Tom's Fuel Map Controller + TRD Racing Spark Plug

[CTScott]

Originally Posted by cfeng

VIP Auto Salon, a distributor of Tom's in Orange, Ca is offering these for $280 shipped. I'm considering picking one of these up and trying it.

Do a web search and read some of the reviews before you drop the money. It inserts between the MAF and the ECM and fools the ECM into thinking that more air is coming in, so that the ECM will feed more fuel. The problem with it only overriding that side (and not the feedback side via the O2 sensors), is that the ECM adjusts the trim accordingly, so the improvements will only be temporary, unless you routinely clear out the short term data by disconnecting the battery for a couple of minutes.

[Bluevitz-rs]

Originally Posted by CTScott

Do a web search and read some of the reviews before you drop the money. It inserts between the MAF and the ECM and fools the ECM into thinking that more air is coming in, so that the ECM will feed more fuel. The problem with it only overriding that side (and not the feedback side via the O2 sensors), is that the ECM adjusts the trim accordingly, so the improvements will only be temporary, unless you routinely clear out the short term data by disconnecting the battery for a couple of minutes.

You're on the right track, but your messing with the wrong signal.

What other sensor is inside the MAF sensor?...... Intake air temp. What would the ECU do if it was sucking in -40° air? richen the fuel mixture up permanently until it saw warmer air being drawn in.

All the toms unit does is adjust the resistance of the intake air temp sensor so the signal going to the stock ECU thinks it's in cold weather and adjusts the fuel trim accordingly. I leaned this trick while sitting in on an advanced engine management course when I worked at Toyota Canada.

[CTScott]

Originally Posted by Bluevitz-rs

You're on the right track, but your messing with the wrong signal.

What other sensor is inside the MAF sensor?...... Intake air temp. What would the ECU do if it was sucking in -40° air? richen the fuel mixture up permanently until it saw warmer air being drawn in.

All the toms unit does is adjust the resistance of the intake air temp sensor so the signal going to the stock ECU thinks it's in cold weather and adjusts the fuel trim accordingly. I leaned this trick while sitting in on an advanced engine management course when I worked at Toyota Canada.

Whether is messes with the MAF or the IAT, either way, when running closed loop, the ECM will see the effects on the O2 sensor readings and will compensate. My point is that since the system runs primarily closed loop, you have to trick the ECU on both the input and output sides to have a long term effect.


This is from the Toyota T874 course:

The ECM uses the front (S1) A/F or O2 sensor(s) to make corrections to injection duration in order to keep the engine running at a theoretical 14.7:1 (for gasoline) (stoichometric) air/fuel ratio during most engine operating conditions such as idle, cruising, etc.

Feedback from the O2 or A/F sensor (S1) influences short-term fuel trim, which influences long-term fuel trim.