High Altitude timing?

High altitude and high compression do not mix.
Rule of thumb is for every 2000ft above sea level you should add one pt of octane. Advancing the timing is tough out there. Retarding will actually help the pinging but not the best thing for performance..
Ever watch the Nat's at Bandimere? The big boys (Top fuel) just can't get em to run fast. Turbo cars excell in altitude.

before you read this i want to point out that im JUST applying basic theories of physics and thinking them out logically. these are my thoughts and rational opinions, however physics laws are not called laws for nothing.

from what i understand is that your ecu as a few spark tables. one for sea level and another for altitude. the spark table for altitude uses a more aggressive spark curve. its becasue when your in altitude there is less o2 which means less air.

when you compress air very fast like your car does it heats up.... less air means less heat..... less heat means that you can run a bit more timing before detonation. i have not taken physics specifically for "how cars operate in altitude" but the idea is the same.

increase timing, richen up your MAF. try to get the car to think there is more air coming in than there is, the trick is to keep the fuel injectors and PW the same so they dont increase fuel. the reason why cars run slower in altitude is because of the lack of VE or volumetric efficiency..... less 02 means less efficient combustion, obviously.

Spook302 said:

Should I run the same plugs? How Do I richen up withthe mass air? I have a 72 c&l in it right now. The car with the 347 is going to get chipped or a whole new management. But it would be nice to get it to run good for a little. It runs pretty good, then it will die and take 3 pumps to get it fired up again, when it does it shoots out a big black cloud of smoke. definetlly running rich when it dies.

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i had a similar problem with my dirtbike. it would run rich and i was not winding it out enough so it would "load up" and foul plugs. if you have a really hot cam then your rpms need to be revved more to prevent loading up.

but other than that i dont know. i would guess thats happening because the whole-less o2 where your living- thing. makes sense. its rich because of the same amount of fuel but less oxygen to burn.

do you have a tuning device? like a tweecer? if not it it very hard to tune your MAF without getting it professionally done.

i dont know about the plugs, but since your running RICH i would suggest advancing timing a bit. you can have 50* of timing, its all about detonation and i doubt you would detonate running as rich as you are. but in NO WAY am i telling you to advance to 50*, that was just an example. haha

these are just my thoughts though. i have never delt with that kind of problem.

GTOReturns said:

High altitude and high compression do not mix.
Rule of thumb is for every 2000ft above sea level you should add one pt of octane. Advancing the timing is tough out there. Retarding will actually help the pinging but not the best thing for performance..
Ever watch the Nat's at Bandimere? The big boys (Top fuel) just can't get em to run fast. Turbo cars excell in altitude.

Click to expand...

I could be wrong, but I've always been of the opinion that with higher altitude you can run less octane. There is less oxygen in the air (just try going on a run here at over 7,000 feet) and therefore the car will run richer and hence less chance of pinging. I had my GT tuned here at altitude, and asked the tuner to add another tune for when I went home to a lower altitude. for the lower altitude tune, he slightly richened up the fuel tables.

The reason I think that the top fuel dragsters can't run as fast is because of the thinner air, not because they have to retard the timing.

But then again, I could be completely wrong here...

parchisi said:

I could be wrong, but I've always been of the opinion that with higher altitude you can run less octane. There is less oxygen in the air (just try going on a run here at over 7,000 feet) and therefore the car will run richer and hence less chance of pinging. I had my GT tuned here at altitude, and asked the tuner to add another tune for when I went home to a lower altitude. for the lower altitude tune, he slightly richened up the fuel tables.

The reason I think that the top fuel dragsters can't run as fast is because of the thinner air, not because they have to retard the timing.

But then again, I could be completely wrong here...

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physics would have to agree with you.

see if you can pull fuel (dont know how without a tweecer) and advance your timing. higher altitude is like higher octane, if there is less o2 then it makes it HARDER for things to burn. ask a firefighter if he as ever tried to start a fire engine in the midst of a forest fire. the fire burns up just enough o2 so the truck wont start. as soon as the o2 content drops even to 19% your vehicle wont run....same idea as altitude.

parchisi said:

I could be wrong, but I've always been of the opinion that with higher altitude you can run less octane. There is less oxygen in the air (just try going on a run here at over 7,000 feet) and therefore the car will run richer and hence less chance of pinging. I had my GT tuned here at altitude, and asked the tuner to add another tune for when I went home to a lower altitude. for the lower altitude tune, he slightly richened up the fuel tables.

The reason I think that the top fuel dragsters can't run as fast is because of the thinner air, not because they have to retard the timing.

But then again, I could be completely wrong here...

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Sorry about that. I had it backwards. I lived there 10 years ago and used to deal with the same thing.

You are 100% rite, thats why 85 octane can be had there at every gas station. Thanks for the polite correction.