Running out of Voltage @ WOT....WTF?!....

[MandTPhotography]

Just trying to figure out some things...

I have a 1997 S13 blacktop, stock turbo and injectors, Walbro 255, FMIC, etc;... all the other stuff isn't important.

What I'm wondering is WHY I am running out of voltage at WOT. I have an AFC Neo to measure all that and whatnot. When I start running out of voltage my AFR goes up, obviously.

It only happens during night-time, which would lead me to believe that there is too much draw on on my alternator/battery so I got that checked out at Autozone. Autozone hooked up the little machine thing and it said my starter/battery/Alternator was good, so WTF.

It's not so much of a problem right now, but when I put on all my new stuff (GT2871R/550/Tial38mm in my room right now..) it's not like the problem will go away...I need to find out what's up before it becomes a real big problem.

For some reason it doesn't happen in 2nd, just third and up....WTF.

Lemme know what's up, I'm so damn confused.

[IanS]

You say running out of voltage, what do you mean.

Is the voltage dropping?

How are you measuring the voltage?

[MandTPhotography]

I have a AFC Neo which has a Voltage measuring setting.

Yeah, my voltage is dropping the higher the RPM's go, so it's drawing power obviously. My question is why the hell is it drawing so much.

My Voltage will go from 11.8ish (Night, cruising) to 9.X area (Night, WOT).

I know that voltage is supposed to be like 14, but my battery and alternator is good.

Is there any possibility that my fuel pump isn't wired with the right gauge wire or what?

[IanS]

I have a AFC Neo which has a Voltage measuring setting.

Yeah, my voltage is dropping the higher the RPM's go, so it's drawing power obviously. My question is why the hell is it drawing so much.

My Voltage will go from 11.8ish (Night, cruising) to 9.X area (Night, WOT).

I know that voltage is supposed to be like 14, but my battery and alternator is good.

Is there any possibility that my fuel pump isn't wired with the right gauge wire or what?

You will normally see a drop in voltage as REVs increas, but you have low voltage to begin with.

You have a charging system problem, 11.8 is far too low. I would check all the connections between your battery and alternator, and I would check that your alternator belt is good and tight, and free from oil.

Then I would take it somewhere else to have the charging system checked.

[MandTPhotography]

Arghhhh.

Yeah that's what I thought the problem was, so they checked the charging system and said it was good.

I'll check the alternator belt today.

This is really annoying.

[MandTPhotography]

Alternator belt was good....

Is there any possibility that the fuel pump was wired with the wrong gauge or something?

I don't know what to do aside from checking those connections. The test said my battery was at 12.7 volts (Full charge) and my alternator was getting 14 volts.

My results for the Charging system were:

No Load Loaded--------- -----------14.04v 13.77v5.1 A 1.4A

Why would that be though? My AFC reads less than that while the car is running anyways, so I'd think that the AFC wasn't reading right.

But WHY then would the car be leaning out at WOT?...

[drzsnapj]

i have the same problem but for me it drops when i'm slowing down to a complete stop. i've checked the charging system and it comes out all good.

[Sentientbydesign]

Have you verified that all of the grounds are clean?

Improper fuel pump wire (only applies if too small) would cause the fuel pump to pump slower/less or the wires to fry (in the case of excess current draw).

You can check the fuel pump wires to make sure they aren't melted, but I doubt that's the problem.

I'd bet that a ground or the alternator recharge wire has issues. Is the SR distributor or coil (Don't make fun, I drive VQs with 6 cylinders).

[MandTPhotography]

It's a coil design.

I'll recheck the grounds again to see.

I surely do appreciate the help, I'll keep you updated!

[IanS]

Those alt tests are indeed normal.

I would guess that the S-AFC is acting up. Ive never trusted those things.

As far as leaning out, how lean are you getting, and where/how are you reading the air/fuel ratio?

Are you even sure you are leaning out?

I would be very wary of the S-AFC in general, it could be the cause of the problem.

[MandTPhotography]

Hmmm...I've always wondered if the SAFC is acting up, but it's hard to ignore a giant blinking 9.X and flashing.

I've got a PLX Wideband in my car so I'm reading off of that.

My tuner also said it felt like it was losing fuel up top during my dyno tuning.

I can try to add more fuel, but my stock injectors are maxed out as it is..

I might just lower the boost and see if it still happens when I add fuel.

I'm thinking you might be right, but I can't push away the fact that when it's losing voltage or whatnot it feels like I'm going slow as Feck WOT.

[IanS]

How much boost are you running?

[MandTPhotography]

14lbs on stock turbo.

Which would lead me to believe the whole leaning out up top thing would be because of fuel starvation (Injectors peaking) but the A/F doesn't support this theory.

And why would it feel so slow in the mid-range as opposed to just up top when it's running out of fuel?

I'm hoping once I throw on my New stuff (PE1420, DW 550's, Tial 38mm, RAS) and get it tuned, I won't have that problem anymore.

[IanS]

You should be fine running 14 PSI, though it is near the limit.

Do you have any ECU codes, you could be running in limp mode.

[MandTPhotography]

I imagine in limp mode it's REALLY slow...it's not like that.

I couldn't tell you if I was throwing codes...I'm not sure, myself.

[MandTPhotography]

I honestly think the problem is my AFC is a POS.

If it my alternator is putting out 14.0 volts and my Battery is putting out 12.7, then there isn't a problem....right?

[IanS]

I imagine in limp mode it's REALLY slow...it's not like that.

I couldn't tell you if I was throwing codes...I'm not sure, myself.

Actually limp mode isnt as bad as you might think. The ECU locks the timing to stop detonation, and it adds slightly more fuel. Some people would not even notice it, except for a decrease in gas mileage. The car will feel like it comes onto boost late, lacking power in the mid range, but feeling fine near redline.

I would strongly suggest checking for ECU codes, because most swapped cars will not trigger the check engine light.

I honestly think the problem is my AFC is a POS.

If it my alternator is putting out 14.0 volts and my Battery is putting out 12.7, then there isn't a problem....right?

Well, its hard to say, it could be a problem that only occurs at high RPM. A full load test is the only way to really test it.

[MandTPhotography]

Hmm.....very true.

I mean s***, I barely pulled on an IS250 in 3rd today FFS.

I'll try to find out how I can scan my ECU for codes...that could be it.