Rotus Project Build

[Jamie R]

it

Got my Christmas lights up.

And if I can't tell I've got low oil pressure then I need dragging to one side and beating


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[Casey]

Blimey, you can't miss that 

[Eccentric shaft]

Blimey! It's like one of those flashing photo boxes that send you right into the woods! 

[MattScott]

You'll catch a sun tan from that

[MattScott]

Your colour scheme is catching on

[Jamie R]

Your colour scheme is catching on

Legendary see lol


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[Jamie R]

So..........

Not really posted anything worthwhile for ages, time for a big update.

Well, the Rotus runs! Well for 3 secs at a time. Most people will know about disconnecting the battery and the ecu loses partial memory on e shaft and fuel trimming etc. Well we think we got that scenario.

Firstly i need to thank Jon for being there for me multiple times over the weekend to try and sort the obvious items. Also shout out to Malcolm confirming our suspicions.

Items we have checked to rule out to understand why it wont run longer than 3 secs
1, Fuel pressure maintains 4 bar on position 2 on key and 4 bar on cranking engine.
2, no obvious signs of coolant or other oddities in the chamber on this new build.
3, Changed MAF
4, Changed E shaft sensor
5, Changed Barometric sensor,
6, verified all ignition coils have correct wiring plugs
7, verified all injectors have have correct wiring plugs..
8, verified all relevant fuses and relays are working as they should

Onto brass tacks ... namely the 20 brake stomp test / ECU re learn.

Looking at the wiring diagram there are 4 wires that go to the back of the brake pedal switch to the ECU and its grounded out when pressed, first pic attached.

The R/G wire goes from the pedal to the ECU and when position 2 on the key is activated then you have 8 sec to carry out 20 stomps for the oil gauge to do a sweep and youre ready to start the engine and it will do its thing.

1 problem, my Rotus only has 2 wires not 4, So does my other RX8 and so does Malcolms RX8. Oh Mazda you sneaky buggers.

Now ive done the stomp test successfully on my RX8 and so has Malcolm, so the only logical eplanation is the ABS unit detects the stomps when pressure is applied and send a signal down the canbus to the ECU which in turn sends a signal to the binnacle for the oil gauge to do its sweep.

BRILLIANT !!

second problem, Im not running the stock ABS system.

Observe second picture with the mad professor on the computer with my old ABS unit on the desk hooked up to the micro processor.

Long story cut short, there are 2 main power wires which weve hooked up, an ignition wire which is sorted, the 2 x earths AND the canbus wires.

So on "start up" we can see the ABS unit powering up drawing 0.3 amps, hear the solenoid kick in and it "SHOUTS" a lot!

Its shouts down the canbus messages from the wheels sensors amongst or codes pertaining to the DSC light coming on etc..... to the tune of 200 codes a second !!!

So I have a request, does ANYBODY know, or know a Mazda tech guy, who knows the code thats spat down the canbus for the 20 stomp or the oil gauge sweep? It will save us sooooo much time.

We need to lie to the ECU and get the gauge to do its thing so we can do the ECU re-learn or the Rotus may never see the road.

Not a valid attachment ID.Not a valid attachment ID.  Thanks in advance

J

[Casey]

Jamie, would you like me to raise this, on your behalf, over on the RX-8 OC?

I've not checked the wiring diagram yet (hopefully will get to look later today) and will look to see if the brake switch/lights are connected to the ECU in any way, with the 2 pin brake switch build. It seems very overly complex to detect the stomping via the ABS unit and then CAN bus signals. Not impossible, of course, we are talking Mazda here!

[Jamie R]

If you could that would be great.

Im pretty postive looking at the wiring that its true as the two wires from the pedal go to a noise filter. the black/blue wire and black/red terminate at the filter that cleans the electrical signals then a black yellow wire go to

Rear brake lights x 3
Auto transmission if fitted
ABS
DSC

Theres no other connection from the pedal to the ECU other than the canbus wires from the ABS.

Further to my previous post, we have found out that the ABS is actually more noisy than we has thought. As a safety feature, just the wheel speed sensor codes alone, 1 code is spat down the bus every 20 milliseconds and the other codes shouts at 4 every millisecond.

Its a very busy unit indeed!

[Casey]

Give me a call Jamie. I have some ideas from the Spin Doctor on the RX-8 OC that are worth checking out.

[clive]

OK, Just a thought, back to basics/

I have a feeling that because the ECU is seeing wrong information, the immobiliser is cutting in. 

3 seconds is about the right time for the fuel system to lose fuel pressure if the fuel pump is shutting down.

So two things, do you know the pump is running correctly, also with the race car we had to give the pump a full 12Volts and not the soppy initial 5 volts.

Next up, are you sure you still have power going to the coils after start up.

Lastly, can you hear the throttle resetting itself when turning on the ignition as I have the feeling if the ECU is not receiving the information correctly it wont let engine run for long.

If it was me I would be inclined to false feed both the pump and the coils with 12Volt feeds and see what you get.

p.s. I did try and phone back Friday.       

[Jamie R]

OK, Just a thought, back to basics/

I have a feeling that because the ECU is seeing wrong information, the immobiliser is cutting in. 

3 seconds is about the right time for the fuel system to lose fuel pressure if the fuel pump is shutting down.

So two things, do you know the pump is running correctly, also with the race car we had to give the pump a full 12Volts and not the soppy initial 5 volts.

Next up, are you sure you still have power going to the coils after start up.

Lastly, can you hear the throttle resetting itself when turning on the ignition as I have the feeling if the ECU is not receiving the information correctly it wont let engine run for long.

If it was me I would be inclined to false feed both the pump and the coils with 12Volt feeds and see what you get.

p.s. I did try and phone back Friday.       

Hi Clive,

All valid points, so to recap. Fuel pump is great and runs tip top at 4 bar can confirm more in a sec.

The butterfly on the throttle is moving as it should, it fully closes on start up then slightly opens for tick over, and fopens fully with pedal pressed, I stuck my phone on video in front of the throttle body whilst i did that. When the engine dies, i put my foot on trhe throttle and it fully opens, so the relay still working.

As for 5V, I bypassed the low power relay as per jons instructions a while back. It only runs on 12v.

Had the car running tonight for about 50 secs but only by blipping the throttle. Its definately mapping as it ran for that period of time at 4 bar of fuel pressure and the immobilser question I verified at the weekend, so not that.

Its running rough as a dogs arse for that peroid of time, but running is running. The neutral switch and the clutch switch work too.

[Jamie R]

https://zircotec.com/motorsport/resources/news/one-of-a-kind-1972-lotus-elan-2-build/

A few errors on their parrt on the write up....... but hey ho

[clive]

https://zircotec.com/motorsport/resources/news/one-of-a-kind-1972-lotus-elan-2-build/

A few errors on their parrt on the write up....... but hey ho

OK you may not be 100% happy but it is recognition of all your hard work.

[clive]

So did the fuel pressure drop and the engine then stop ?