Voltage dropping at WOT pulls. Need Help!

[Badwill95]

Did anyone find a fix for this? My car is currently at my tuner and after 5k the voltage drops to 11 volts, car goes lean and maf sensor goes off. My tuner is leaning towards the Alternator being the the problem.

Reference Thread.
https://www.svtperformance.com/forums/threads/voltage-dropping-at-wot-pulls-need-help.1013070/

 

[Soap]

Need more info about your charging system. You on stock alternator? Stock power and ground cables?

--Joe

 

[MG0h3]

I'd do the "big 3" upgrade and go from there. Could easily be either the cables or the alt.

 

[Badwill95]

Yes stock alternator, after 5k voltage drops to 11volts. Also boost falls off too, I’m going to pick up my car from the tuner in a couple hours to find out more information

 

[MG0h3]

Huh? Belt slip. Only thing on the ALT drive belt is the blower. Do you have a snub idler?

 

[Badwill95]

Yes I have the dual bearing UPR idler kit, it comes set with 3 100mm idlers and 1 90mm idler that is supposed to be the aux idler. I’m thinking if I switch the 100mm to be the aux idler, that should solve my belt slip problems. Then just upgrade to the 200amp alternator and should be in good shape

 

[whitedevil95]

Its your ALT, do J2fab alt and his BIG 3 wire upgrade.

 

[me32]

Its your ALT, do J2fab alt and his BIG 3 wire upgrade.

Do this. The stock alts on the cobras were not very good and known to fail.

 

[bigmoose]

Yes stock alternator, after 5k voltage drops to 11volts. Also boost falls off too, I’m going to pick up my car from the tuner in a couple hours to find out more information

Some boost drop off is normal on a pullied Eaton. My old cobra with a ported Eaton would drop 4psi up top (18-14). If you had belt slip you'd see excess belt dust.

 

[procharger]

Sounds like the voltage regulator. This part is often overlooked or must people don't know some can be replaced or upgraded. I would use a handheld meter to load test the alternator, also load test the pumps and FPDM. I would think voltage shouldn't drop under load, but maintain a steedy 13+ voltage.

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[Badwill95]

Thanks for the advice guys. I ordered the j2 200amp alternator, with big 3 wire upgrade. Also have a Gates HD green belt on the way. Maybe my alternator failed because of a bad battery? The battery in my car is over 7 years old

 

[whitedevil95]

Thanks for the advice guys. I ordered the j2 200amp alternator, with big 3 wire upgrade. Also have a Gates HD green belt on the way. Maybe my alternator failed because of a bad battery? The battery in my car is over 7 years old

Might as well have it tested while its out and your doing the install of the ALT. But ALTs on these cars just fail. Usually due to heat.

 

[me32]

Thanks for the advice guys. I ordered the j2 200amp alternator, with big 3 wire upgrade. Also have a Gates HD green belt on the way. Maybe my alternator failed because of a bad battery? The battery in my car is over 7 years old

Replace the battery