nicklim208

Upon tuning I found out through my standalone Link ECU that my voltage reading (from laptop live tuning) drops till as low as 11.7v. It may not be safe for tuning. Alternator, battery and wirings all new as car has just been rebuilt in October.

Anyone who has encountered such cases please advise. Need help here.

BillAce

iTrader: (2)

If this only happens when accelerating hard I would start by looking for a loose ground on the drivtrain or chassis. If that's ok measure current draw on main engine fuses. It would have to be a larger circuit with the issue otherwise the fuse would blow with that much of a voltage drop.

nicklim208

Checked already on all grounding wires. All wirings are good. Whole car voltage is stable as well. So ur saying that I might have a blown fuse?

BillAce

iTrader: (2)

doubt a fuse is blown but since they take >2x current to blow a larger circuit >25a is probably where the extra draw is coming from to cause that large of a voltage drop without a fuse actually blowing if that makes sense. If you can measure current on those circuits and find one with higher than expected draw it should give you a better idea of where to look.

It is possible the alternator isn't outputting when spinning faster or the regulator doesn't like the higher voltage that should create. Have you disconnected the alternator from the battery and measured output?

nicklim208

All voltage around the car measured. Same voltage and stable. 13.9v.

BillAce

iTrader: (2)

You want to measure current changes. There has to be a draw under load that is higher than normal or a loss of available current from the charging system. That causes the voltage drop.

At idle your alternator will only put out <50% of its rated current and rated current at 6K rpm (of the alternator shaft) you are either not putting out sufficient current at full speed (>6k alt rpm) or demanding more current than it can provide which causes the voltage drop. If alternator current is good at rpm than than you need to find the circuit that has too high of a current demand.
https://www.lifewire.com/understandi...ratings-534785

nicklim208

I get what u mean. It’s gonna be damn tedious job. Dunno how to get workshop to get started. Sigh!

nicklim208

What’s ur voltage level at high rpm? Would u be able to check for me at ur different rpm stages?

BillAce

iTrader: (2)

I would start by disconnecting the alternator +12v output that leads to the battery then measure the current at idle and as the car revs to around 4k. It should double if the alternator is working properly. If the alternator is good then it becomes a pain in the a$$ to find the circuit that has the issue. Start with the higher current fuses and measure the current draw across them. They shouldn't be above the fuse rating and if one is there's a good chance that's where you're issue is. Fuel pump could be sticking motor or minor short. This is harder when a fuse doesn't blow to do this for you, If you're lucky its the alternator of voltage regulator that's the problem.