Thread: Elevation and the Turbocharger (very technical)

Awesome point. The exhaust side is affected as well. Very much over looked. I didn't even mention it, and it is very important. Good work.



This makes sense as blow-by will increase as pressure in the crankcase decreases due to altitude. The odds of boost leaks would increase too I'd bet.

There's the meat of the argument again right there. Very well said.


Now your beard and plaid flannel are really shining through here. WTF less oxygen concentration at altitude? Makes sense, but I never thought about it. It's time to move to the coast man!

I've run a small turbo on a large engine past it's efficiency range on the dyno at the request of a customer (went from 15 to 18 psi) and I'll be damned if the temps didn't spike and power went down the toilet.

Or those running Holset and similar diesel turbos designed for massive boost pressure ratios. =]

I think this part of your discussion is important enough and big enough of a topic to warrant it's own thread. It's infuriating to watch dyno operators (Dyno Dynamics in this case) leave the intake temp sensors and such on the bench instead of probing the intake air because "that gives inflated numbers".

!!!!!!!!!!!!!!!!!!!!

I bet!

No, thank you.

Thanks for taking the time to read it Ben. The only thing is the math, and it is something that can be a little confusing.
12.5 is only 85% of 14.7, (this is where you get 15%)
but 14.7 compared to 12.5 is ~18% increase

I like to think of it this way: 150 out of 200 is 75%, but the difference between the two would be 200/150, or ~33%.

Math make sense now? Trust me, it checks out

If you raise boost from 40 to 50psi, you made a 25% increase in pressure, even though 40 is only 80% (20% away from 50psi).

Numbers are funny sometimes. I love the big bold quotation. Thanks again.

This was a nice read considering I just got back from running 2 turbo diesels at 14-16k feet in -35 temps. Not a lot of people will get all of it, but none the less it would be nice if people had a small grasp on how the turbo on their car works in different environments. Thank you for the write up.

Has anyone seen or experienced this in person? I have a few guys here who have dynod at sea level and up here, and their corrected numbers are really really close.

Here is a dyno chart from up here:



This is a stock cam vs S4 cam on a W10 motor. 6psi. Do you think these numbers are too high? 195whp. Car is using the stock W10 manifold with a big t28 and a 2.5" exhaust. 3" intercooler piping.

Here is a stock engine G20 with a t25 on 9psi. this setup was a budget build. 190whp.



Here is my dyno chart on 19psi: look at setup in sig.



Does anyone think that these numbers are too high for the setups they have? Are these SAE corrected numbers too high? Because if we used no correction factor, these numbers would be very low. My uncorrected number for this dyno would be only 340whp.

With the s4 W10, uncorrected number would be only 177whp. On the G20 uncorrected power would only be 171whp. What are your thoughts?