Members Page/Grm Racer/Trigger Setup

This page is to help with setting up the Primary Trigger option

Specifically for the VAG 60-2 wheel, but it will contain general information

VAG wheel & setup info

[primary] trigger setup image from Megatune

[Image] of transition trigger being used for a 60-2 setup. Its not 100%, but it does work.

With this setup I found ingition events occuring on (0 degree advance makes math easier)

Tooth 14 and tooth 46 thats 32 teeth apart I am going out on a limb here and we'd like this 30 teeth apart :-) otherwise there is a 12d difference between spark events and crankshaft rotation

Moment of Clarity

So to setup the primary trigger events..

Measure the angle of the crankshaft in reference to TDC that the missing teeth cross the VR sensor.

In a VAG 60-2 wheel that is 90d btdc

Then determine if that event is between 60degrees and Max desired ignition advance, or alternatively set it to 60 degrees

In a VAG 60-2 wheel that would be 90d = 15 teeth, 60d = 10 teeth
- 15-10 = 5: the primary trigger event occurs on the 5th tooth.
- clarification do we count the missing teeth for this calculation? It does not look like it on the scope image.

MembersPage/PeterNassy question moved to the top.

But this also depends on what type of trigger wheel you use,right.I mean if i use a cam driven 5 window triggerwheel,time between valid trigger events cannot be the same if i would use a crank 60-2.Also want to know what is valid trigger event.

Lets talk about a 5 cyl.If camdriven 5 window hall,every window,right?If 60-2,every 60/5=12th teeth?Or every missing teeth?

\\NanssyPeter

Peter, (assuming 4cycle engine)

These settings are for a crank trigger. That assumes a 720d rotation for one cycle. For a Camshaft triggered event (360d per complete cycle) the period length is generally multiplied by two. I will be making a set of pages that describe how to do all this for these types of configurations, but right now this is limited to crank trigger driven events.

The plan is to have a page that describes how to get the values for a crank trigger and a cam trigger, followed by several pages that specifically address the different types of engines 4clyn, 6clyn(even/odd/straight), V8, V10, V12.. My expertise lies with the 4clyn VW/Audi (VAG) products. But there will be lookup tables for both crank and cam trigger. This is mostly because I actually have both solutions that I have to do. the NA GRM car is a 4 window Hall sensor (cam) and the Turbo GRM car is a 60-2 VR crank sensor.

______

MegaTune is an easy way to setup the trigger values, but you need to know what you are changing.

current decimal values

Primary Trigger	GRM setup	Mcel
Edge	Rising	Rising
Type	Multitooth	Multitooth
Filtering	Disabled	Disabled
Tooth Relation (Usually Disabled)	Disabled	Disabled
Trigger Settings
TDC after trigger (degrees)	60.0	60.0	VAG wheel on ABA block is 90d off TDC at the center of the missing teeth via calibrated eyeball
Number of teeth on wheel	58	58	actual nubs
Trigger Tooth	3	15	The third nub after the space actually the missing ones are counted, 3= the first after the space	VAG ABA wheel appears to have the center of the missing teeth @ 90d off TDC, would this make this value 2
Next Trigger Tooth	15 (V8)/20 4clyn	15	Manual states NextTrigTooth= imaginary teeth * 2 / cylinders (60 *2 / 4 = 30)
Crank minimum period (usec)	1280	1280
Tooth Width
Engine Phase, when reset	240	240	determines toothwidth unit; (equivalent to 720 crankdegrees = 2 crankrot= 120 teeth)
Angular width of tooth	2	2	120 teeth is 240, so 1 tooth width is 2
Angular width of missing tooth	6	6	3 times the above (2 missing teeth)

This part needs to be made either transparent to the end user or extremely well explained with a shortcut on howto do it.
Tooth Relation to Normal (usually 181)	181	181
Tooth Relation to Missing (usually 118)	118	118

These are all you settings, but these are not normally how motorheads describe thier motors or triggers.

