I was wondering if there are any light weight alternator options out there that would work with our cars. I'm not talking about brackets but the alternator itself. I know some people switch to another one when supercharging but that's because of directional change I think.
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Alternator options
- Thread starter Stephen@NCAutoUSA
- Start date
Hey Stephen, i have a custom billet light weight bracket and smaller alternator.
supposedly its the only one in existence, was made in Australia.
bracket saves 9.5lbs plus alternator saves 4lbs
total 13.5lbs saved
<a href="http://s172.photobucket.com/user/tiago3/media/20151015_174650.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/20151015_174650.jpg" border="0" alt=" photo 20151015_174650.jpg"/></a>
all stuff it replaces
<a href="http://s172.photobucket.com/user/tiago3/media/Mobile%20Uploads/bacc7423-22a4-4acf-ba5d-6f1c2cf15b16.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/Mobile%20Uploads/bacc7423-22a4-4acf-ba5d-6f1c2cf15b16.jpg" border="0" alt=" photo bacc7423-22a4-4acf-ba5d-6f1c2cf15b16.jpg"/></a>
original installed you can see how large it is
<a href="http://s172.photobucket.com/user/tiago3/media/Mobile%20Uploads/20160121_202535.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/Mobile%20Uploads/20160121_202535.jpg" border="0" alt=" photo 20160121_202535.jpg"/></a>
smaller alternator and lighter bracket, you can see how tiny it is
<a href="http://s172.photobucket.com/user/tiago3/media/58820a3e-3f5f-407b-9e0a-6b6e4896c48f.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/58820a3e-3f5f-407b-9e0a-6b6e4896c48f.jpg" border="0" alt=" photo 58820a3e-3f5f-407b-9e0a-6b6e4896c48f.jpg"/></a>
supposedly its the only one in existence, was made in Australia.
bracket saves 9.5lbs plus alternator saves 4lbs
total 13.5lbs saved
<a href="http://s172.photobucket.com/user/tiago3/media/20151015_174650.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/20151015_174650.jpg" border="0" alt=" photo 20151015_174650.jpg"/></a>
all stuff it replaces
<a href="http://s172.photobucket.com/user/tiago3/media/Mobile%20Uploads/bacc7423-22a4-4acf-ba5d-6f1c2cf15b16.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/Mobile%20Uploads/bacc7423-22a4-4acf-ba5d-6f1c2cf15b16.jpg" border="0" alt=" photo bacc7423-22a4-4acf-ba5d-6f1c2cf15b16.jpg"/></a>
original installed you can see how large it is
<a href="http://s172.photobucket.com/user/tiago3/media/Mobile%20Uploads/20160121_202535.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/Mobile%20Uploads/20160121_202535.jpg" border="0" alt=" photo 20160121_202535.jpg"/></a>
smaller alternator and lighter bracket, you can see how tiny it is
<a href="http://s172.photobucket.com/user/tiago3/media/58820a3e-3f5f-407b-9e0a-6b6e4896c48f.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/58820a3e-3f5f-407b-9e0a-6b6e4896c48f.jpg" border="0" alt=" photo 58820a3e-3f5f-407b-9e0a-6b6e4896c48f.jpg"/></a>
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Which alternator is that?
But I was browsing around last night and came across these. There's one that only weights 6 lbs and produced enough amps for the Nsx I believe. Anyone have some insite? It says single wire hook up and I believe the pulley would need to be changed to fit our cars and the direction would need to be the same as well. But am I missing other concerns?
Does anyone know how much a stock alternator weights? I think I came across online where someone mentioned 15lbs but you know how that goes sometimes.
http://www.ecae.com/alt1.html
Never mind. I misread the ultra mini vs the super mini options on that site... The ultra that's 6lbs only goes up to 55amps which is half what's needed for our cars... I'm going to call Tuesday when they reopen and see if it's possible to make one that's higher amps for our cars that's 6 lbs.
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Hi Patricio!
Do you have any issues using the small alternator? How many Amps is your lightweight alternator?
I've been looking into this also...
