Obviosuly, the hydraulic servo as we know it is very difficuilt to implement on this engine. Something else is needed, and I had an idea :idea:
There is ever growing electrifying movement where people get for peanuts older cars with usually very worn or broken engines and convert them to electric propulsion. By doing so they face pretty much the same challenge as I did (notice the 'did' :wink: ).
The solution is this
This is electrohydraulic servopump from Toyota MR2 spider (2001-2005). It is extremly compact and all in one unit with everything. In it is the ECU running it, on top is the feeder tank. This is the brillint piece of kit (Domo arigato, Toyoda-san! :thumbs: ) as it is compact and reliable, and, most importantly, used on pre-canbus car.
The EHPS (electro hydraulic power steering) systems have been around for some time. To the best of my knowledge, the first car to utilise this system was Citroën Saxo/Peugeot 106 who were using this electric pump in diesel engined versions.
Similar pump is in existance for Renault Mk2 dCi. Both are very simple and run at constant speed having just two wires to connect (12V and ground). That would mean the steering would be overassisted at higher speeds and I would need some kind of controller to wind it down at speeds. Since that thing uses like 80 amps for operation, that needs some industrial type of controller.
Electroguys use also vauxhall astra H/zafira B (made by ZF) EHPS pump as well as Mk2 focus/Volvo S40-V50 (made by TRW). But, both these pumps need canbus for running and if canbus is not there simply run at their peak speed. Again, not good for feel and also not good for longevity of the pump.
One other option is EHPS from Mini R50/R53 which is also precan car, but not sure on steering sensors for that. Some conflicting information floating around and also know that these pumps (made by ZF) were prone to failures.
So, back to Toyota MR2 solution. It needs 12V and ground, switchable 12V and that is it. It has inbuilt pressure sensor. When you turn the wheel, the pressure drops and the inbuilt ECU winds it up. Just what is needed! Also, there is provision for VSS to be wired in, and then at certain speed it switches itself off. Toyota uses standard Asian VSS signal (square, 4 peaks pre engine revolution). Puma uses something like 7-9 (can't find definitive answer to that) so it would switch the pump off sooner.
Since the B6 gearbox has no VSS, I will be using a hall sensor at rear wheel(s). The idea is to drill a hole in rear hub carier (same as it is for the ABS sensor) and point the sensor to the back of wheel bolts. There are four of them and that is the 4 peaks per wheel revolution needed.
PCM can be calibrated to suit the instrument cluster and that should do.
For the electrical wiring of the MR2 pump got myself the small fuse/relay box from honda accord. It contains everything needed, but needs uprating to 50 A. It should make it more reliable and for a neat installation (domo arigato, Honda-san!)...
I have bought the MR2 pump on eBay and wait for it to be delivered. Also, need to send the engine loom to SCS-Delta for modification and then the fun can start.
I would just need some clarification regarding the puma servo system. It has a cooler at the front; that is part of pressurised line, I would presume? The line goes from pump to the cooler, and from cooler to the rack?
Ta in advance,
PS. If someone sees some flaw in my reckoning and planning, you are welcome to share your thoughts. We say a man and a donkey know more than just a man alone... (and I consider myself a donkey here)