70 AMP Alternator.... enough power???

[mkassab]

As many of you know, I have a build tread going for my '35 truck (link in my signature below). I'm in my planning stage and buying what I can before the FF kit is delivered.

I'll have a series of these "Specific Question" treads so to keep topics separate.

This Thread is regarding the Honda 70 Amp alternator specified by FF, i.e, Autozone, i.e., 2001-03 Honda Civic DX 1.7L MFI SOHC Alternator – 12308

Since my build is for a daily driver with all the bells and whistles, I'm a bit concerned that a 70 amp alternator will be straining to keep up with the current draw. I'm fully aware that every electrical item won't all be on at the same time.... but under "normal" driving, it could easily have the following running at the same time, e.g., engine, coolant fans, radio/amp, windshield wiper, lights (headlights, tail lights, dash lights), A/C or Heat with blower fan and compressor, etc. A lot of newer auto have at least 100 to 200 amp alternators.

Does anyone have opinions, good or bad experiences and / or suggestions they can share? I don't think there are too many options except some "cheap off brand" China made alternators out there?

Thx Mark

[TxMike64]

Don't forget EFI ECU, TCU, and Fuel Pump. 70A seems a little on the low side. Battery choice will affect this as well. The PC925 battery they spec doesn't have a lot of reserve either. I would start by adding up your amp draws, then see where you are. But it sounds like you would probably want a minimum 100A and consider using a larger battery.

The horsepower draw from a 120A alternator is not significantly different than a 60A unit. I'm not up to speed on Coyote engines so not much help there.

[Bob Cowan]

You can decrease your amp draw by replacing all your lights with LED's.

One of the problems is that the factory Coyote alternator is rather large. I wonder if FFR recommends that alternator because of it's size?

In any case, there are a few companies that can rebuild alternators for greater output. Here's an option: https://www.amazon.com/HIGH-OUTPUT-ALTERNATOR-2001-2005-CIVIC/dp/B00AY28QYG

[edwardb]

...I'm not up to speed on Coyote engines so not much help there.


...One of the problems is that the factory Coyote alternator is rather large. I wonder if FFR recommends that alternator because of it's size?

Due to the size of the Coyote, and the narrow front frame of the hot rod and truck, the Coyote alternator won't fit in the stock location. Factory Five's solution is a Honda alternator mounted inboard and reversed using brackets that they've designed. Haven't personally done it, but have seen it on multiple builds. Perhaps there's a larger model of the Honda alternator that would fit? 70 amps does seem a little light for a fully featured build. But as suggested, do the math and all LED's certainly helps. Fortunately, the truck comes with LED headlights and tail lights. So off to a good start. The stock battery location is somewhat small and just fits the recommended PC925 battery. A mod or different location will be required to go bigger. FWIW, I have the same PC925 battery in my Gen 3 Coyote powered Coupe. Heat, A/C, wipers, cooling fan, 255 lph fuel pump, all LED lighting, etc. It's worked fine for three driving seasons.

[mkassab]

So... update. Honda alternators basically come in 70 Amps size and must run counter clockwise (CCW). I did fine one rated for 80 AMP....

Then, I discovered this alternator to be a direct replacement for the Honda alternator that is CCW and rated for 160 AMPs. I just received it yesterday. It came with all the test data sheets showing the volts and amps by RPM. The alternator spins around 3 to 4 times more RPMs than the engine RPM due to its smaller pulley.

I bought this alternator from Alterstart Systems, Inc. out of Dallas, TX https://www.ebay.com/itm/202482284648

Mark


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