R.Pires

Hi,

There seems to be many differences in ignition timing degrees, between model years and US and ROW cars.
My car is 83S Euro and, for the technical specifications booklet the correct ignition timing should be 26º BTDC at 3000rpm with vacuum line detached of the distributor. Is this correct?
If it is, what will be the correct values at idle and at 5.000rpm?
Thanks in advance.

Regards

Ricardo Pires
83S Euro 5spd

SharkSkin

More info on this subject than you can shake a stick at here.

IcemanG17

X2

Charley B

I'm probably missing something, but I have been through that thread a few times and I don't see info specific to an '83 Euro. In fact, in post #9 you mention "assuming it's a US car."

Jim Bailey had a post in the last few day's mentioning the difference in timing for a Euro but now I can't find it.

R.Pires

Hi,

I have already read that thread but, as Charley B refers, there is no mention of the values for an 83S Euro.
I have the WSM but I guess it is for US cars or mine are missing the Euro pages, because there is no specific information for the M28/11 and M28/12 engines. Mine is the M28/11.
In the WSM, I can find 3 different degrees values for timing, 20º, 23º and 31º all at 3.000rpm.
As I mentioned before the Specs Book mentions specifically for the 83S Euro with M28/11, 26º BTDC at 3000rpm with vacuum line detached.
I was just curious about the values at idle and at 5000rpm should be, cause I can't find those values anywhere.

Regards

Ricardo Pires
83S Euro 5spd

123quattro

I'm pretty sure for a US car it's 23 @ 3000 and a Euro is 28 @ 3000. You can't time it at 5000 because the crank timing marks go that far out.

SharkSkin

OK, I didn't re-read the whole thread but IIRC there was some pretty comprehensive info including vacuum curves. It seems that the confusion arises from the fact that your specific model year is not called out, but I think the info is there. Double-check what engine # you have. Anyway, to be clear:

M 28.11/12/19/20(Model 80/81/82/83)
26° before TDC at 3000 rpm without vacuum
*Ignition timing Mod. 80/81/82/83 for Australia 23° before TDC at 3000 rpm without vacuum

Ref. "'81-'82 928, '80-'84 928S Dimension Tolerances.pdf" From Jim's Tech Docs CD -- Someone else with this info please double-check me)

AFAIK There is no mention of what the timing should be WITH vacuum, but IIRC Wally had some good info in that in the thread that I linked.

R.Pires

Hi,

SharkSkin, thanks for your answer.
My engine is the M28.11, considering the timing is adjusted at 26º before TDC at 3000rpm without vacuum, I was just curious to know after that what will be the values at idle (between 4º and 8º?) and at 5000rpm (no more than 36º?).
These are the values for the US cars that are in the WSM.
Do you think the Euro values will be a lot different or if they stay between these values they are ok?
Thanks

Regards

SharkSkin

I imagine it's pretty close to the same. It seems that all mechanical advance is in @ 3K RPM, so any changes beyond that should be due to the vacuum pot. No more than 36° max advance is pretty typical.

RicerSchnitzzle

36* is way too high at 5000rpms. That would be the spec for a 78 or 79 Euro with lower compression.

For Euro S models with higher compression it should be 28* BTDC @3000rpm. That is just about the point of max advance by the distributor so at 5000rpm it will still be 28* +/-2*. I run a tad advanced about 30*.

The distributors on the early Euro's (Models with vacuum and retard lines) can go to 36* as they have more mechanical advance left, and compression is lower.

Straight from the Porsche "Models, Dimesnsions and Tolerances" manual. Cool little book that has lots of specs the WSM skips. Torque values for about every bolt on the engine. Also great vacuum diagrams missing from the WSMs.

Not sure about idle level but can check mine tomorrow.

SharkSkin

36° is just a rule of thumb number -- you generally won't want more than that on any engine.

As to the spec, we seem to be looking at different data. I gave my source above, here is a screenshot:

RicerSchnitzzle

Info I had was through Euro S '82. Looks like in '83 they dropped 2 more degrees for the slightly higher compression. Here's what I have which shows no rise in timing after 3000rpms on the M09/10.. Of course the '83 with twin dizzy could have a different timing curve above 3000rpms. I would still be worried about anything over 28* at 5000rpms with the 10.4:1 compression.

R.Pires

Hi,
Thanks for the info.
I don't know if I understand correctly the expression "twin dizzy", but I guess it refers to the double distributor, right?
Mine has a single distributor, the twin distributor in Euros only came in 84 cars.
About the compression, and according to the Specs Booklet the 83S with M28.11 and 12 it's 10.0:1. Only the 84's have 10.4:1 compression.
So at 5.000rpm I should have 26º+/-2º, that is an aceptable value?
What about the idle value, between 4º and 8º it's an aceptable value for the M28.11?

Regards