spacer for gas pedal
Thread Starter
Registered User
Joined: Aug 2009
Posts: 771
From: las vegas
spacer for gas pedal
hey guys I was wondering if this is a good idea for the throttle cable,i want to have 100% throttle when I push the gas,is a spacer safe just exactly what this guy shows in video
Administrator
Joined: Nov 1998
Posts: 71,110
From: Hell was full so they sent me to NJ
Re: spacer for gas pedal
Without actually looking at the blade position, the whole video is totally pointless. He may actually be over-rotating the blades.
Last edited by Injuneer; Jul 23, 2017 at 08:37 AM.
Registered User
Joined: Dec 2015
Posts: 194
From: St. Paul, MN
Re: spacer for gas pedal
Why not pull the boot off the throttle body and check it like Injuneer is suggesting. If you don't actually look at the Throttle Body Blades you are only assuming you have done it correctly. Only takes a couple of minutes to pull the boot and then you know for sure what you are really doing.
Administrator
Joined: Nov 1998
Posts: 71,110
From: Hell was full so they sent me to NJ
Re: spacer for gas pedal
The throttle percent reading you see on a scanner is not a DIRECT measurement. The PCM looks at the throttle position sensor (TPS) voltage, and determines the percentage open from that. And it's not a simple calculation.
First, there is no adjustment on the LT1 TPS. The PCM looks at the TPS volts at "key on" and as long as the reading is between ~0.30 volts and ~0.80 volts, the PCM sets that reading (usually around 0.67 volts on a stock, unmolested TB) as 0% open. Then the PCM appears to add ~4 volts to that number, and sets that as 100%. Then as the voltage changes, the PCM appears to prorate the percent open based on those extremes. Whether it's a simple linear interpolation, or something non-linear, I have no idea. Apparently the guy in the video was not aware of any of this.
Bottom line - assuming the 100% (some scanners limit that field to 99% in the display) percent that shows on the scanner is accurate is pointless. What if the TPS is "off"? You have to look at the blades with the accel pedal on the floor (make sure the floor mat isn't in the way) and make sure they are exactly "flat" (horizontal) with reference to the air flow, and providing minimum obstruction. If the blades over-rotate, they provide the same flow restriction as not being fully open. As I recall there is a "mod" for the LS1 throttle body because over-rotation was common.
Look at the blades and look at the scanner reading at the same time. Then determine if a fix is needed. Double check your TPS voltage. What is the reading fully closed? ..... fully open (horizontal)? Rotate the blades open slowly and watch the TPS volts increase, making sure there are no spikes or dropouts. Check your IAC counts at idle, to see if they are in the range of 20-40 counts.
First, there is no adjustment on the LT1 TPS. The PCM looks at the TPS volts at "key on" and as long as the reading is between ~0.30 volts and ~0.80 volts, the PCM sets that reading (usually around 0.67 volts on a stock, unmolested TB) as 0% open. Then the PCM appears to add ~4 volts to that number, and sets that as 100%. Then as the voltage changes, the PCM appears to prorate the percent open based on those extremes. Whether it's a simple linear interpolation, or something non-linear, I have no idea. Apparently the guy in the video was not aware of any of this.
Bottom line - assuming the 100% (some scanners limit that field to 99% in the display) percent that shows on the scanner is accurate is pointless. What if the TPS is "off"? You have to look at the blades with the accel pedal on the floor (make sure the floor mat isn't in the way) and make sure they are exactly "flat" (horizontal) with reference to the air flow, and providing minimum obstruction. If the blades over-rotate, they provide the same flow restriction as not being fully open. As I recall there is a "mod" for the LS1 throttle body because over-rotation was common.
Look at the blades and look at the scanner reading at the same time. Then determine if a fix is needed. Double check your TPS voltage. What is the reading fully closed? ..... fully open (horizontal)? Rotate the blades open slowly and watch the TPS volts increase, making sure there are no spikes or dropouts. Check your IAC counts at idle, to see if they are in the range of 20-40 counts.
Last edited by Injuneer; Jul 24, 2017 at 08:46 AM.
Thread Starter
Registered User
Joined: Aug 2009
Posts: 771
From: las vegas
Re: spacer for gas pedal
The throttle percent reading you see on a scanner is not a DIRECT measurement. The PCM looks at the throttle position sensor (TPS) voltage, and determines the percentage open from that. And it's not a simple calculation.
First, there is no adjustment on the LT1 TPS. The PCM looks at the TPS volts at "key on" and as long as the reading is between ~0.30 volts and ~0.80 volts, the PCM sets that reading (usually around 0.67 volts on a stock, unmolested TB) as 0% open. Then the PCM appears to add ~4 volts to that number, and sets that as 100%. Then as the voltage changes, the PCM appears to prorate the percent open based on those extremes. Whether it's a simple linear interpolation, or something non-linear, I have no idea. Apparently the guy in the video was not aware of any of this.
Bottom line - assuming the 100% (some scanners limit that field to 99% in the display) percent that shows on the scanner is accurate is pointless. What if the TPS is "off"? You have to look at the blades with the accel pedal on the floor (make sure the floor mat isn't in the way) and make sure they are exactly "flat" (horizontal) with reference to the air flow, and providing minimum obstruction. If the blades over-rotate, they provide the same flow restriction as not being fully open. As I recall there is a "mod" for the LS1 throttle body because over-rotation was common.
Look at the blades and look at the scanner reading at the same time. Then determine if a fix is needed. Double check your TPS voltage. What is the reading fully closed? ..... fully open (horizontal)? Rotate the blades open slowly and watch the TPS volts increase, making sure there are no spikes or dropouts. Check your IAC counts at idle, to see if they are in the range of 20-40 counts.
First, there is no adjustment on the LT1 TPS. The PCM looks at the TPS volts at "key on" and as long as the reading is between ~0.30 volts and ~0.80 volts, the PCM sets that reading (usually around 0.67 volts on a stock, unmolested TB) as 0% open. Then the PCM appears to add ~4 volts to that number, and sets that as 100%. Then as the voltage changes, the PCM appears to prorate the percent open based on those extremes. Whether it's a simple linear interpolation, or something non-linear, I have no idea. Apparently the guy in the video was not aware of any of this.
Bottom line - assuming the 100% (some scanners limit that field to 99% in the display) percent that shows on the scanner is accurate is pointless. What if the TPS is "off"? You have to look at the blades with the accel pedal on the floor (make sure the floor mat isn't in the way) and make sure they are exactly "flat" (horizontal) with reference to the air flow, and providing minimum obstruction. If the blades over-rotate, they provide the same flow restriction as not being fully open. As I recall there is a "mod" for the LS1 throttle body because over-rotation was common.
Look at the blades and look at the scanner reading at the same time. Then determine if a fix is needed. Double check your TPS voltage. What is the reading fully closed? ..... fully open (horizontal)? Rotate the blades open slowly and watch the TPS volts increase, making sure there are no spikes or dropouts. Check your IAC counts at idle, to see if they are in the range of 20-40 counts.