main fuse with FD alternator
 

I have an extra FD alternator with a double FC pully that I am going to put on my TII. Since its 100A and not 80A like the factory one do I need to change the main fuse from 100A to a 120A like the FD uses?

Thanks

Subscribing to this thread!!!

I'm looking at doing the same alternator swap. Which pulley are you using? I found an Ebay pulley for FCs but made to fit on FD alternators.

http://cgi.ebay.com/ebaymotors/ws/eB...TQ:MOTORS:1123

I'm not too into the rotor on the end, but it's the only pulley I've seen that combines not being underdrive and doesn't need to be machined to fit an FD alternator.

I found this thread...at the end someone posts to put in a 100A fuse, don't know if that's helpful or not. But I found the information about the alternator post useful.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/just-installed-fd-alternator-keep-blowing-main-fuse-302628/

Found this one also.....

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/new-s6-alternator-upgrade-main-fuse-578886/https://www.rx7club.com/showthread.php?t=578886

I never changed my main fuse and haven't had any problems.

also never changed fuse it's been good for over two years now with fd alternator

You don't need to change the fuse.

That's bad advice. You shouldn't upgrade the MAIN fuse for the same reason you should upgrade any other fuse.

Upgrading the alternator does not suddenly increase the current flowing through the fuse. The electrical system will draw exactly as much current as it did before, you just have more spare capacity.

If you're upgrading the alternator to handle additional electrical devices like stereo gear or an e-fan, nothing like that should be running through the stock electrical system anyway. They should be fed from dedicated circuits run directly from the battery with their own fuses.

So like Aaron said, you don't need to change the fuse, and in fact you shouldn't. :)

The FD alternator has a max output of 100A just like the RX8 alternator, so I think a stock 100A fuse from an s5 would be fine.

Did you read my post? The alternator's output is irrelevant; the fuse shouldn't be changed.

Then why did the factory progressively upgrade the fuse rating? The only part of the car that varied significantly in amperage was the alternator. Each time the factory changed the alternator, they also changed the fuse. We change the alternator...what should we do? :scratch:

They also changed the wiring, which is what the fuse is there to protect. As I explained above, there is no need to change the fuse.

You are seriously continued to prepare debating the difference in whether or not to change a +10 amp, 5 dollar fuse, aren't you? :lol:

;)

I really don't care whether someone does it or not, and long as they don't claim you need to. That would be BS, and there are some of us who try to keep the technical sections BS-free. :)

I would agree that you dont need to, but I would say that you dont need to do the alt conversion to begin with...so if we went around refusing to discuss things that we dont need to do, we would all be driving bone stock 20 year old cars, and it would be kind of boring, dont you think?

If someone need the extra amps, (car audio, Efan, whatever reason they need more power) then they will need the alt upgrade. You are arguing just to argue.

I don't think it would be too good of an idea to raise your fuse in almost any circumstance. It would just give greater tolerance if something did go wrong (a ground out or something).

Bollocks, plenty of people need to upgrade there alternator because they've added high-current electrical equipment to their car. If you haven't done that then an alternator upgrade is pointless.

Dude, we're talking about a fuse. That may be an exciting upgrade to you, but I doubt many would think that way. :rlaugh:

I'd just like to say that I did not in fact fling the first poo, I simply provided links to threads with related topics, which I did not in fact endorse or deny. I plead the 5th!!!

I'll be hiding behind the couch with Lysol....
May the force be with you!!!

That's a really, really, really ignorant thing to say...

Are you trying to imply the FD3S has the EXACT same current draw as the FC3S?
Think about it...
One obvious point is that the FD doesn't have a mechanical fan, and it runs twin electrical fans; there's your 10A+ current draw right there.

This is not a question about upgrading...

Unless you change the CURRENT DRAW through the stock electrical wiring on the FC, why would you need to change the fuse?
Do you change fuses cause you run bigger batteries???


-Ted

Replacing the 80 Amp fuse with a 100 Amp fuse will allow 100 Amps to pass through an 80 Amp circuit in the event of a short. This means that the circuit and components will be damaged before the fuse breaks to protect it. So your logic defeats the whole purpose of a fuse :wallbash:

It doesn't matter what the power supply is capable of producing, you have to look at the rating for the circuit drawing power. You can hook the car up to a nuclear power plant producing gigawatts of power and still protect it with an 80A fuse because the car is still only pulling 80 amps. All the rest of the shit you add to the car like an electric fan, aftermarket stereo, etc... has its own fuse and is not usually connected to the main engine fuse circuit so it does not increase the draw beyond 80amp. These things will usually be attached directly to the battery since they have their own fuse to protect them.

Geez guys I did not know it would cause such a big deal. :-) My car has the 100A main fuse since its 91 RHD TII and I just wanted to ask if it is better to change it. I have no electrical problems with the car and now that i think about it it is not such a good idea to change the main fuse. I am running a mechanical fan (which I think nothing cools better than it) but I was thinking of putting an electrical fan (Flexalite FLX 180) which draws 18amp just for clearing out my engine bay. I am using a Ron Davis Racing radiator which is almost 70mm thick. I will put the FD alternator in only if I switch to an electrical fan.

Thanks

Zenki FC's run an 80A fuse.
Kouki FC's run a 100A fuse.
I think the FD's run a 120A fuse?

Doesn't matter...it's still down to current draw.


-Ted

in short Do NOT change the fuse, the WIRES are rated at 80 AMP so if you allow 100A to run through them they will melt and will catch on fire and you will not have a car...
the wires may handle 100a but its doubtful they are old and frail to begin with, so just be safe and don't tempt fate.

edit: just looked at the amps you are running again, it really doesn't matter what you have you should never up the amps of a fuse, the wires are rated at just over that fuse, so that if it say spikes to 105amps the fuse will blow, but the current still spikes in the wires, so they can handle higher than rated fuse, but not for long periods of time,

What I have learned in my short history with forums is that you can post saying the sky is blue and asshattery will start with someone saying it's not blue, it's azure. Often times degrading to comments such as "You wouldn't know blue if your own balls slapped you in the face!"

With that said, I agree that changing the fuse from the factory rating is not a good idea.

BTW I ordered a dual belt pulley last night

http://www.rotaryinnovation.com/new_products1.htm

I haven't gotten an FD alternator yet and am more concerned with having no air pump with a single belt alternator pulley. On the hottest day of the summer I sheared off my alternator pulley on the highway, before I realized what had happened I blew the top off my radiator. Luckily, there was no damage to the engine and I ended up getting a nice Koyo.

Learning is such an expensive road....

At 100A, the stock wiring will be fine as long as it's in good shape. Even in poor condition, it won't melt and cause a fire at 100A if it didn't at 80A. And keep in mind that if you are drawing a continuous 100A, the FD alternator is probably not a good choice anyway.

That's not how a fuse works. First, fuses have a tolerance like any other electrical component. 105A will run through a 100A fuse practically forever, as will 110A and probably 115A. Above a certain value, the fuse will blow after time. At 120A it may take 3 or 4 hours for the fuse to pop. 150A will pop it in a few minutes, 200A should blow it in under a minute, etc.

Even if you did that, there'd be no need to touch the stock MAIN fuse because the fan would be powered directly from the battery via its own fuse. The current through the MAIN fuse wouldn't change. :)