Cummins Timing

5.9

5.9

I JUST WANT TO GO FAST
Hey guys I am tuning my truck with the Smarty UDC and wondering what is the safest MAX timing that I could use for a hot street tune. I will be driving this tune most every day but I don't wont to lift the head either. Any suggestions??
 
With the setup in your sig? How much pulse?

I use 10° for every 1000us @ 3000rpm as a starting point. Your setup may like more / less. The only real way to find out is on the track or dyno.
 
I mean that right now I have the tune at the highest point is 1700us. I know I could go a lot more but I don't want to blow it up. The pump is fine past 800hp I just am looking for a good fun to drive street tune and max rpm would be about 3500. I just don't want to push the timing to far where I will do something bad to the motor. I am pretty new to the tuning scene.
 
That's a longer duration for a street truck. In order to get all that fuel in you would have to have about 30* of timing at 3000 rpms. Not sure I'd crank it up to 30* though.
 
That duration is shorter then a stock burst......... And I am just looking for a safe timing number so I don't blow the head off but can still mess around if I want.
 
At 3500RPM and a 1700uS you only need 35.7* of total injetor on time to get all of the fuel in. I would have your timing at about 21* BTDC on that tune.
 
So how do you know that it will need that timing?? Is there a secret equation to find this stuff out or is just just know how??
 
5.9 said:
So how do you know that it will need that timing?? Is there a secret equation to find this stuff out or is just just know how??
Click to expand...

If you gather up some information, you could build a calculator.

You'd need to base it on rotation and how that effects the distance of the piston from the injector nozzle. You'd need to know your spray angle and bowl size. Then you'd start at a case where engine speed in approaching zero. At that point, factor in how long it takes fuel to travel at a given pressure, and that'll make you need more advance based on rpm. Knowing the time between electrical input to the injector and actual injection event (needle moving) would be helpful too.
 
5.9 said:
That duration is shorter then a stock burst......... And I am just looking for a safe timing number so I don't blow the head off but can still mess around if I want.
Click to expand...

It's just not an efficient duration. That was my point.
 
That is a very efficient duration. And as far as figuring out the amount of degrees of injector on it's a fairly simple equation. Take your desired max rpm multiply by 360, divide by 60 and multiply by the desired duration. So 3500x360=1260000 divide that by 60 and you get 21000. 21000x.0017 equals 35.7* of injector on time. I then multiply that by .6 and get 21.42. That would be 60% of your injection event going in before top dead center at 3500rpm and a 1700uS pulse.
 
JWhite said:
With the setup in your sig? How much pulse?

I use 10° for every 1000us @ 3000rpm as a starting point. Your setup may like more / less. The only real way to find out is on the track or dyno.
Click to expand...

Dom_c13b said:
That is a very efficient duration. And as far as figuring out the amount of degrees of injector on it's a fairly simple equation. Take your desired max rpm multiply by 360, divide by 60 and multiply by the desired duration. So 3500x360=1260000 divide that by 60 and you get 21000. 21000x.0017 equals 35.7* of injector on time. I then multiply that by .6 and get 21.42. That would be 60% of your injection event going in before top dead center at 3500rpm and a 1700uS pulse.
Click to expand...

Using your equation at 3000 rpm you get 18.3°. Pretty close

:pop:
 
Yes, that's what I get at 3000rpm. I usually don't run 60% BTDC until 3000rpm and after. On pull trucks I'm up to around 75% BTDC. 60% is good for a street truck though.
JWhite, I also use your method for a quick reference sometimes. I just figured I'd show these guys that there is some method to the madness.
 
You must log in or register to reply here.
Back
Top