28SI Alternator vs 27SI

M

mark sawyer

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Aug 20, 2015
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So I'm working on a project to increase the capacity on the factory alternator above 100 amps, and I came across this page on the Delco Remy website
which I believe says the 27SI was superseded by the 28SI.

http://www.delcoremy.com/find-a-part/product-details/27si-alternator

The dimensions of the 28SI seems roughly the same as the 27SI, and they both seem to use the same "J180" mounting style. The 28SI seems to be used a
lot on heavy duty trucks, school buses, etc. and is offered in factory amperages of 130-200 which slots in nicely above the 27SI.

I have an email inquiry in to Delco Remy to see if they can confirm this information, but wanted to check here to see if anyone may already be running
a 28SI.

Looking online, it appears you can find aftermarket 200amp 28SIs for a little over 100 bucks... And Genuine Delco Remys for a little over 200 bucks.

Either way, I will post back here with what I find.
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
> So I'm working on a project to increase the capacity on the factory alternator above 100 amps, and I came across this page on the Delco Remy
> website which I believe says the 27SI was superseded by the 28SI.
> http://www.delcoremy.com/find-a-part/product-details/27si-alternator
> The dimensions of the 28SI seems roughly the same as the 27SI, and they both seem to use the same "J180" mounting style. The 28SI seems to be
> used a lot on heavy duty trucks, school buses, etc. and is offered in factory amperages of 130-200 which slots in nicely above the 27SI.
> I have an email inquiry in to Delco Remy to see if they can confirm this information, but wanted to check here to see if anyone may already be
> running a 28SI.
> Looking online, it appears you can find aftermarket 200amp 28SIs for a little over 100 bucks... And Genuine Delco Remys for a little over 200
> bucks.
> Either way, I will post back here with what I find.

Mark,

What do you hope to get with a larger alternator? Even if the house bank has been relocated to the rear and you ran a pair of welding cables to it,
It will still take about 5 or 6 hours to recover a 4D or pair of GC2s from 50%SOC to 95%. Another issue I will caution you about is that the 28SI is a
much larger frame than the 27SI, so be sure to collect the real dimensions before you go too far.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
> > So I'm working on a project to increase the capacity on the factory alternator above 100 amps, and I came across this page on the Delco Remy
> > website which I believe says the 27SI was superseded by the 28SI.
> > http://www.delcoremy.com/find-a-part/product-details/27si-alternator
> > The dimensions of the 28SI seems roughly the same as the 27SI, and they both seem to use the same "J180" mounting style. The 28SI seems to be
> > used a lot on heavy duty trucks, school buses, etc. and is offered in factory amperages of 130-200 which slots in nicely above the 27SI.
> > I have an email inquiry in to Delco Remy to see if they can confirm this information, but wanted to check here to see if anyone may already be
> > running a 28SI.
> > Looking online, it appears you can find aftermarket 200amp 28SIs for a little over 100 bucks... And Genuine Delco Remys for a little over 200
> > bucks.
> > Either way, I will post back here with what I find.
>
> Mark,
>
> What do you hope to get with a larger alternator? Even if the house bank has been relocated to the rear and you ran a pair of welding cables to
> it, It will still take about 5 or 6 hours to recover a 4D or pair of GC2s from 50%SOC to 95%. Another issue I will caution you about is that the
> 28SI is a much larger frame than the 27SI, so be sure to collect the real dimensions before you go too far.
>
> Matt

Thanks Matt...

I took another look and you may be right, it may be too deep... But, I don't have heads on my coach right now, so just kind of guessing what kind of
clearance there is.

The 28SI has an internal fan instead of the external on the 27SI... That is part of the additional depth. But I still think there is a about 2
inches more depth front to back over the 27SI. The mounting holes and overall diameter look to be about the same if you go with the "J180 Short
Hinge" version.

The reason for the larger alt is to run an electric AC unit through my inverter without having to run the generator. The AC uses 6-700 watts plus
whatever is lost through the inverter. I can't find anything larger than a 100amp 27SI, which is what I have now... And that's sort of pushing it.
Especially if the dash ac fan is on, headlights, etc. I am not looking to charge up the banks so much as keep up with the running load if I add in
the electric AC....

I already have 2/0 cables feeding the batts and inverter..... I will need to update the cable from the alternator to the combiner though for sure.
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
The other option I was looking at is the CS-144... But in 200 amp form, those get pretty pricey... This rebuilder has some interesting vids on
youtube.... And those dual rectifier alternator conversions he offers look pretty impressive... And are pretty impressively priced...

https://alternatorparts.com/cs144-series-high-output-alternators.html

That's why I was looking at some of the medium and heavy duty truck alternators like the 28SI... I would think they would be as durable as those
upgraded CS144s. but at a better price....

