AMR500 kits versus built N/A engines
AMR500 based supercharger kits are a fairly niche application. They work best on stock 1600 engines as a bolt on kit. This will give you the best HP per Dollar / Pound / Euro / etc. That's not to say that they cannot make more power, or be used on larger capacity engines, but this usually follows the law of diminishing returns (as David Vizard once described it). This is the philosophy that the cost of initial horsepower has a far higher HP / $ return than any subsequent horsepower. i.e. it gets more and more expensive to extract horsepower from any engine, the more horsepower you extract.
The truth of this can be easily seen when you compare the cost of making power with an AMR500 compared to the cost of building a typical normally aspirated engine. Fortunately the cost of building N/A engines is readily available when you look at something like CB performances' 'builders choice' engine kits, which gives a US$ cost versus capacity and expected power...
Of course it is a simplified breakdown as there are other cost considerations such as carburettors and labour, but it gives a resonable baseline for comparison. We've added the $/HP column to help demonstrate our point.
CB 'Builders Choice' engine kits
Cost | Engine Size | Target HP | $/HP |
| US$6067 | 1904cc (90.5 x 74) | 90 | 67 |
| US$6053 | 1776cc (90.5 x 69) | 105 | 58 |
| US$5916 | 1915cc (94 x 69) | 120 | 49 |
| US$6195 | 2017cc (90.5 x 78.4) | 140 | 44 |
| US$6328 | 2110cc (90.5 x 82) | 150 | 46 |
| US$6883 | 2176cc (94 x 78.4) | 160 | 43 |
| US$7303 | 2276cc (94 x 82) | 180 | 41 |
| US$7345 | 2332cc (94 x 84) | 200 | 37 |
| US$7889 | 2387cc (94 x 86) | 220 | 36 |
Lets take a look at what you can achieve with an AMR500 based kit on a 1600 - Baseline pricing is in USD and includes performance kit, blower and carburettor. Boost figures are from our Boost Calculator
Cost | Boost | Target HP | $/HP |
US$1800 | 6 | 80 | 22 |
US$2300 | 8 | 90 | 26 |
US$2300 | 10 | 100 | 23 |
US$2300 | 12 | 110 | 21 |
As you can see at 6psi, you can run with a locked out distributor and get a reasonable 60% increase at a fraction of the cost of building a mild N/A engine. This is the sweet spot for AMR500 kits. Low risk, cheap reliable power without splitting the case. It's the best HP/$ return that you can get with an AMR500.
Increasing the boost requires a smaller blower pulley and some form of boost referenced ignition control, so the cost increases accordingly. So now we're still in a pretty good HP/$ area. We're at about a third of the cost of the 1904cc kit, the boost is well managed and we're still making reliable horsepower.
Moving up to 10psi to hit 100hp we're still in a good place compared to the CB 1776 kit which makes the same power. However, with the increased boost, we are starting to push towards the limit of safe horsepower. At 10psi, proper ignition control is critical to managing detonation. There's also the added risk that running poor / low octane fuels increases the detonation factor.
At 12psi we are about as high as you can get with the AMR on a 1600. We're still at the same price point, still about a third of what you would pay for the 1915 kit but we're at the edge of safe boost levels and detonation risk, and also at the edge of what the blower can supply in terms of cfm and boost at this capacity. Any failure or hiccup in the ignition management is likely going to result in detonation, which could be catastrophic under high boost / load conditions. So we're making boost and power, but it's a little more risky than running less boost. Hence whilst this is the cheapest HP that you can make, it's not the best way to make it. (unless you are a total reckless anarchist)
If you want to target higher power than this, you are looking at adding other engine mods such as an increase in engine capacity in addition to the supercharger kit, so you are effectively looking at the cost of the CB 1776 builders choice kit in addition to the cost of our supercharger kit, which is a cost of $8350 all up. Dyno testing has shown that this exact setup (Panchito heads + Joe Blow cam) can net you about 140hp. But that's likely the absolute limit of what you can do with off-the-shelf parts, and it is at a much greater cost than either just the performance kit on a stock 1600, or building a N/A 2017+ capacity engine which nets the same power.
Built 1776 with AMR Performance kit + JoeBlow JB300 cam
Cost | Boost | Target HP | $/HP |
$8550 | 10 | 140 | 61 |
In summary
As you can see, the HP/$ return of our Performance kit used on the stock 1600 is pretty good. In fact it's far better than any of the N/A builds, but it is limited in how much power you can make. It can get you over the 100hp mark, but that is not without proper ignition management and a certain level of risk.
If you are targeting more HP than this, then it's better to look at a different solution. You can still increase power by running more boost - by running a larger blower, but running 1Bar+ of boost on a stock VW engine is in reality little more than an experiment, unless you specifically love pushing boundaries. If you are looking for reliable HP in the 110+ hp range, a built N/A engine is generally the way to go.
By the same token, if you're building a blown setup using an AMR500, as soon as you split the case and invest time and $$$s in increasing capacity, you might as well just build a larger N/A engine to meet whatever power goals you have. The cost difference between the 1776 and 2180 is less than a grand.
Of course, a blown 1776 is a great setup. 140hp is nothing to be sniffed at, and the torque curve is a very different animal to the N/A build. If you have a specific application or if it's specifically an AMR500 based blown engine that you're looking at, this is the ultimate setup, but that is not without cost.
Feel free to critique the figures above, they're only there to give you a general idea. Mostly to demonstrate that the use case for AMR500's is pretty narrow, but they are very good at making cheap bolt on horsepower.