Electrical gurus: How can my charging system be doing this?

[hemi twofifteen turbo]

"I think it might get a bit expensive to buy two current/amp gauges capable of up to 100 amps (not to mention the cranking current much higher) to check the battery vs alternator loads."
sorry don't know how to properly quote! you don't need 2 multimeters and they don't have to be 100amps. The main positive feed to the car is not the positive terminal but smaller (but still larger than most) white wire (if memory serves me right) The large wire goes directly to the starter motor can be ignored. When you ran direct wires to the alternator did you remove the other wires or just piggyback the direct positve on top? It's best to test with the other part of the loom disconnected. Although everything might have been fine with your old engine, fitting a new engine means there could have been a time where the engine pinched the loom against the engine bay and severed some wires etc etc. Maybe if you have a big open area you can do a power run in a high gear to check for belt slip? (engine RPM acceleration will be limited, while still loading up the engine the same as lower gears) if it doesn't go down it's belt slip, if it does it's a bad connection somewhere. Also If your charge light works, it would come on with excessive belt slip too. Although free revving is pretty much the same thing, and if it doesn't do it then....

Do you notice the problem is worse with more electrical load (headlight + heater + stereo + wipers)?

[1JZ-Rolla]

Dredging this one back up.......

Since last posting, I have completely revised the drive belt setup, so that I now have the same pulley coverage as the original factory setup, so belt slip is eliminated... but the problem still persists.

Also re-routed the battery sense wire to where it should be to eliminate potential of voltage drop... still no fix!

2 batteries, two alternators, changed belt configuration and rewire for no result, i'm going crazy!!

[The Witzl]

Sucks to hear it's still happening!
I'll be honest, I'm a little stumped with this one.

[BMWTurbo]

I'd suggest under 'load' the extra current draw from the coils/injectors etc due to the assocaited load increase is putting strain on the alternator and it can't supply enough current to overcome the increased requirement.

[rms]

If it is related to boost what is the fuel pump doing ?
Rising rate reg ? What is the pump rated at ?

[1JZ-Rolla]

I'd suggest under 'load' the extra current draw from the coils/injectors etc due to the assocaited load increase is putting strain on the alternator and it can't supply enough current to overcome the increased requirement.

I'd REALLY love to work out just how much extra current the injectors and coils can pull under load, as a 100amp alternator should hardly be struggling on a car with so little in the way of current drawing devices, FFS the panelvan is lucky to have an interior light its so basic! High impedence injectors, what will they take, 4 amps to energise the solenoid, 1 amp to keep them open? So larger duty cycle only means longer time at 1 amp, and then only one at a time, so 2 tenths of fk all i'd guess? The coils are a little harder for me to get my head around, if the charge time is 3.5ms, then it should only become saturated with more revs, not load, yet I can't replicate the problem in neutral.

If it is related to boost what is the fuel pump doing ?
Rising rate reg ? What is the pump rated at ?

Fuel pump is pumping fuel
Sard 1:1 reg, pump is Bosch 044, 600hp

[rms]

Bosch 044 pump - 15.5amps ( or more ?????)

[1JZ-Rolla]

maybe so, but why would the current draw be massively different between 40 psi at idle, vs 60psi at full boost? I wonder if bosch releases these specs?

[rms]

Current draw is from Bosch specs assuming the pump is not starting to sieze rollers.

What else can increase electrical load relative to engine boost, load ?

The fact that there is a voltage drop when boost comes on and then recovers, yet on cruise there is no drop. Fuel delivery rate and pressure changes, pump load changes.

[BradW]

Dredging this one back up.......

Since last posting, I have completely revised the drive belt setup, so that I now have the same pulley coverage as the original factory setup, so belt slip is eliminated... but the problem still persists.

Also re-routed the battery sense wire to where it should be to eliminate potential of voltage drop... still no fix!

2 batteries, two alternators, changed belt configuration and rewire for no result, i'm going crazy!!

Are you certain the belt is still not slipping? I can't think of any other possibility going on what you have said.

I'll assume it is a multi rib belt so it SHOULD be getting good grip on the pulley surfaces. Is the tensioner new/ good condition?
Something stupid, is the tensioner the right one for the engine and fitted the right way?
Does the tensioner try to push on the belt when you rev the engine or does it try to move away from the belt? If it is trying to move away from the belt, then the belt would be slacking off abit. This, combined with the rapid rise in revs due to boost, could cause slipping.
Do you have access to a dyno? You could load it up on the dyno and get it to play up while your looking at the engine.

I don't think it is from something drawing too much current. As you said it is a 100A alternator so it would need a BIG current draw to make the charge rate drop like that. Something along the lines of a main battery cable shorting out.

Hope you get it sorted.

[1JZ-Rolla]

Can't be sure its not slipping, but if it slips, so should a factory setup, cause thats the way the belt runs. Belt is brand new, tensioner is OEM and tight-as.

Its really hard to see the tensioner pulley with the engine running to diagnose as there is almost no clearance at the front of the motor, joys of a 1JZ sitting where a 4AC should be

[BradW]

Can't be sure its not slipping, but if it slips, so should a factory setup, cause thats the way the belt runs.

Yeah but factory engines don't make the HP yours does or come on boost as hard .

[lexsmaz]

As i said a while ago are you getting excessive heat into the pulleys, if they are slipping that badly you would just about burn your fingers on the alternator pulley ...

[oldcorollas]

I'd REALLY love to work out just how much extra current the injectors and coils can pull under load, as a 100amp alternator should hardly be struggling on a car with so little in the way of current drawing devices, FFS the panelvan is lucky to have an interior light its so basic! High impedence injectors, what will they take, 4 amps to energise the solenoid, 1 amp to keep them open? So larger duty cycle only means longer time at 1 amp, and then only one at a time, so 2 tenths of fk all i'd guess? The coils are a little harder for me to get my head around, if the charge time is 3.5ms, then it should only become saturated with more revs, not load, yet I can't replicate the problem in neutral.
Fuel pump is pumping fuel
Sard 1:1 reg, pump is Bosch 044, 600hp

injectors, if either high or low Z, should pull about 1amp max each.. so thats 6 amps. it will ramp up with load, but at 50% duty, 2 or 3 amps?
high impedance take about 1 amp each total. low imp take about 4 amps to open and then less than 0.5 to hold (0.3?), but the initial 4 amp is so short, the average is abotu same as for high imp.

coil? the coil current is fixed by the primary coil resistance, and shouldn't change with load. the resistance of air gap of plugs will change, but the primary coil resistance stays same (res gets higher with heat tho, = less current). i think not coil

100amp should be enough for almost anything on a car, except for stupid sizes stereo .

question, can you replicate it on a dyno?
if you can replicate on dyno, without G forces, then it is electrical or mechanicl in engine/fixed stuff.

if you can't then it is something to do with either loose wires/parts, or stuff touching under accel etc. will tell you if you need to look at outside stuff or inside stuff..

[1JZ-Rolla]

Good info oldrolly

Yes I can replicate it on the dyno, so its not G forces

Will go for a drive tonight with the multimeter between the output post of the alternator and positive battery terminal to measure voltage drop.