Camshafts for elevation

[RevTheory]

Since the altitude is reducing the mass in the engine, you handle the cam kinda like you would a restricted inlet engine. Only difference is, a restricted inlet engine, the mass reduction increases as the RPM's increase.
Of course you want to increase the compression. If the air density is down 20%, increase the compression by 20%.
As for the cam, you run the same intake duration you would run at sea level, but with more lift, and on an earlier intake closing point. On the exhaust, you run less duration and lift, with the same exhaust closing point that you would run at sea level.

I wish the forum platform had a "thumbs-up" emoji. Great post.

[CamKing]

So running a less ratio rocker on exh would help out? 1.73 to 1.6?

yes

[CamKing]

I've driven turbo cars since 1978 and it's definitely my thing. It took Ford, Chevy, Mercedes, BMW, et al another twenty-five years to understand, but all their entry level performance cars are 2-liter turbo fours.

My dad gave a speech at an SAE conference, and proclaimed that the future of production automotive engines would be small displacement, inline-4, turbo engines. That was in 1973.

[PackardV8]

Mike, some say the most important decision one ever makes is choosing parents; you chose well. Thanks for sharing one more of your dad's long list of accomplishments. Some can just see over the curve of time.

[englertracing]

Well i do have a 07 gt500 and i do like it no doubt about it. If i was going to do something it would be that style. Rig up a roots style or if you know how to set up turbo car to get around that popping and farting on line im in. Im old school I dont get that even though they do haul a**!

these use a roots, with a turbocharger that bypasses the roots.
I feel that its just awsome, that little 1600cc motor, would take a while to spool a large turbocharger, even with the help of a bunch of fuel and spark retard, and all that racket.
draw a little horsepower running that supercharger, supercharger blows some induction in, more exhaust comes out, Turbocharger spools verry early, and off idle was already covered from the supercharger
so the little 1600, made 400hp but had heard reports of 600hp for special occasion, all over a HUGE powerband!
to me its just so much more elegant than a nasty popp and cackle antilag
today you would use a small twin screw

https://youtu.be/ARvesNfkXAs
https://youtu.be/5HlqEkJ3VGM?t=207
https://www.youtube.com/watch?v=NeRTQJOzwj4&t=94s
darn things have nothing but boost at all rpm and throttle positions other than closed
They are uglier than shit, but I think they are about some of the coolest damn things ever built
https://youtu.be/ViGgVVNrhtI

[engineguyBill]

It has been my experience (years ago at 7000' altitude) that camshaft timing does not necessarily impact high altitude drivability at high elevation. Carburetor jetting was very important and current engines have overcome much of the rich/lean issues with the advent of electronic fuel injection and even more so with the availability of modern turbochargers.

[rp930]

So running a less ratio rocker on exh would help out? 1.73 to 1.6?

yes

If I chose to do that on my current cam where would I notice the difference? And since I’m running exhaust manifolds (BBC) how does that affect things?