how do you retard the ignition?

[johnono]

just read a fuel thread, saw a mention of pinking due to lower octane ratings. suggest retarding the ignition to compensate... how?

[Ant]

Remap mate, no knock sensor so the timing is effectivly fixed to the look up table(map)

it one of the reasons there are country variations of maps

[kam-325i]

On engines with a Dizzy, cant you just rotate it to either advance or retard it, this is how i used to do it on ford engines.

But no idea on a dizzyless system. On vauxhall engines of the same era, there is a coding plug that was flipped around according to what ocatne fuel you was using.....

[hoshy]

depends on the car dude. Can't remember what you've got. Modern fuel injection (I think m20 and m40 is included) have knock sensors to automatically retard it. Modifying requires chip, piggy back ecu or standalone management. (or perhaps some trick with resistors or some rubbish. do these systems automatically creep up the advance to take advantage of higher octane fuels???

Older cars, like my corsa and my mates accord (which uses a rover system) you set the base advance on the distributor and from then on the curve is preprogrammed (higher revs = more advance)

And right back to non efi I think it was done using either vacuum advance connected to inlet manifold or an advance spring in the distributor itself.

Not a perfect explanation really mate but hopefully something that can be built upon.

[320Touring]

Ants right Johnono- in that post from John G Burns I put up,

I was referring to m20's but the bit about retarding the timing only applies to pre facelift m20's with the L-jetronic,

to change the timing on a motronic, you'll need some tasty electronics

[johnono]

aw sugarnuts

[320Touring]

aw sugarnuts

awww, there there, it'll all be better once babby has the m50 in

[JimmyC]

The joys of a jetronic mine will be running super/optimax and will be setup based on that

[hoshy]

is the jetronic easily tweakable then?

[JimmyC]

Indeedy

[Turbo-Brown]

Assuming that the jetronic used a 'clockwork' dizzy, you can only really alter the base point of the map, i.e. adjust the dizzy by 1 degree and the whole curve moves 1 degree.

[hoshy]

Assuming that the jetronic used a 'clockwork' dizzy, you can only really alter the base point of the map, i.e. adjust the dizzy by 1 degree and the whole curve moves 1 degree.

Ah ok, same as my corsa (and lots of other dizzy cars) then.

I really wish the law made it so that engine maps etc had to be documented for owners. New ECUs are even encrypted! The bastards are taking away the tweakability and geeky bits for the enthusiast.

Hm, am I ranting again.

[Andy_magic]

Just a thought but you may be able to use a boost retard unit, AFAIK these go between the crank position sensor and the ECU and you dial in an amount of retard for a given boost, you could probably dial in a few degrees at atmospheric pressure, but you would need to check the maker of the boost retard box.

Faliing that, make a new mount for the crank position sensor thats adjustable and manually move the sensor to get the desired amount of retard.

[Ant]

Its an idea Andy but would result in the fuel timing being altered along with ignition.

exception could be the early cars with 073 ECU, they have switchable maps for diff regions giving up to 3 degrees each way from stock and +/- 6 % total fuelling or combintaions of both.

[Turbo-Brown]

Could do that, but again you'll just be moving the whole map around which might give an ideal value at one speed/load site, but everywhere else might be wrong

That said, it's the same with the clockwork dizzy.

Pretty convinced that electronic ignition is why my 325 did pretty much the same mpg as my 1.9 205GTi.

EDIT: Wouldn't have thought that the fuel timing being out would make any difference TBH, bearing in mind that the fuelling's only in sync with two cylinders (probably 1&6) anyway, and that all the others are 120degrees and 240degrees out.

[Andy_magic]

Ant, would that be with the ECU's with the DIP switches inside??

I hadn't really thought that one through.