TPS upgrades? effects?

[Four0Sport]

I used a 95 mustang cobra TPS--it is a bit higher$$ but the 95 mustang TPS goes to 4.2v. cobra goes to 4.9v Believe it or not.

Got that in the sticky JTSmith has up about the 70mm throttle bodies. Got me thinking, would a TPS off of a mustang help the performance of a relatively stock 5.0? By relatively I mean that all I have done to mine is an air intake, MSD coils, and im mysteriously minus 2 rear cats.

 

[IZwack]

I dont think a TPS from a Mustang would aid in engine performance.

A TPS merely indicates to the rest of the system at what position the cable actuated throttle valve is at. It is just a sensor. A larger throttle body on the other hand potentially "flows" more air -- it is not just a sensor. Swapping TPS is like swapping the CKP sensor, it wont make much of a difference (unless the original sensor is defective)

 

[Four0Sport]

Bare with me, electronics are not my thing. But to me it seems that a TPS with a higher range of resistance would enable the ECU to adjust fuel/air beyond that of stock range, maybe get a little better performance? even w.out the added air from a larger TB? I dont know, maybe its just the tropical punch kool-aid talking.

 

[aldive]

Like IZ said, its just a sensor.

 

[RubySlow]

Id do the throttle cable mod

 

[IZwack]

a higher range of resistance would enable the ECU to adjust fuel/air beyond that of stock range

I dont think thats true .. if the system is recieving a TPS voltage beyond the norms, a P0122/P0123 will be thrown. Plus I think the computer self-calibrates to the range the TPS reports (per OBDII standards).

 

[CDW6212R]

Ditto, the TPS voltage matters for any PCM before OBDII or newer. 86-95 Mustangs have EECIV computers, those do not self calibrate. They assume idle voltage of .980 volts, anything away from that affects the engine performance etc.
Skip the TPS sensor, they either work or not, the range is 0-5.0 volts. Regards,

 

[Turdle]

You guys are correct in one respect--the PCM has an input range of 0-5v

now--go measure your WOT voltage--

Mine goes closer to 5v than yours does--I'll bet ya--

The problem here is that a mustang TPS will only fit on a mustang throttle body, so as everyone says-it is not a good mod unless you change the throttle body.If you do, you will NEED to change the TPS

 

[410Fortune]

 

[IZwack]

You guys are correct in one respect--the PCM has an input range of 0-5v

now--go measure your WOT voltage--

Mine goes closer to 5v than yours does--I'll bet ya--

The problem here is that a mustang TPS will only fit on a mustang throttle body, so as everyone says-it is not a good mod unless you change the throttle body.If you do, you will NEED to change the TPS

For fun, I measured my TPS at WOT and its 4.70v -- of course i have a tiny tinnny 4.0 SOHC so I'm speaking out of context here (since the discussion is about the 5.0)

 

[Turdle]

For fun, I measured my TPS at WOT and its 4.70v -- of course i have a tiny tinnny 4.0 SOHC

dammit now I have to go measure mine--

I think mine is actually 4.85, or 4.95, one of those 2
I'll go make sure--

 

[gijoecam]

The TPS would be a waste of time. It has to do with the way the OBD-2 system interprets the signal. The actual numbers make very little difference. I'm not going to paraphrase. Here's the scoop from the shop manual:

Throttle Position Sensor
The throttle position (TP) sensor (Figure 42) is a rotary potentiometer that provides a signal to the PCM that is linearly proportional to the throttle plate/shaft position. The sensor housing has a three-blade electrical connector that may be gold plated. The gold plating increases corrosion resistance on terminals and increases connector durability. The TP sensor is mounted on the throttle body. As the TP sensor is rotated by the throttle shaft, four operating conditions are determined by the PCM from the TP. Those conditions are closed throttle (includes idle or deceleration), part throttle (includes cruise or moderate acceleration), wide open throttle (includes maximum acceleration or de-choke on crank), and throttle angle rate.

Furthermore:

Idle Speed Control Closed Throttle Determination
One of the fundamental criteria for entering rpm control is an indication of closed throttle. Throttle mode is always calculated to the lowest learned throttle position (TP) voltage seen since engine start. This lowest learned value is called "ratch," since the software acts like a one-way ratch. The ratch value (voltage) is displayed as the TPREL PID. The ratch value is relearned after every engine start. Ratch will learn the lowest, steady TP voltage seen after the engine starts. In some cases, ratch can learn higher values of TP. The time to learn the higher values is significantly longer than the time to learn the lower values. The brakes must also be applied to learn the longer values.

