ECMlink Voltage issues and RPM sensor sporadic

[mopowerman]

Hey Everyone, I picked up a Talon last year and got it tuned. I have one known issue where my voltage drops like crazy under boost and when the meth injection comes on. I also was wondering if the RPM signal looks ok? Its pretty sporadic and I'm wondering if it is also an issue?
Thanks
List of mods:

Magnus build 2.3. Hyundai crank, Caprillo rods, Magnus pistons, ARP main bolts, HKS 272, adjustable cam gears. VRSF front mount and piping, 1g throttle body, Evo3 intake, FP manifold, FP3052 ball bearing turbo Tial housing and wastegate, RC 1200 injectors, Walbro 255 pump, Water meth injection.

 

[1990TSIAWDTALON]

Where do you have the water/meth set to come on at? Boost or RPM's? Something is pulling on the charging system at/around 4000 rpms. I notice that you need to set your TPS. It needs to be at .63-.65v at idle with the throttle closed. How much boost, I don't see any boost on the log.

 

[mopowerman]

Thank you so much for the reply. I'll have a look at setting up my TPS. The meth is set to come on at 4500 rpm, I'm currently running a max of 32 psi. I know I'm missing a lot of stuff on this log and I apologize. I logged this a while back before winter, before I knew what values to capture in my logs.

With the values of voltage drop I'm seeing would you say that this is simply an issue of a weak alternator or battery. Or could this be the result of a poor wiring job? I really appreciate any info/wisdom.

Sorry, I also was wondering if these rpm spikes are ok, or if i should also dig into potential issues with that sensor?

Thanks

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[1990TSIAWDTALON]

Are you keeping a steady foot throttle when this fluxuation is happening?
I am suspecting the voltage drop is coming from powering the big water/meth pump. I have one in my stick 90 Talon also but I quit using it when I switched over to E85/Flex fuel capabilities.

 

[mopowerman]

I'll try to take some other logs today, weather has been good. I believe my pedal is constant

 

[1990TSIAWDTALON]

Check the connection at the TPS on the Throttle Body to make sure it is not loose.

 

[mopowerman]

Hey thanks again for the replies, I loaded up the 20psi no meth tune and went for a drive. It seems like the voltage drop is entirely rpm dependent. I tried slowly accelerating to high rpm to simulate a low load condition and the voltage seems to drop with high rpm. Really unsure what could be causing this. I know it doesn't have a DSM alternator, I think its a saturn alt. Could the alternator have some type of highspeed cutoff

 

[enriquez2000]

I had an alternator go bad only at 4k rpms.. to the point my battery light would flicker... cause me hell trying to figure out why i couldnt get fuel right(voltage deadtimes were adding fuel due to drop)

When testing at idle it would read 14v but after 4k would come down...

Just a thought

 

[mopowerman]

I had an alternator go bad only at 4k rpms.. to the point my battery light would flicker... cause me hell trying to figure out why i couldnt get fuel right(voltage deadtimes were adding fuel due to drop)

When testing at idle it would read 14v but after 4k would come down...

Just a thought

Thanks for the reply! Sorry your alternator caused you headaches, sounds frustrating and also sounds very similar to what I'm dealing with. I'm also worried about how it could potentially effect my tune, I'd hate for my car to lean out randomly because my fuel pump isn't getting the proper voltage. It's just really weird for my alt to already be fried though, cause I'm pretty sure it's pretty new. I guess I'll look more into it. Thanks again

 

[enriquez2000]

Thanks for the reply! Sorry your alternator caused you headaches, sounds frustrating and also sounds very similar to what I'm dealing with. I'm also worried about how it could potentially effect my tune, I'd hate for my car to lean out randomly because my fuel pump isn't getting the proper voltage. It's just really weird for my alt to already be fried though, cause I'm pretty sure it's pretty new. I guess I'll look more into it. Thanks again

Mine actually went rich since the deadtimes are shorter with voltage drop. I was tuning and getting frustrated as no matter how much fuel I pulled the afr was rich.

Im on my phone so I cant see the log but I assume your dropping to at least 12v or less at high rpm?

