Porsche turbo boost reference timing retard

[Gareth]

Hi all, after some opinions/experiences/thoughts,

Have a Porsche in the shop atm, has two DFI modules from a commodore running 12 plugs, not sure how the dwell is being controlled at this stage but do know that timing still increases with RPM - no boost retard and therefore knocks under higher boost levels.

So what have people used to fix this, MSD have some products but unsure if they will work controlling DFI?

Cheers.

[Jayme]

DFI modules are pretty dumb... they need something to tell it what advance to run, otherwise its locked at whatever the crank trigger is at. something must be controlling dwell/advance?

[Holden202T]

ummm .... what computer is controlling it all ? I would expect if its factory turbo it should have some sort of retard for boost ??

[Gareth]

sorry, read my first post, should have added more info

Its a mechanically injected, original distributor motor that has been heavily modded. Im sure something is controlling dwell/advance but it clearly has no boost reference, have had a timing light on it under boost on the dyno with timing not backing off with boost climb. Has no computer as such.

[antus]

it sounds likely its just a static 10 degrees timing across the board, and its too much under boost. If something is controlling it then it's either using the computer interface (check if EST/BYPASS lines from DIS are connected) and if not then must be applying some modification to to the signal input from whatever is CAS, so check for boxes on those wires. Why 12 plugs? Could be a massive improvement to remove 6 of them and run spark timing from an '808.

[vlad01]

ummm .... what computer is controlling it all ? I would expect if its factory turbo it should have some sort of retard for boost ??

factory for that model was all mechanical injection and traditional dizzys. This one is highly modified so it needs to be sus'd out.

[vlad01]

it sounds likely its just a static 10 degrees timing across the board, and its too much under boost. If something is controlling it then it's either using the computer interface (check if EST/BYPASS lines from DIS are connected) and if not then must be applying some modification to to the signal input from whatever is CAS, so check for boxes on those wires. Why 12 plugs? Could be a massive improvement to remove 6 of them and run spark timing from an '808.

I know that Porsche and also VW engine hugely benefit from twin plugs. For efficiency, more torque and power.

Is there a way to make 2 DFI work in tandem?, would be a great shame to loose it on this engine. Yes I seen and studied it closely while it was in the shop. Its running a 930 engine.

[vlad01]

sorry, read my first post, should have added more info

Its a mechanically injected, original distributor motor that has been heavily modded. Im sure something is controlling dwell/advance but it clearly has no boost reference, have had a timing light on it under boost on the dyno with timing not backing off with boost climb. Has no computer as such.

did the timing move at all?

[Gareth]

Yes it did, about 34 total...

Its back in the shop tomorrow, ill sus whats controlling the dwell then.

Has anybody got a recommendation for what to use to give DFI ignition, boost retard timing?

[vlad01]

delco it of course

and f**k off the mechanical and rpm controlled auxiliary injection altogether. Thats my suggestion.