I think CT uses a 80 Amp alternator with their SC package (that rotates the oposite direction of OEM because of the alternator relocation) so maybe a 80 or 90 amps light weight altertanoter could work...
I contacted spoon in the past to see what light weight alternator they used when building the spoon NSX-R - See it here (posts 760, 761 and 763):
http://www.nsxprime.com/forum/showthread.php/78963-Unofficial-weight-reduction-thread/page31?p=1861848&viewfull=1#post1861848
i really like the idea of a light weight alternator as this is rotational weight and for each spin of the crank you will have at least doulbe that on the alternator!
I think a 90 Amp Honda Accord 2.7 V6 Alternator (31100-P0G-A02 or 31100-P0G-A03 - Denso 210-4124) could work but this would save only 2~3 lbs
Really interestd on your research Stephen! 6 lbs would be great!!!
Yeah hopefully others will chime in too who have been down this road. Does anyone know how heavy the oem one weights? I think from my memory it was pretty heavy
hey Stephen,
OEM alternator is 13 lbs 8 oz
i need to look into what alternator Im using. its early 90's honda
<a href="http://s172.photobucket.com/user/tiago3/media/Mobile%20Uploads/1ae86fd3-ecfd-41cc-85e0-7505af51fcf8.jpg.html" target="_blank"><img src="http://i172.photobucket.com/albums/w15/tiago3/Mobile%20Uploads/1ae86fd3-ecfd-41cc-85e0-7505af51fcf8.jpg" border="0" alt=" photo 1ae86fd3-ecfd-41cc-85e0-7505af51fcf8.jpg"/></a>
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What type of voltage does the Nsx alternator put out? I found one that's 7lbs and puts out 14.5-14.9 volts and is 80amps. I'm going to continue looking.
I sold Patricio that alternator.. according to my notes it's:
Nippondenso # 100211-3660
BTW what is your car weighing in at these days?
That is an 88-91 CIVIC/CRX 60 Amp Alternator! Have you tried it before selling to patricio? Did it work trouble free on the NSX with just 60 A? 
hey hows it going?
prym8, that alternator did not work it was not compatible because its prior to obd1, i had to get a different one.
BBVNSX, I believe the one that I has been working on my car for almost 1 year now is a 92+ civic alternator. quite a few known local nsxprime members have driven the car. it is working and holding around 13.5 volts.
car was around 2440lbs before turbo install, now its around 2490-2500, I have not re-weighed but did weigh / calculate most parts during install. ill have it corner balanced soon once I'm done with some additional modifications.
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I think this is a very promising option. It can be made for 100amp applications and weights 2.35kg without the pulley installed. I'm not sure how much a billet aluminum pulley weights but I can guess not much depending on size.
Looking at the rpms of the alternator you have a max speed of 18,000 rpm. Taking the 7 inch crankshaft pulley and using the formula of crankshaft pulley size divided by potential alternator pulley size and then multiplying that by the engine rpm equals the rpm of the alternator. If the Nsx engine is a 7 inch crankshaft pulley then it would be safe to say a 3.5 inch pulley on that alternator would work? That would put the alternator rpm at 16,000 at engine speed of 8,000 which is within the alternators range.
Coupling this alternator with a lightweight bracket can save 20lbs.
http://www.brise.co.uk/Brise-50A-Motorsport-Alternator-4Si-50.html
Looking at the rpms of the alternator you have a max speed of 18,000 rpm. Taking the 7 inch crankshaft pulley and using the formula of crankshaft pulley size divided by potential alternator pulley size and then multiplying that by the engine rpm equals the rpm of the alternator. If the Nsx engine is a 7 inch crankshaft pulley then it would be safe to say a 3.5 inch pulley on that alternator would work? That would put the alternator rpm at 16,000 at engine speed of 8,000 which is within the alternators range.
