IGNITION TIMING AND MEGAJOLT
Turbo Mini Forums

Alright chaps, I am having some problems with excessive heat I can literally start the car and run it on tickover for 2-3 mins and the gauge is in the critical area, it's a little better whilst moving for obvious reasons but still very hot. I was wondering what the timing should be set at at idle. On the mj at present it is reading 15 degrees at 850 / 1000rpm I'm at little confused as the Haynes manual states 7-8 degrees at 1500rpm but people who I've spoken to have said higher ignition at idle and the engine runs cooler but be ware of detonation. Any help appreciated, lay mans terms would be better as i'm thick.
Cheers.
Andy

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the 7-8 deg quoted in the manual is measured with the vacum pipe disconected so actual idle advance can be quite a bit more than this,

mine seems to like about 20 deg, but my lumps a bit odd so not a good guide.

try upping it to 18 and see if its smoother, aparently what you are looking for is to get the vacum as high as possible at idle.

also, is the engine actually getting too hot? the gauge could be lieing.

You are unlikely to get any detonation when the engine is not loaded, e.g. no throttle no boost, so don't worry too much about that at idle speed.

15 degrees sounds something like, but you can try advancing it a bit, and see if the engine likes it or not. Too retarded and the head will run hot due to the mixture burning out in the exh ports.

If your engine's standard, the 7 deg btdc setting should be ok. This is set at 1500rpm with the vac advance disconnected.
If your engine's modified with a low compression you'll find you need more advance, mines set at 18 degree with the above settings.

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At idle the vacuum is round about 27psi blip the throttle and back off it will go to 30 so i reckon that is ok. I will have a look at the thermostat and maybe the gauge

I am nobody, nobody's perfect. Therefore I am perfect

27 psi?

that cant be right.

the most cavum possible is 14.7 psi,

that's what the gauge is reading, brand new equipment too

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i thought it was high too, i have it teed into the old servo point on the inlet which also goes to the dump valve.
I might get rid of all the crap and put it back as standard i'm getting fed up with it tbh

I am nobody, nobody's perfect. Therefore I am perfect

Are you sure it's reading psi and not "Hg (inches mercury).

Inches mercury is a rather old fashioned (or prefered in the USA) pressure measurement and 30" (negative) is approx a perfect vacuum, ie 0bar(abs) or -14.7psi

If everyone used S.I. units, it would be so much simpler :)

Schrödinger's cat - so which one am I ???

i'll check and report back

I am nobody, nobody's perfect. Therefore I am perfect

I'm a pillock.. You are right it is in hg, 1 the vacuum half of the gauge is hg and the boost side is psi.

I am nobody, nobody's perfect. Therefore I am perfect

lol

27 is about right then.

lol. I was working on the the fact that i was told more vacuum on idle is better and seeing as my gauge was nearly off the scale i thought can't be that bad. as already stated i'm a pillock

I am nobody, nobody's perfect. Therefore I am perfect