ign curves

Nedavno Mrcheerful napisa:

This is not simple. I have 1987 BMW 316 (E30). But for our market (Serbia - was Yugoslavia), and Greece market BMW fitted 1.6 litre engine in 316. Rest of the world got 1.8 litre.

So my engine is M10B16. It's from BMW 315 but not E30 model, but E21. Perhaps you should look up 315 produced from 02/81 to 08/82. I think that it's the same engine as I have - at least according to this:

All I could find (and I tried talking to BMW importer - no info there) is that timing is 25 deg BTDC @ 2300 rpm.

I removed distributor cap, and measured movement of the rotor. At the diameter of 51.5mm movement was 6.6mm -> ~15 deg centrifugal advance at the distributor -> ~30 deg at the crank.

Moving the rotor I noticed that it resist movement in two stages - with less resistance ~8 deg (16 at the crank) and than much stronger resistance.

But when I rev my engine up to the red line I get max 20 deg centrifugal advance (at the crank) plus whatever I set for static advance.

If I set timing at 25 deg @ 2300 rpm I get ~13 deg at idle (static advance). Too much I think.

Plus I got programmable ignition module, so I want to set ignition timing as close as I can to the original, but I do not have the correct data, and that's why I am asking here.

The figure you have above is for the 16 4v b engine from the 315 e21

The M10 B16 engine you have was fitted to the 1602 from 67 - 75 (autodata)

25 deg at 2000 (vac disconnected) 8 - 14 deg at 1000 29 - 35 at 3000 40 - 46 at 4500

the vac advance is either 10 -14 deg or 8 -12 (probably depends on fuel available in country of supply (at a guess)

hopefully this will help a little

that should have read 1975 -77, and there are two different distribs, hence two vacuum amounts

Nedavno Mrcheerful napisa:

Yes, and I have this engine. 16 is probably 1600cc "4v b" I do not know. And yes it was fitted to e21 315.

This (M10) engine was designed quite long time ago, and was fitted into BMW cars up to '89-'90 ranging from 1500cc - 2000cc. It was even fitted to Formula 1 where it delivered more than 1000 HP and won a lot of races.

Data for 1602 is for the engine with distributor with points (for which I have ignition curves), but I have newer version (without points)

Not much :-(

What I am puzzled with is the difference in timing advance for the same engine with different carburetors. Here:

"Measured with vacuum hose removed.

| 1502 | 1602 & 1802 |

-------------------------------------------------

1000 rev/min 5-10 23-27 1500 rev/min 16-20 25-29 2000 rev/min 26-30 30-34 2500 rev/min 32-37 34-38 3000 rev/min 34-38 38-42 .....

Max range measured at crankshaft 42+-3 44+-2

Vacuum advance at crankshaft / 8-12

-------------------------------------------------"

1502 and 1602 are the same - 1600cc only the carburetor (and perhaps cam) is different, 1802 is 1800cc.

How can you have 27 deg advance at idle? Isn't that too much? And 44+-2 deg max mechanical advance + 8-12 vacuum. That is potentially max 58 deg advance.

The vac advance doesn't occur at idle, so an idle figure is typically a few degrees BTDC, 8 degrees would be very common.

I have run racing engines at 36 degrees at idle !!

If you go for an idle of 8 degrees and a full advance of 40 you won't be far out for a start. Push the advance a far as seems to give extra power without pinking/melting plugs

Nedavno Mrcheerful napisa:

I am about to set it up that way. I measured vacuum, and at no load (car stationary) vacuum kicks in at ~1200rpm and maxes out at ~1400 rpm

At BMW 1602 in my example that would give ~40 deg advance at 1500 rpm! Way too much I think. And what I have looks like factory repair manual.

That rarely runs at idle :-)

I looked at few ignition maps, and most of them stay below 40 (32-37) at full load. I read somewhere that petrol today does not tolerate high advance.

