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Citroën A-Type Tuning

Non Citroën Engines

© Copyright: J.Cats.

Disclaimer: This page only provides information based on the personal opinion of the author. The author can't be held responsible for damage in any way that could result from modifications mentioned here.

Some things to think about:

  • 50bhp is maximum useable power for normally aspirated 2 cylinder Citroën boxer engines
  • 100bhp is maximum useable power for normally aspirated 4 cylinder Citroën boxer engines
  • higly tuned engines have a greatly reduced life expectation
  • tuning is VERY expensive
So if you are not emotionally attached to the Citroën engine and you like to get decent power for reasonable money, now is the time to bin that Citroën engine!

There is one thing that seriously limits the number of engines suitable for transplantation. The Citroën engines mentioned above are all so called "boxer" engines with a horizontally opposed cylinder layout. These engines have all engine mounts at the bottom of the engine. This is good since that's where the chassis is.

Below are engines that are suitable for fitting on an A-type platform chassis with these limitations in mind.
  • Motorcycle twin
    Suitable and cheap alternative for any state of tune 602 or 652 engine. Bike engines are cheap to get, small and provide lots of power with additional high rev capability. Moto-guzzi engines have been fitted to lomaxes as have BMW twins. BMW twins have more power then tuned Citroën G series engines!
    Companies that have done this before:
    Auto Bouw Service (NL), Guzzi engine on a lomax
    Duckhunt (NL), Guzzi engine on a lomax
    Der Franzose (D), Guzzi engine on a lomax
    Pembleton (UK), BMW engine on a trike
  • Motorcycle four
    Suitable and cheap alternative for any Citroën flat four engine. Most have power outputs of over 100bhp and they are very light. The 4 in line engines are fitted transversly in the bike with the output sprocket on the left side. This makes packaging for FWD conversions a bit difficult.
  • Alfa Romeo 33 / Alfasud flat four
    Although not a brilliant engine in any shape, it's a good alternative to a GSA engine. 16V DOHC 1700 delivers 130 bhp, which is hard to beat with any GSA engine, no matter what state of tune. The 16V engine is quite wide but the 8 valve is exactly the same width and length as a GSA engine. Plenty of tuning equipment available as the 33 is quite common as rally equipment. There are several 2cvs and Amis with Alfasud/33 engines. Biggest problem is space for the radiator either in front of the engine or on top of the gearbox. One major disadvantage is that the alfa engine is always a bit heavier then the GSA engine. It might be good to know that the Alfa sud gearbox has inboard brakes and fits the 33 engine.
  • Subaru Impreza / Legacy flat four
    This is an extraordinary engine. All alloy, high capacity (2000cc) with power outputs of over 100 bhp in any shape. Best of all is of course the 210bhp Impreza Turbo engine, providing you can built a chassis that can cope. These engines are widely available. Lots of tuning equipment available. Engine mounts are in the same place as on the Citroën flat four engines and the subaru engine is shorter then the alfa engine. These engines are cheaper then any seriously tuned Citroën flat four engine and deliver much more power with longer engine life then a standard GSA engine. As far as I know, this hasn't been done but should not be more difficult then the Alfa engine. Biggest problem is space for the radiator either in front of the engine or on top of the gearbox. The engine isn't that much heavier then the GSA engine.
  • Mazda RX7 Rotary
    Quite a small engine, it's certainly different. With twin 654cc rotors it delivers over 100bhp in any shape. It can stand high revs and is very quiet. Twin turbo examples deliver over 200 bhp. Lots of tuning equipment available. These rotary engines were fitted to GS(A)s in Australia/New Zealand by owners looking for more go. Twin radiators were fitted in front of the front wheels. More specific info on this is not yet available. The engines are very light and very compact, so there will probably even be space for the radiator in front of the engine.
Fitting non Citroën engines
  • non Citroën car engines
    If you really want too, any engine can be mated to any gearbox. Since these pages describe how to fit a GSA gearbox into any A-type, and fitting other gearboxes will be quite a bit harder and probably won't have inboard brakes, i'll be working on the asumption you're using one of these. First of all, after removing the bellhousing the input shaft can be removed without splitting the gearbox, and so it can be replaced by a lengthened one if needed. If needed the bellhousing can be left out and a plate bolted directly to the box, but then a clutch release mechanism has to be made. For fitting the engine to the gearbox you'll need some large pieces of thick paper. Put a piece of paper on the gearbox, noting the center and then marking the moutning holes. Do the same on the engine. Getting the center right is VERY important! You can check if you have found the exact center by measuring from the center to all mounting holes and checking to see you get some identical measurements. Now you have to have 2 thick metal rings made up. The inside diameter of the rings is about 20mm less then the smallest measurement from mounting hole to center. The outside diameter of the rings is about 20mm more then the biggest measurement from mounting hole to center. The 2 rings are exactly the same. Bolt 1 ring to the engine, making sure the center of the ring is exactly the center of the crankshaft. Bolt the other ring to the gearbox, making sure the center of the ring is exactly the center of the input shaft. The 2 rings can be bolted or welded together, depending on how much distance you need for the clutch. On the engine flywheel holes are drilled for the Citroën presure plate, or the Citroën clutch disc if fitted within the original engine pressure plate. If this is not possible, a flywheel will have to be made from scratch, being bolted to the engine and taking the Citroën clutch. All that's left is making sure the clutch will disengage.
  • non Citroën bike engines
    The Guzzi and BMW engine have a flywheel just like the original engine. These engines can be fitted by having a flywheel made that will bolt to the bike engine and takes a Citroën clutch (disc and pressure plate). Bolt engine and gearbox together in such a manner that the clutch will disengage and you're done! Other bike engines have an integral gearbox.
    Here you'll have to do a lot of engineering, especially if you also want a reverse. One option is to mate the bike output shaft or sprocket to a G-series gearbox which gives you the differential and reverse you need. If you don't need reverse, the sprocket on the bike gearbox can be linked to a chain driven differential. Check out mid engined bike powered kit cars like the westfield XTR2 and MK GT1 for ideas.

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