State of Rex hacking?

[Woodfie]

[Woodfie]

Have now amassed enought parts to enable spark on firstly one cylinder of the REX'S engine .

A Bmw sensor for what is possibly tacho and timing to go on the speeduino track has now arrived, for after a more basic approach.

The magnet wheel, Hall sensor, Pre conditioning amp, Coil Driver kit, Ballast bulb, up to the Coil and plug.

Lots of bits to eliminate a set of Mr Ketterings Points.

[Woodfie]

The spark set up, now delivers a slender, but firm mini bolt

On running the generator as a starter, the revs still oscillate maybe +/-500rpm, at around 1 Hz, bit like a teenager on a small scooter sound..

Setting up to check the ball park timing, and garden plumbing " throttle " butterfly

Only going to run ONE cylinder first, as have discovered the crank is 90 degree between pistons, or crossplane configured, which messes with my 180 degree timing wheel set up.. Also haven't figured yet if it's 270 degree lead, or follow (I e. 540 degree lead ), or had considered 90 degree lead or follow... Makes my head hurt thinking about it, as cannot rotate the engine slowly, with the 8mm nut on the resolver being only access at present.m

[jrbe]

I'm kind of surprised it's an odd fire twin, but they do make good torque for their size.

Speeduino works with odd fire setups but it likely has some specific triggering requirements to do it.

1 magnet on the trigger wheel with 2 Hall sensors spaced 90° or whatever the offset is could work to rig it for now. 1 for each coil. It will be tricky to time / adjust though.

[Woodfie]

Yes, I was surprised by it also, but that's the learning.

It would seem that it now is the trend in recent cycle engines, and although not necessarily required for a generator setup, I guess Bmw used what they had under their umbrella.

[Woodfie]

Another step, satisfactory single cylinder test run, second cylinder Inlet blanked off.
Observed power returning to the battery , brief run, as no coolant to lubricate the pump, and extract an expected 4 or 5 times waste heat portion of fuel use.

Also evident is an unloading to zero amps at around 3kw output... and over stressing of the lightweight phase test wires.. Work to do..

[Woodfie]

Water circulating system gor the Kymoco, twin cylinder now running as a single for test purposes., has been fashioned for short running.. No radiator or heat exchange yet, but coolant in pimp and block.

A stumbling block has appeared...Once a clamp meter indicated 14A into the 250V battery occurs, the charge drops to zero. Reducing the throttle, then initiates the charge, but again will cut out at 14A.
The Nissan leaf inverter which is being used with the Valeo motor generator from the REX unit, is controlled by a Thunderstruck V1.0 vcu.
Increasing values of
max Battery V for regen,
Idleregen,
and brakeregen settings has not made any difference.

Also have activated the Brake switch control input, and no improvement yet achieved.
The reason for the limit is not yet understood.

[jrbe]

There are no errors or messages showing in the thunderstruck vcu?

Its likely that there is some limit at 14A or 3500watts that is triggering it to cut regen. Could be a missing / incorrect input like temp, voltage, amperage, etc. What can you see in the thunderstruck vcu that looks out of the ordinary?

[Woodfie]

Thanks jrbe, the Thunderstruck V1.0 vcu is one of the very first releases, looking to re find the manual . Had used it before with Leaf inverter to drive a ED Smart car, which had done it's graveyard mode shutdown. Have not used the brake function, or more than mild regen, so had not seen this limit till Rexing.
Will see how to find/read errors, for clues.

Searching for the V1.0 manual

I know this V1.0 vcu will not operate a Gen 1 Leaf inverter, which was my first choice, A later V3.1 vcu which can run Gen 1 or Gen 2, has-been suggested, I believe it maybe better doc supported..

[Woodfie]

Have located the relevant manuals , and so far have not found , what may be missing.
Have also now tried the V3.1 vcu, with the same result, so pointing towards something the inverter, possibly an input not satisfied.

[Woodfie]

Activation of brake switch, Changes to regen config settings of brake, idleregen, and turning all off, seem to have no effect, still 3.5kw or 14A on clamp meter, and it unloads.
Finally some variation can be gained by retarding the resolve setting some degrees, and 7kw or 30amp on bus clamp meter observed. However there is then low starting torque to crank the engine at the present Nm settings, unless advanced to around the original selected resolver position.
Looking at trace info, you see of anything can be gleaned.. Wondering if this charging is somehow dictated by the inverter , perhaps some default setting... WIP

[Scrappyjoe]

I have no real knowledge, but am following with interest, so would like to throw in some possibly silly thoughts. Ignore at will.

1. Could this perhaps be some incompatibility between the inverter and motor? Something that is not noticeable at low loads but that kicks the inverter off at higher loads? Perhaps test by running the generator as a traction motor and see if you have the same problem in drive mode.


OR


2. Could this be some issue between the VCU and the inverter in regen mode? Test by swapping the BMW motor with a known working leaf motor, and see if regen still breaks at the same spot.

Basically I’m thinking it would be good to isolate if root cause is between VCU and inverter, or between inverter and motor.

[Woodfie]

Yes thanks for the thoughts,
Had considered the 2 plan, leaf motor is not easy connect to present BMW engine , had a small water blast stationary motor, but figure not enough to get to the unloading limit, but would help figure out the regen not functioning.

[Swing]

Well, all I can say is keep up the good work.

The BMW REX might not be perfect, I think it is one of the only options around for DIYers looking for a compact range extender.
All the alternatives are much bigger engines integrated into a drivetrain.

[jrbe]

The Hyundai HSG starter / generator could be another option for testing.

[Woodfie]

Re: State of Rex hacking?
Contemplating putting a Leaf motor in the empty engine space of the Test Bmwagon. And use MG1 to rotate the splines shaft at up to the desired say 12kw,
This would check out the Thunderstruck, Leaf inverter , and Leaf motor and its regen operation, to see if the present anomalies experienced can be better understood