RV8 timing marks & Motec
Discussion
I've been checking the accuracy of the timing marks on the damper on my RV8. Did it 3 times with a dial gauge in no.1 plug hole, and arrived at a TDC which equates to 8 deg ATDC on the damper. Not overly concerned as I understand that the marks can be inaccurate. Hooking up the timing strobe (connected to no. 1 lead) shows the timing as follows:
in relation to the original TDC mark: at 1100 rpm = 12 deg advance
at 2000 rpm = 15 deg advance
in relation to my new TDC mark: at 1100 rpm = 20 deg advance
at 2000 rpm = 22 deg advance
The distributor is locked and timing is controlled solely by the ECU -i.e. no vacumn / mechanical advance. During these checks the ECU more or less agrees with the advance figures based on the original marks. They are set at 14.4 deg advance at 1000 rpm and 17 deg advance at 2000 rpm in the ECU. The small differences may be down to the viewing angle with the strobe as I didn't take the bonnet off. So I conclude that I must have mis-measured TDC with the dial gauge, but I can't understand how having done it 3 times. Or have I missed something else?
7.
in relation to the original TDC mark: at 1100 rpm = 12 deg advance
at 2000 rpm = 15 deg advance
in relation to my new TDC mark: at 1100 rpm = 20 deg advance
at 2000 rpm = 22 deg advance
The distributor is locked and timing is controlled solely by the ECU -i.e. no vacumn / mechanical advance. During these checks the ECU more or less agrees with the advance figures based on the original marks. They are set at 14.4 deg advance at 1000 rpm and 17 deg advance at 2000 rpm in the ECU. The small differences may be down to the viewing angle with the strobe as I didn't take the bonnet off. So I conclude that I must have mis-measured TDC with the dial gauge, but I can't understand how having done it 3 times. Or have I missed something else?
7.
If you have accuratly measured this with a dial guage then this will be correct.
Is the plunger on the dial guage sitting at 90deg to the piston crown? If not then this may give you a false reading.
Th method I used is as follows....
Install cam timing disc to the front pully along with a suitable marker pointer and set it so it coresponds to somwhere near tdc.
Get an old spark plug and smash off the electrode and insulator.
Weld a piece of rod to the centre of the plug so that it will interfere with the piston when the piston is on it's way up. No sharp edges!
Turn the engine so that No 1 in 90deg or so BTDC.
Screw in modified plug
SLOWLY turn the engine until it stops.
Set the timing disc to zero.
Remove the plug and turn engine until No1 is 90deg ATDC and re insert the plug.
SLOWLY turn the engine back until it stops again.
What ever the difference is on the timing disc, half of this is TDC. e.g clockwise = 0, Counter clock = 30. TDC = 15 on the disc.
Remove the plug and turn the engine so No1 comes to the figure you arrived at above and this will be TDC. Make your mark.
Hope this is of help.
If, when you have made your mark and checked with a timing light it seems wrong, you will need to adjust you CrIP in the General Setup menu of the MOTEC.
Let us know how you get on.
Steve
Is the plunger on the dial guage sitting at 90deg to the piston crown? If not then this may give you a false reading.
Th method I used is as follows....
Install cam timing disc to the front pully along with a suitable marker pointer and set it so it coresponds to somwhere near tdc.
Get an old spark plug and smash off the electrode and insulator.
Weld a piece of rod to the centre of the plug so that it will interfere with the piston when the piston is on it's way up. No sharp edges!
Turn the engine so that No 1 in 90deg or so BTDC.
Screw in modified plug
SLOWLY turn the engine until it stops.
Set the timing disc to zero.
Remove the plug and turn engine until No1 is 90deg ATDC and re insert the plug.
SLOWLY turn the engine back until it stops again.
What ever the difference is on the timing disc, half of this is TDC. e.g clockwise = 0, Counter clock = 30. TDC = 15 on the disc.
Remove the plug and turn the engine so No1 comes to the figure you arrived at above and this will be TDC. Make your mark.
Hope this is of help.
If, when you have made your mark and checked with a timing light it seems wrong, you will need to adjust you CrIP in the General Setup menu of the MOTEC.
Let us know how you get on.
Steve
Dont forget. The timing you see on the ecu, will only refer to TDC or xx deg BTDC in relation to the crank trigger itself.
So if TDC on the trigger wheel is in the wrong position, then your timing isnt going to be where you think it is either.
You must ensure that TDC on the trigger wheel actually refers to TDC on the engine, and that the CrIp on the Motec is also in sync with both of them.
So if TDC on the trigger wheel is in the wrong position, then your timing isnt going to be where you think it is either.
You must ensure that TDC on the trigger wheel actually refers to TDC on the engine, and that the CrIp on the Motec is also in sync with both of them.
.. of course you don't *have* to move the offset at all if you don't want to .. if this is a one-off and you won't be transferring the figures across to another car it doesn't matter what you have in the map or on the offset (within reasonable limits anyway) as you just give the engine the number it needs to make the power and no more than that.
.. if you wanted to see if the numbers *looked about right* compared to other cars though, or want to transfer your settings to another car then an acurate TDC is needed .. but in reality for a one-off who cares if the TDC mark is 5 degrees out? certainly not the engine or ecu ..
.. if you wanted to see if the numbers *looked about right* compared to other cars though, or want to transfer your settings to another car then an acurate TDC is needed .. but in reality for a one-off who cares if the TDC mark is 5 degrees out? certainly not the engine or ecu ..
trackcar said:
.. of course you don't *have* to move the offset at all if you don't want to .. if this is a one-off and you won't be transferring the figures across to another car it doesn't matter what you have in the map or on the offset (within reasonable limits anyway) as you just give the engine the number it needs to make the power and no more than that.
