![]() |
|
|
|
Registered
|
CIS Ignition Tuning
Ok heres the deal got my cams back re-ground to 964 specs, have my 9.8:1 pistons coming. Should start the rebuild soon. My question is whats the ultimate ignition timing specs for my 3.0L SC? I have decided to stay with the CIS as it is/was working fine and I want to keep the motor as close to original as possible. Do I need to have my distributor re-curved or will it be ok as stock. I will be fitting an MSD 6AL box as well.
__________________
Davy 82 911 SC Targa Sold 12 Audi A5 Sportback 3.0 TDI Quattro 03 996 C4S |
||
![]() |
|
Registered
Join Date: Dec 2000
Location: Norway / Merritt Island FL
Posts: 220
|
Suggestion: Get the programmable MSD 6 box. Then you can fine tune the curve by the help of a computer with a seriel port.
__________________
Sigurd 73.5T 3.2SS EFI X87 944S 3.0 |
||
![]() |
|
Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
|
Davy,
Your flexibility with ignition timing is really based on your compression ratio (its high for CIS) and what octane fuel you will use. I would recommend that you check your AFR's to make sure you are not too lean.
__________________
Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
||
![]() |
|
Registered
|
Steve I have 95 octane at the pump hence using the 9.8:1 which is what the stock motor (euro) had. Another question how should the cam timing be set retarded or advanced?
__________________
Davy 82 911 SC Targa Sold 12 Audi A5 Sportback 3.0 TDI Quattro 03 996 C4S |
||
![]() |
|
Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
|
I'm assuming you are using factory Mahle pistons.
Given the use of 95RON fuel, I would not use more than 32-33 degrees total timing. With 98RON, you have more leeway. ![]() Cam timing affects where the power is in the RPM range so this depends how you use the car. Normal 964 timing is 1.26 and thats where I would set it.
__________________
Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
||
![]() |
|
Registered
|
Steve no I am going to be using JE pistons.. Car is a daily driver which sees very little track use
__________________
Davy 82 911 SC Targa Sold 12 Audi A5 Sportback 3.0 TDI Quattro 03 996 C4S |
||
![]() |
|
Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
|
Quote:
Porsche's CR spec using Mahle or Kolbenschmidt pistons was always higher than measured values and thats what afforded the flexibility with fuel & timing. With custom JE's made right to factory published specs, that detonation margin is all gone, especially with lean-running CIS engines.
__________________
Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
||
![]() |
|