Are you getting any dash lights flickering? Usually low volts will trigger the abs light as well if you have it. Mine would literally be the faintest flicker so at first I thought something shorted. Try revving in neutral and watch your dash close at the rpm it drops.

If you have a known good alteenator to test its an easy swap. I keep one on spare at all times.

This vid shows whay mine did... and volts "appeared" ok at battery... testing the "L" terminal on the alternator proved it to be the alt itself

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[mopowerman]

Oh OK that makes sense, mine actually drops to like 11V. Abs light has been pulled from the dash so it doesn't flicker. But my headlights dim when it happens maybe I'll try to rig up something to spin the alternator off the car to see the output. Or I guess I may be able to just use the post on the alt to test while the cars running

 

[enriquez2000]

Try this

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 it doesnt its your alternator.

If thats not it youll have to measure current draw in your fuses to find the issue

Have you tried turning off the meth pump and revving?

 

[mopowerman]

Ok sounds good, if the weather holds up today I'll test the alternator out. Yeah the second datalog I shared was with the meth completely turned off. It still drops like crazy even when its not under load

 

[enriquez2000]

Ok sounds good, if the weather holds up today I'll test the alternator out. Yeah the second datalog I shared was with the meth completely turned off. It still drops like crazy even when its not under load

I apologize for not looking at logs... wish our phones could let us see them.

 

[mopowerman]

I apologize for not looking at logs... wish our phones could let us see them.

Hey no problem at all, I'll let you know what happens today. Thanks

 

[mopowerman]

Hey so I did a little bit of digging into my alternator setup so see what alt is being used and how its wired up. It is indeed a AC Delco Saturn Alternator. I searched through some of the forums on this topic and I tried tracing the wires off the alt and they all seem to be wired correctly. I haven't done a test on the alt yet because the bat wire is a pain in the ass to get to with the alternator being tucked under my intake. Could there be an issue with the battery light circuit? I believe this is the wire responsible for turning the alternator functions on or off from what I've read. On a side note, I'm pretty sure once upon a time one of the front axle boots tore and flung greese onto the alternator.

 

[enriquez2000]

When i tested mine I just back probed the L terminal and found my answer..

Oil can absolutely kill an alternator... leaky power steering pumps have killed hundreds.

 

[mopowerman]

what would be the difference of testing it from the L terminal as opposed to reading battery voltage? I thought the L terminal was there just to read electrical load and tell the alt to charge more or less?
I do have a volt gauge inside the car and confirmed that the voltage does indeed drop.

Thanks

 

[enriquez2000]

what would be the difference of testing it from the L terminal as opposed to reading battery voltage? I thought the L terminal was there just to read electrical load and tell the alt to charge more or less?
I do have a volt gauge inside the car and confirmed that the voltage does indeed drop.

Thanks

Probably none.. the drop at 4k and up really points to either something creating a draw... bad regulator in your alternator... or possibly belt slip at that rpm...

Its usually the easy one.

You really need to test the alternator at 4k and up.

 

[mopowerman]

Hey thanks everyone for the replies, I bought a new alternator for it Saturday, installed it and tested it yesterday. Looks like my voltage issues are gone!

 

[enriquez2000]

Hey thanks everyone for the replies, I bought a new alternator for it Saturday, installed it and tested it yesterday. Looks like my voltage issues are gone!

BAM.. JUST LIKE THAT!

 

[allezgrand]

Did your erratic RPM issues go away as well?? I had a similar log to yours today with voltage drops and wildly erratic RPM, but I replaced my alternator within the last few hundred miles when it was failing and causing 19v spikes.

 

[enriquez2000]

Voltage drop will mess with rpm due to deadtimes and weak spark usually

 

[mopowerman]

Did your erratic RPM issues go away as well?? I had a similar log to yours today with voltage drops and wildly erratic RPM, but I replaced my alternator within the last few hundred miles when it was failing and causing 19v spikes.

Hey, just looked over a log I made after fixing the voltage issues. looks like the rpm is pretty smooth/stable now. If you're having sudden voltage loss then that's probably the issue.