I'm sure this should be a FAQ but searching hasn't yielded an answer for me.
In a standard Ford 4-cyl trigger wheel setup (wasted spark, 36-1 crank wheel, missing tooth at 90deg BTDC) what should the ignition settings be? My understanding is:
Trigger-offset = -90 (to account for the 90deg BTDC alignment of the missing tooth)
Trigger wheel teeth = 36
Missing teeth = 1
Skip teeth = 18
Delay teeth = 9 (again due to 90deg BTDC alignment of the missing tooth - not sure that this is correct)
Dual spark options = single crank wheel
Offset (advance) for output #2 (degrees) = 90 (fire cyls 2+3 on ign2 output 90 deg after cyls 1+4 on ign1)
Is all that correct?
Ford 4-cyl dual spark setup
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Read the manual to see if your question is answered there before posting. If you have questions about MS1/Extra or MS2/Extra or other non-B&G code configuration or tuning, please post them at http://www.msextra.com The full forum rules are here: Forum Rules, be sure to read them all regularly.
Re: Ford 4-cyl dual spark setup
There is some new documentation on this that should come out in the next few days that will hopefully explain all this better than it has been. Plus Bruce is working on a GUI that should automate and simplify the process. Ultimately only you can pick these parameters because you know your engine better than anyone else. But you need rules and definitions and hopefully that is what the new documentation will provide. But one thing I suspect is wrong is that this is not an odd-fire engine, so the offset for Ign2 should be left as 0. This offset is only for odd-fire engines where one bank of cylinders fires at an offset relative to the other bank. It should not be used for standard even-fire engines.
The wheel parameters, including skip_teeth (fire a pair of coils every 180 deg) look correct. That leaves trigger offset and delay teeth. Here's where you need to understand what they are, since you know where your sensor is relative to CTDC of no. cylinder. Here are some rules/ definitions:
Synch occurs on the 1st tooth after the missing tooth section. You then define the first tach pulse by how many Delay Teeth you choose. Subsequent tach pulses occur every skip teeth thereafter. There is no single correct answer to the delay teeth. What you are mainly trying to achieve is to put CTDC of the no 1 cylinder such that the first tach pulse occurs about roughly 10 deg PAST CTDC no 1. This would make trigger offset, which defines where the tach pulse is relative to CTDC, be -10 deg. You want to pick Delay Teeth (which moves the first tach pulse) to achieve this, but I can't tell you what the exact number is because it depends on where your sensor is located. That is the purpose of Delay Teeth - so you don't have to physically move the sensor. The purpose of the 10 deg ATDC is that then you have 2 full tach cycles (360 deg) - max advance (say 60 deg) - 10 deg trig offset = 290 deg in which to start and finish dwell and still have max advance + 10 deg slop for prediction error and cpu delay in which to spark. A figure in the documentation will illustrate this. There are other considerations as well, such as moving injection timing around, but the preceding should get you up and running.
The wheel parameters, including skip_teeth (fire a pair of coils every 180 deg) look correct. That leaves trigger offset and delay teeth. Here's where you need to understand what they are, since you know where your sensor is relative to CTDC of no. cylinder. Here are some rules/ definitions:
Synch occurs on the 1st tooth after the missing tooth section. You then define the first tach pulse by how many Delay Teeth you choose. Subsequent tach pulses occur every skip teeth thereafter. There is no single correct answer to the delay teeth. What you are mainly trying to achieve is to put CTDC of the no 1 cylinder such that the first tach pulse occurs about roughly 10 deg PAST CTDC no 1. This would make trigger offset, which defines where the tach pulse is relative to CTDC, be -10 deg. You want to pick Delay Teeth (which moves the first tach pulse) to achieve this, but I can't tell you what the exact number is because it depends on where your sensor is located. That is the purpose of Delay Teeth - so you don't have to physically move the sensor. The purpose of the 10 deg ATDC is that then you have 2 full tach cycles (360 deg) - max advance (say 60 deg) - 10 deg trig offset = 290 deg in which to start and finish dwell and still have max advance + 10 deg slop for prediction error and cpu delay in which to spark. A figure in the documentation will illustrate this. There are other considerations as well, such as moving injection timing around, but the preceding should get you up and running.
Re: Ford 4-cyl dual spark setup
Thanks Al.
So for a Ford wasted spark 4cyl with the factory trigger setup of crank sensor at 90deg BTDC is -90 for trigger offset and delay teeth of 9 right then? Having read the documentation quite a number of times I'm still not clear on it.
If there is new documentation coming through from Bruce then that will clearly help but it strikes me that some example settings for the most common installations may be a very easy way to help an awful lot of people with minimal effort.
So for a Ford wasted spark 4cyl with the factory trigger setup of crank sensor at 90deg BTDC is -90 for trigger offset and delay teeth of 9 right then? Having read the documentation quite a number of times I'm still not clear on it.
If there is new documentation coming through from Bruce then that will clearly help but it strikes me that some example settings for the most common installations may be a very easy way to help an awful lot of people with minimal effort.
Re: Ford 4-cyl dual spark setup
There are all sorts of sample settings and timing diagrams on www.microsquirt.info, dual spark link on the left sidebar. Most of these are for 1 and 2 cylinder, but the 4 cylinder just follows from that.
As far as your engine, what you need to specify is where is CTDC 1 when the missing tooth section has just passed the sensor and a pulse has been sent from this first tooth (rising/ falling edge has just passed the tip of the sensor). By this I mean, if the wheel position is as described, then by how many degrees or teeth do you have to move the crank BACKWARD in order to achieve CTDC 1. If this is 90 deg, then the tooth 1 pulse comes in at -90 deg ATDC and this would be your trigger offset with delay teeth = 0. If you delay by 1 tooth, then you would be -100 deg ATDC when the first tach pulse arrives, so trigger offset would be -100 deg.
As far as your engine, what you need to specify is where is CTDC 1 when the missing tooth section has just passed the sensor and a pulse has been sent from this first tooth (rising/ falling edge has just passed the tip of the sensor). By this I mean, if the wheel position is as described, then by how many degrees or teeth do you have to move the crank BACKWARD in order to achieve CTDC 1. If this is 90 deg, then the tooth 1 pulse comes in at -90 deg ATDC and this would be your trigger offset with delay teeth = 0. If you delay by 1 tooth, then you would be -100 deg ATDC when the first tach pulse arrives, so trigger offset would be -100 deg.