oh, I was just going by the information on the chevy thunder page. It said that the MAF system allows for more engine wear and upgrades unlike the map system that dosent respond well to upgrades at all. Now Im not planning on doing any major internal work for a while. So I should be alright. But I do have an rv cam so Im hoping I won't have to do any tuning to get this thing to run right. Looks like I'm still considering what system I'll go with now.
Heres that page if you want to see what I was talking about.
MAF and Speed Density
MAF sensor systems were used on the tpi cars from 1985 through 1989. The maf sensor is a special device with its own miniature computer. The sensing wire in the air stream is heated to around 100 degrees Fahrenheit above the temperature of the incoming air. As the air is drawn across, it tends to cool the wire, the sensor then tries to maintain the heated wire at its preset temperature, the potential or difference is converted into a voltage that is used by the ecm along with other sensors to calibrate the proper fuel injection rate. What makes the MAF sensor unique that is is capable of measuring the exact weight of the air due to the effect that humidity, temperature and barometric pressure, and rate of flow has on how fast or slow the cooling effect takes place on the sensing wire. It is extremely accurate. To keep this sensing wire accurate is that when the engine shuts down, a special relay heats the sensing wire to 1000 degrees F, to burn off any oil and grime from the wire. The MAF system will allow for wear of engine components, and still perform over the lifespan of the engine. The MAF system will also tolerate a change of around 10% or so in flow rate due to cam, head and exhaust modifications.
The MAF system did have some minor changes over its life. 1985 MAF system was unique, as it had the MAF controller "piggyback" on the ecm. The ecm service Number was 1226870, and had a separate prom with a 32K chip and separate calpak chip to act as a back up limp home mode in case of ecm failure. This harness and computer will not interchange with the later harness/ecm systems. In 1986 the separate MAF controller was eliminated and the ecm service number changed to 1227165. The prom and calpak was combined into one module. The prom capability was changed to a 128K. This remained unchanged until 1989, when the cold start injector was eliminated and the cold start enrichment was added to the prom calibration. Another thing to remember on the 1988 and later ecm's will have the VATS (Vehicle Anti-Theft System) encoded on the prom.
Speed density was installed on the 1990 and later TPI engines. This eliminated the MAF, and depended on the MAP sensor, O2 sensor, coolant sensor, air temp. sensor and TPS to calculate the fuel requirements. The ecm service number was changed to 1227730, and the prom memory was increased to 256K. This is due to the fact that the ecm had to do some serious number crunching to get the fuel requirements as accurate as possible. It is to be noted that the speed density system is calibrated to that particular engines configuration. The system is not forgiving when it comes to modifications, or when the engine components degrade over time, changing the way the ecm reads the MAP, which is based on reading the amount of vacuum or engine load. If you use this system and have anything more than a basic stock engine, you will need a new prom chip made.
