Alternator Overvoltage under load
Alternator Overvoltage under load 2005 Suprecharged C6 - ECS 1500 kit. 80lb injectors, racetronix hotwire, KB BAP 20, stock pump.
I have been having fluctuating AFRs for a long time and I just noticed when the car has load on it and is at higher RPM, my voltage gauge goes through the roof (16+). If you rev freely, there is no over voltage.
I am curious if the two are related as the pump will work harder with more voltage. Has anyone ever experienced this? I ran the car without the BAP and still had the same issue.
I have been having fluctuating AFRs for a long time and I just noticed when the car has load on it and is at higher RPM, my voltage gauge goes through the roof (16+). If you rev freely, there is no over voltage.
I am curious if the two are related as the pump will work harder with more voltage. Has anyone ever experienced this? I ran the car without the BAP and still had the same issue.
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Thoughts...
You're voltage should not exceed what the regulator is set to limit it to, usually 13.6-14.4 volts. Guessing the voltage regulator is faulty or on it's way out. What alternator do you have? Are you drawing amperage near it's rated output? I had a stereo (good power, but not huge by today's standards) melt the power stud off 3 cheepo stock replacement alternators in a row. Similar behavior for a few weeks before they fell off. High voltage under high demand, but not when new. They seemed to last a few months before going haywire. Can't prove anything, but I think the cheep regulators they put in the basic stock replacement deals are junk for anything that actually draws more than a stock vehicle requires... or they're just not designed to put out their rated amperage often and/or continuously. Pulled the stereo and haven't had to replace the alternator in a few years now.
Fueling...
If you're running a return style fuel pressure regulator, even if the voltage jumps and the pump flows more, your rail pressure shouldn't increase unless your return line isn't capable of accommodating the increased flow.
I know the ECU compensates for voltage variances for coil dwell time, but I don't know if it also compensates for injector opening time. That's really the only place I could see high or varying voltage causing a fluctuation in AFR's
It's altogether possible it could be related in some way. I certainly don't know all there is to be known. Good luck.
You're voltage should not exceed what the regulator is set to limit it to, usually 13.6-14.4 volts. Guessing the voltage regulator is faulty or on it's way out. What alternator do you have? Are you drawing amperage near it's rated output? I had a stereo (good power, but not huge by today's standards) melt the power stud off 3 cheepo stock replacement alternators in a row. Similar behavior for a few weeks before they fell off. High voltage under high demand, but not when new. They seemed to last a few months before going haywire. Can't prove anything, but I think the cheep regulators they put in the basic stock replacement deals are junk for anything that actually draws more than a stock vehicle requires... or they're just not designed to put out their rated amperage often and/or continuously. Pulled the stereo and haven't had to replace the alternator in a few years now.
Fueling...
If you're running a return style fuel pressure regulator, even if the voltage jumps and the pump flows more, your rail pressure shouldn't increase unless your return line isn't capable of accommodating the increased flow.
I know the ECU compensates for voltage variances for coil dwell time, but I don't know if it also compensates for injector opening time. That's really the only place I could see high or varying voltage causing a fluctuation in AFR's
It's altogether possible it could be related in some way. I certainly don't know all there is to be known. Good luck.
Last edited by SethU; May 5, 2016 at 02:47 PM.
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Isn't that meant to just boost voltage to the pump? In that, unless you're monitoring voltage from somewhere between the Boost-a-Pump and the pump, voltage should read typical vehicle voltage?
Guess that brings us back to dbert86's question... Where is the voltage being read from?
Couldn’t tell you. I just wired an MSD fuel pump booster up this week. I’ll let U know what mine does after this weekend. Testing it in the shop, it appeared to only effect pump. Didn’t see my lights get super bright or anything. I’ll data log at track.
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Verdad Gallardo The voltage is the reading on the dash (overall system voltage) - I can unhook the BAP and my voltage still skyrockets. That makes me believe the BAP has nothing to do with it. The reason the AFRs are random is it's not consistent. Could go up to 14 or 15 then 16 or just sit at 15. I'm thinking its the alternator regulator but I thought i'd see what everyone thought. I don't see it when I rev up but there is no load..
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From: Norn Iron
I know the ECU compensates for voltage variances for coil dwell time, but I don't know if it also compensates for injector opening time. That's really the only place I could see high or varying voltage causing a fluctuation in AFR's
It's altogether possible it could be related in some way. I certainly don't know all there is to be known. Good luck.
But really if you're seeing such large voltage changes, you have a problem that needs fixed, voltage should be stable ! Injector dead times should not be a fix for a fucked up setup that has wildly varying voltages.
This is why some people obsess about correct injector data, injector dead times and other nonsense. If these are correct, then voltage fluctuations should not alter fuelling too much, or at all.
But really if you're seeing such large voltage changes, you have a problem that needs fixed, voltage should be stable ! Injector dead times should not be a fix for a fucked up setup that has wildly varying voltages.
But really if you're seeing such large voltage changes, you have a problem that needs fixed, voltage should be stable ! Injector dead times should not be a fix for a fucked up setup that has wildly varying voltages.
I think I have a few issues - I noticed my FP was 62psi at idle the other day, so my regulator may be getting over run when the voltage spikes. I'm installing a Z06 fuel pump & regulator now since I already had it sitting around. Going to replace the alt and see if that fixes the overvolt.