Adjustable TPS for the LT1?
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Race Director
Joined: May 2001
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Adjustable TPS for the LT1?
I'm looking at my factory service manual and I see that the TPS is supposed to read .5 volts at idle or full closed and close to 5 volts at WOT.
At idle I have a TPS voltage of .31 volts, WOT seems to be 3.76 volts, I think.
Datamaster shows a TPS from 0 to 100% How can it read 100% if 5 volts would be 100% Does it just have a learned value?
Also what about open loop? At WOT is datamaster supposed to actually supposed to show open loop? Because it isn't on mine, if this is the case it is never actually going open loop at WOT, and I suppose I'll need to adjust my TPS.
That brings me to the other question, how? The LT1 unit bolts down solid. I'm sure it's a problem with my Holley TB. Is it something that I can file out the TPS and make it a slot rather than just a bolt hole, more like the L98 design? I think I saw something like this pre-made in Ecklers but I'm sure it's way over priced.
Thanks
At idle I have a TPS voltage of .31 volts, WOT seems to be 3.76 volts, I think.
Datamaster shows a TPS from 0 to 100% How can it read 100% if 5 volts would be 100% Does it just have a learned value?
Also what about open loop? At WOT is datamaster supposed to actually supposed to show open loop? Because it isn't on mine, if this is the case it is never actually going open loop at WOT, and I suppose I'll need to adjust my TPS.
That brings me to the other question, how? The LT1 unit bolts down solid. I'm sure it's a problem with my Holley TB. Is it something that I can file out the TPS and make it a slot rather than just a bolt hole, more like the L98 design? I think I saw something like this pre-made in Ecklers but I'm sure it's way over priced.
Thanks
Thread Starter
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Joined: May 2001
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Re: (scorp508)
Here's the Ecklers product. Is this simply an earlier model TPS rigged up to work?
http://www.ecklers.com/product.asp?p...dept%5Fid=1306
http://www.ecklers.com/product.asp?p...dept%5Fid=1306
Thread Starter
Race Director
Joined: May 2001
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Re: (scorp508)
I think I might have just found my answer by reading further in the book.
"The ECM has the ability to auto-zero the TPS voltage if it is between about .3-.9 volt. This means that any voltage in this window will be determined by the ECM to be 0% throttle. A failure in the TPS circuit should set a Code 21 or 22. The Tech 1 has the ability to display the throttle angle and should be 0% when the throttle is closed"
So I can assume datamaster is doing the same thing, and as such it is going all the way to 100%. Fair enough, that's some money and effort I can save. Learn something new every day by just reading.
"The ECM has the ability to auto-zero the TPS voltage if it is between about .3-.9 volt. This means that any voltage in this window will be determined by the ECM to be 0% throttle. A failure in the TPS circuit should set a Code 21 or 22. The Tech 1 has the ability to display the throttle angle and should be 0% when the throttle is closed"
So I can assume datamaster is doing the same thing, and as such it is going all the way to 100%. Fair enough, that's some money and effort I can save. Learn something new every day by just reading.
Burning Brakes
Joined: Oct 2002
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From: Wichita KS
Re: Adjustable TPS for the LT1? (Nathan Plemons)
The Holley T-Body I have has incorrect clocking on the mounting holes for the TPS. This threw off the voltage reading & would not let the car idle (ran at something like 1500-1800 RPM) I found the problem using Datamaster. My local auto parts store (Advance Auto Parts) sells a Sorenson adjustable TPS for something like $12 it simply has slotted mounting holes & you turn it until you read .59? volts at idle. I thought at the time it was just my T-body as it was originally for an F-Body.
Racer
Joined: Apr 2002
Posts: 389
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From: Micco FL
Re: (Nathan Plemons)
Our TPS is adjustable if you remove it, and use a file or dremmel to elongate the holes. However be extreemly careful in this process. A couple hundreths of a volt will make a difference What are you trying to do? Are you getting codes or is it just running a little rich or lean?
Burning Brakes
Joined: Aug 2000
Posts: 984
Likes: 1
From: Cincinnati OH
Re: Adjustable TPS for the LT1? (superlund)
The Holley T-Body I have has incorrect clocking on the mounting holes for the TPS.
