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No, I was headed to the dyno, shooting for 350hp+. Figured I'd need them, didn't end up having time to wire it, and didn't even have spark issues at 330hp. I have other priorities to fix, so I ended up selling them.
Alright all you cool cats and kittens. I was able to get my MS3X running correctly using TC4427 on the proto area of the MS base board. I made one modification to the recommended layout. Instead of using the LED spark outputs I took the series resistors off of the current MS3X ignition outputs of U13. This way I could retain knock sensing functionality. It goes something like this.
Any idea what the signal current draw is for the R8 coils? Wondering if I can get away with just one TC4427 and leaving them running in wasted spark (don't feel like running more wires to the engine bay).
About 330mA. The entire chip is rated for 1.5A, so 750mA per output. You may want to reconsider though, as the chip is also rated for 470mW of power. At higher RPM, you may find yourself in a 50% duty cycle on the coil signals, so 0,33A*5V*0.5 = 825mW, well over the design limit.
Assuming a 3ms dwell time, and a max duty cycle of 25% to be below the power limit, your max RPM will be around 5800rpm.
330 was the number I was looking for. Thanks for doing the math on that too, yeah, I would want to do one coil per chip output if I go this rout.
Though it looks like a max dwell around 2.4ms and 2.1ms at red line for this coils, so it would be clooooose to being ok, but the engineer in me likes safty facotors.
Another satisfied customer. I installed these in my '99 N/A running a MS3Pro_PnP, wasted spark. I did have an issue with the harness, but FlowForce sent me a new one after some troubleshooting and everything is running well now.
I have yet to run spark C and D out to the coils. Just returned from a 3700 mile road trip with the car running the suggested dwell table with many gears pulled to redline. Am I at risk of burning out one of the drivers?
I have yet to run spark C and D out to the coils. Just returned from a 3700 mile road trip with the car running the suggested dwell table with many gears pulled to redline. Am I at risk of burning out one of the drivers?
Sounds like you followed the instructions. What would make you worry about burning out drivers?
I was confused by Rev's comment about duty cycle and being limited to 5800rpm. If you look above, I was able to successfully run my MS3X with two TC4427's with no issue following your dwell table.
I was confused by Rev's comment about duty cycle and being limited to 5800rpm. If you look above, I was able to successfully run my MS3X with two TC4427's with no issue following your dwell table.
I was referring to x_25 who said that he wanted to use only one if possible. With two, there's no issue.
Well technically I am only running it with one right now as I haven't run Spark C and D out to the coils yet (Running wasted spark). Assuming a dwell of ~2.0 at 7000rpm (x2 for wasted) wouldn't a 4 ms dwell only be around 25% duty?
I have foolishly installed these R8 coils without doing any research or reading up and realized that have gotten myself into a bind. I'm trying to buy the stuff to make that driver circuit above but Digikey has like 30 different TC4427's but only 5 in stock. Can anyone point me in the correct direction to which one to buy? They have TC4427VUA713, TC4427MJA, TC4427EUA, TC4427VPA, and TC4427COA713 available and all look like they all have the same specs. Some are surface mount and some are through mount and some are $2 and some are $40.
You will want the VPA version as it is an 8 pin DIP package which has through hole connections that are compatible with the proto area of the megasquirt.
09-19-2021, 01:03 PM
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