Timing

[Kind]

I know it has been somewhat covered in previous threads but it only seems in the sense of being told not to do to much.

I was doing some reading last night about diesel timing and it seems like most Cummins and Duramax trucks are being timed up to 30* at 3000rpm with a 3200us pw on stock fuel. Obviously we aren't injecting anything past 2200us so that would attribute to lower needed timing as well in comparison to stock Cummins and Duramax we were injecting with a little bit higher pressures, again requiring less advanced timing.

But reading some more they were talking about ignition delay, something that is usually similar with most diesel fuelled engines. In that article it states at 3000rpm a diesel would need to inject at +30* to have a complete burn cycle and +15* at 1500rpm. Our timing tables are no where near that tho. Again I am aware not every motor is the same as rod length, piston shape, injector spray pattern, injection quantity, humidity, altitude, cetane rating and boost all playing a role.

Currently on my truck I'm running +22* at 4000rpm and I want to know what is a safe level?

 

[ckrueg]

I'm used that calculator to get a starting point. I set it up to inject around 60-30percent of the fuel btdc depending on load and rpm. Like for high rpms and very little load I run as much as 60 percent btdc and for high load low rpm I run closer to 30 percent

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[ckrueg]

I know it has been somewhat covered in previous threads but it only seems in the sense of being told not to do to much.

I was doing some reading last night about diesel timing and it seems like most Cummins and Duramax trucks are being timed up to 30* at 3000rpm with a 3200us pw on stock fuel. Obviously we aren't injecting anything past 2200us so that would attribute to lower needed timing as well in comparison to stock Cummins and Duramax we were injecting with a little bit higher pressures, again requiring less advanced timing.

But reading some more they were talking about ignition delay, something that is usually similar with most diesel fuelled engines. In that article it states at 3000rpm a diesel would need to inject at +30* to have a complete burn cycle and +15* at 1500rpm. Our timing tables are no where near that tho. Again I am aware not every motor is the same as rod length, piston shape, injector spray pattern, injection quantity, humidity, altitude, cetane rating and boost all playing a role.

Currently on my truck I'm running +22* at 4000rpm and I want to know what is a safe level?

I know the canned h&s hd tune runs 20* at 3450 rpms so 22 at 4k doesn't seem overly aggressive. Also I'm betting that article was talking about an engine with single shot injection. I read on efi live forums and guys were saying without pilot injection they run up to 8 degrees at idle and 15 cruising. Also most older diesels without pilots have much less precise injectors which causes worse atomization and more delay. There's quite a few studies on diesel combustion on google. Very interesting stuff.

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