[Roadsters] Carburetor tuning at high altitude

[Gary Boone]

Michael,
You can likely get a better tune by leaning it out a bit because if your tune is 
ideal for sea level, you're running too rich at 4500 ft.  But even if you get 
the mixture perfect for 4500 feet elevation, you'll still have less air density 
available, around 15% less than sea level, so you'll only be able to get 85% of 
the power at sea level.  I feel your pain, because I live at 6200 feet, so I 
lose 20% of full power at sea level, verified by my MAP sensor in my ECU for my 
EFI U20.  The only way to get it back is more air density which requires forced 
induction (turbocharging or supercharging).  

Gary  



----- Original Message ----
From: Michael Knorr <mhknorr at msn.com>
To: Datsun Roadster Listserver <datsun-roadsters at autox.team.net>
Sent: Mon, July 12, 2010 8:28:07 PM
Subject: [Roadsters] Carburetor tuning at high altitude

There's a Grand Prix going on near my city of residence (about 4,500 feet
elevation). The local newspaper interviewed the team members for a Porsche 911
GT3 who said their car lost about 30 horsepower at that high of an altitude
(and the summer heat here) even after they tuned the car to altitude. Five
years ago, Keith Williams tuned my carbs at Solvang -- basically at sea level
-- and I've kept them adjusted at around the same specs with apparently no
problems other than a high idle (about 1200-1500 RPM) when I drive up to about
a mile high in the local mountains. But I'm wondering, am I missing out on the
full 96 horses my little four-banger should be getting? If I can find a decent
mechanic at my elevation, are my odds good that he could adjust my carbs
better than Keith did?



Michael Knorr

1966 SPL311-03639