What's the stock RMS and peak load for the 20B alternator? Thanks.

 

the fd is about 130 so the 20b is probably at least that if not more. evil aviator is the only one who actually tested his though, he might have an actual ##

mike
1959 tr3a

 

Yes, I took it to the alternator shop, but I just wanted to know if it worked. To tell you the truth, I could care less about that info. The test was free, so I would imagine that a nearby shop could do the same for you.

 

FD is 100 A.

 

I'll be most likely replacing it with a low to mid 200 amp alt. then since 100 will not nearly be enough for my application but I was just wondering if it would be to get me by for the time being. If the FD is 100A than I would suspect that the 20B should be the same if not a little more because of the excessive electronics the JC had. Thanks everyone.

 

Good call on that one. The JC had a TON of electronics onboard... I should take a picture of all of the wiring harnesses and vacuum **** that I pulled off of my engine... its amazing

Anyhow, the 20b Alternator will get you by... especially if you aren't going to be running a stereo and **** when you step on it

Are you going to be running a T76 right off the bat, or is that a mod that is soon coming?

 

Right off the bat InitialD FC made the manifold for me and I should have the turbo within a week.

And...I found out from Paul Ko over at K2RD that both Cosmo motors are 90 A according to the manual. There's a local guy for me who made a large alternator for another customer at the shop I'm at which was 160 A continuous and 190A peak. Sounds good to me since I most likely will be playing the stereo loud when I'm stomping on it...at least after the initial buzz of listening to the motor wears off The amps alone are peaking at 180 A...don't want to throw them into clipping and blow something like the computer on accident from a feedback and/or ground loop

On another note...
Kurgan...you going to send me that intake elbow soon?

 

I know a few people who have used Powermaster GM alternators on both FC and FD motors without much work.

 

Thanks 13B...that's what I was initially looking at in the Summit catalog. There's a 200A version for $389 so my guy better come in at least 20-30% cheaper since it's a home-grown. When I get pricing I'll post it on here to help others out.

 

Definitely let us know.

 

Give us details!
I've been staring at those things (140A for $180 is good enough for me) for the past few years now.&nbsp I think my alternator finally gave up the ghost on me, so I might just try this conversion real soon!


-Ted

 

You just have to get the one with the mounting ears in the same position as your alternator. It bolts in pretty easily. My friend did it on an FD motor, and another guy I know did it on a TII motor. I forget which one required modifying the pulley, but it was probably the FC. The wiring was pretty simple.

I'll check with my friend to find out exactly what he did. It was 4 months ago. so I can't remember too well.

 

Yup, 90A just went out to the garage and checked. There is a sticker on the side of the alt that has the info.

 

What I'm worried about is the shaft diameter...
I don't care about mounting points, as I can redo the entire mounting system I need to.&nbsp I can measure the pulley offset from the stock set-up.&nbsp Most of the alternators are one-wire, so wiring is super easy.&nbsp I do run a Racing Beat double-pulley, and having it bored is precision work; yeah, I know, it's relatively minor, but I wanna keep this a "backyard conversion" - I'll be doing a write-up on it on my web page with details, so the less sub-let work for the conversion, the better it is for the readers.

I'd appreciate any details you can find, especially on the shaft diameter!


-Ted

 

Man if your drawing that much amperage you need at least one battery if not two. And if you moutn them inside the car you DO NOT want a standard battery. You will need and Excide or an Optima battery. A standard battery releases toxic fumes as they charge and should never be placed in the cabin with you.

 

Thanks for the interest in safety (I'm a safety engineer) but I run a single yellow top Optima for just that reason.

And not to rip on you or anything but...it's vapors, not fumes that are given off by a standard lead-acid battery. An example of a fume is what the smoke is that's given off by welding. Vapors are liquids that changed physical states to become a gas.

You don't need two batteries unless you're sitting in a parking lot like an idiot with extremely obnoxious bass and the alternator is running at a low output level and therefore the battery(s) have to take up the slack load, or with the car off. Normal driving/RPM's should keep your working amps high enough to drive your system for most listening levels and if your not driving the amps hard. I.E., I will not be dropping bass.

Keep in mind that the 180A is just the total of the three amps (60A fuses in each). You should never go above 80% capacity on an electrical system anyhow but it's always better to have more room in case of a surge. So even at (.80*180)=144 A, plus the rest of the vehicles on-board systems which might be at worst case, another 40A, you're still looking at 184 for worst case RMS demand load and 220A for peak...assuming we have everything on at once, and at full output...not likely.

 

Another side note...
You shouldn't even get close to RMS.
We usually estimate steady state current load average at half your RMS current numbers.&nbsp Unless you're crazy enough to listen to full sine waves, the amps produce more transient peaks rather than high level steady current draw.&nbsp Don't let your (sub) amps run full sine waves for too long - things break when you do this for over 10 minutes.


-Ted

 

I forgot to call my friend, but I'm pretty sure that he was able to put the FD alternator pulley right onto the Powermaster alternator. That would mean that you'll have to bore out the RB pulley. I may be needing a new alternator too. So I'll be trying it out. At first I thought something was wrong with my fuel pressure regulator because it was lower than normal, but I think I'm not getting enough of a charge to keep my fuel pump happy.

 

RETed...so you've been experimenting with full powered low frequency sine waves? You're not sitting on the trunk hatch and smiling are you?

Couldn't remember my terminology but yes, transient was the term I was referring to. It's most likely I'll be drawing a 40-50% load at the max. so if I go with the 160A constant that should more than enough to keep everything supplied and not even worry about it.

 

More than likely 90A to 100A output.

B

 

We did some pretty crazy stuff just for the sake of "experimentation". I was messing with an set-up with two isobaric pairs of 8" JL Audio "Pros" back in the day.&nbsp It was loading a PPI 2150AM amp down to 2-ohm stereo.&nbsp Just for kicks, we ran 20Hz to 80Hz sine waves through that just to tune the crossover frequency.&nbsp I also wanted to see if I could trip the amp protection circuitry - it did in 10 minutes. The amp got stupid hot super fast!&nbsp It had no fan cooling, so it was purely convection cooled, and it had never tripped before, even with massive bass music in 90&#176F+ heat during Hawaii summers.&nbsp I knew the sine waves were the biggest input loads the system could handle, so I just wanted to try.&nbsp Oh yeah, I managed to tear all four spiders on those speakers.


-Ted

 

The only time I got the chance to play with an oscilloscope was college in physics. I tried to convince the prof to let me borrow it to tune my system but he was concerned with liability for some reason

That's very interesting that you tripped out the fault protection that quick, but that seems very reasonable given what you were forcing it to power under that load. There's not a lot of amps out there that can handle a stable 2 ohm load for long under normal circumstances, goes to the testament of that manufacturer.

Here's something to stay on topic... What are the loads that some of the equipment draws in the FC such as:
Blower fan (on, and max.)
AC
Headlights/Taillights
Wipers

 

well you can get some idea from looking at the fuses. notice the defroster has a big fuse. so do the power windows.

mike

 

OMG...sorry, I had a senior moment and totally forgot about that. However, the fuses are there to indicate when the circuit will trip and has exceeded it's maximum capacity, not RMS and/or normal current load draw which I am also interested in.

I've got to make a spreadsheet with all this information on it for quick reference sometime...

 

Ted: You didn't want to try a square wave!