Electronics > Projects, Designs, and Technical Stuff
Catching car's ignition signal
cmcraeslo:
@joeqsmith - Like everything in life, having anything fixed is bad. Usually, you monitor the gear position and let it cut for as long as needed. So it differs from gear to gear. Also, retarding the ignition, rather than cutting it, is much smoother and effective.
mikerj:
--- Quote from: cmcraeslo on August 04, 2020, 01:57:49 pm ---Fuel cut on the other hand is very slow and not really useful in my case
--- End quote ---
Why would fuel cut be any slower than ignition cut? With either one a cylinder could be cut for a single firing cycle if needed.
joeqsmith:
--- Quote from: cmcraeslo on August 05, 2020, 01:15:41 pm ---@joeqsmith - Like everything in life, having anything fixed is bad. Usually, you monitor the gear position and let it cut for as long as needed. So it differs from gear to gear. Also, retarding the ignition, rather than cutting it, is much smoother and effective.
--- End quote ---
There are many many things in life that I like constant but I thought you were working on an ignition kill and not your philosophy of life.
On the older bike, the ignition timing, boost, shift points and kill times are all fixed. It's KISS and reliable. The gains from the shift down track would be small compared to say adding another PSI of boost or just going on a diet.
I assume you have data showing the effects of the shift using various techniques. That would be very interesting to see. No need to disclose anything proprietary about what you are doing but rather just show the end result.
cmcraeslo:
--- Quote from: mikerj ---Why would fuel cut be any slower than ignition cut? With either one a cylinder could be cut for a single firing cycle if needed.
--- End quote ---
On full throttle, the amount of fuel going into the intake is huge, basically, you could fire all injectors at once all the time and it would not make a difference (would just be more fuel consuming). It takes some time for the air and fuel to mix so cutting 1 or 2 cycles of the injector, does not make a a lot of difference in reality. This is needed when shifting gear because the reaction needs to be instant and the longer you unload the engine, the harder it will shift. Ignition on the other hand is what drivers the car so every interruption in that, disturbs the car, which is what is needed.
cmcraeslo:
--- Quote from: joeqsmith ---There are many many things in life that I like constant but I thought you were working on an ignition kill and not your philosophy of life.
--- End quote ---
LOL :)
--- Quote from: joeqsmith ---On the older bike, the ignition timing, boost, shift points and kill times are all fixed. It's KISS and reliable. The gains from the shift down track would be small compared to say adding another PSI of boost or just going on a diet.
I assume you have data showing the effects of the shift using various techniques. That would be very interesting to see. No need to disclose anything proprietary about what you are doing but rather just show the end result.
--- End quote ---
Unfortunately, I cant show you the graphs as this is the knowledge we've gathered in the last 15 years in motorsport industry.
It's not just about the shift speed gain - the duration of the "cut" (and the cutting strategies used) determine other factors - stability of the bike/car in tricky conditions, smoothness of the shift (engine likes smoothness and so does the gearbox and all other components). If you have 24 hour race rough fixed shifting, you'll probably end up failing the race.
If you're too long on the cut, this brings all kind of troubles, so does cutting too fast. Each gear is different - let say you start loosing a gear in a race. Once this starts happening, with fixed timing, you'll just destroy everything and not finish. Cutting the engine (with combination of rev matching) helps on downshifting as well, cutting too long will drop the rpm and make it rough as hell, possibly loosing the grip. This can be a huge problem in the rain. Just to name a few.
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