Typical Descriptions

TDC -- Regular meaning when #1 cylinder is at top of rotation
Number of actual teeth on wheel
Number of missing teeth on blank spot on wheel if there were teeth there
Relation of blank spot to TDC this would be in degrees
- Leading edge angle from TDC
- Trailing edge angle from TDC

So using these values how do we get the other ones.

Suggestion

Do the number trunkation etc in the make mtt portion. Most NON - EE/CompEE/CS engineers will not get the howto about converting decimals to an arbitrary (seemingly) number less than 255 ( 8-bit micro unsigned issue)...

So basically a good picture and straightforward equation, IF it is not automagically done for the config. If they don't care, they should copy a working example and not mess with the numbers they don't know.

Min Crank Period (review this statement)

This definately needs to be calculated somewhere else.. I thought it was for "cranking" aka starting the car. but it is directly related to Rev limiter.. you could call this the OVERREV point or something. I'm guessing its an early variable.

Angular width, etc.. This should all be auto-calculated.

since an 8bit number only can goto 255 (8-bit unsigned) so the whole point of this is scaling.

Example 60-2 wheel

1 its a ratio..

720d / 255 = 120teeth/ x ; x = 8bit approximation of degrees / tooth but this has to be rounded down so that it is a nice root ie. divisible and integer like.

2 Given the number of teeth in a 720d rotation what is the new number in this ratio

120teeth/ rounddown(x)= 720d / y
y is the new normalied max value (y <= real angle per tooth )
- (y)(number of teeth) = engine Phase
Engine phase refers to the new number y * number of teeth that represents 720d
The proper name would be scaled 720d value

3 Scaled Tooth angle is y
4 Scaled missing tooth angle is y * # of missing teeth

Proposed table

[Excelsheet]

Typical Meaning		Variable names	1-10	1-12	1-16	1-36	60-2
Total Teeth	Entered	internal	10	12	16	36	60
missing teeth	Entered	Number of teeth missing	1	1	1	1	2
Teeth Present	Calc	Number of teeth on wheel	9	11	15	35	58
Crank Rotations per complete clycle	Entered	internal	2	2	2	2	2	(2 for 4cycle 1 for 2 cycle)
Degrees per complete cycle*	Calc	internal	720	720	720	720	720
720 / Total Teeth = Angle Per tooth (degrees)	Calc		36.0	30.0	22.5	10.0	6.0
Total Degrees scaled to 8 bit unsigned: 255/total teeth	Calc		12.8	10.6	8.0	3.5	2.1
Truncate for integer math	Calc		12	10	7	3	2
Scaled degrees per cycle	Calc	EnginePhase when reset	240	240	224	216	240
Scaled degrees per tooth	Calc	Angular width of tooth	12	10	7	3	2
Scaled degree of missing spaces(teeth+1)	Calc	Angular width of missing tooth	24	20	14	6	6

Now you have to Determine what the next trigger tooth is

Number of Clynders
4clyn	Entered	4	Good	Good	Good	Good	Good
Teeth until next clyn event	Calc	Next trigger tooth	5.00	6.00	8.00	18.00	30.00
	Calc	Scaled deg/ cylinders	60.00	60.00	56.00	54.00	60.00

5clyn	Entered	5	Good	NotValid	NotValid	NotValid	Good
Teeth until next clyn event	Calc	Next trigger tooth	4.00	4.80	6.40	14.40	24.00
	Calc	Scaled deg/ cylinders	48.00	48.00	44.80	43.20	48.00

6clyn	Entered	6	NotValid	Good	NotValid	Good	Good
Teeth until next clyn event	Calc	Next trigger tooth	3.33	4.00	5.33	12.00	20.00
	Calc	Scaled deg/ cylinders	40.00	40.00	37.33	36.00	40.00

8clyn	Entered	8	NotValid	Good	Good	Good	Good
Teeth until next clyn event	Calc	Next trigger tooth	2.50	3.00	4.00	9.00	15.00
	Calc	Scaled deg/ cylinders	30.00	30.00	28.00	27.00	30.00

