Ignition Advance Curve for Turbo

[Lengrep]

My recently imported Turbo is "blessed" with an E21 Bosch distributor...which has a radically different curve from what I can tell.  Since I doubt I'll find the correct Bosch distributor, I've decided to install a 123 Ignition Tune 4+ programmable distributor.  There are countless postings on the tii application, but I haven't found detailed factory curve information on the Turbo application--other than a very simplistic (maybe it's complete?!) spec from the folks at 123.

 

Help!

[jgerock]

Do you have a BMW service manual?

Edited November 16, 2017 by jgerock

[Lengrep]

Yes, but it doesn't cover the Turbo.  I have conflicting info from a UK Turbo supplement (with typos), and the standard curves supplied by 123 Ignition.

[Einspritz]

Here it is for you.

 

Does the  123 distributor have a programmable vacuum / boost circuit?

 

If not, then you are going to need that.

 

I can't stress enough that if you are trying to tune the engine properly, it is imperative that the distributor follow the curve. As with the other components of the injection system, it will be hard to make it run properly, or as it was designed to run.

 

An alternative would be to reproduce the 014 with a good core; it is definitely NOT a Tii 008 0or 002, it just would not have the proper numbers. I think this was covered in a previous post.

 

I can direct you if that is the tact you want to take.

 

In addition, I have installed a supplemental J&S system with rev limiter and knock sensor which reduces the advance by 2 degrees on the offending cylinder. Had it since about 1985. It uses a high voltage coil as well, so it always fires up.

 

Worth considering, if you are not using 100 Octane fuel, and particularly if you are using any blend of Ethanol.

 

HTH

[jgerock]

5 minutes ago, Einspritz said:

Here it is for you.

 

Does the  123 distributor have a programmable vacuum / boost circuit?

 

If not, then you are going to need that.

 

I can't stress enough that if you are trying to tune the engine properly, it is imperative that the distributor follow the curve. As with the other components of the injection system, it will be hard to make it run properly, or as it was designed to run.

 

An alternative would be to reproduce the 014 with a good core; it is definitely NOT a Tii 008 0or 002, it just would not have the proper numbers. I think this was covered in a previous post.

 

I can direct you if that is the tact you want to take.

 

In addition, I have installed a supplemental J&S system with rev limiter and knock sensor which reduces the advance by 2 degrees on the offending cylinder. Had it since about 1985. It uses a high voltage coil as well, so it always fires up.

 

Worth considering, if you are not using 100 Octane fuel, and particularly if you are using any blend of Ethanol.

 

HTH

Interesting details. Thank you for sharing!

[Einspritz]

I need to make a correction.

 

The J&S retards the spark under specific knock frequency conditions by 2 degree increments up to IIRC 50 degrees.

 

A display shows that activity.

 

On the fuel side, I have a lambda sensor as well to monitor the fuel ratio.

 

HTH

[Lengrep]

This is great.  Yes, the 123 Ignition Tune+ allows for vacuum retard.  I will make appropriate adjustments now!

 

The knock sensor is a great idea.  We have limited availability of 100 Octane "racing" fuel.  The street version of premium fuel in California is a low octane ethanol blend.

[Einspritz]

I live in the S.F. Bay area so I know about the gas. For "Street Gas" I have used Chevron exclusively in all my cars. IIRC the ethanol for California is between 10% and 15% depending on the season, and you will have to tune for that; your brand of gas as well.

 

For track use and when I had to SMOG the car I used 100, 105, or 110 depending on a host of factors. Beware though, as race gas will ruin the rear decal under the filler neck.

 

........And the knock sensor is matched with the calculated frequency, you just can't use, say, a Bosch sensor. Those send out a signal that has to be interpreted and parsed at the ECU end, which the J&S could not do. Things have changed in 30 years or so.

[S14SEAN]

Here is my timing map that I used on a 1980 320I Turbo project a while back. It was running 12psi and ran great in all conditions on 91 octane. Hope this helps.

[Luc]

I've got an old service-memo from BMW Netherlands about ignition timing for the Turbo. This is all they say:

At 850 revs it should be retarding between 2 till 8 degrees retard.

Mechanical advancing ends at 1500 revs and should be 25 degrees . So the curve should be very conservative.

[Luc]

I found some German posts. See pictures. You see there are 2 different distributor nrs. If you need translating, I'll be your guest. The vacuüm box should give 10 degrees advance. 'Fliehkraft' means 'mechanical advance'. 'Unterdruck' means vacuüm.  Hope this helps a bit.

[Lengrep]

So great to have all this factory documentation! As others have noted, the difference in fuel quality/octane is a huge factor to take into consideration as well. That seems to be why everyone sets the mixture overly rich while maintaining conservative ignition settings.


Sent from my iPhone using Tapatalk

[m6smitten]

Is there only one distributor listed on the bulletin? I am curious because my car has the other nr, mentioned - 0 231 168 026.

vielen Dank

[Einspritz]

18 hours ago, m6smitten said:

Is there only one distributor listed on the bulletin?

 

Yes, and having searched my library, I have found no mention of your distributor model number.

 

Have you looked it up?

[Einspritz]

18 hours ago, m6smitten said:

0 231 168 026.

 

 

Ok here you go for your your part number; page 4

 

But no curve to show it is the same as the 014; perhaps it is a catch all for the '02 cars?

 

0231168.pdf