What's the ignition timing curve for an 87 3.2 or 3.3 turbo?

[purplehaze]

Does anyone have a basic map or curve, showing timing?

Curious, and looking for a base of reference when tuning my 87 3.3 turbo (EFI), in non-boost or NA conditions.

I know, it depends. I'm just looking for the basic trends.

Thanks!

[Alan L]

If I could I would post a pic - but I think it depends on which dizzy you have too - US or Calif.
"Cars in California version are equipped with a
distributor having a double action pressure box
At idle speed the intake vacuum produces ignition
control toward retard, which is eliminated
again when the throttle is open just slightly.
The charge air pressure is used for full throttle
retard ignition control, to avoid coming into the
range of excessive advance ignition at full throttle
with the ignition timing which is 5deg earlier than
the USA version."
Alan

[purplehaze]

Alan, thanks. I had no idea how they handled CA cars.

It's a non-CA car, actually non-CIS now as well. Running the 3.6 twin plug distributor, rotating backwards.

Just looking for some rough numbers.

[Alan L]

Centrif adv from 0 to 8 deg at 1200 rpm, dropping to 7 deg at 3400rpm.
Vac retard 0 deg up to 130 mbar, retards progressively 10 deg up to 250 mbar, and holds thereafter.
This info is up to 1984 model I think. But the info I have also has update for type 68 WUR - this is your engine era, so I am presuming there is no dizzy update from this info.
The Calif curve is quite complex.
Alan

[Alan L]

I have no idea how this equates to 26 deg BTDC max adv at 4000 rpm, which is type 68 timing spec.
But these curves are fairly similar across the previous models, as is the timing specs.
Someone else more familiar with the dizzys may be able to explain that bit.
Alan

[purplehaze]

Alan -

Thanks. I thought it might advance as high as 28-32 degrees or something.

Glenn

[Alan L]

I don't really understand it - but none of the advance curves do.
They are quoted as centrifugal advance, and vac retard curves. But they dont go up to 30 deg.
I wonder if the boost has some advance curve too - but it is not specified in the curves.
Hopefully someone more knowledgeable can clear it up - but none of the centrifugal curves run beyond 10 deg.
Alan

[purplehaze]

Well, I actually tack welded the advance mechanism to lock in the rotor. Any advance will be handled through haltech, as opposed to vacuum.

I've since read the other posts on the benefits of indexing distributors, etc, but it is what it is right now. I can always undo it. Also, I thought any centrifugal advance wouldn't work when it spins backwards from design.

Any other tables, like load and ignition?

Thanks!

[Alan L]

From memory, for a type 68 motor, it is 5 deg ATDC at idle, no vac, and 26 deg BTDC at 4000 rpm (when no vac will exist anyway). So, how they get this much adv I dont know.
The curves I have are for the stock 930 dizzys based on rpm (cent adv) and vac (vac retard).
I have read some 930 threads where this topic is discussed in detail.
May pay to search around a bit.
Alan

[ChrisBennet]

Originally Posted by purplehaze

Well, I actually tack welded the advance mechanism to lock in the rotor. Any advance will be handled through haltech, as opposed to vacuum.

I've since read the other posts on the benefits of indexing distributors, etc, but it is what it is right now. I can always undo it. Also, I thought any centrifugal advance wouldn't work when it spins backwards from design.

Any other tables, like load and ignition?

Thanks!

If the distributor will still be "distributing" the spark, won't you still need some sort of mechanism to keep the rotor in the right vicinity when the spark occurs?
Even though the 3.2 and 964 ignition advance is determined by the DME, the distributor stills has a mechanism to advance/retard the rotor.

For the sake of example, say your rotor was locked to point right at the dist cap contact with the engine off.

If the computer advances the spark to 31 degrees, the rotor will actually be 31 degrees away from the contact it was supposed to be "distributing" the spark to - in fact it will be closer to the previous contact.

(The distributor has a contact every 60 degrees (360/6) so half way would be 30 degrees.)

-Chris

[purplehaze]

Chris -

Interesting. I think I get your point. Unfortunately.

For a stock setup, using vac advance, I guess the amount of vacuum advances the rotor to match the amount of ignition advance set in the DME (or ignition table), right?

So, how do Haltech/Motec/others do it when they dial in more advance ignition? How does that impact the distributor?

Good thing I kept those distributor advance pieces, huh.