AMR Supercharger Tech info

Sourcing an AMR500 or AMR300 supercharger is starting to get a lot harder than it was back when we started doing this. There are numerous aftermarket manufacturers that sell what look like genuine superchargers for bargain basement prices, but you will find that those cheap clone units are not suitable for VW applications. They work fine as a replacement for the original application (low boost, low rpm and used in blow-through configuration i.e. dry), but as the typical VW application pushes the AMR500 to its limits, the aftermarket units have a tendency to fail.

Blower failure modes

Typical failure modes of the cheaper units involve rotor coating separation and bearing failure. The rotor coating on the original AISIN units is teflon and is both heat and fuel resilient. This makes them suitable for use in draw-through configuration, and also also capable of handling the elevated temperatures that we see with the typical VW application.  

Heat is a by-product of compressing air, the more you compress it, the hotter it gets. If you remember back to being a kid and pumping your bike tyres up, you'll remember how hot the hand pump got. The same thing happens in the blower. The higher the boost, the more heat is generated. In a VW application this pushes the aftermarket units past their limit resulting in premature failure.

The coating used on the aftermarket blowers is some form of thermoplastic which has a tendency to disintegrate when used with fuel, and is nowhere near as heat tolerant as the original teflon. The bearings in the aftermarket units are also low quality and not rated for the same speed that the genuine units are. The main input shaft bearing is also physically smaller which means that it cannot handle the elevated loads generated in a typical VW application (more boost = more force required to turn the blower)

For this reason we ONLY recommend using genuine Aisin superchargers.

How to tell a genuine AISIN unit

Genuine AMR500's are pretty bomb-proof and provided that the rotor coating is not damaged, pre-used units are generally serviceable after a clean up. Bearings rarely fail as they are a high quality ABEC spec sealed unit. For the bearing to get to failure point, the rest of the blower would generally have many tell-tale signs that it has been abused or not maintained. 

Look for the green foil AISIN stickers on the mounting lugs. All AISIN units have a green foil sticker that has the AISIN logo, part and serial number. Avoid the units that come with Vee pulleys or small diameter PK pulleys and plastic manifolds as those are generally aftermarket units. The original AISIN units have a 70mm pulley, none of the aftermarket units do. 

Our advice is to purchase a used genuine AISIN unit (like the one pictured). This way you know that you are getting a genuine unit and it has not been messed around with.

In our experience of sourcing blowers from many vendors over the years, the units that claim to be 'rebuilt' are often just run through a chemical dip to remove the dirt and grease, and then fitted with new hardware and a re-plated front cover. The case is not even split. If you strip them down you will see that they have their original bearings and that the cleaning process did not reach the bearing wells (the area behind the bearings), indicating that the units were not stripped down before being cleaned. It is much better to buy an untouched unit and clean it yourself, especially as once they have been cleaned up, it is pretty much impossible to tell if it is genuine or not from just a photo.

Can they be rebuilt?

The short answer is yes, but it's not a job that the home mechanic can easily carry out. The rotors are not keyed on the shaft and so require a special tool to set the alignment on reassembly.

The front bearings can be easily changed, but it is unusual that they fail as they are sealed units. The more common failure is the rear bearings which are not sealed and rely on the oil from the gearbox to lubricate. Generally if they have been run dry to the point of bearing failure, there will be evidence of a leak. Avoid any units which have oil at the rear of the unit around the rear cover as this is fair indication that the gearbox is leaking.

Can you rebuild it for me?

We used to offer rebuilt and warrantee'd AMR blowers, but we found that we simply could not compete with Temu prices and bargain hunters. Given the prevalence of inferior units on the market we may look at this again in the future but do not have any current plans right at this moment.

We do not offer a rebuild service for customer supplied units.

In Summary

Generally if you are sourcing a genuine, used un-modified blower and it looks like it's in good condition on the outside, then there is a high probability it will be absolutely fine. If you can get the vendor to send you some photos or a short video of the rotors you can make a pretty good judgement call. Bearings rarely fail and if you avoid the units that look like they been flogged then you will most likely be okay.

If you are buying a 'rebuilt' unit, then you are essentially taking a bit of a gamble. Not only is it hard to tell if it is a genuine AISIN unit, but even if it is, there is no guarantee that it has actually been properly rebuilt. 

So whilst most people would like to buy a 'remanufactured' or 'rebuilt' unit for peace of mind, in our experience you are actually at a higher risk of getting a unit that is prone to failure. The only real way to know that you are buying a genuine AISIN unit is to buy one that's unmolested.