All PCM functions are done using this ratch voltage, including idle speed control. The PCM goes into closed throttle mode when the TP voltage is at the ratch (TPREL PID) value. Increase in TP voltage, normally less than 0.05 volts, will put the PCM in part throttle mode. Throttle mode can be viewed by looking at the TP MODE PID. With the throttle closed, the PID must read C/T (closed throttle). Slightly corrupt values of ratch can prevent the PCM from entering closed throttle mode. An incorrect part throttle indication at idle will prevent entry into closed throttle rpm control, and could result in a high idle. Ratch can be corrupted by a throttle position sensor or circuit that "drops out" or is noisy, or by loose/worn throttle plates that close tight during a decel and spring back at a normal engine vacuum.

The way I read it, the engine doesn't care what the specific voltage reads. It only cares which state it's saying the throttle is at: Idle, part throttle, or WOT. It's not going to set the fuel trim based on the TPS unless the MAF sensor takes a dive. Normally it'll set the fuel trim from the MAF and O2 sensors.

-Joe

 

[CDW6212R]

Thanks Joe, that's a better explanation.

 

[Space Truckin']

On an electronic fuel injection system, the TPS serves the same purpose as an accelerator pump on a carburetor. It really is that simple. It keeps the engine from bogging when you initially step on the gas.

 

[Four0Sport]

throttel cable mod?

 

[Four0Sport]

On an electronic fuel injection system, the TPS serves the same purpose as an accelerator pump on a carburetor. It really is that simple. It keeps the engine from bogging when you initially step on the gas.

well in that case my explorer bogs and hesitates when i lightly press the throttle. so im looking at TPS? and whats this throttle cable mod? i searched but to no avail on a real explanation.

 

[CDW6212R]

The throttle often does not open fully with the pedal. The trick is to have a person sit and press the gas to the floor, while you look at the throttle blade. It should come open completely. Good luck,

 

[gijoecam]

On an electronic fuel injection system, the TPS serves the same purpose as an accelerator pump on a carburetor. It really is that simple. It keeps the engine from bogging when you initially step on the gas.

Uuuh, no. The accelerator pump had a mechanical linkage that squirted the fuel into the intake. The TPS tells the system a whole bunch of other things, specifically, closed throttle, open throttle percentage, and rate of opening/closing.

-Joe

 

[Lazzman]

I believe you can use the same TPS.

I recently installed a MAC 70mm TB made for a Mustang on my '98 4.0 sohc and I was able to transfer over the TPS from my X and do not seem to have any problems.

Are you saying that I should now get a TPS made for a Mustang 5.0?

 

[Space Truckin']

On an electronic fuel injection system, the TPS serves the same purpose as an accelerator pump on a carburetor. It really is that simple. It keeps the engine from bogging when you initially step on the gas.

Uuuh, no. The accelerator pump had a mechanical linkage that squirted the fuel into the intake. The TPS tells the system a whole bunch of other things, specifically, closed throttle, open throttle percentage, and rate of opening/closing.

-Joe

Of course the accelerator pump on a carburetor is mechanical, and yes, it squirts a small amount of fuel into the intake when you initially step on the gas. You can customize the accelerator pumps fuel curve (amount of fuel and length of time to deliver) by changing the pump cam, pump lever, pump lever pivot point, fuel discharge nozzles, etc. Fortunately, the TPS replaced all this.

On an electronic fuel injection system, the computer uses the voltage from the TPS to calculate all the things you listed. But then what does it do with the information? Usually nothing, it almost always ignores it! However, if the computer decides the TPS voltage means you just stepped on the gas it briefly overrides the normal fuel curve and adds more fuel, by temporarily changing the injector pulse, so the engine will not bog. That is why I said in the original post, the TPS is the modern electronic equivalent of an accelerator pump.

The only other TPS function is to indicate a closed throttle or WOT condition. In either case, the computer then reverts to preset fuel curves until the TPS signal changes.

Your post did not list an alternative purpose for the TPS. If I am wrong and it does not replace the accelerator pump, what does the computer do with the signal? Why does the system need a TPS?