Hello from Colorado

I have a 2011 AMG G55 and am here to learn a little about tuning it, as well as improve my wiring skills as I upgrade my truck to prepare it to be a better off-roading and camping vehicle. I live at >8000' elevation and frequently am wheeling at 9-12' above sea level so one of the things I want to learn is how to size the right supercharger pulley I should be using at this elevation as my G-Wagon is feeling pretty weak up at this elevation.

Current mods I am in the middle of working on at the moment:

38.5" tires

Portal axles with 5" lift and 1.3:1 gear reduction

Central Tire Inflation System

AiM Sportline PDM32 to control accessories, additional sensors, and cameras

Rear Mirror and 360 surround cameras

-Shane

Hello!😎

Very nice to see a G-Wagon being actually used as it's intended, rather than on a grocery run.

Portals would be a good idea, if you can actually use the tyres, as they'd both help correct the gearing (and speedo') but also give more body clearance - depending on source (UNIMOG?) you may gain some track width, too, which will give back some steering lock and stability.

With the supercharger drive, a base-line may be to convert the nominal OEM boost to absolute pressure, and figure out the multiplier for the drive ratio from that for your altitude(s). Other than supercharger speed (which may be an issue of it's own, and maybe a larger capacity may need to be adapted) that should keep you close to the OEM operating loads.

IIRC, some supercharged Merc' engines had issues with head studs/bolts - I'd suggest checking reliability issues, if you haven't already done so.

The portals are designed around 38.5" tires and have the gear reduction and speed sensor ring to make the computer think they are stock. Should be showing up Monday. I'm not sure what normal sea level boost is, but at my altitude I only get 6psi wide open, I'll ask others who are at sea level and find out what kind of boost numbers they see to help figure out what size pulley I should go to. I have a chart that shows supercharger rpm and when it gets out of the reasonably efficient range, so if that happens I'll have to bump up to a 3 liter supercharger instead of the stock 2 liter unit. Thanks for the tips.

I made a point of mentioning the boost because "boost" is only the pressure above the ambient, and that can make a big difference on what the engine is actually getting. I can't find anything on the OEM boost number(s), and M-B may be bleeding some off in the lower gears to save the tranny, but if you use this program - https://www.mide.com/air-pressure-at-altitude-calculator - you can see the ambient air pressure drop by altitude.

This means if there is 10PSI of boost at sea level the absolute pressure in the engine is 10 + 14.7 = 24.7 psi absolute.

At 8k feet, the ambient is 10.92 psi, which with 10 PSI boost (and it will normally be proportionally lower, as the volume drawn in is the same but the mass is lower) gives 20.92 PSI gauge. That is a theoretical difference of 3.78 PSI or 15.3 % drop. At higher altitudes it will be even worse as your 6 PSI may normally be 8PSI at sea level.

You should be able to safely increase the boost by the same amount the air pressure drops to maintain the same manifold absolute pressure.

Nice, thanks for the link.

It's coming along. This is the height it will sit when the wheels are on. Next up I need to tackle some wiring, I'll need to extend my brake pad wear sensors and ABS wheel speed sensors on all four corners as they are now too short to reach the calipers.

Got it all together, just having some issues with the wheel speed sensors but other than the current non-functioning ABS it's working perfectly.

I wonder if wheel speed sensors are directional? I may have installed some backwards as there are two ways they can be installed into the portals.