--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
Mark,

While a dual foot version of a CS 144 with a dual sheave has promise, as I recall, the CS series requires inputs from the ECU. Best look into that.
This was the result of an emissions issue. The extra load of the alternator made the cold engines runt too rich to stay running.

There is also a supplier that I used before the depression (and the end of my shop) that can supply just some ama$ing hardware.

Look up and maybe even call . If I had spare money, I would have one of theirs and the correct regulator in my coach.

Another consideration.... Put the inverter close to the alternator. Less copper to buy and longer run of the 120V lines.

Next thought, refrigeration compressors do not need pure sine. Mine (about the same size runs just fine on a CCV 1500/750 from Hazard Fright and has
for years now. One burned out on us one day, so for less than 50$us I just stopped and bought another. This on, I paid for the protection and then
took the smoked one back, so now I carry a back-up that I have not needed in 8(IIRC) years. The reefer pump runs just a little hotter (~5°F on the
case) on the inverter than it does on shore power. It still makes ice real fast.

Matt

--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
There was an optional 145 amp alternator offered in 1978. Roger Black had one on his coach. I researched it one time about 15 years ago after seeing
it on Roger's engine when we swapped it out of a GMC transmode people mover.

Try finding a 1978 Z87 GMC Motorhome parts book. I have it in a .pdf file and it is 32.2 meg. Billy might all so have it on his bdub web site.

It is in section 7.02H with a part number of

7.02H GENERATOR—145 AMP DELCOTRON (1978)
1117148 GENERATOR-145 AMP (w/RPO L04)

It might be a one wire alternator. Check carefully before using.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
There are 2 re-manufactured ones on ebay right now

https://www.ebay.com/itm/1117148-Delco-Remy-Alternator-/174340221725

> There was an optional 145 amp alternator offered in 1978. Roger Black had one on his coach. I researched it one time about 15 years ago after
> seeing it on Roger's engine when we swapped it out of a GMC transmode people mover.
>
> Try finding a 1978 Z87 GMC Motorhome parts book. I have it in a .pdf file and it is 32.2 meg. Billy might all so have it on his bdub web site.
>
>
> It is in section 7.02H with a part number of
>
> 7.02H GENERATOR—145 AMP DELCOTRON (1978)
> 1117148 GENERATOR-145 AMP (w/RPO L04)
>
> It might be a one wire alternator. Check carefully before using.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
https://surplusman.com/item/delco-remy-alternator-pn-1117148/4003/Sent from=
my U.S.Cellular=C2=A9 Smartphone -------- Original message --------From=
: Ken Burton via Gmclist Date: 11/21/20 1:20 AM =
(GMT-06:00) To: gmclist Cc: Ken Burton =
Subject: Re: [GMCnet] 28SI Alternator vs 27SI There was an optional 145 amp=
alternator offered in 1978.=C2=A0 Roger Black had one on his coach.=C2=
=A0 I researched it one time about 15 years ago after seeingit on Roger's e=
ngine when we swapped it out of a GMC transmode people mover.=C2=A0 Try fin=
ding a 1978 Z87 GMC Motorhome parts book.=C2=A0 I have it in a .pdf file an=
d it is 32.2 meg.=C2=A0 Billy might all so have it on his bdub web site.=
=C2=A0=C2=A0 It is in section 7.02H with a part number of 7.02H GENERATOR=
=E2=80=94145 AMP DELCOTRON (1978)1117148 GENERATOR-145 AMP (w/RPO L04)It mi=
ght be a one wire alternator.=C2=A0 Check carefully before using.=C2=A0 -- =
Ken Burton - N9KB76 Palm BeachHebron, Indiana______________________________=
_________________GMCnet mailing listUnsubscribe or Change List Options:http=
://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
At least some of the CS144 are not ECM controlled. An example is 86-87 Turbo Regal. Those use the Volts light in dash aa does TZE. They were 120A and
up to 200A available aftermarket. They were for serpentine belt so pulley swap needed and rotation should be double checked but should be same as
pulley is grooved.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Ken,

That 145amp "DELCOTRON" is a beast.... It looks to be a "40SI"... Which if I'm reading the specs I see online correctly, goes up to like 375amps in
the largest versions.... As I mentioned, I do not have heads on my motor right now, but I can't imagine that alternator fitting in my engine bay....