Coupling this alternator with a lightweight bracket can save 20lbs.
http://www.brise.co.uk/Brise-50A-Motorsport-Alternator-4Si-50.html
nice find now where is Foundry3 at with that bracket
Thanks! I haven't talked with Chris yet. I know he's busy with his oem alternator one and testing it. I want to make sure I consider everything for an alternator replacement before buying one seeing if someone can fabricate a bracket first.
I emailed Brise about the possibility of using their alternator on the bracket we are testing. I think it's a great suggestion and would save a lot more weight. The Brise alternator in conjunction with our bracket would save nearly 20lbs.
it would make the perfect combo for track guys, hurry up :smile:
Those are great news!!! And i assume that a billet aluminum pulley would be an easy task for you! :wink:
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Hopefully they give good news!
Just wanted to update this thread, I am having conversations with Brise about a viable option. The racing alternator from them does not output much amperage at low engine speeds which is how they are able to be made so light. For a racecar this is not a problem, however, for a road going car, I'd imagine it would be a big problem. I'll keep you updated.
To answer your original question, the B series alternators will fit our cars with a longer tensioning through bolt and an aluminum spacer, which happens to be 5lbs lighter than OEM and can be had in 95 amp configurations IIRC.
That's not bad. I bet an aluminum pulley can be made for the spacer too.
Did you ask about pulley size options since the amount of amps put out are determined by the rpm they spin at right? Depending on their charts and since nobody knows what the oem one outputs for that fact at rpms it's hard to say. Pulley size could drastically make or break this. Am I right or wrong in this? I don't know much about alternators but just what I've been reading.
I did ask about pulley size and they can match our size for easy fitment.
From my limited understanding of alternator output, pulley size is relational to the internal capacity and ability to stay within optimal operating temperature. Also from my limited understand on alternators there is a threshold where a normal street driven car will function without an issue of electrical shortage that is below most OEM alternators at RPM's above 2k (assuming OEM pulley size). Alternator swaps are very common in the Honda community due to the many variations of Honda engine to chassis fitments.
Short of getting a firm to test our alternators and other viable replacement options we can't know without testing.
I think the DENSO 2100203 which I believe is what is in the NSX is listed as a 120 amp alternator.
You can make an alternator smaller in size; but, in general you will have to spin it faster in order to maintain an acceptable output voltage (13.4 V or higher) when the current output is the same as a physically larger alternator. That is why most of the smaller alternators that I have seen have a higher operating RPM requiring a smaller diameter pulley. You may find that with any 'practical' diameter pulley, the small alternator is operating below its design RPM at idle speeds meaning that the alternator will not be able to deliver rated current or, in a worst case, anything close to rated current when the engine is idling. This will result in loading of the battery and the operating voltage in the car dropping to 12 volts or lower. Protracted driving in stop and go traffic could be interesting. Air conditioner operation under those conditions would probably be a no-go. You may be able to get a pulley arrangement that spins the alternator fast enough to deliver 'enough' output at idle. But, with the NSX's 8000 RPM redline, you may end up torching the alternator if you make frequent journeys to the red line.
Race cars do just fine with tiny alternators and batteries because words like AC, power windows and idling in traffic do not enter the lexicon.
For reference, my recollection is that the large heavy duty Bosch alternators on trucks have a design maximum alternator speed of 12,000 RPM (alternator speed - not engine speed). I also remember seeing a rating curve for Delco alternators which went from 1200 - 8000 RPM (alternator speed). That does not mean that the RPM limit was 8000, that is just where the curve ended. If the NSX's 8000 RPM red line puts your alternator speed above 12,000 RPM, you may be running in an alternator unfriendly zone. You would need to check max alternator speed with the alternator vendor. What was interesting about the Delco rating curve was that the alternator only delivers 80% of its rated output at 3000 RPM (and less at lower RPMs). For any reduced size alternator that you are going to consider, ask the vendor for an output versus RPM curve. A 200 amp alternator that needs to be spinning at 8000 RPM to deliver 200 amps is not the same as a 200 amp alternator that can deliver 200 amps a 4000 RPM.
Alternators are a mature technology. There is no magic in how to squeeze down the size, it just comes with a trade-off in terms of reliability, effective performance and cost.
