Rotus Project Build

[Casey]

Jon will be so disappointed 

Are they made of fibreglass though? 

[Jamie R]

Thankfully not malcolm lol

[Jamie R]

A lightweight car calls for a lightweight loom.

I didn't like any of these colours !!!


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[Casey]

It would be cheaper and easier to bulk buy black cable and use that for everything - much prettier too 


.... rewiring half done.......


........now was that black lead a +ve or -ve lead?


......big flash and Jamie's beard has a quick singe and trim 

[Jamie R]

It would be cheaper and easier to bulk buy black cable and use that for everything - much prettier too 


.... rewiring half done.......


........now was that black lead a +ve or -ve lead?


......big flash and Jamie's beard has a quick singe and trim 

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[Jamie R]

It would be cheaper and easier to bulk buy black cable and use that for everything - much prettier too 


.... rewiring half done.......


........now was that black lead a +ve or -ve lead?


......big flash and Jamie's beard has a quick singe and trim 

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Sounds like Mazda great idea of 20 odd purple wires all for the rear lights


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[Jamie R]

Good Morning all, very productive weekend in terms of Rotus development.

Firstly pulled one of the original stock sensors out the offside rear hub and fitted the Jamie counterpart. This obviously threw a warning light but the car drove absolutely fine regardless. (First pic)

Armed with a nutty professor and his oscilloscope we set about measuring the peaks and troughs of the toothed wheel on the drive shaft, which show up on the scope as a square wave. We took recordings of frequencies at 30, 40, 50, 60, 70, 80, 90 mph and then a bit more, all on a closed non public highway ahem.

Compared all the data from the scope to the spreadsheet ( next pic) and the sensor is spot on! Nice square waves too, that still blows my mind.

Next was to hook up the Jamie sensor to a laptop and run a spare RX8 speedo and see if the real speedo matches the spare one..... Problem!

The spare speedo was half the speed of the real speedo -1 mph so 60mph in real life registered as 29. Hmmmmm.... back to base.

I wanted to make sure the corresponding tyre to the sensor was actually of the right circumference to our program data.

Some data shows 225/45/R18 as 2042mm circumference, some show 2072mm circumference. So I physically measured my part worn, they come out at 2064mm

An hour later of coding in the program and working crap out mathematically and were back out.......... so we found an error in the program which was halving the speed, fixed! and the -1 mph differential was the circumference of the tyre discrepancy.

The nutty professor is building in a function where by if I park my car near the WiFi in the house with the ignition on, I can fine tune the calibration by altering the circumference of the tyre ... from my phone !!! and it will make the speedo accurate.  Handy when I could be swapping between 18" RX8 alloys and 17" steels depending on tyre choice etc.

We also found a noticeable lag in the spare speedo in comparison to the real speedo, so when I shout to Rich 40mph! his speedo reads 40mph 1 second later........... back home.

A quick alteration in the program where the counter calls for a reading every 0.5secs instead of every 1 sec, back out.... its very much improved, but at a later date we will change that again to call for readings every 0.25 secs. So imagine the RX8 stock set up with 4 x wheel sensors, each calling for readings every second but staggered 0.25 secs after one another, the one sensor will be running as the same accuracy as the stock set up.

Next test, another electronic wizardry box of tricks plugged into my OBD2 port, a pootle round and we record all the data sent down the canbus..... why? well its simple, the time Richard and I can meet up is limited, so he can take the data run it on his laptop and plug in the spare binnacle / speedo on his desk at home and get the tacho and warning lights and speedo  and replicate the exact journey in terms of what the binnacle was doing on that drive. Handy if you want to alter the program and test it without being in the car.

Last test, box of tricks plugged into OBD2 port, and spare binnacle plugged in. The box of tricks has several functions, one called "bridge" so when we drive along, every bit of data displayed on the real binnacle, is mimicked on the spare binnacle at exactly the same time.

Next one called 201 Modify, so you may remember from a previous post, "201" codes are 8 characters long and consist of data for the speedo and the tacho. So rich put a random number of 63mph into the program, so when we drive around in the same situation as the bridge test, everything is the same except for the speedo which will be 63mph ahead of the real speedo.

This is a very important and significant result as it means we can "split" the 201 codes. So when the Rotus is finished the binnacle can display all the data from the original Canbus, and out box of tricks can fill in the data on the 201 code from the mph generated by the Jamie wheel sensor.

So now youve digested all that crap, what does it mean. Well I guess if you have an RX8 or a derivative in my case, and want to bin the stock braking system and run a bias pedal box or whatever and want to run the stock speedo.... well it can be done 

[Casey]

Awesome Jamie 

My head is spinning, trying to absorb all the info that latest post, but the fact you've been out and driving the Rotus is a major milestone achieved 

[Jamie R]

Awesome Jamie 

My head is spinning, trying to absorb all the info that latest post, but the fact you've been out and driving the Rotus is a major milestone achieved 

Noooo you're getting confuzzled.

The testing was done in the rx8 in readiness for the rotus




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[MattScott]

Awesome Jamie 

My head is spinning, trying to absorb all the info that latest post, but the fact you've been out and driving the Rotus is a major milestone achieved 

Noooo you're getting confuzzled.

The testing was done in the rx8 in readiness for the rotus




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Still impressive !!

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[Casey]

Awesome Jamie 

My head is spinning, trying to absorb all the info that latest post, but the fact you've been out and driving the Rotus is a major milestone achieved 

Noooo you're getting confuzzled.

The testing was done in the rx8 in readiness for the rotus




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I thought you must have been very busy! My head was clearly spinning reading your post 

[Sprint13B]

Will you be using the full loom in Rotus with the factory immobiliser.

Does your box of wizardry control the ECU or just the speedometer side. 

[Jamie R]

Will you be using the full loom in Rotus with the factory immobiliser.

Does your box of wizardry control the ECU or just the speedometer side.

The majority of the loom with the crap like air bags, seat heaters, abs, stereo removed. Immobiliser stays.

The box of tricks listens to the data on the canbus , when it hears a 201 code it adds in the mph values only. This makes the binnacle work.

The ecu is busy doing everything else but the mph value. Our box will run in parallel.

That's how I understand it anyway lol


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[Eccentric shaft]

crap like air bags, seat heaters, abs, stereo removed.

I like the way you're thinking! 

[Sprint13B]

crap like air bags, seat heaters, abs, stereo removed.

I like the way you're thinking! 

Similar to my choice.
Air Bags.  Gone
Seat heaters  Keep
ABS Gone 
Immobiliser Keeping.