Cps Position

[309PUG 2 1 Cars]

Just curious how you confirm the exact angle of the crank to TDC No1 cylinder, I have attempted to position mine at 90deg and this is what I have set the map to in the basic settings. However in reality it may be 89 or 91 deg or worse, how do you establish the exact angle, it surely has an important impact on overall engine performance ??? or am I talking rubbish.

 

Chris

[Sandy 189]

With a timing light, it's the only sure fire way and trim the lead angle.

[Owain1602 0]

As above says, use a timing light and adjust the offset value untill the advance requested in the map is equal to what the timing light is saying. Its adjusted differently on different management.

[309PUG 2 1 Cars]

As above says, use a timing light and adjust the offset value untill the advance requested in the map is equal to what the timing light is saying. Its adjusted differently on different management.

 

Hi,

Thanks for your replys, sorry if this sounds rather numptyish but are we talking about the same thing here, I am trying to establish what angle the CPS is BTDC. Are you saying if I use a strobe light this will tell me what the angle is, then all I do is type that angle in the map basic settings file in my DTA.

Chris

[petert 550]

The most important thing is to accurately mark a reliable external timing mark you can see. The best is the flywheel. It's easy to see near the starter motor if you have throttle bodies. Accurately mark TDC, using a dial guage down a plug hole.

 

Some ECU's allow you to "lock" the ignition timing at a preset value. The locked software setting must equal the external mark. If you can't lock it, set all the values around idle at zero, so the ECU can't interpolate between load/RPM sites.

 

Adjust your sofware setting 88, 89, 90 or whatever, to make the software/hardware settings match.

[Malachy 0]

bosch motronic uses a 60-2 wheel and the sensor is 120deg btdc when tooth number 1 is passing the sensor.

so that means

when the engine is at TDC then the sensor is over tooth 20 or 120 deg around the wheel

i think thats what your after

Edited February 22, 2007 by Malachy

[petert 550]

I know this sounds rediculous, but it depends on the ECU. For example, on my Autronic, I have to set the angle at 64 degrees, but on a Haltech 90 degrees gives the same result. I can't get my head around it, maybe someone else can.

[Malachy 0]

I know this sounds rediculous, but it depends on the ECU. For example, on my Autronic, I have to set the angle at 64 degrees, but on a Haltech 90 degrees gives the same result. I can't get my head around it, maybe someone else can.

yeah there have been similar things with megasquirt its more to do with the algorithm doesn't decode the "real" trigger angle it only uses it as a reference, then calculates from there. there are usually some settings along the lines:

 

trigger angle = (set degree before top dead centre here this can be anything between 0-90 usually)

tooth number (set the tooth number on the flywheel that matches the angle set above)

number of teeth

number of missing teeth

spark a at tooth number

spark b at tooth number

 

the ecu can then work the rest out from that

 

well at least this was the old way of ms setting up now its more "normal" you just put in the angle of the engine when tooth 1 is over the sensor (120btdc) number of cylinders, and number of teeth, number of missing teeth. ecu sorts rest again.

 

im not familier with autronic and haltech though but possibly they use a similar setup to the old ms code

[Owain1602 0]

Yes, they only use it as a reference point to know where its at. The Omex shows it quite clear because the offset is set like this.

I have a 36-1 trigger wheel and sensor if mounted with missing tooth 90deg before TDC.

The coarse adjustment (Miss to MAM) it the actual number of teeth that has to pass the sensor after the missing tooth for the engine to be at a certain point, so you'll have a figuer like 5 or 6. Then obviously you then have the fine adjustment.

Sorry if thats confusing, its a bit awkward to put in to words.

[309PUG 2 1 Cars]

Thanks for the replys chaps, I now know whats required.

 

Chris