52 or 58mm TB/ tune changes
Instructor
Joined: Oct 2000
Posts: 152
Likes: 0
From: des plaines, il
1. Use your scanner to record MAP before engine start. You should see ~100 kpa near sea-level.
2. Find a road where you can hold WOT in second gear for 5-10 seconds. Record the MAP @ ~5K RPM.
3. If the WOT MAP is 97+ kpa, there is no restriction to air flow. Changing TB will make zero difference to the engine.
4. If you measure a pressure drop, be sure the TB is opening 100% when the gas pedal is all the way down.
5. Also be sure the restriction is not caused by the air filter.
If you have enough cam/heads/exhaust to see an actual air-flow restriction from the TB @ WOT:
Reducing the pressure drop will add air @ WOT. That typically requires more fuel, less spark on the 100 kpa line.
2. Find a road where you can hold WOT in second gear for 5-10 seconds. Record the MAP @ ~5K RPM.
3. If the WOT MAP is 97+ kpa, there is no restriction to air flow. Changing TB will make zero difference to the engine.
4. If you measure a pressure drop, be sure the TB is opening 100% when the gas pedal is all the way down.
5. Also be sure the restriction is not caused by the air filter.
If you have enough cam/heads/exhaust to see an actual air-flow restriction from the TB @ WOT:
Reducing the pressure drop will add air @ WOT. That typically requires more fuel, less spark on the 100 kpa line.
