#1  
Old 06-06-2022, 01:16 PM
JLMounce JLMounce is offline
Ultimate Warrior
 
Join Date: Sep 2005
Location: Greeley, Colorado
Posts: 3,679
Send a message via AIM to JLMounce
Default Voltage Offset

I'm hoping somebody may have some experience with this.

The problem I'm currently running into that cropped up about a year ago is that my FiTech EFI system reads out between .8 to 1.2v lower than recorded on the car itself.

I'm not electrically inclined, so I'm working at kind of the bleeding edge of my ability here.

I've tested continuity across the circuits in the car. My alternator outputs 14.5v at the stud, the nut and the terminal. I see 14.5v at the solenoid on the main battery wire as well as from the alternator. The battery seas 14.5v across it's terminals.

I've additionally tested volt drop across the power and ground paths everywhere on the car. There's less than .03v drop on the power side and almost no voltage drop on the ground side. I've tested across the alternator case, the mount, block, and grounds. My EFI system itself shows 14.5v across the unit and at the main harness connector for both the constant power and switched 12v wires.

Everything in the car functions normally.

However because the readout through the system is typically about a volt lower than actual, the system is shutting down fuel deliver on cranking when the main junction at the solenoid sees between 10.6-11.2 volts. The EFI system displays to me roughly 9.7v, below it's crank threshold for fueling.

There is a voltage offset that I'm aware of in the procal software, but the values appear to be in milliseconds. Maybe I'm reading that incorrectly at millivolts?

I know that some EFI software systems use a voltage offset to correct some of these issues. I'm wondering if anyone has an experience with that?

For now I've turned up my prime fuel multiplier which allows the engine to fire off and run for a quick second until the voltage picks up and fueling begins. This works better on a cold engine as it tends to flood the engine if it's warm but has set for a bit.

__________________
-Jason
1969 Pontiac Firebird
  #2  
Old 06-06-2022, 01:49 PM
Scott65's Avatar
Scott65 Scott65 is offline
Ultimate Warrior
 
Join Date: Jan 2002
Location: Houston, Texas
Posts: 1,991
Default

Mine uses voltage offsets for dwell, injectors, and pwm IAC functions. My cranking pulsewidth changes vs time. I.E. the longer you crank, the smaller the pulsewidth becomes. It could conceivably go the other direction. Maybe your offset you speak of can be used to increase cranking fueling and taper by time( the milliseconds you mentioned)?
ETA: I can also taper the cranking pulse by event( basically engine revolutions) Are there any dropdowns offering an option besides time on yours?

__________________
'65 Tempest 467 3650# 11.30@120.31

Last edited by Scott65; 06-06-2022 at 01:51 PM. Reason: Addition
  #3  
Old 06-06-2022, 02:13 PM
JLMounce JLMounce is offline
Ultimate Warrior
 
Join Date: Sep 2005
Location: Greeley, Colorado
Posts: 3,679
Send a message via AIM to JLMounce
Default

I will have to dig a bit deeper. This seems to be a global modifier of some sort, entered in a value from 0-7000. I'll have to continue digging. It's still possible I have a continuity issue here. This is a very early unit that had known issues with the harness.

__________________
-Jason
1969 Pontiac Firebird
  #4  
Old 06-06-2022, 05:18 PM
Formulajones's Avatar
Formulajones Formulajones is offline
Ultimate Warrior
 
Join Date: Jan 2012
Posts: 10,794
Default

I've changed the voltage offset on one of the sniper 0-100 psi transducers to make it read exactly with the mechanical gauge I had on the car.

Is that sort of what you're talking about? Or is the charging system reading a completely different scale setup than a transducer??

__________________
2019 Pontiac Heaven class winner

https://youtu.be/XqEydRRRwqE
  #5  
Old 06-06-2022, 05:30 PM
JLMounce JLMounce is offline
Ultimate Warrior
 
Join Date: Sep 2005
Location: Greeley, Colorado
Posts: 3,679
Send a message via AIM to JLMounce
Default

This is actually an accuracy issue with what my handheld is displaying as system voltage vs what is actually occurring. I believe it's causing excessive cranking at startup because the system is not accurately reading 10+ volts during crank.

__________________
-Jason
1969 Pontiac Firebird
  #6  
Old 06-06-2022, 05:50 PM
Formulajones's Avatar
Formulajones Formulajones is offline
Ultimate Warrior
 
Join Date: Jan 2012
Posts: 10,794
Default

That's what I had, an accuracy issue.

I trusted that 35 year old mechanical oil pressure gauge more than I trusted the new Holley electronic transducer, so I went in those tables and adjusted the transducer to match the mechanical gauge.

I have the same problem with the fuel pressure. Nice (expensive) Autometer mechanical gauge reads 60 PSI and the darn holley transducer reads 55 psi.

But these are added sensors, and they have a calibration table. I'm just not sure if there are calibration tables on anything that the handheld displays that doesn't use a sensor, like voltage for instance. I may go in there and dig around to see.