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Burning Brakes
Joined: Feb 2000
Posts: 824
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From: Camden SC
Re: Adjustable TPS for the LT1? (Vince Ivanc)
Your further reading paid off.
TPS is a 3 wire transducer. Puter sees starting voltage (between .3-.9, whatever) and assumes 0% throttle position. The "auto-zero" software then calulates throttle position from that base value. This value is noted with key on during start up. Another reason to keey your foot off the pedal during start up.
You do have a SMALL amount of wiggle room when setting up the nonadjustable TPS.
Are you having problems?
dlmeyers 90 coupe zf6 3 speed shocks
TPS is a 3 wire transducer. Puter sees starting voltage (between .3-.9, whatever) and assumes 0% throttle position. The "auto-zero" software then calulates throttle position from that base value. This value is noted with key on during start up. Another reason to keey your foot off the pedal during start up.
You do have a SMALL amount of wiggle room when setting up the nonadjustable TPS.
Are you having problems?
dlmeyers 90 coupe zf6 3 speed shocks
Thread Starter
Race Director
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Re: Adjustable TPS for the LT1? (dlmeyers)
No, no problems at all, just curious. I had read that 5 volts was the top end and it was only reading 3.7 @ wot so I thought that maybe there was something wrong. But like you said with the auto zero deal, it's in range, no matter how close it is to the bottom of that range, it's working just fine.
I'm just trying to figure out if anything is out of the ordinary with my data logs other than my O2's not being heated.
I'm just trying to figure out if anything is out of the ordinary with my data logs other than my O2's not being heated.
Burning Brakes
Joined: Oct 2002
Posts: 1,152
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From: Wichita KS
Re: Adjustable TPS for the LT1? (Nathan Plemons)
Mine never seemed to find an auto zero, the engine just would not idle down, may have been out of spec for auto zero seems like it was about .2V or something close to that lost my 1st 1/2 dozen Datamaster logs on a laptop hard-drive crash, Nathan I have a heated Bosch o2 you can have, no cost only about 2 months old I'm pulling it from my Pass side 3rd position it would get you one step closer to heated o2's.... :)
Thread Starter
Race Director
Joined: May 2001
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Re: Adjustable TPS for the LT1? (superlund)
I appreciate the offer, but I bet that O2 won't work for me. It's probably a 4 wire which means it has 2 signal outputs, I only need a 3 wire.
Thanks though :cheers:
Thanks though :cheers:
Le Mans Master
Joined: Feb 2002
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Re: Adjustable TPS for the LT1? (Nathan Plemons)
Nathan,
Eckler's sells an adjustible TPS for LT1's. Same price as OEM style, $39.95. I bought one and installed it. It works fine. It ahs the slotted torx bolt holes so you can rotate it to get the voltage range you want, then tighten it down. You have to firm the torx bolts up pretty good-- seems to want to move on you for the first few hours of driving unless you firm them down good- sorry I don't have a lb-in of torque value to use on th torx bolts though. Still, the highest I could get mine to read was 3.9v approximately. On my '95, if the idle voltage goes beyond approx 0.64v it causes the IAC solenoid to reset the IAC pintle as soon as you turn key on (without touching pedal). My base is set to about 0.55v right now if I remeber right, so my range is like 0.55v - 3.9v. All I have is an analog voltmeter, so it's hard to be precise.
[Modified by Lone Ranger, 7:14 PM 11/4/2002]
Eckler's sells an adjustible TPS for LT1's. Same price as OEM style, $39.95. I bought one and installed it. It works fine. It ahs the slotted torx bolt holes so you can rotate it to get the voltage range you want, then tighten it down. You have to firm the torx bolts up pretty good-- seems to want to move on you for the first few hours of driving unless you firm them down good- sorry I don't have a lb-in of torque value to use on th torx bolts though. Still, the highest I could get mine to read was 3.9v approximately. On my '95, if the idle voltage goes beyond approx 0.64v it causes the IAC solenoid to reset the IAC pintle as soon as you turn key on (without touching pedal). My base is set to about 0.55v right now if I remeber right, so my range is like 0.55v - 3.9v. All I have is an analog voltmeter, so it's hard to be precise.
[Modified by Lone Ranger, 7:14 PM 11/4/2002]
