I did the TPS adjustment and...

[Cats Van Bags]

I did the TPS adjustment and I set it to .65 and noticed a real difference in the way it drives. It seems that my car is more tourqey then before but through 2nd and 3rd it feels like it doesn't pull as hard as it did before. I'm not saying I dislike this change all together, but I was wondering what number I should set it at to have the best of both worlds. Also, the IAT mod that I have read about, I have seen people saying on some sites that it can increase HP anywhere from 5-20hp, if I buy this lil mod what can I actually expect?

[snailman153624]

Truth be told the TPS setting shouldn't matter (so long as it's between .5 and 1 volt), if it does it's because your sensor is failing.

The computer uses a circuit to take the derivative of the voltage signal, which means it measures CHANGE not absolute. A computer in general does not need TPS input to run a motor, but many car manufacturers implement it to improve throttle response. The computer senses the change in throttle position because an increase means you want more power (in advance of the motor actually responding), whereas a decrease means you want to decrease power output (again, irrelevent of what the motor is actually doing).

So in short, a worn sensor will provide an erratic (jumpy) signal which can produce a discontinuous derivative. You can adjust it out of the range of the worn spot if it's near the factory idle spot, otherwise it's time for a replacement.

[spada]

in the case of the Probe GT, the TPS isn't just used to calculate the change in it's voltage.
It plays a big part in ignition timing, and of course, tells your computer when to go into open loop mode. Along with sending the signal to the ECU when to cut fuel in deceleration, and when to operate the Idle Air Control valve.

The reason that the motor feels more peppy, is because it's giving a higher spark advance at a lower throttle position, so you think that you dont have to push on the gas as hard as you used to, in order to accelerate. At wide open throttle though, everything is exactly the same, and it's likely that your car won't idle correctly if you start increasing the voltage blindly

[ouch1011]

Originally Posted by Cats Van Bags

Also, the IAT mod that I have read about, I have seen people saying on some sites that it can increase HP anywhere from 5-20hp, if I buy this lil mod what can I actually expect?

That depends on what IAT mod you are talking about.

The guys with the 4EAT automatic transmission with Probes will do something they call the IAT mod where they basically hook the IAT up to switch, so they can turn its signal on and off. When they want to go fast, they will switch off the IAT signal, which causes the computer to do a bit of a default setting, part of which includes making the computer remove the fuel cut when shifting, and increases line pressure in the transmission, so it shifts significantly faster. As in, fast enough to bark the tires into 2nd. This does work, and many people have seen that it dramatically reduces their 1/4mi times, and it is a MUST for anybody running nitrous on their ATX, because any fuel cut while spraying=boom!

Now, alot of ignorant "tuners" out there who don't know how a fuel injection system works will do the "IAT Mod" on their car in an effort to get more power. The idea behind this is that they put a resistor inline with the IAT to change the sensors output and make the computer believe it is getting a much cooler, denser charge of air, which will make it advance the timing more and add more fuel... seems like it should work right? Nope, doesn't work. In pretty much every case, it will make the car run very rich, which is not good for power, and the timing advance is often negated by the rich run. This mod does absolutely squat, except ruin your gas mileage, catalytic convertor, and possibly cause carbon deposits in the engine.

[stinkyP]

Don't stick any resistors in your MAF it will make ir run rich and just waste fuel
, the timing is mostly affected by the TPS anyhow,
on my car 0.7 volts seems to be the spot where it will feel like more power, however any higher than that and it starts to increase the idle speed. at 0.8V it doesn't want to idle lower than 1000 RPM, Yours might be different +or- 0.1V, a lot of people are running 0.65 or 0.6