How much power will my engine make?

How much power will my engine make?

The actual power made will depend a lot on the specification and condition of your engine.

Generally speaking an increase of about 60% is a good estimate for our budget kits on a stock engine running moderate boost of 5-6psi. This will give you a reliable increase in power without putting too much strain on your engine. It is also a bolt on modification which gives you a good hp per $ return as you do not need to make internal modifications to your engine. To give you some idea of what to expect, installing our budget kit on a stock 1600 twin-port engine increased the output power from 50hp to 83hp when tested on the dyno. When you consider that a stock 2.0 Type 4 engine makes 71hp you can see that the kit is a worthwhile addition. For more power you can easily change the drive ratio to increase the level of boost. However there are limitations on how far you can go related to the maximum speed of the blower and the capacity of your engine (More on that later), as well as power transmission related to belt slip.

If you want to maximise the power gains,  you can also make other sympathetic modifications to your engine. The following modifications will help you to make the most from your kit

  • Improved head work – We recommend something like the CB performance Panchito 35.5 x 40mm heads
  • Increased capacity - We recommend 1776
  • Proper merged collector header like a sidewinder
  • Boost referenced ignition control. We recommend using one of our crank fired distributor-less ignition systems but a CB black box, MSD or similar boost referenced controller will also work. 
  • One of our custom camshafts. – Our cams are developed specifically for use in blown applications and are available in a few different grinds depending on your setup.
  • Using our performance kit with higher flowing manifolds
By employing modifications such as these our customers have managed to see massive improvements. The best results reported so far are 138hp from a 1776.

If you are chasing ultimate power, the other question to consider is how much boost can your engine handle? You can increase the drive ratio to give you more boost, but the more boost you push into the engine, the more supporting modifications need to be done. Higher boost applications require additional modifications such as boost referenced ignition control, water methanol injection and forged pistons to help manage detonation. 138hp is also getting towards the top end of what the stock crank and rods can handle.

As the old adage goes... "how fast can you afford to go?"  (Cheap / Fast / Reliable - pick any two !!)

Capacity Limitations

Traditionally blowers are selected based on the engine specs and application. Just like with a turbo, you need to calculate the air consumption of the engine, your target boost and then select the blower accordingly.  But with the AMR500, what happens is essentially backwards. The blower choice is made first and the spec is therefore fixed, so you need to design the engine to suit the blower.  This also means that if you have an existing performance engine it may not be suitable for an AMR500 despite what you may read / wish

At 16,000 rpm the AMR is at its maximum design speed and will move around 200-220 cfm of air.  To put this in perspective, this is about the same as what a 1500cc engine running 12psi consumes, or a 1915 running 6psi. This is also measured at max engine speed.. So if you want to increase capacity, or boost or engine rpms past this (i.e by fitting a larger camshaft), you will exceed the maximum rpm limit of the blower which will increase the risk of blower failure. This is also with the blower running at 100% duty, which is not the ideal place to run a Rootes style blower as the efficiency drops off considerably. At rpms that exceed the design limit, the centrifugal force also has a tendency to seperate the rotor coatings from the rotors, this in turn causes the rotors to touch, which then sends shards of shattered rotor coating into your engine. Add to this that 99% of blowers on the market are all pre-loved with unknown provenance and the risk of rotor failure increases even more. So an important consideration is to operate the blower within its design constraints.

Rotor coating separation

As a result we generally recommend 1776 as the optimum capacity for performance applications, which takes into consideration the increased engine rpms you will see from a performance cam and head work, the optimum operating range of the blower and also the boost versus capacity tradeoff. So if you want to use the AMR500 on a non stock engine in a performance application, the setup will be dictated by your engine capacity and max rpms, what boost you want to target and the application. You can trade some points off against each other, like running a larger capacity at a lower boost level, or overdriving the blower slightly for a street application which will rarely see max engine rpms, but we do not recommend moving too far from this combination. The further you move away from this, the more one of the design constraints will be compromised. Also, the more performance you are building your engine for, the more attention you need to pay to the details. Building a performance blown engine is not simply a case of bolting a blower on.

We do not generally recommend targeting engine capacities much larger than this as the AMR500 cannot push enough air to make meaningful boost without overdriving the blower and running it outside of its optimum range. Of course the internet experts and even the other copy-cat blower kit manufacturers will tell you that the AMR500 can support ridiculously large capacity engines up to 2.1 litre but the truth of the matter is that it cannot. At 6k rpm with the blower maxed out you will only see 1.8psi on a 2100cc engine, which most likely is not enough to overcome the sacrificial losses of driving the blower. Also don't believe the marketing hype other kit sellers feed you. The HP figures I see are massively overstated and are based on operating the blower well outside of its optimal reliable range. Sure you can make more boost by overdriving the blower for an insta-worthy dyno run and inflated HP figures, but that blower will not last long and nor will the engine it feeds (see above photo). If you are impressed by inflated HP claims, you should also ask yourself the question, 'how can a competitors kit give you more reliable HP using exactly the same components?' The short answer is that it cannot. The compromise is reliability.

If you are interested in building a performance engine based around the AMR500 (or AMR300), we are happy to help. Feel free to reach out.

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