I gave up on the stock speed sensor. Perhaps its a case of almost 30 years and a couple of hundred thousand K's........
So, after a little research I came up with an elegantly simple solution, this:
A simple inline Hall Effect speed sender from a Terratrip rally computer!
70 buckeroonies off the shelf at the local speed shop and we are in business!!! The ecu needed to be calibrated to the sensor and now I have a rock steady and believable speed indication!!!!
So, having this now means the launch/anti-lag function is working perfectly. WOT and stationary and it sits at 2700rpm at 8psi boost!!! Should be good fun for fast traffic light getaways!!!!
Another function the requires a reliable speed signal is boost thru the gears. The ECU looks at the wheel speed and the RPM in each gear and determines which gear its in and sets the boost pressure I have set in the boost control table according the the RPM and the gear!
Currently I have stock wastegate pressure, 8psi in low, which is still way too much power but traction control will have to take care of that.
10psi in 2nd
16 psi in 3rd and up.
I need to do some testing to sort it out to get maximum power without wheelspinning.
Again, traction control will take care of any issues beyond that.
Another handy feature I have enabled now with a cammy and tuned engine is closed loop idle control.
The ECU will only invoke closed loop idle either in neutral or stationary. Since i dont have a neutral switch, its roadspeed related only.
Here, the ECU takes full authority over idle speed rather than just presetting a fixed amount of air going in via the idle valve as is the case now.
Idle speed can vary quite a lot depending on various factors and the engine will sometimes race a bit and then chug away at too low revs. The flywheel is very light and cam is pretty tough. The engine runs very happily and reliably at 1150rpm idle but go much slower and it runs quite roughly and inconsistent on idle.
So now, the ecu attempts to control idle speed via the idle valve alone and its quite cool watching the idle effort in the guages window scaling up and down keeping the engine in a control band! Cool stuff!
Often with engines, especially tuned engines, a sudden big blip of the throttle on idle will result in a quick rev and then the engine drops down past the desired idle speed and then "catches" back up. however, often they will stall.
Altho the ECU does have 2 "recovery" rpm presets where it will idle up to catch a stalling motor, if the engine is not fully warmed, or shut down and run again a few minutes later how, the idle speed will often "bounce" on the first recovery step and sit there alternately revving up and dying down a couple of hundred rpm until things stabilise which is a pain and sounds stupid!!
The closed loop idle control takes care of all that and the idle simply drops off after a blip and gracefully fall down to preset rpm.
I also added some "Calmdown" effort which is a few steps of air (dashpot) on throttle off to slow down the rate of rpm loss as the engine approaches preset idle speed!!!!!!
Working beautifully. Ive got to do a couple of cold start logs and a few driving logs to have a look at whats going on idle and boostwise!!! I need to set the boost control to just explore wheelspinning and then let traction control take over.
Its easier to control marginal traction that try to control stupid power and crazy wheelspinning!!!
So, what remains is to fit a single Hall Effect sensor to a rear wheel and then i can invoke full traction control to maximise everything I have under the bonnet now.
Im looking forward to that task. The car suspended quite stiffly and is very prone to wheelspinning when cornering even at highway speeds and pedaling the engine to reduce wheelspin is very slow way to go.
Letting the electronics handle the task is quite a cool idea to me!!!!
Strange feeling thing tho is that Im getting towards the end of development for this little car and i have no further plans as far as any more power is concerned. Its making very good power at 16psi on the fast setting, something around 140Kw, and I see little if any reason to add any more other than purely for bragging rights. Not interested in that.
Dyno Figures alone are for fags as far as Im concerned.
I like to drive and ENJOY the thing!!! Im tempted to do a coupl e of local hillclimbs to be honest!
Oracle