.. if you wanted to see if the numbers *looked about right* compared to other cars though, or want to transfer your settings to another car then an acurate TDC is needed .. but in reality for a one-off who cares if the TDC mark is 5 degrees out? certainly not the engine or ecu ..
Thats a good point joolz, i hadnt thought about that Im transfering the ecu from the chim ( using the dissy as a sensor) to the tuscan using a crank trigger... im going to have to think about this doh
Thanks all for the help. I'm not actually too bothered about what the ECU is doing at the moment, my concern was that, having measured where TDC was manually, it did not seem to bear a sensible relationship to the timing obtained from the strobe - I find it difficult to believe that the static timing is 20 deg. BTDC. I'm not quite sure what sort of angle the plug sits at relative to the piston crown, but does it matter? Won't measuring the max. lift at any point on the piston still be equivalent to TDC? Sorry if that's a simplistic view, but I'm no engineer or mechanic. The engine makes good power, and I believe is running correctly. There is no trigger on the end of the crank, timing is taken from the 8 toothed wheel in the distributor. If the new mark which I have made is actually accurate, presumably I need to move the distributor to bring the timing into line, but if the engine is already running correctly, this does not make sense 
7.
7.
Swinging the dizzy will in your case bring the marks in line .. but another thing to consider is to make sure you wind off all the trimming from coolant and air temp sensors and any baro sensors you may have etc and put the same value in the ignition map everywhere to stop interpolation effects if you don't target a load cell precisely .. only then will you get the true reference position.
Instead of swining the distributer, you can adjust the software for the Motec ECU.
Opern the ECU software, go to ignition and select Crank index Position (CrIP).
This will fix the timing regardless of Air/Engine Temp compensations. The amount of test advance can be adjusted by yourself to a figure where the engine runs smoothly.
Re check your timing. The difference in what you measure and what the test advance is needs to be added/taken away from the CrIP.
e.g
If you test advance is set to 10 deg BTDC and you measure 15 deg BTDC you need to take 5 deg off the CrIP.
What ECU are you useing?
Steve
Opern the ECU software, go to ignition and select Crank index Position (CrIP).
This will fix the timing regardless of Air/Engine Temp compensations. The amount of test advance can be adjusted by yourself to a figure where the engine runs smoothly.
Re check your timing. The difference in what you measure and what the test advance is needs to be added/taken away from the CrIP.
e.g
If you test advance is set to 10 deg BTDC and you measure 15 deg BTDC you need to take 5 deg off the CrIP.
What ECU are you useing?
Steve
stevesingo said:
Instead of swining the distributer, you can adjust the software for the Motec ECU.
Opern the ECU software, go to ignition and select Crank index Position (CrIP).
This will fix the timing regardless of Air/Engine Temp compensations. The amount of test advance can be adjusted by yourself to a figure where the engine runs smoothly.
Re check your timing. The difference in what you measure and what the test advance is needs to be added/taken away from the CrIP.
e.g
If you test advance is set to 10 deg BTDC and you measure 15 deg BTDC you need to take 5 deg off the CrIP.
What ECU are you useing?
Steve
I'm using a very early 2 Group system - I think it was maybe a prototype that Rovercraft were developing before they passed the Motec distribution on. It needs the cabling between the ECU and PC with their own modem as well, which is a pain. Now I didn't set this up, and although I've not looked at all aspects of the software, I don't recall seeing anything like a CrIP, only the overall trim field. I've just found something in the manual: "Ignition trim may be used to align the ignition table advance with the actual engine advance. This is necessary because the reference signal is normally positioned approx. 10 degrees BTDC which is used as the advance during cranking, this is called the static advance. To compensate for a static advance of 10 degrees set the ignition trim to -10 degrees. To set this parameter accurately the value should be adjusted until the actual ignition advance (use a timing light) is the same as the advance indicated on the screen." But there is no value in the trim field, so I'm still confused.
7.
You enter your own value in the trim. You can advance the whole map forwards or retard it backwards by as many degrees as you like. It's a good way of looking for improvements quickly before you enter final settings, ie the cars running a bit rough at 3k rpm under 80% load so you advance the map 5 degrees and see if it gets better. If it does then you add 5 degrees at that load site and enter that into the timing map. Ot you mey decide to remove 5 degrees depending on what happened. Does this unit have a socket for a handheld calibrator in the interface?
Boosted
Boosted
Boosted Ls1 said:
You enter your own value in the trim. You can advance the whole map forwards or retard it backwards by as many degrees as you like. It's a good way of looking for improvements quickly before you enter final settings, ie the cars running a bit rough at 3k rpm under 80% load so you advance the map 5 degrees and see if it gets better. If it does then you add 5 degrees at that load site and enter that into the timing map. Ot you mey decide to remove 5 degrees depending on what happened. Does this unit have a socket for a handheld calibrator in the interface?
Boosted
Thanks Boosted. It does have provision for a calibrator, but I don't have access to one - and it doesn't give as much info. as the pc screen.
7.
Number 7 said:
You enter your own value in the trim. You can advance the whole map forwards or retard it backwards by as many degrees as you like. It's a good way of looking for improvements quickly before you enter final settings, ie the cars running a bit rough at 3k rpm under 80% load so you advance the map 5 degrees and see if it gets better. If it does then you add 5 degrees at that load site and enter that into the timing map. Ot you mey decide to remove 5 degrees depending on what happened. Does this unit have a socket for a handheld calibrator in the interface?
Boosted
Thanks Boosted. It does have provision for a calibrator, but I don't have access to one - and it doesn't give as much info. as the pc screen.
7.
I had one of those units. The handheld was very useful as I left it plugged in on a more or less permanent basis so could always make improvements if I found a quirk whilst driving.
Boosted.
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