Weber Altitude Adjustment

We're putting Weber 32/36 dgev and Redline pressure reg. on a 64.5 170 ci and I had a question about how to set it up for Colorado. I don't have much experience with carbs at all, so I asked the place where we purchased the carb what jets to use. They said to leave it jetted the way it was, but to increase the fuel pressure to 4 psi. My limited experience is with ATV's and the like and they always get jetted for high altitude. Is just increasing the fuel pressure the right thing? We live right at 6300 feet.


Thanks

i would start by following the recommendation you were given, and see what happens. with webers it is easy to out of range and have to restart everything from the beginning. if oyu decide you need to change the jetting after trying just an increase in fuel pressure, then try that.

shawn30. The advice sounds fair enough.


Fuel pressure limits are from as low as 2.5 psi to as high as 4.2 PSI. Webers don't like really low pressure, either.

Using the FPR as a crutch should only happen when you can determine the loss in on the flat ground acceleration from 30 to 50 mph in 3rd gear. or air fuel ratio under wide open throttle.

The only way to do that is use a Cell phone application or an Innovate wide band AFM to measure actual Exhaust Gas Temperature EGT

I personally wouldn't bother. I'd go to a service station with an IM test dyno, and have them check air fuel at wide open throttle under load and be done with it. If you have two stations 2500 feet different in Reduced Level, then that would be as good as anything.

Webers are self compensating. They emulsify fuel, and the venturi action self corrects. There is power loss, but its not signifcant.

That's why in 1970 when calibrating the triple Weber 248 hp E37 and 306 hp E49 Chargers, the Australians used an old US Valiant Hartop and a 20,000 mile drive around Italy, including Stelvio Pass (below).

Generally:-

Basic Altitude Compensation: Example:
0-5000 feet: Ave RL = 2500. Zero feet increase stock jetting : 150 main jet
5000-6500 feet: Ave RL = 5750. 3250 feet increase 1 jet size smaller than stock : 145 main jet
6500-9800 feet: Ave RL = 8150. 5650 feet increase 2 jet sizes smaller than stock: 140 main jet
9800-13000 feet: Ave RL = 11400. 8900 feet increase. 3 jet sizes smaller than stock : 135 main jet


https://www.youtube.com/watch?v=0UWkTn7bOs0




Maybee Mt Harvard might help






See http://community.ratsun.net/topic/6117- ... ing-guide/
http://www.e9coupe.com/forum/threads/al ... ers.16047/