Timing retard under boost question

[mobythevan]

So the general rule is to pull 1 degree timing for each psi boost.

 

At sea level I might have my timing table set up then so at 100kpa timing is full advanced at say 32 degrees. Then at approx 107kpa I would pull a degree and have 31. I think 7kpa ~ 1psi.

 

Now at my altitude atmospheric pressure is 77kpa, instead of 100kpa at sea level. So should I set 32 degrees at 77kpa and 31 degrees at 84 kpa, or should I leave timing at 32 degrees up to 100kpa and the set to 31 at 107kpa just like if I was at sea level?

 

Following through in both cases I end up with timing of:

sea level case : 107kpa -- 31 degrees

high altitude case: 107kpa -~ 27 degrees

 

So I am talking a 4 degree difference based on the outcome of this argument.

 

And of course the timing continues to be pulled all the way up be 1 degree/psi

 

Initially it seems I would pull timing above 77kpa, but effectively cylinder pressure is low because of the low atmospheric pressure. This is with a nice FMIC so is heating going to be a part of the argument?

 

Here is an example table that uses 34 degrees as full advance under no boost. It may not pull exactly 1degree/psi but illustrates that I started pulling after 100kpa, instead of 77kpa.

 

[dr_hunt]

I guess this is why good tuners are never out of work.

 

IMO, you add timing with elevation. So I'd go with the sea level case.

[mobythevan]

I guess this is why good tuners are never out of work.

 

I hear you, it seems the more you know, the more there is to know.

[Thumper]

I think you should pull timing after 100kpa. I think this in terms of absolute pressure and not boost. At 150kpa which is roughly 7.25psi for me and 10.5psi for you I will roughly have the same amount of air going in as you. So our timing tables should be able to be the same. Now if you were tuning off of boost pressure then yes you would be pulling timing at a different time then me but since we are running map no need. I hope this makes sense.

 

Also I found you can run alot more timing under vacuum then you are running. The next chance I get i'll post my timing map.

[mobythevan]

Also I found you can run alot more timing under vacuum then you are running. The next chance I get i'll post my timing map.

 

that map is from my Talon, just FYI

[Clifton]

I don't know how to paste a cpoy of my timing map or I would but I run 38* until 135kpa and it drops to 32*. I can send you my map if you want. LMK.