Speed Pro Voltage Poll

[Jeff Rand]

Trying to track down a low voltage data log reading at wide open throttle. I was wondering what you guys are seeing on your data log? (At idle 13.5v and during a run it drops to 12.6)
Thanks,
Jeff

 

[NastyGn]

Jeff, this has been brougt up before in other posts. I have found that once the voltage on the Fast system gets below 13.8 the system has a hard time running right. What I think I see is the injectors are not all getting enough voltage to stay open as long as needed and the system gets eratic.

This is also where I started to use a battery charger in between runs to keep the voltage up in the battery. I found that if I got to the track with a fully charged battery, that each pass the voltage on the Fast system went a little lower. And after about 4 passes I was getting into the 13.8 range and bad things would happen.

Check your wiring harness and other things. I had a pod installed on my alt and set it at 14 all the time.

Take Care

 

[Jeff Rand]

Neal, I have been all through the electrical system and have upgraded my alternator to 200 amp. I did find that by adding an additional wire from my fuse block to the switched +12 volt wire on the Speed Pro, I could get the volts to 13.8 at idle and 13 volts at WOT.
Jeff

 

[TurboDave]

Originally posted by Jeff Rand
Neal, I have been all through the electrical system and have upgraded my alternator to 200 amp. I did find that by adding an additional wire from my fuse block to the switched +12 volt wire on the Speed Pro, I could get the volts to 13.8 at idle and 13 volts at WOT.
Jeff

Hey Jeff!! How's it going???

You're suffering the same dilemma I've had with my stock ECM/Electricals for several years. System runs at 13.8 at idle and all other situations all day long.
But make a WOT blast down the track and voltage likes to stay down around 12.9-13.1
Never have tracked it down, and nothing seems to suffer as a result.

 

[JeffB]

I went through this last year... voltage would drop WAY down under WOT... i tried running big power and ground wires straight to the ECU and no dice... i sent my ECU for a firmware upgrade and that helped a little... but what finally kicked the problem was PTE's voltage regulator... it plugs right into the alternator and has a pot on it to adjust the voltage to whatever level you want... my 9 year old factory alternator puts out a constant 13.8V under all kinds of loads... i see at most +/- .2 V now... call Harry!

 

[Jeff Rand]

Originally posted by JeffB
I went through this last year... voltage would drop WAY down under WOT... i tried running big power and ground wires straight to the ECU and no dice... i sent my ECU for a firmware upgrade and that helped a little... but what finally kicked the problem was PTE's voltage regulator... it plugs right into the alternator and has a pot on it to adjust the voltage to whatever level you want... my 9 year old factory alternator puts out a constant 13.8V under all kinds of loads... i see at most +/- .2 V now... call Harry!

Jeff, I did add a Caspers volt booster to the mix and that did not solve the problem. I think the voltage the Speed Pro displays is from the switched +12 volt feed. I am going to try and find a feed that will only supply the FAST unit without any interferance from other accessories.
Jeff

 

[Craig Smith]

I've raced a bracket car (not my own) with a 12 volt battery and NO alternator. Car was deadly consistent maintaining 12.0 to 12.2 volts all the way down the track. Just threw a 40 amp charger at it between rounds. It's not the way that I would do it on my own car, nor would I recommend it this way, but it will do it.

 

[Jeff Rand]

Thanks Craig, if you are OK with the 13 volts that my FAST is displaying then I will move on to the next project.
Jeff