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BoostCreep posted:That is certainly a good option. Are those easy to read while on a track? In low light? The CAN bus is one (well, actually two) of the protocols allowed by OBD2, which is basically just a funky connector with multiple different serial ports in it. Most cars I have inappropriately touched electronically have had the CAN bus, and sometimes another one too, and from what I've gathered many of the cheap OBD2 things only do CAN. If things are "slow", that all comes down to implementation details. Depending on bitrate (I've seen 125-500kbps in ECU CAN buses) there's room for a couple thousand packets per second, so it can easily push some data items at 100/s and shitloads more at a few/s. I don't think 18/s is necessarily too low an update rate for an RPM gauge (unless you need a shift light for an F1 engine), but there can certainly be delays in other parts of the system. From what I've seen when looking closely, the ECU spits out RPM numbers at a pretty fast pace (at least 10/s, possibly faster, not sure) without any "filtering" where the last two digits just look like they're randomly jumping around, and then the gauge has some kind of smoothing/filtering/being mechanical. The latter bit, where the gauge itself is making the signal "look nice" is where I would expect the most slowness to happen.
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Nov 2, 2016 08:07
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| # ¿ May 3, 2024 11:10 |
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kastein posted:that's why "OBD2" data sample rates are so slow Not sure what you mean but it doesn't quite make sense to me. Some of the protocols/buses in OBD2 are slow, if it's CAN it can be fast. "OBD2-CAN" is still "OBD2". I may be blessed by only messing with japanese or swedish cars, but they've always had a decent (250/500kbps) CAN interface in there. Manufacturer-proprietary stuff usually smells of poop regardless of how nice it may seem. I've become decently good friends with the CAN bus in Megasquirt though, and have managed to build a couple of useful Arduino-based accessories for it.
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Nov 2, 2016 22:53
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BoostCreep posted:And that is to add protection to the alternator and ignition from surges when the power is cut. Out of curiosity, how does that alternator protection thing work here? I've seen kill switches where it just had the alternator field winding go through the switch (and disconnected or shorted it, not sure which one), but this one is obviously something else. It pulls the starter solenoid to ground via a 3Ω resistor, but what does that do? BoostCreep posted:It's a tiny little sealed AGM battery, but apparently it has no problem cranking fully dressed 5.7 and 6.0 LS engines. It will probably be just fine for track use. Problems with those batteries come when it's cold outside (harder to crank engine + less current from battery), or if you have an engine that doesn't start very reliably as you might just get what amounts to 3-4 starting attempts out of it before it will no longer crank fast enough. Also, since you're deep-cycling it more often and relative to it's size just pushing it harder, it will usually wear out a lot quicker than a normal-size battery. If you're working on the engine and need to start&stop it often, you might want to hook up a bigger battery just for those occasions. Also if you want to spend more money and save a little bit more weight, you can get a lithium battery.
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Dec 1, 2017 08:52
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BoostCreep posted:From Pegasus: That actually makes sense. Loading it will very effectively reduce the spikiness (this is what the battery normally does). Shorting to ground over a 3Ω resistor is a well above its 10W rating though (more like 50-60W depending on voltage), but those ceramic resistors do have a fair bit of thermal mass and should be fine for a couple seconds. And I guess stopping the engine using the kill switch isn't something you do more often than necessary. BoostCreep posted:It's a pretty popular battery for LS swaps, and people who have used this in LS equipped cars generally report it working for 2 years before needing to be replaced. That's not bad for $110. If it can last 2 years for something daily-driven and started a couple times a day, I guess it could last you years and years in a reasonably well-maintained track car. And even if it turns out it doesn't, it's pretty a pretty cheap consumable item all things considered. That said, it might be a good idea to bring a booster pack or something along to the track, if the battery starts going weak or you have some engine issues requiring more cranking. When I was wrenching on (and occasionally racing) a car with a tiny lithium battery and no functioning camshaft position sensor, we had a small handcart around with a full-size battery on it and a pair of permanently attached jumper cables. We also on occasion had races in April where temperature was just above freezing in the mornings..
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Dec 2, 2017 09:37
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I just feel like bumping this thread since there are a bunch more videos since the last post here, and I always enjoy watching them. Also, looks like there's not too much left before it can actually drive.
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Jun 8, 2018 07:44
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One thing confused me a bit with the kill switch install watching the video the other day, and each night since then I've been laying sleepless trying to figure it out It's that switch between pins 3&4 (which closes when you hit the red button) that runs any leftover energy to ground via a 3Ω resistor. While the engine is "winding down" (which can take a couple of seconds if it's on higher revs) the alternator will still be going and cranking out the juice, and it all has to go through that tiny 1/4W resistor (and any other loads that may or may not still be connected). Even if it's just for a second or two, it can be at least 10's of amps which should make it go pop very quickly. I'm sure the manufacturer has thought about this even more and probably have a good reason for doing it, but I don't quite get it. When I installed a similar switch, we ran the alternator field winding through that switch, to just have it stop making any power.
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Jun 21, 2018 07:54
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| # ¿ May 3, 2024 11:10 |
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The thing about connecting ignition power through the switch makes perfect sense to me. Cut that, and engine will stop no matter what, every (gasoline-powered) car has it, and it is (at least almost always) a separate +12V fused circuit. The alternator field winding I guess is usually harder to find (if it is even accessible on an external pin everywhere), and it would make sense for their very brief instructions to try to be as universal as possible. Still, the "drain energy" setup via a tiny resistor does seem odd. Randomly googling for wiring diagrams on this shows others doing it so it's definitely A Thing, but some have an 11W 3Ω resistor there instead which does seem a bit more appropriate. 11W at 12A means just shy of 1A, but it should be able to handle short bursts of lots more (and in any case waaaay more than the tiny one in your kit). Also found some that tell you to wire up the alternator field winding too.
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Jun 21, 2018 13:00
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