That's a bandaid and isn't ruling out anything. It will not overcome a weak/dying battery, it will prevent the charge from getting through the rest of the circuit. It will also not compare to the benefit of doing the big3 - more power, better MPGs, brighter lights, stronger blower/fans...all from experience. The fact that the headlights dimmed WITH the battery charger on there is even more telling...you have a charging problem that is causing/contributing. You asked for advice, you got some good suggestions, not just from me and yet you keep finding reasons not to act on most/all of them. Act on the cheapest ones first. Remember, your tuner is not a trouble shooter, that's probably not what he's good at and definitely not where he makes his money. You need to solidify the charging system on your TWENTY YEAR OLD CAR. If you do nothing, you will keep chasing your tail and be unhappy.

 

Sanity returns.....

 

Not sure I would conflate sanity with accuracy. You can be both right AND crazy...entirely separate questions.

 

lol it been a day since you responded, may be taking this out of context but you seem to think im not willing to take advice and want **** to just fix itself. you misunderstood me when i said headlights dimmed, they dimmed while i was driving it at night....why would headlights be on during a dyno pull unless this a thing......if you are saying that the charging system will still react poorly even with a poor battery and hooking up a charger than thats cool, figured that would be the case. besides the big 3 what good suggestions did i miss that i havent given a response for?

the guy who tuned the car runs a full service shop and simply does performance stuff to keep his sanity in check. cant do ball joints and brakes everyday and still be happy even tho its easy money. hes also a fabricator, engine assembler, does transmissions and has worked for one of the most well known shops on the east coast. im not saying you think he doesnt know how to trouble shoot, but just wanted to throw it out there why i let him keep the car a lot longer than he should have had it......cause i trust him with it.

and btw not becuase of this but i decided to sell the car and move onto a c6. that platform fits me car goals much better. but i will address the charging stuff.

 

If they dimmed during normal driving, that's an even bigger indicator of a charging problem. I can tell you it's not standard practice to put a battery charger on during dyno runs - or at all unless there is an issue.

 

it only dimmed under WOT at night time. it wasnt on there every time it dynoed. car would sit for weeks or months at a time then battery would be dead when he would mess with it again so the charger went on at the beginning of the dyno pulls cause battery had nothing in it snd obviously you need juice for tuning it. as stated, he had tons of pulls into this and if he did ever put it on to "see what it would do" it was to try and find an issue since he literally was trying to think of every possible thing it could be. assumed charging issue was on that list, and after i brought that suggestion to him when you guys mentioned it, thats when he told me he thought that at one time as well hence throwing charger on there just for kicks

 

Isn't there a point where the alt gets cut for over speeding? Being a truck alt maybe it was being over spun.

 

I mentioned in an earlier thread that truck alternators are not designed to spin past 6k so that could definitely be an issue. 5.3 and 6.0 trucks had a factory redline around 5200 rpm. This is the range that ALL the accessories were designed around, so spinning 1000+ rpms past this, it is definitely possible power is dropping due to this. I know for a fact this is true with AC compressors. We saw this pretty commonly in 6 speed cars but not in vettes, apparently a better design kept it from being a common issue in vettes. Just because an engine is overbuilt enough to mechanically handle a higher redline, doesn't mean the accessories are.
2 additional key items I have not seen addressed:
1. If only one of the 255lph pumps is on, that could be causing this. The power level he is making is at/just past the capacity of the 255 pump, assuming it has full current available. It was recommended early on to use and tune for both pumps.
If he is using both pumps, this will be a significant extra draw on the charging system - it was designed for 1 pump and they are hogs.
2. He should put a mechanical FP gauge on the car at the rail and run the thing again to verify he is getting enough fuel on the top end.

 

im down to replace the alt.....which one should i get along with the big 3

 

Why is there a torque dip at 4,000 rpm?

 

basically all 427 builds have some dip there as far as ive seen

 

Had a similar problem, it was a couple month old alternator and it would stop charging after 5000 rpm, putting in a new one solved the problem . This was a truck alternator . Lucky I didn't blow my engine up , I'm running my fuel pump right to its flow limit and once the voltage dropped to 11volts the AFRs spiked to 14:1 and this was at 14lbs of boost lol .

 

Power master XS

 

I run Powermasters and love them. If it ever *****, you send it back to them and they fix for the cost of parts only. Solid American piece. You could go Mechman but that's probably overkill($$) unless you are also running a kilowatt+ sound system. You probably need a new battery too. I replace mine at 3 years because this Texas heat kills them. I just replaced 2 in my truck (dual setup) that were 4 years old and it fixed a driveability issue I was having. Your charging issues didn't do it any favors either, it's really common for a bad/weak battery to kill an alt, and vice versa can happen too. I like the Everstart Maxx from Communistmart, to get any better you have to spend double - like DieHard Platinum. An alt, the Big 3, and a new battery - you're around 500-600 in parts. You will be shocked at the difference and I am betting will fix, or at least improve your situation. I'd still pop the second pump on, you are at the limit of a single 255 that is getting enough current.

 

none of the aftermarket ones say anything about rpm limits......

 

They range from 16,000-20,000 rpm. Since your balancer is way bigger than alternator pulley a lot of time the ratio is 3 to 1 so 6,000 motor is 18,000 alternator. Check your pulley sizes. I think the mechman is like 20,000 rpm. A lot of times the higher amp ones use a small pulley to get amps up but you got to watch it on the top end.

 

Jmilz29,
your responses are very educational. I would of never consider a truck alt could cause issues like that

thanks,
Jim

 

keep in mind tho, my tuner said on a car the truck alt can function at rpms higher than 6000 rpms since the car alt is 1 inch smaller.......still no updates yet

 

so i installed a new battery, no change.
added a new 1/0 positive alt to bat
added a new 1/0 alt ground to frame
added a new 1/0 battery ground to frame
all no change


got a mechman 250 with larger pulley and......

 

So the alternator was weak, thanks for the follow up - where's the new numbers?