Timing question for high altitude

[Black dawg]

there can be so many variables, that sometimes you just have to experiment a little. When I first got my meter, I set them all to 8.5 (by the book). Found that most trucks with 1 to a couple hundred thousand, would have timing in the 3-5 degree range, if they were set correctly to begin with. On the na trucks 8.5 was always better all around, but on several of the turbo trucks I got complaints of black smoke and sluggish low end power. Basically anything over stock factory turbo calibration I set with less timing.

 

[sjwelds]

there can be so many variables, that sometimes you just have to experiment a little. When I first got my meter, I set them all to 8.5 (by the book). Found that most trucks with 1 to a couple hundred thousand, would have timing in the 3-5 degree range, if they were set correctly to begin with. On the na trucks 8.5 was always better all around, but on several of the turbo trucks I got complaints of black smoke and sluggish low end power. Basically anything over stock factory turbo calibration I set with less timing.

So in your honest opinion, should I bump my timing down some more? See truck details in sig. I actually push a little over 10psi, with egt's 1000 or so max. I do get some smoke down low before boost builds. So probably not quite factory settings anymore . Would you go down to 6 or 7 or how picky do I need to be?

Wish I had my own meter....

 

[Black dawg]

I have heard this on here before, but have also found it to be true myself, that the sound of the rattle should stay pretty much the same from light throttle to wide open. If it has a destinctive growl when getting on it you probably have too much timing for your fuel rate. With my truck right now, I get a slight growl with maxed fuel screw and 7 deg timing.

 

[blacksmoke94]

This is getting deeper by the post but all the input is great reading. Thursday is timing day for me. I'll get the reading before any adjustments are done just so there's a baseline and go from there. In the 1200/1600 rpm range on mine, if I don't step on it so it downshifts it belches out black smoke like crazy. Higher in the range, under full throttle hardly any smoke at all. Since mine has no low end power, would that mean the timing needs to be advanced or retarded? My mind says advanced but I've never messed with the timing on a diesel. Only gassers. Will be interesting. Just wanted to get this done before our upcoming road trip.

 

[Black dawg]

retarding the timing will cause less black smoke (incomplete burn). Less black smoke with no change in fuel rate must mean it used that fuel more efficiently right?

 

[blacksmoke94]

Makes sense. I know now that my mind was working backwards on this matter. Isn't the first time and wont be the last. Advancing the timing moves the power band higher into the rpm range and retarding it moves it lower into the rpm range. Right?

 

[Mtorg]

Not to steal a thread here, but i was wondering the same thing, but for a higher elevation... I live at 7200 and often go 9000-10000. She smokes a lot (still some gray at WOT) and little low end power. Any ideas? Im installing new injectors next weekend so what should i set it at?

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[79jasper]

I think some were doing 6-7 and seeing good results.

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[Agnem]

OK hang on here guys.... where is the science in this idea? Altitude affects the oxygen content in your cylinder. THAT'S ALL. Timing is the event measurement for when we want combustion to begin. When you light a match, it doesn't matter if your at sea level, or 5,000 feet, that match is going to burn all the way. When you inject fuel in a diesel engine, all of that fuel is going to burn at that instant, and if there is too much fuel, then its going to burn until all the oxygen is depleted. Changing your timing is going to have no beneficial effect on improving performance at altitude, unless someone can explain to me scientifically, why it would. Hi altitude versions of this engine are limited to 155 HP by the calibration of the pump (reduced max fueling), since they know you have less oxygen in your cylinder, and have reduced the output of the pump to match it. But the timing spec is still the same, which is 8.5 BTDC @ 2000 PRPM (Pulse RPM). We have adjusted the timing on the dyno at the 2011 IDI weekend, and found no notable performance change between 8.0 and 9.5. Above or below that you start to loose power.

 

[sjwelds]

So what's your response to the many guys who swear up and down here and on FTE that they get more power at 6 or 7 deg? Is torque increased and that's what they're feeling? Is it placebo effect? Or is it just a bunch of baloney?

