Physical Range of 90mm LS2 vs 78mm TB
11-14-2006, 12:05 AM
#21
Originally Posted by yurs78
I just bought an 03 1500HD and the first 30% of the throttle feels like milk toast. It drives me crazy. What equipment are you using to change/monitor all of these things on your trucks. Is it a laptop? what kind of software are you using. I'm trying to read and understand all of this stuff but my head is swimming.
I live in SW Wisconsin. Is there anyone local that can help me out with all of these tuning concepts? Thanks.
I live in SW Wisconsin. Is there anyone local that can help me out with all of these tuning concepts? Thanks.
Bill
11-17-2006, 07:33 PM
#22
Well I am able to log actual sensor values now.
Full sensor range on a 78 mm TB is from 0.5 to 4.2V. While the full range on a LS2 90mm is 0.5 to 4.5V. Both TAC modules(02 and 04) report 39.2% TP at 3.9V which the PCM somehow interprets as 100%. After 3.9V the 39.2% wraps back to 0% and starts over. But the TAC system will not allow the TAC motor to move the blade past this point. Assuming a linear correlation, 3.9V represents 92% of the 78mm's full range of travel(stop to stop), but only 85% of that of the 90mm. It looks like the 78mm TAC systems were designed to cease opening a little short of hitting the stop which leaves a 90mm using the same TAC module even more short of being fully open. So neither TB is openig as far as you can push it open.
Something would have to be done to bring down the top end a little while leaving the outputs unchanged at the closed throttle end, and maintaining the correlation between TPS1 and TPS2. Gets a little trickier with both sensors moving in opposite directions.
Full sensor range on a 78 mm TB is from 0.5 to 4.2V. While the full range on a LS2 90mm is 0.5 to 4.5V. Both TAC modules(02 and 04) report 39.2% TP at 3.9V which the PCM somehow interprets as 100%. After 3.9V the 39.2% wraps back to 0% and starts over. But the TAC system will not allow the TAC motor to move the blade past this point. Assuming a linear correlation, 3.9V represents 92% of the 78mm's full range of travel(stop to stop), but only 85% of that of the 90mm. It looks like the 78mm TAC systems were designed to cease opening a little short of hitting the stop which leaves a 90mm using the same TAC module even more short of being fully open. So neither TB is openig as far as you can push it open.
Something would have to be done to bring down the top end a little while leaving the outputs unchanged at the closed throttle end, and maintaining the correlation between TPS1 and TPS2. Gets a little trickier with both sensors moving in opposite directions.
11-17-2006, 08:25 PM
#23
Notorious BIG
iTrader: (6)
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 1,744
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by LBSBLOWN
I tried both TB's on my 2005 truck and the 78mm opened all the way 100%.
but the 90mm with the supplied 2002 TAC and harness will only open 85%.
here's the pics:
78MM
90MM
but the 90mm with the supplied 2002 TAC and harness will only open 85%.
here's the pics:
78MM
90MM
mine looks/acted EXACTly the same on my '03
11-17-2006, 08:31 PM
#24
Originally Posted by DrX
Well I am able to log actual sensor values now.
Full sensor range on a 78 mm TB is from 0.5 to 4.2V. While the full range on a LS2 90mm is 0.5 to 4.5V. Both TAC modules(02 and 04) report 39.2% TP at 3.9V which the PCM somehow interprets as 100%. After 3.9V the 39.2% wraps back to 0% and starts over. But the TAC system will not allow the TAC motor to move the blade past this point. Assuming a linear correlation, 3.9V represents 92% of the 78mm's full range of travel(stop to stop), but only 85% of that of the 90mm. It looks like the 78mm TAC systems were designed to cease opening a little short of hitting the stop which leaves a 90mm using the same TAC module even more short of being fully open. So neither TB is openig as far as you can push it open.
Something would have to be done to bring down the top end a little while leaving the outputs unchanged at the closed throttle end, and maintaining the correlation between TPS1 and TPS2. Gets a little trickier with both sensors moving in opposite directions.
Full sensor range on a 78 mm TB is from 0.5 to 4.2V. While the full range on a LS2 90mm is 0.5 to 4.5V. Both TAC modules(02 and 04) report 39.2% TP at 3.9V which the PCM somehow interprets as 100%. After 3.9V the 39.2% wraps back to 0% and starts over. But the TAC system will not allow the TAC motor to move the blade past this point. Assuming a linear correlation, 3.9V represents 92% of the 78mm's full range of travel(stop to stop), but only 85% of that of the 90mm. It looks like the 78mm TAC systems were designed to cease opening a little short of hitting the stop which leaves a 90mm using the same TAC module even more short of being fully open. So neither TB is openig as far as you can push it open.
Something would have to be done to bring down the top end a little while leaving the outputs unchanged at the closed throttle end, and maintaining the correlation between TPS1 and TPS2. Gets a little trickier with both sensors moving in opposite directions.
11-17-2006, 09:35 PM
#26
This issue WILL NOT die... as in I will continue to work on it from a couple different angles. Others will also. Others lurking... just continue to do so. We WILL solve this problem one way or another. I have money into one potential solution (NO guarantee's)... perhaps more info on that after the holidays. Others are working the software route... and I encourage them to continue to do so.
Bill
Bill
11-17-2006, 10:41 PM
#27
in case i missed it somewhere. do the tbss tb open all the way or the vett? if so can we not use there tac's or pcm? pcm should plug right in, right? i guess if this fixed it then we would know for sure if its a pcm or tac. and if its a pcm then we just need the table to adjust.
11-17-2006, 11:31 PM
#28
Originally Posted by 4.8T
in case i missed it somewhere. do the tbss tb open all the way or the vett? if so can we not use there tac's or pcm? pcm should plug right in, right? i guess if this fixed it then we would know for sure if its a pcm or tac. and if its a pcm then we just need the table to adjust.
Bill
11-17-2006, 11:37 PM
#29
FormerVendor
iTrader: (3)
Join Date: May 2002
Location: Reseda, CA
Posts: 1,853
Likes: 0
Received 0 Likes
on
0 Posts
Thank you for all your technical work on this DrX. You've made great strides in pin pointing the problem. I believe I've heard from several individuals that the '02 pcms acctuate the 90mm ttbs to virtually 100%. I would like to see if we can confirm this. That would narrow down the issue to the '03 and later pcms.
Richard
Richard
11-17-2006, 11:56 PM
#30
Originally Posted by Richard@WCCH
Thank you for all your technical work on this DrX. You've made great strides in pin pointing the problem. I believe I've heard from several individuals that the '02 pcms acctuate the 90mm ttbs to virtually 100%. I would like to see if we can confirm this. That would narrow down the issue to the '03 and later pcms.
Richard
Richard
If its 02... then I would understand, electricly speaking, similar characteristics on the C5 Corvette Throttle Body... which, appearance wise, is essentially identical to the C5 throttle body except the acuation motor is on the opposite side... take a look at the pics... here is a comparison of how much different the "older" TB's are. Note that the last pic is a C5 Corvette throttle body already converted to 90mm... via a billet throttle body and factory gearing / electronics...
Bill
