Technical Retarding Timing Standard setup

[GhostWKD]

Kinda a novice question but non the less; With my decomp plate until i get a adjustable pulley its impossible to time the cinq perfectly, as it's half a tooth out unless i dont tension it properly... and i'd rather have it half a tooth retarded than half a tooth advanced,

My question though is which pulley needs to be retarded for the ignition to be retarded? Im guessing its the Crank as thats where the ECU gets its TDC reading? so in esscense when the cam pulley is timed up, the crank will be half a tooth away from lining up?

Does this sound about right?

Cheers,
Alex

 

[arc]

you can't.

you'd have to move the crank pulley out by a tooth as you've said, but this will mess up everything.. and you can't move it tooth at a time. you can only adjust the cam/valve timing. not the ignition timing.

and to do that, because of the way the cam pulley turns (ie in large steps) you're going to have to adavnce the crank pulley to past TDC and then but the belt on. This way, when the engine turns and is at TDC, the cam will be a tooth off it's normal TDC point. ala retarded cam/valve timing.

but tbh, in the grand scheme of things.. can't see it making much difference. variance is like 4 deg before you'd notice anything.

 

[GhostWKD]

drives fine iirc and after adjusting the throttle the idle was fine also (probably smoother than before truth be told) was just bit worried about the half tooth out timing and thought better to be trying to ignite later than earlier, but as said not something im too cosher with

Edit: Have just been thinking, when crank is at TDC the cam is just past TDC by 1/2 a tooth, this wont be a problem will it?

Worked on theory that 104 teeth so its .5/104 = 1/208 out, so less than 2 deg out i think...

 

[Italian Coke Can]

When i got my car it was soo slow. Poke around and carried out a cambelt change. Compared the old timing to the new one and the last "mechanic" had fitted it one tooth retarded.

Run ok, just lacked omph.

 

[fingers99]

Have just been thinking, when crank is at TDC the cam is just past TDC by 1/2 a tooth, this wont be a problem will it?

Probably not -- just don't whack the boost up in big increments until you know what you've got or can tell that everything is OK. If you're going by the marks on the belt or the cam it'll be a good way out anyway.

 

[Fivehundred]

Might be worth having a look if there are any offset woodruff keys around for this application, Mercedes use them fairly commonly.

 

[balidey]

Might be worth having a look if there are any offset woodruff keys around for this application, Mercedes use them fairly commonly.

Doesn't work on the FIRE engine, the cam has a simple notch cut in it, the pulley has a dimple pressed into it, this sits in the notch. Its not like other engines with a woodruff key where you can buy different offset keys. Its adjustable pulley or nothing.

 

[balidey]

GhostWKD, I may be getting this a bit 'backwards' but I think you are talking about two very different things here.

Cam timing and ignition timing.

You are in the position where you have raised your head, the cam timing (as you rightly said) needs adjusting to get the cams opening and closing at the right time to suit the piston position. You must do this with the cam pulley.

If you adjust the crank pulley, again you are right in what you are saying, it affects the timing marks, but these are IGNITION timing marks. The ECU handles advance and retarding, but it must know the crank position to do this, so do not 'adjust' the crank pulley.

If you adjust the crank pulley to bring the CAM timing correct you will then have put the ignition timing out.

I think you are best just getting an adjustable crank pulley. Its a shame they are about £120. Ford engines are much more popular and adjustable pulleys for those are only about half the price.


EDIT: sorry, I see Arc has already mentioned the differentce between ignition and cam timing. I must learn to read ALL posts, not just skim over them

 

[GhostWKD]

Thing is though crank and cam timing are run off the same belt, so when 1 is in the other will be out, its not a case of 1 being right other being wrong kinda thing surely?

Adjustable pulley is on the list but not for a few months i just dont have the money, infact if i get through next month without going into my overdraft i'll be shocked...

Is it better for the crank TDC or the cam TDC to come first by half a tooth?

Yes i know neither is good but at the end of hte day i have to run it this way even if its just to get it home...

 

[balidey]

Well, if its an emergency to get you home, I would rather the cam timing was out (as we all know there's no chance of pistons and valves hitting) because if the timing is out you could be getting sparks when you don't want it. And the ecu 'may' adjust the timing to suit the engine when its running (although i wouldn't rely on it). As the cam will be out it may run a bit rough, but like you say, its only one tooth out.

 

[arc]

Thing is though crank and cam timing are run off the same belt, so when 1 is in the other will be out, its not a case of 1 being right other being wrong kinda thing surely?

no, they're controlled by different things. the ecu uses the cutout on the crank wheel to determine when the bottom end is at TDC. you cannot adjust this. that wheel is fixed in that place, you cannot adjust it. the ignition and fueling is all controlled via the ECU, which needs that reading to be correct else odd things would happen.

the cam timing can be played with though, however because the way the cam turns against the valve springs you can't really turn it by one tooth etc - it jumps in phases.

set the bottom end and cam to TDC. rotate the bottom end past TDC by half a tooth and put the belt on. Your cam timing is now retarded. its 'TDC' is half a tooth behind the blocks actual TDC. The ignition timing wont be affected as that is controlled by the trigger wheel, and you've not altered that.