| Author | Message | ||
     Joseph Lau (Joe_lau) New Member Username: Joe_lau Post Number: 1 Registered: 07-2003 |
Anyone have the idea or know the function of these tune resistors are and their exact locations?. Red LR Part no. PRC8005 Yellow LR Part no. PRC8007 White LR Part no. PRC8009 Green LR Part no. PRC8172 Blue LR Part no. AMR2016 | ||
| Shaun Power (Shaunp) Member Username: Shaunp Post Number: 121 Registered: 05-2003 |
Joseph the ECU has 5 different fuel maps stored in it for different markets. The tune resistor selects the map. In fact they are just a 1/2 watt resistor in a piece of coloured plastic. Each market has a different value/map to meet local regulations. The resitor is straped to the wiring loom just back from the ECU connector. Red = 180 ohm and selects the Australian non cat map Yellow =870 ohm and selects Saudi non cat map Green = 470 ohm and selects European non cat map White = 3900 ohm and selects USA/Euro cat map Blue i'm not sure about but I suspect it some sort of US emission one. By changing the resistor you can select a different fuel map ie if you removed a white (usa cat) and fitted a red (Oz non cat) the engine no longer needs O2 sensors to run. You dont need to buy them from LR just go to Tandy/ Radio shack and buy a 1/2 watt to the value you want, cut of the old one and solder in the new. If you change maps you will need to tune the engine ie timing,base idle and MAF adjustment. | ||
| Joseph Lau (Joe_lau) New Member Username: Joe_lau Post Number: 2 Registered: 07-2003 |
Shaun, Could you advise these resistors are the same one and situated near to the ECU but in different colour only for different type of Disco. I checked it out my Disco was equipped with a Blue one near to ECU. There is a another one with clear plastic cover situated near the "Air Flow Meter", what is it?. My Disco was modified with a full Janspeed exhaust system and low range Canshaft. The trouble is the rough idle !. Also, all the IAC, TPS and Fuel Temperature Sensor were replaced recently. So, do I just replace the existing with a "Red" one. Many thanks!. | ||
| Shaun Power (Shaunp) Member Username: Shaunp Post Number: 122 Registered: 05-2003 |
Joseph It depends on what you are trying to do and what spec your car is, ie does it have o2 sensors/cats. You don't need to buy one from landrover just go to an electronic parts supplier and buy a 1/2 watt resistor of the correct value and solder it in. As for the one near the air flow meter I'm not sure what it does, I know some people do similar tempory repairs to fix out of spec air flow meters. What is the value of the blue resistor fitted to your car, just measure it with a multi meter. Have a look at this web site. there is a bit about tune resistors here. http://www.rpiv8.com/carbs-2.htm | ||
| Joseph Lau (Joe_lau) New Member Username: Joe_lau Post Number: 3 Registered: 07-2003 |
Shaun, The existing resistor is measured at about 3900ohm. My Disco is still equipped with a pair of O2 sensors but no cat. O.K. as U say different value of ohm will run different fuel map. For example, If I change a Green resistor, it means the ECU run on its designated fuel map and abandon the purpose of the O2 sensors ?. At idle , the ECU pre-set certain amount of fuel to the engine instead obtaining the temperature reading from O2 sensor to release the fuel ?. If yes, what is effect of the value of the resistor ?. Larger ohm means using less fuel ?. Thank you!. | ||
| Shaun Power (Shaunp) Member Username: Shaunp Post Number: 128 Registered: 05-2003 |
Joseph if you run a map that doesn't use the O2 sensors you will need to set the the adjustment on the air-flow meter to give as close as you can get to 1% CO at idle with the engine hot. In practice it is hard to get to 1%co on an old car so anything less than 3% is ok. I don't know which map uses the least fuel. You can richen/lean by adjusting the air-flow meter on a non o2 map. You must be carefull not to lean out the mixture to save fuel. By leaning the Airflow meter you lean out the entire fuel map which could cause burnt valves/pistons when the engine is under high load. |
