I've been researching posts on the power wire concept which has been interesting. But I have a question: Has anyone tried putting resistance in parallel with the IAT sensor to increase the IAT to try to increase MPG's?

Reasoning rattling around my head is, I've noticed that during the winter months my truck's IAT (monitored on my Scangage) reads around 40-50 degrees and it gets 15-16 average MPG on my 21 mile trip on a 4 lane highway to work. Recently though the weather has warmed up and the IAT is reading 105-115 degrees and I'm getting 19-20MPG on the same route. Winter/summer blends of gas isn't an issue since the days can be cold one day and hot the next this time of year, and I've seen the difference on the same tank of gas. The key seems to be in the IAT.

Can a variable pot be put in parallel and be adjusted after engine warmup to a higher IAT during cold weather to fool the ECM into leaner fuel commands? Are there other factors involved, other temp related inputs to the ECM for fuel control? Water temp runs at 197 degrees regardless of weather, therefore that's a constant and I wouldn't think it would be involved here.

Seems to me that a variable pot can be used, with a zero setting to put the system back to factory values when necessary for normal power. However at cruising speeds I'm not too concerned about horsepower...more about this summer's coming increase in fuel prices.

Anyone tried this?

 

If you lean it out too much you may risk damage to the engine. The extra fuel allows the engine to run cooler and smoother.

 

4.7K lowers the IAT temps 22*. At some point the PCM auto corrects itself and cancells this out.

Also keep in mind tricking the PCM into thinking the incoming IAT temps are 22* less means more fuel gets dumps, not less. However, because in closed loop running (normal driving) the PCM monitors the fuel trims and AFR and correctly itself and cancels the powerwire. At WOT or open loop running the PCM does not monitor the fuel trims and AFR so it actually DOES get the extra fuel dumped. This is why guys feel it at WOT and not normal driving

 

Thanks for the responses guys.

After doing some more online research, I found that the IAT probe output to the ECM is what the ECM uses to set AFR and engine timing. It uses the reading to determine air density. The warmer the air, the less dense it is, so the fuel pulse width is decreased (less fuel is needed). If the air is cold, the pulse width is increased.

I did some preliminary testing with this idea this afternoon. I unplugged the IAT connector and wired in a 0-70K pot.

I set my scangage to monitor IAT and gallons-per-hour of fuel being used, as well as loop state and water temperature. The outside air temp was at 80 degrees.

I varied the pot from 20 degrees IAT to 115 degrees, both values well within the ECM's mapped values.

With the engine warmed up and at an idle, I set the IAT to 20 degrees. The scangage showed .75 gallons per hour. At 115 degrees it immediately dropped to .55 gph with no degradation of idle quality. This is significant and encouraging.

My next step will be to install a relay for switching between the IAT probe and the pot so I can do some road tests. With 115 degrees being normal, I'm hoping the truck will run as good when it's cool outside as it does when it's warm. The next couple of days are supposed to be cool so I should get a good checkout of this idea.

 

Not trying to burst your bubble but you are going where guys have already been, including me.

 

After 178 miles, I'm still seeing a 3-5 mpg increase with no performance change with the IAT control. The PCM hasn't caught on yet...The 4.7 in this truck has never before seen 23.4 mpg average. This is great!