TheDarkSideOfWill wrote:
It's not just dwell, it's duty cycle. If you're running 4ms dwell on a 5ms cycle--80% duty--you may very well see 10A draw, but that's 12,000 RPM on coil per cylinder. The duty cycle and thus time averaged current draw will be lower at lower RPM... So far it sounds like Mark's pretty hesitant about going over 9,000.
At 1,000 RPM idle, the same 4ms dwell is only 6.7% duty.
Madhatter wrote:
Duty cycle is a function of dwell, but we're splitting hairs here. We also have to account for the 'timing window'. Lets use 3k rpm as a point. So at 3k rpm there is a window of .02 sec per rev. The otto cycle is 720*. using sequential ignition we can use the entire otto cycle - yea! OK so that gets us up to .04 sec or 40ms for 720 degrees. Now lets say we want 30* BTDC timing. 720-30 = 690*. that's 38.3 ms of time left to charge the coil for the next event, however the laws of physics tend to get in the way and we need to account for the time it takes to build and discharge the magnetic field. That's tricky as it's specific to the coil construction and inherent properties. lets use an avg of 4ms. so at 3k rpm there is a window of ~34ms between ignition events for coil on plug sequential. waste spark is ~14ms. This highlights why a single large coil for even one bank can run into charge time saturation problems. Looking at the big old american V8's single coil, 3k rpm with 8 ignition events! poor coil is getting hammered!
Aww he's got to spin it out to the moon, what's the point of all the sensors then
Here's a good article covering sample rates and frequencies. The new automotive stuff samples at very high rates and data transfer is also fairly quick too.
http://www.dataq.com/blog/faqs/really-n ... mple-rate/The age of software and computers has made hot rodding very complex and expensive. Race cars are very specific bare bones data, still fairly complex but holds nothing to the daily driver that's a rolling living room. Esp now that integration with wifi, celluar networks and multi-platform comm.
I screwed up in that I was thinking of a 360 degree cycle instead of a 720 degree cycle... so the numbers I posted above were accidentally for waste spark instead of coil per cylinder... so 1000 RPM idle is about 3.3% DC at 4ms dwell.
If the DC exceeds 8.3% there will be overlap, as that's 1/12 of the 720 degree cycle, but 12,000 RPM is only going to be about 40% duty cycle at 4ms dwell, so 5 coils will be charging at once at 12,000 RPM.
Login
Register
FAQ
Members
