Firstly, Yes, do it! Would be great fun.
Secondly, page 25 onwards, I remember reading this build a while back. Some good hands on stuff about how he got his set-up there, with bypass and pop off valve.
forum.retro-rides.org/thread/198109/1967-morris-oxford-traveller-where?page=25Thirdly, try to get hold of a tuning book that covers supercharging. I have an old copy of 'Forced Induction Performance Tuning' that was published by Haynes. Looks like it out of print now, but a resource like that helps with understanding the basic theory and having the equations and alike that help you get the basics working.
Would it need an intercooler to function correctly or could I just connected directly to the engine like the old Shorrock units?
I would probably use a 1 3/4 carb in a draw through arrangement.
In basic terms, the intercooler is there to cool the air coming out of the supercharger/turbo. This is for 2 reasons; 1. If you have hot air going into the engine, then the cooling system needs to work harder. It also raises combustion temperatures, which can potentially cause issues with pre-ignition and detonation. 2. Hot air is less dense, which means for a given air pressure there is less available oxygen, which means less power. Compressing air makes it hotter, and the more you compress it, the hotter it gets.
For an averagely efficient set-up, up to 7-8psi (0.5bar. Let's use bar as it makes the maths much easier!) without and intercooler you will gain horse power. Past this point, the rise in pressure is matched by the rise in intake temperatures to the point that you wont gain any more power, and in fact may actually loose power compared to the lower boost level. In practice this works out at approx 40% power gain over the standard engine is possible without inter cooling, but you won't get much more.
Intercoolers allow much higher boost level,s by cooling that air down, so you simply get the gain in pressure ( and therefore oxygen) with none of the downsides of the heat. I have driven my first turbo mx5 back to back at 7psi without intercooler and with, and even without raising the boost there was still a significant gain by fitting the intercooler, and then another gain when I could wind the boost up to 14psi!
There are other ways to cool the intake charge, notably water or methanol injection, the evaporation of which when meeting the hot air will cool the intake, but whilst they have a time and a place they are not as efficient as an intercooler (AFAIK).
With superchargers (and turbos) with carbs there are two basic options for setting it up. You can 'draw through' the carb, where the intake goes carb > blower/turbo > engine. This is easier to set-up because the carb doesn't need to do anything special, it just sees more air flow and will need to be jetted appropriately. The evaporation of the fuel as it mixes with the air can help cool the intake charge a little, and also the fuel mixture can help with supercharger rotor sealing, making it a little more efficient. But, you cannot use an intercooler, as you cannot control where fuel will drop out of suspension and puddle inside the intercooler. You have a large volume of compressed air fuel mixture, and with one backfire essentially have a bomb!
With 'blow through' set-ups, where you have blower/turbo > carb > engine, you can use an intercooler. The air coming out of the blower/turbo has no fuel mixed with it, so you do not have the same risks as with draw through. You can run higher boost levels and make more power, whilst stressing the engines cooling system less. The downside here is that you need a carb that is suitable for blow through, likely this means modification of the car itself and the fuel supply to it. On EFI set-ups they often run a dual throttle, one on the intake manifold and another infant of the supercharger, so help manage efficiency and throttle response. I don't have enough carb experience to know how this is managed.
If you're keeping it simple, I'd say draw through, no intercooler, keep it to 7psi. to start with.
How fast would I need to spin it? I understand the 500 in AMR500 relates to the swept volume of 500cc per revolution but if I span it at 1.5x engine speed and allowed a 20% loss that would be 1200cc per revolution compared to a 1098cc engine less its volumetric efficiency which would possibly be around 933cc so a potential worthwhile increase.
I understand the units have a maximum speed or around 16500rpm so at 1.5x engine speed would be running at around 4.5-6000rpm in normal driving.
I wouldn't expect that much of an air pressure loss, you will loose efficiency/power to heat etc, but the maths for calculation the boost you will produce can be more direct that that. The n/a volumetric efficiency is not so relevant once you start forcing the air in!
As I understand it, you are correct that the blower volume is 500cc. Your engine is using 1098cc of air every 2 revolutions of the crank (4 strokes). Aiming for 0.5 bar boost, that means you need thew blower to supply 1.5x the original 1098cc, which is ~1650cc per 2 revolutions of crank. So thats 825cc per rev of the crank. 825/500 = 1.65. So the blower needs to be driven approx 1.65x the crank speed.
Presuming you're not running the engine past 10,000 rpm, you're not going ot have a problem with max blower speed!
What would the compression ratio need to be for it to work?
How long is a piece of string? There are many factors which come together to say what compression ratio a turbo engine will handle. Modern factory turbo cars often have compression ratios of 10:1 or more and with complex engine management are OEM reliable. In the old days, it was consider necessary to drop the compression ratio to make for safe force induction applications.
As I understand it, theres two factors here. 1. is the physical geometry of the engine and its resistance to detonation. A better designed modern engine has better squish in the cylinder head and cools better which allows for a better overall resistance to detonation. 2. The higher the compression ratio the less margin for error there is in tuning before detonation is likely.
The old rule to thumb would be to be aiming for something in the region of 8.5:1 - 9:1 for a forced induction build. Given that the A series is old tech and you're using a carb, this seems a good place to start to me.
Other options seem to be the BMW Mini supercharger or a small Mercedes one but they all seem a lot bigger than the AMR500.
The Eaton M45, as used in the Mini and smaller Mercedes, is a really good efficient supercharger. I would hazard a guess that it would be more efficient than an eBay special AMR. The M45 is a 750cc capacity supercharger, so it will be physically bigger than the AMR500. And obviously you'd need to spin it slower.
I'm doing a lot of reading but there is a lot of conflicting advice.
Welcome to the internet. It's full of armchair experts, myself included!