10clyn	Entered	10	Good	NotValid	NotValid	NotValid	Good
Teeth until next clyn event	Calc	Next trigger tooth	2.00	2.40	3.20	7.20	12.00
	Calc	Scaled deg/ cylinders	24.00	24.00	22.40	21.60	24.00

12clyn	Entered	12	NotValid	Good	NotValid	Good	Good
Teeth until next clyn event	Calc	Next trigger tooth	1.67	2.00	2.67	6.00	10.00
	Calc	Scaled deg/ cylinders	20.00	20.00	18.67	18.00	20.00

The min_crank_per describes the minumum time between 'valid trigger events. If you use this table select your # of clynders and RPM limit. and then just plug in that number

____

minmum period in microseconds(us) between trigger events
Assumes Crank Trigger	# of clynders

RPM limit	Safety Margin	2 or 4 cycle	4	5	6	8	10	12
1000	1000	4	15000	12000	10000	7500	6000	5000
1500	1000	4	12000	9600	8000	6000	4800	4000
2000	1000	4	10000	8000	6667	5000	4000	3333
2500	1000	4	8571	6857	5714	4286	3429	2857
3000	1000	4	7500	6000	5000	3750	3000	2500
3500	1000	4	6667	5333	4444	3333	2667	2222
4000	1000	4	6000	4800	4000	3000	2400	2000
4500	1000	4	5455	4364	3636	2727	2182	1818
5000	1000	4	5000	4000	3333	2500	2000	1667
5500	1000	4	4615	3692	3077	2308	1846	1538
6000	1000	4	4286	3429	2857	2143	1714	1429
6500	1000	4	4000	3200	2667	2000	1600	1333
7000	1000	4	3750	3000	2500	1875	1500	1250
7500	1000	4	3529	2824	2353	1765	1412	1176
8000	1000	4	3333	2667	2222	1667	1333	1111
8500	1000	4	3158	2526	2105	1579	1263	1053
9000	1000	4	3000	2400	2000	1500	1200	1000
9500	1000	4	2857	2286	1905	1429	1143	952
10000	1000	4	2727	2182	1818	1364	1091	909
10500	1000	4	2609	2087	1739	1304	1043	870
11000	1000	4	2500	2000	1667	1250	1000	833
11500	1000	4	2400	1920	1600	1200	960	800
12000	1000	4	2308	1846	1538	1154	923	769
12500	1000	4	2222	1778	1481	1111	889	741
13000	1000	4	2143	1714	1429	1071	857	714
13500	1000	4	2069	1655	1379	1034	828	690
14000	1000	4	2000	1600	1333	1000	800	667
14500	1000	4	1935	1548	1290	968	774	645
15000	1000	4	1875	1500	1250	938	750	625
15500	1000	4	1818	1455	1212	909	727	606
16000	1000	4	1765	1412	1176	882	706	588
16500	1000	4	1714	1371	1143	857	686	571
17000	1000	4	1667	1333	1111	833	667	556
17500	1000	4	1622	1297	1081	811	649	541
18000	1000	4	1579	1263	1053	789	632	526
18500	1000	4	1538	1231	1026	769	615	513
19000	1000	4	1500	1200	1000	750	600	500
19500	1000	4	1463	1171	976	732	585	488
20000	1000	4	1429	1143	952	714	571	476
20500	1000	4	1395	1116	930	698	558	465
21000	1000	4	1364	1091	909	682	545	455
21500	1000	4	1333	1067	889	667	533	444
22000	1000	4	1304	1043	870	652	522	435
22500	1000	4	1277	1021	851	638	511	426
23000	1000	4	1250	1000	833	625	500	417
23500	1000	4	1224	980	816	612	490	408
24000	1000	4	1200	960	800	600	480	400
24500	1000	4	1176	941	784	588	471	392
25000	1000	4	1154	923	769	577	462	385
25500	1000	4	1132	906	755	566	453	377