LB9 305 advance timing
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Joined: Jul 2020
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From: Australia
Car: Corvette 1958
Engine: GM LB9 TPI 1985
Transmission: TH700R4
LB9 305 advance timing
I have a 1985 TPI which I believe is stock, managed by an ECU with a HEI distributor (without vacuum advance as this is handled by the ECU).
The ignition map is set for 6 degrees BTDC at idle, which allows for an easy start and smooth idle and take off. What is the general consensus for full advance degrees BTDC. It’s a 4-speed auto, so cruise speed sits around 2000 revs. It shifts gears under medium load at around 3500 rpm.
To map the advance curve in the ECU, should the full advance be set around 2000 to 2500 revs without load which is where the car generally sits in cruise, or is this engine speed too low for full advance? OR Should I set full advance higher in the rev range to meet the load requirements for the gear shifts? This means that it will be less than full advance at cruising, or doesn’t this matter?
The ignition map is set for 6 degrees BTDC at idle, which allows for an easy start and smooth idle and take off. What is the general consensus for full advance degrees BTDC. It’s a 4-speed auto, so cruise speed sits around 2000 revs. It shifts gears under medium load at around 3500 rpm.
To map the advance curve in the ECU, should the full advance be set around 2000 to 2500 revs without load which is where the car generally sits in cruise, or is this engine speed too low for full advance? OR Should I set full advance higher in the rev range to meet the load requirements for the gear shifts? This means that it will be less than full advance at cruising, or doesn’t this matter?
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