camsync setup

[Seight-v8]

so been thinking about camsync on my 4.6 rover v8 engine over the xmas break and winter layup.

but i ant still struggling with finding the info i need to make it all work.

as my engine is a v8 thats 720deg revolution per engine cycle, thats 2 crank rotations and one camshaft rotation, with this in mind i think i need one pulse for vems to sync the camshaft.

questions are.

1. Where's best for this pulse to take part in the engine cylce of 720deg.

2. As the camshaft only goes round once in the 720deg cycle, does this mean i really need 2 camsync pulses from my trigger wheel on the camshaft, as 180deg of the camshaft is 360deg of the crank.

3. As the crankshaft goes round twice in a engine cycle how will vems know which cycle its on, as there's is now way to tell from just the flywheel pickup, this would be the either be the compression or intake of the cycle.

4. if i make a new trigger wheel to make this all possible from the camshaft, what are the benefits and will it even work in vems?.

more questions than answers.....so far i have emailed vems hq, but not getting any reply

any help appreciated.

thanks

scott


 

[mattias]

1. Depends on your primary trigger on the crank. Missing-tooth currently means avoid the missing teeth co-inciding with the cam sync pulse. Simple trigger on the crank (one tooth per cylinder event) requires you to avoid a race condition, so place the cam sync pulse in between two primary trigger pulses.

2. No you need only one pulse per cam rotataion (full 4-stroke cycle).

3. If you have a distributor ignition system then the ECU doesn't need to know where the engine is in the 4-stroke cycle, but it helps if you want to fine-tune the injection events timed to the camshaft.  If you have some kind of DIS-ignition you only need to rotate the ignition output table until the strobe light shows you that spark events for each cylinder occurs on the correct spot on the crank/flywheel timing marks. With wasted spark this is correct on each crank revolution, for separate (coils) sequential ignition you need to find the rotation that is on the compression stroke which is easy to try as there is only two different orders of the ignition output table that puts the spark in the correct cycle - if it doesn't start at first, rotate and it will fire up if all is well.

4. What will work, when how? Did I already answer your question?

You seem confused about how the engine works in relation to timing and how it can sync with the ECU. I hope I cleared up some things.

[Seight-v8]

thanks for the reply.

yes i definately need to understand this more first before i go ahead with anything thats going to be expensive, i've done a cad model of my current cam wheel and was planning of getting a bespoke one made to suit the vems pulses, once i understand what needs to happen.

I am sure this will keep me busy thinking for a while to come.

regards

scott

[mattias]

As you already have a 36-1 crank mounted trigger (according to your sig) then you just need one tooth on your cam or whatever else you have running at "cam speed". Do you still have the distributor shaft on your engine? Do you have an easy accessible cam wheel on your engine? Is that a stock item with some form of trigger pattern? Details.. details.

[Seight-v8]

no the engine has wasted spark, with four coil packs each doing 2 cylinders, the cam wheel is stock for the rover v8 4.6 (GEMS) engine, i cant find out how worked in the originall engine other than what the land rover manual says, but this wheel does currently give 4 camsync pulses per 720degs of engine rotation, so i need to make a new on with just one pulse.

Unfortuneatly its quite a disassembly route to get access to it, front pulley, front cover, radiator.

this is the stock cam wheel from land rover.



but think more like this for what vems needs.



This would put the first pulse at TDC, but i could move it to wherever it needs to be, if i make a bespoke one.

more pictures of my engine are also here which may help to understand the settup.

http://s875.beta.photobucket.com/user/seight-v8/library/Westfield%20Kit%20Car

cheers

scott

[dnb]

I think 50 (crank) degrees before TDC would be about right from memory - there shouldn't be any events overlapping this time.  I'm still thinking of a nice way to do cam sync on my V8, but I have the older front cover so haven't got much room for a trigger disc...  Wouldn't mind discussing a couple of things with you.

[Seight-v8]

hello dave,

sure if you want to post in here or i'll send you my direct email address via private message.

regards

scott