__________________
2019 Pontiac Heaven class winner

https://youtu.be/XqEydRRRwqE
  #7  
Old 06-07-2022, 04:02 PM
JLMounce JLMounce is offline
Ultimate Warrior
 
Join Date: Sep 2005
Location: Greeley, Colorado
Posts: 3,679
Send a message via AIM to JLMounce
Default

Spoke at decent length with FiTech about this issue today. Their system has no global voltage offset. The setting I found in procal is for injector timing as Scott appeared to believe, but it intended more for their ultimate LS models as injector timing on a TBI system is less important than a port system.

The tech I spoke with did state that they have seen this issue crop up every so often and that typically a factory reset will cure it. I'm somewhat hesitant to do that because my tune is so spot on these days. However I may take the opportunity to update to the most recent software if I'm going to that trouble anyhow.

__________________
-Jason
1969 Pontiac Firebird
  #8  
Old 06-07-2022, 04:23 PM
Scott65's Avatar
Scott65 Scott65 is offline
Ultimate Warrior
 
Join Date: Jan 2002
Location: Houston, Texas
Posts: 1,991
Default

Do you have the ability to save the current tune on your laptop, then reload it afterwards? Tunerstudio saves my tune automatically as a "restore point" right before a firmware update. I get warnings on 1st time boot with new firmware of any settings that may be being handled differently by the new firmware. Hopefully you can save your file some way.

__________________
'65 Tempest 467 3650# 11.30@120.31
  #9  
Old 06-07-2022, 04:30 PM
JLMounce JLMounce is offline
Ultimate Warrior
 
Join Date: Sep 2005
Location: Greeley, Colorado
Posts: 3,679
Send a message via AIM to JLMounce
Default

If I don't update the software, yes I can save the tune and reload it.

__________________
-Jason
1969 Pontiac Firebird
  #10  
Old 06-07-2022, 04:35 PM
Scott65's Avatar
Scott65 Scott65 is offline
Ultimate Warrior
 
Join Date: Jan 2002
Location: Houston, Texas
Posts: 1,991
Default

But it won't work with the new software? That sucks

__________________
'65 Tempest 467 3650# 11.30@120.31
  #11  
Old 06-07-2022, 04:48 PM
JLMounce JLMounce is offline
Ultimate Warrior
 
Join Date: Sep 2005
Location: Greeley, Colorado
Posts: 3,679
Send a message via AIM to JLMounce
Default

No and I don't think you'd want it to. There are fundamental ways that the software calculates things that could make a great tune with the t195 software absolute crap on the t198 release.

I could of course manually edit the VE table based on my current long term trims. I'd need to road tune pretty much anything that touches the blended alpha-N features, which would make manually modifying the VE table somewhat useless and redundant.

__________________
-Jason
1969 Pontiac Firebird
  #12  
Old 06-07-2022, 05:03 PM
Scott65's Avatar
Scott65 Scott65 is offline
Ultimate Warrior
 
Join Date: Jan 2002
Location: Houston, Texas
Posts: 1,991
Default

Well that sucks. I'm glad I don't have to deal with that. Shame you couldn't divorce the unit from the ecu. A Microsquirt would run all that and you could use Tunerstudio to tune with.

__________________
'65 Tempest 467 3650# 11.30@120.31
  #13  
Old 06-07-2022, 05:05 PM
JLMounce JLMounce is offline
Ultimate Warrior
 
Join Date: Sep 2005
Location: Greeley, Colorado
Posts: 3,679
Send a message via AIM to JLMounce
Default

Quote:
Originally Posted by Scott65 View Post
Well that sucks. I'm glad I don't have to deal with that. Shame you couldn't divorce the unit from the ecu. A Microsquirt would run all that and you could use Tunerstudio to tune with.
Don't think for a second that I'm not trying to use this little, inconsequential issue as a reason to move to sequential port injection. I'm thinking Haltech personally.

__________________
-Jason
1969 Pontiac Firebird
  #14  
Old 06-07-2022, 05:10 PM
Scott65's Avatar
Scott65 Scott65 is offline
Ultimate Warrior
 
Join Date: Jan 2002
Location: Houston, Texas
Posts: 1,991
Default

I understand. I really like their new(ish) unit that has the power control module built in. I think Krisr has one he's working towards installing. Looks very interesting. I won't need another one probably ever. But it's still interesting to see how things evolve.

__________________
'65 Tempest 467 3650# 11.30@120.31
  #15  
Old 06-07-2022, 05:17 PM
JLMounce JLMounce is offline
Ultimate Warrior
 
Join Date: Sep 2005
Location: Greeley, Colorado
Posts: 3,679
Send a message via AIM to JLMounce
Default

Yeah the power control part of the setup is pretty intriguing. I also like the direct sensor management for alcohol content that is available on the Elite 1500. While I'm lucky to only be paying $5.04 for premium right now, the fact that e85 is at every pump I go to below $3.00 is pretty tempting to make the switch.

That of course would also involve changes to the fuel system as well. I don't have enough pump at minimum.

__________________
-Jason
1969 Pontiac Firebird
  #16  
Old 06-07-2022, 05:25 PM
Scott65's Avatar
Scott65 Scott65 is offline
Ultimate Warrior
 
Join Date: Jan 2002
Location: Houston, Texas
Posts: 1,991
Default

Wish I could find E85@ $3 a gallon! Same as regular unleaded right now... I've still been using it, and mixing with regular unleaded to avoid premium prices.

__________________
'65 Tempest 467 3650# 11.30@120.31
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 03:28 AM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017