I did not hear my engine pinking, but I am afraid to push it to far, I am not sure I can recognize pinking (I can hear it on my Fiat at high load at low speed).

I guess I'll have to test, it seems that I can not find ignition curve anywhere on the net (I contacted BOSCH bout got no reply).

That doesn't sound far out at full vacuum

Only if you're comparing it with five star.

autodata has info about the mbar of suction, but I don't know if you have a way to add that on (ie a calibrated vacuum sensor).

The figure you want to aim at is the mechanical advance figure, which in your case is a minimum of 8 degrees at idle and max of 40 or so at 4500, if it is mappable then add in the 30 at 3000 figure,

the vac advance does not occur under load, it will only occur when the throttle is eased back, (the extra vacuum advance will then give cleaner running and more economy.)

you may well have a non loaded timing of close to 40 degrees at 2000, but on the move and accellerating that would drop back to 25

Nedavno Duncan Wood napisa:

At 1500 rpm? How then do you explain the big difference in timing advance for two engines that (as far as I can tell) have only different carburetors?

At 1000 rpm model 1502 has ~8 deg advance and model 1602 has ~25 deg. With vacuum advance 1602 would have up to 39 deg advance (1502 does not have vacuum correction). Again at 1000 rpm.

So there is the difference of ~17 deg at 1000 rpm.

Nedavno Mrcheerful napisa:

Yes I can, I have a calibrated vacuum sensor. As I wrote I have programmable ignition module, so I want to set ignition timing as close as I can to the original, but I do not have the needed data.

Again you are talking about different distributors. I have timing curve for distributors that were used in 1502. For that model you are supposed to set timing at 25 deg bTDC @ 1900 rpm. For the distributor I have timing is set at 25 deg bTDC @ 2300 rpm.

When I found ignition curve for BMW 1502 I thought I found what I needed, as I have that exact engine. But I than noticed ignition curve for 1602 and got completely lost. How can timing change that much (17 deg @ 1000 rpm) for basically the same engine?

And add to that the fact that I now measure non-ported vacuum (below the throttle plate) which adds to my confusion about idle timing...

Probably different because of emissions regulations and quite possibly different camshafts.

do you have the part number for the distributor?

ignore vacuum at idle, just use mechanical setting

It's fairly insensitive, you won't get detonation at that sort of load & revs unless you've got something else wrong so as much advance as you can persuade it to ignite at is best.

Nedavno Pete M napisa:

Yes, it's BOSCH 0 237 005 009 - BMW part No: 12 11 1 285 079 used in BMW E21 315 from 09/1982 to 12/1983 (and in my '87 E30 316)

Made in (according to Bosch on-line catalog):

Broadwater Park UB9 5HJ Denham, Uxbridge Telephone: 0044/1895-838310 Fax: 0044/1895-839310

BTW Bosch did not respond at my email.

Yvan (Yvan ) gurgled happily, sounding much like they were saying:

It certainly wasn't _made_ there...

Nedavno Adrian napisa:

That's what BOSCH on-line catalog displayed...

Nedavno Mrcheerful napisa:

Yes, but do I set it at ~8 (as for 1502) or at ~25 (as for 1602)?

I tested my distributor vacuum correction. In my garage (car not moving) slowly pressing throttle vacuum correction starts at ~1100 rpm and is at max 15 deg at ~1400 rpm.

If I set it as for 1602 I'd have 30-35 deg at 1500 rpm (with vac hose connected). Is that OK?

Right, the ignition advance figures for that distributor as as follows.

Basic ignition timing (without vacuum)25 deg BTDC @ 2300 rpm

Advance without vacuum as follows;

Degrees / rpm

14-22 / 1000 26-33 / 3000 39-45 / 5500

Vacuum range +13 to +17 deg. Vacuum starts @ 100 mbar Vacuum ends @ 420mbar Idle speed should be 850 +/- 50 rpm

HTH.