 

[Black dawg]

Honestly never researched it scientifically, and like I said, I dont know if it is true that the ignition event is advanced at higher elevations. BUT from how my trucks have acted and sounded, (I know, maybe worse than a butt dyno) I have had no reason to doubt this. My trucks DO run better and smoke much less with timing set much less advanced than factory spec. I live at 3500ft.

Also, like I said low fuel rate trucks seem to be OK with higher timing advance, but all of my turbo trucks, benefit greatly from retarding the timing.

 

[Black dawg]

We have adjusted the timing on the dyno at the 2011 IDI weekend, and found no notable performance change between 8.0 and 9.5. Above or below that you start to loose power.

At what elevation though? turbod trucks with some more fuel, lots more fuel, na trucks?

Just too many variables involved to say that a certain timing number is as good as it gets.

 

[Agnem]

At what elevation though? turbod trucks with some more fuel, lots more fuel, na trucks?

Just too many variables involved to say that a certain timing number is as good as it gets.

OK, so that is a good point, and if there is conventional wisdom at those altitudes that yield better results, I won't dispute them. But it made me think about it, and consequently research it. I found an interesting patent that seems to cover it pretty well. http://www.google.com/patents/US6286480 So I do see a need to adjust the timing. However, everything I can find suggests that the time should be advanced, and not retarded at high elevations. So I am still confused as to why high altitude guys say 6 BTDC is better.

 

[Black dawg]

OK, so that is a good point, and if there is conventional wisdom at those altitudes that yield better results, I won't dispute them. But it made me think about it, and consequently research it. I found an interesting patent that seems to cover it pretty well. http://www.google.com/patents/US6286480 So I do see a need to adjust the timing. However, everything I can find suggests that the time should be advanced, and not retarded at high elevations. So I am still confused as to why high altitude guys say 6 BTDC is better.

I wont have time to look at the link for a little while. I guess it could be a combination of quicker spool and less smoke, that less timing provides, but there is also a low end torque (off idle) increase that is very easily noticed. At this point, the power really isnt an issue for me, but less smoke always is a good thing (with no mpg penalty).

With my current truck (non wastegated, 6.0 intercooled, 7.3) with timing set at 8.5 (and maxed fueling) it is very smokey and feels pretty lazy. With timing set at 5 deg it is smoke free even at 8000+ ft and loaded. The reason I tend to set it around 6.5-7 is starting can be slightly lazy with the slower settings.

 

[blacksmoke94]

That's an excellent ( and long ) article and thank you for taking the time to do such deep research. I think what they're saying the issue with the altitude is that while there is still the available amount of "air", there isn't the same amount of actual O2 in that air, thus slowing the burn and making it happen later. I compare it to lighting a cutting torch. You ignite the acetylene or propylene, it's just a flame burning off of the available O2 in the air we're breathing. But when you open up the pure O2, that's when the real and complete burning happens. There's a pass near me that reaches 8900ft. When I first moved here, we drove over it and I really thought my engine was going to blow up from the way it sounded. I got rid of the factory air box and made a cold air intake that allows at least 3 times the air intake to the engine over factory. I also turned my pump up at that time. I've driven over that pass many times since and the engine has sounded completely normal. This doesn't have anything to do with the timing but it did show me that getting the extra air into the engine really helped out. I had never considered timing to come into play. My timing was checked yesterday and it was at 9*. If we weren't leaving on our road trip tomorrow I would have played with it but I figured messing with something that was "working" right before we leave wasn't the best idea. The 9* explains why my low end power and torque are lacking. If I'm sitting at a stop and punch it, there's a ton of smoke and a lag, then she takes off. If I power brake it up to about 2k and let off the brake and punch it, it will smoke those 35" tires like crazy until it shifts into second and then it lags off again. I don't try this with my new tires but I did with my old ones before I changed them out. I did read an article once about people advancing the timing for a higher altitude and also added that you had to be careful if you went to lower elevations as your engine would tend to run hotter and could overheat. I guess it comes down to each persons needs and have to find what works best for them with the countless variables that come into play.