know how much timing you can run cruising down the freeway at say 70 mph?
 

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Jody,

The definitive number as you put it really depends on how much fuel you're using at cruise. It's important to remember the goal of increasing timing is to position the maximum cylinder pressure event as close to TDC as possible.

On one of these engines at cruise it takes about 7 crank angle degrees of injector on-time to load the cylinder with fuel. Because the pilot injection events have already started to ramp up cylinder pressure and heat, the main pulse starts burning almost immediately once it's introduced to the to cylinder.

Increasing the timing to say 12 degrees would mean that for 5 degrees after the main pulse is injected, the piston is fighting its way to TDC. This is not a good thing for for efficiency/economy.

Hope this helps a little,

Nick
 

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Jody,

The definitive number as you put it really depends on how much fuel you're using at cruise. It's important to remember the goal of increasing timing is to position the maximum cylinder pressure event as close to TDC as possible.

On one of these engines at cruise it takes about 7 crank angle degrees of injector on-time to load the cylinder with fuel. Because the pilot injection events have already started to ramp up cylinder pressure and heat, the main pulse starts burning almost immediately once it's introduced to the to cylinder.

Increasing the timing to say 12 degrees would mean that for 5 degrees after the main pulse is injected, the piston is fighting its way to TDC. This is not a good thing for for efficiency/economy.

Hope this helps a little,

Nick
What would indicate if that's happening? I have a tune I really like but at freeway speeds it seems to have a little dead spot where when I lightly accelerate, it seems to loose a little power and then take off. It smokes pretty good while in this "dead spot" which is fun if you want to blow a little smoke at someone but I'd like it more if it just took off.
 

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What would indicate if that's happening? I have a tune I really like but at freeway speeds it seems to have a little dead spot where when I lightly accelerate, it seems to loose a little power and then take off. It smokes pretty good while in this "dead spot" which is fun if you want to blow a little smoke at someone but I'd like it more if it just took off.
Seems like you're experiencing turbo lag. LOG IT!!
 

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Discussion Starter · #5 ·
Jody,

The definitive number as you put it really depends on how much fuel you're using at cruise. It's important to remember the goal of increasing timing is to position the maximum cylinder pressure event as close to TDC as possible.

On one of these engines at cruise it takes about 7 crank angle degrees of injector on-time to load the cylinder with fuel. Because the pilot injection events have already started to ramp up cylinder pressure and heat, the main pulse starts burning almost immediately once it's introduced to the to cylinder.

Increasing the timing to say 12 degrees would mean that for 5 degrees after the main pulse is injected, the piston is fighting its way to TDC. This is not a good thing for for efficiency/economy.

Hope this helps a little,

Nick
thanks Nick, helps a lot. That's why none of these tunes run much cruise timing apparently. Changing my tables now............. :eek::
 
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