The TPS "tweak" myth
03-26-2006, 03:07 AM
#11
Well, to the floor prevents the injectors from firing because the "base" voltage is now 4.0V, which is the universal "WOT" value (or somewhere in that range, might be 3.8v) If you held the pedal down, and it was beyond 1.1-1.2v but not at WOT and you held it there for the entire "probing" period, I think its quite possible that the ECM would see the TPS as out of range and not use its input. Of course if you were just holding the gas for a few seconds while cranking, as soon as the car catches and you let off, I think that is when it does another reference voltage check (when the engine is officially "running") so if its in the proper position then, I think you'd be OK.
03-26-2006, 04:56 PM
#12
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Join Date: Oct 2004
Posts: 536
Originally Posted by OVERKILL
This has been discussed MANY MANY times on a variety of forums and there have been people "in the know" (IE, people who work for SCT, Ford, designers of the TWEECER....etc) who have tried to get the message across that this is nothing more than a myth, yet it continues to propagate across message boards "set your TPS to .98" and the like.
This post is designed to dispell that myth and perhaps give an idea of why the myth exists to begin with.
Many years ago, the entire idea of "modifying" what was going on in the ECM was a very new thing, people were much more accustomed to working on Carbureted cars and knowledge of Computer-Controlled Fuel Injection systems was very limited.
Many people would gain a limited understanding of how part of the system (or its feeback devices, IE, sensors) functioned and would often design "performance" modifications around this limited understanding. This is how I think this entire myth came to be.
A TPS is a potentiometer, basically, its a variable resistance device. The ECM views a variety of feedback sensors in order to make adjustments on how the car runs and responds. The TPS simply tells the ECM where the throttle blade is in relation to where it was when closed. Obviously, the further open the blade is, the more timing the ECM will throw at the engine (over base) and the more fuel it will provide. Many people think that "tweaking" the TPS will cause the ECM to percieve that the blade is further open than it actually is, thus "seeing" WOT sooner as well as reach full advance sooner as well. This is a great theory, but unfortunately, its completely false.
When you turn your key on, the ECM quickly probes all the sensors in the system and then uses some of those values as "base" reference values. So, if you set your TPS voltage to .98 like people recommend, the ECM views that as closed and any value higher than that is relative to .98. BUT, if the TPS is at .52, THAT value is used as the closed value and any value higher than that is relative to .52, the advance curve and fuel curve ARE THE SAME and are relative to base in either instance. WOT is percieved at ~3.8 volts, this typically happens at 3/4 throttle, not actual WOT, so matting the pedal is matting the pedal, no matter what your "base" voltage for the TPS is.
Hopefully, people will find this information helpful. There is a lot of cool, factual information floating around about finding easy/cheap performance out of these cars, unfortunately, this "mod" isn't one of them.
This post is designed to dispell that myth and perhaps give an idea of why the myth exists to begin with.
Many years ago, the entire idea of "modifying" what was going on in the ECM was a very new thing, people were much more accustomed to working on Carbureted cars and knowledge of Computer-Controlled Fuel Injection systems was very limited.
Many people would gain a limited understanding of how part of the system (or its feeback devices, IE, sensors) functioned and would often design "performance" modifications around this limited understanding. This is how I think this entire myth came to be.
A TPS is a potentiometer, basically, its a variable resistance device. The ECM views a variety of feedback sensors in order to make adjustments on how the car runs and responds. The TPS simply tells the ECM where the throttle blade is in relation to where it was when closed. Obviously, the further open the blade is, the more timing the ECM will throw at the engine (over base) and the more fuel it will provide. Many people think that "tweaking" the TPS will cause the ECM to percieve that the blade is further open than it actually is, thus "seeing" WOT sooner as well as reach full advance sooner as well. This is a great theory, but unfortunately, its completely false.
When you turn your key on, the ECM quickly probes all the sensors in the system and then uses some of those values as "base" reference values. So, if you set your TPS voltage to .98 like people recommend, the ECM views that as closed and any value higher than that is relative to .98. BUT, if the TPS is at .52, THAT value is used as the closed value and any value higher than that is relative to .52, the advance curve and fuel curve ARE THE SAME and are relative to base in either instance. WOT is percieved at ~3.8 volts, this typically happens at 3/4 throttle, not actual WOT, so matting the pedal is matting the pedal, no matter what your "base" voltage for the TPS is.
Hopefully, people will find this information helpful. There is a lot of cool, factual information floating around about finding easy/cheap performance out of these cars, unfortunately, this "mod" isn't one of them.
03-26-2006, 04:57 PM
#13
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Join Date: Oct 2004
Posts: 536
Originally Posted by Matt94GT
I found setting my tps then resetting my computer helped big time with my hanging idle.
03-27-2006, 06:25 AM
#15
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Join Date: Oct 2004
Location: Toronto
Posts: 126
Originally Posted by OVERKILL
Well, the 5.0 crowd is where the myth first propogated from 
Just a little confused... so with a car like mine ('89 5.0)... does the TPS require adjusting or not? Is the 'magic' 0.98v value that important?
03-27-2006, 08:10 AM
#17
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Join Date: Oct 2004
Posts: 536
On a 5.0 car, I would put a volt meter on the car, set it to .99-1.00V, reset the battery to clear the KAM and be on your way. This will not make the car go into WOT any sooner or things like that but it will help the car idle much better because your IAC functions, dashpot functions and other idle controls will be much more accurate
On newer vehicles, it is not necessary to do this but if you look at certain company's who make CRAPPY TB's the screw still has to be manually adjusted to OEM spec's. TB's I would never use include BBK.
These settings should never be touched as they are fine from the factory. Once you start changing thins, using crappy TB's you get into problems
On newer vehicles, it is not necessary to do this but if you look at certain company's who make CRAPPY TB's the screw still has to be manually adjusted to OEM spec's. TB's I would never use include BBK.
These settings should never be touched as they are fine from the factory. Once you start changing thins, using crappy TB's you get into problems
03-29-2006, 04:15 PM
#19
Originally Posted by Matt94GT
well even ford sold a kit to adjust the tps...?
As I said, the people that have access to the actual code for the EEC-IV are the ones who are providing this information, people can spend their time doing better things to their car that actually ENHANCE the performance, rather than "Honda modding" by screwing with sensors and thinking they are acomplishing something.
04-22-2006, 07:13 PM
#20
CMOC Veteran
Join Date: Dec 2004
Location: Lidsville, Ontario, Canada
Posts: 407
I agree with OVERKILL.
The TPS mod is a bunch of hogwash... I generally make sure mine are in the range of .87 - .90V. I think the magic number for for wot is 4.5v, and like was mentioned the car will go into power enrichment mode well before that voltage [4.5v] is reached.
Waaaay back in the day in my 89 GT I did the TPS tweak to .98v and the car never ran any different. You have to watch to because at some point over 1.xxv the EEC is going to think you are on the gas and will idle high... i've seen that before.
The TPS mod is a bunch of hogwash... I generally make sure mine are in the range of .87 - .90V. I think the magic number for for wot is 4.5v, and like was mentioned the car will go into power enrichment mode well before that voltage [4.5v] is reached.
Waaaay back in the day in my 89 GT I did the TPS tweak to .98v and the car never ran any different. You have to watch to because at some point over 1.xxv the EEC is going to think you are on the gas and will idle high... i've seen that before.