Edit:
It occurs to me that if you have EPS, the EPS may be a much bigger issue for an NSX with a reduced size alternator than the air conditioning. The EPS system is a bit of a current pig (in assist mode) and seems to have a reputation for voltage sensitivity. Peak load on the EPS is likely to occur at low engine speeds during parking maneuvers / getting out of the garage / whatever and if the alternator cannot maintain adequate voltage during those operating conditions, the EPS may generate an error condition.
You can make an alternator smaller in size; but, in general you will have to spin it faster in order to maintain an acceptable output voltage (13.4 V or higher) when the current output is the same as a physically larger alternator. That is why most of the smaller alternators that I have seen have a higher operating RPM requiring a smaller diameter pulley. You may find that with any 'practical' diameter pulley, the small alternator is operating below its design RPM at idle speeds meaning that the alternator will not be able to deliver rated current or, in a worst case, anything close to rated current when the engine is idling. This will result in loading of the battery and the operating voltage in the car dropping to 12 volts or lower. Protracted driving in stop and go traffic could be interesting. Air conditioner operation under those conditions would probably be a no-go. You may be able to get a pulley arrangement that spins the alternator fast enough to deliver 'enough' output at idle. But, with the NSX's 8000 RPM redline, you may end up torching the alternator if you make frequent journeys to the red line.
Race cars do just fine with tiny alternators and batteries because words like AC, power windows and idling in traffic do not enter the lexicon.
For reference, my recollection is that the large heavy duty Bosch alternators on trucks have a design maximum alternator speed of 12,000 RPM (alternator speed - not engine speed). I also remember seeing a rating curve for Delco alternators which went from 1200 - 8000 RPM (alternator speed). That does not mean that the RPM limit was 8000, that is just where the curve ended. If the NSX's 8000 RPM red line puts your alternator speed above 12,000 RPM, you may be running in an alternator unfriendly zone. You would need to check max alternator speed with the alternator vendor. What was interesting about the Delco rating curve was that the alternator only delivers 80% of its rated output at 3000 RPM (and less at lower RPMs). For any reduced size alternator that you are going to consider, ask the vendor for an output versus RPM curve. A 200 amp alternator that needs to be spinning at 8000 RPM to deliver 200 amps is not the same as a 200 amp alternator that can deliver 200 amps a 4000 RPM.
Alternators are a mature technology. There is no magic in how to squeeze down the size, it just comes with a trade-off in terms of reliability, effective performance and cost.
Edit:
It occurs to me that if you have EPS, the EPS may be a much bigger issue for an NSX with a reduced size alternator than the air conditioning. The EPS system is a bit of a current pig (in assist mode) and seems to have a reputation for voltage sensitivity. Peak load on the EPS is likely to occur at low engine speeds during parking maneuvers / getting out of the garage / whatever and if the alternator cannot maintain adequate voltage during those operating conditions, the EPS may generate an error condition.
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I think it's safe to say a swap to another Honda alternator is the safest although there's no proven data foundry has said they've been doing it for years. The alternator bracket should fit all B series alternators I believe and they weight 8 lbs with their heavy pulley. They need some type of spacer but we could potentially lose more weight with a lightweight pulley with the new spacer machined into the design.
I'm still all for the brise, however don't want my car stranded. It's hard to say though what can be replaced with what without the test of the oem one. It's not like you can visually see or feel it working if it's similar, we have no idea what the oem makes. Brise has a graph which is very helpful.
If you have or can arrange to borrow a clamp-on DC current probe, you could measure the output of the OEM Denso alternator at idle. Do this with the air conditioning running, stereo on, headlights on (and crank the EPS if you have EPS). That will give you an idea of the likely worst case steady operating condition for the alternator (high loads and low alternator speed). If the output curve for the reduced size alternator indicates that it can deliver that amount of current at engine idle speed (after calculating the correct alternator speed) then you are probably good-to-go. Everything gets better as engine speed increases as long as the alternators maximum speed is consistent with the NSX's 8000 RPM red line.
