Real correction factor for turbocharged engines at altitude?

[RAAMaudio]

I have researched this subject quite a bit and getting all sorts of answers and some from claimed engineers that are conflicting.

I know for a fact their are differences as have taken boosted cars, and trucks to sea level and over 7500 ft passes, with and without towing up to a 22,000lb trailer.

Some say no difference at all as it makes it's own atmosphere.

Some say you have to make more boost for the same power level to make up for the lower density of the air.

Some say it is mostly induces more lag, which I can attest to as my Cyborg spools more like a bigger turbo at lower attitudes.

I would like to find the real answer on this, anybody have a link, know for sure, real formula, etc....?

My best VD result, on what is supposed to be 102 Octane Torco tune, is 222 WHP and 240 ft lbs.

The HP is actually great for the altitude and the car pulls hard to red line but the torque starts slower with is possibly part of why lower.

If I went by one quoted correction factor I would be making around 240WHP and 265 ft lbs at sea level.

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I have the Cyborg which I love and SS results proved it is very quick to spool but not like the stocker which spools to fast and then runs out of steam.

I am at 5200 ft, and run a cat which both are probably part of the issue, my cat is a huge one, 5" diameter core with 100 cell count so I am wondering it it is a bit to big, spreading the exhaust gases out so far it could be actually slowing it down, causing the spooling to delay a bit as well as the thinner air.

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I have a road trip to take shortly, car is staying home for this one. When I return I will pick up some E85, 100 miles each way, and get an E85 tune to see what happens.

With the cooling effect we can probably work on more timing and other areas to help bring up the boost quicker, if not much better I might even cut out the cat for testing and see what happens

I will do some research into cats as well as I much prefer to run one, I always do even on a race car if I can make it work.

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Anybody have the real info on turbocharged power loss at altitude?

Thanks
Rick

 

[Ghostwhite]

I'm at 5400ft and my v dyno was 196whp 275wtq. Then I drove to Chicago and my v dyno down there was 212whp 288wtq. I was on the same high altitude tune for both

 

[RAAMaudio]

Thanks, very interesting numbers, not a huge change, did you notice more lag?

Mods done?

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I had a very well modded Forester XT that really got off the line, first time at sea level pulling out of a stop onto a highway, nearly ran off the other side of the road it took of so fast, it was far quicker to spool down there than here in Utah. It was tuned at Cobb here.



S

 

[Ghostwhite]

Haha love the thick air

Lag went down in Chicago and engine felt bigger off boost. Felt great! Mods done are Catless downpipe to stock catback, levels intercooler, Injen intake was running e-tuned mountune file

Also worth noting. 91 octane at 5400ft and 93 octane in Chicago but still running on a 91 oct file

 

[RAAMaudio]

NA engines really suffer up here, my ex 5.7 tundra was still very quick, at sea level it was far faster!

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Best mods, DP, IC and a good tune make a huge difference, mostly the tune though it seems.

Thanks for the info, much appreciated

Rick

 

[Ghostwhite]

Glad I could help