Does anyone know if the 403 has a shorter deck height than the 455.... If it does, maybe that is why it is able to fit since you say it was offered
on a 78? A taller alternator bracket would position the alternator above the valve cover, which I could see working if the engine was a bit shorter
than what I see in my engine bay.

I'd love it if I was wrong, though... As using an OEM spec'd alternator would be the best option for sure...
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
I would weed them out by remote sensing first to shorten the list before form factor. If not you will be under Voltage chronically and batteries junk
in a year from sulfating.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
> I would weed them out by remote sensing first to shorten the list before form factor. If not you will be under Voltage chronically and batteries
> junk in a year from sulfating.

Thanks John. Will verify that for sure. I think a lot of these alternators are available with and without remote sensing... It's just a matter of
making sure you get the correct part number to have the configuration required. Since the 145 amp option on the 78 was offered from the factory, I
would assume it is a remote sensing alternator....

--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
Yes, the deck height on a 403 is about 1" shorter than a 455. Quite a bit
more clearance between the rocker covers and the bottom of the hatch cover.
Never measured it exactly though. Just know there is much more room for my
hands between them.
Jim Hupy
Salem, Oregon

On Mon, Nov 23, 2020, 8:35 AM Mark Sawyer via Gmclist <

> > I would weed them out by remote sensing first to shorten the list before
> form factor. If not you will be under Voltage chronically and batteries
> > junk in a year from sulfating.
>
> Thanks John. Will verify that for sure. I think a lot of these
> alternators are available with and without remote sensing... It's just a
> matter of
> making sure you get the correct part number to have the configuration
> required. Since the 145 amp option on the 78 was offered from the factory,
> I
> would assume it is a remote sensing alternator....
>
> --
> Mark S. '73 Painted Desert,
> Manny 1 Ton Front End,
> Howell Injection,
> Leigh Harrison 4bag and Rear Brakes,
> Fort Worth, TX
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
But remember that if you can't find a remote sensing alternator like you
want, adding a combiner will eliminate the voltage drop across the isolator.

Ken H.

On Mon, Nov 23, 2020 at 11:35 AM Mark Sawyer via Gmclist <

> > I would weed them out by remote sensing first to shorten the list before
> form factor. If not you will be under Voltage chronically and batteries
> > junk in a year from sulfating.
>
> Thanks John. Will verify that for sure. I think a lot of these
> alternators are available with and without remote sensing... It's just a
> matter of
> making sure you get the correct part number to have the configuration
> required. Since the 145 amp option on the 78 was offered from the factory,
> I
> would assume it is a remote sensing alternator....
>
> --
> Mark S. '73 Painted Desert,
> Manny 1 Ton Front End,
> Howell Injection,
> Leigh Harrison 4bag and Rear Brakes,
> Fort Worth, TX
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Matt,

I checked out Balmar Marine Alternators... And I agree... Super nice stuff. But, way out of my price range as well. Their 170 amp kit would
probably set you back close to $1k....

I may consider playing around with my alternator brackets to see if I can move the alt a little more to the left side, clear of the valve cover...
That would bring a whole bunch of less expensive options in to play.
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
> But remember that if you can't find a remote sensing alternator like you
> want, adding a combiner will eliminate the voltage drop across the isolator.On Mon, Nov 23, 2020 at 11:35 AM Mark Sawyer via Gmclist <

>

> [color
>
> Ken H.

Yes, but it will not compensate for the rest of the losses in the system. The fusible link is an example of only one of the voltage loss culprits.
IIRC the remote sense is connected to the terminal on either the horn or fan relay. Both of these are after the fusible link.

Yes a combiner will fix the isolator drop problem but not anything else
like cables losses at a 150 or so amps.

I think a installing a one wire alternator is looking for low voltage problems in several places on the coach.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
All true, Ken, which is why I worded the comment as I did. However, he's
indicated that he intends to replace the existing wiring with new, larger,
conductors. He seems knowledgeable enough to correct those other voltage
issues too. They're really not all that troublesome in a well maintained
system -- witness the many millions of one-wire alternators running today.

Ken H.

On Wed, Nov 25, 2020 at 3:36 AM Ken Burton via Gmclist <

> > But remember that if you can't find a remote sensing alternator like you
> > want, adding a combiner will eliminate the voltage drop across the
> isolator.On Mon, Nov 23, 2020 at 11:35 AM Mark Sawyer via Gmclist <

> >

> > [color
> >
> > Ken H.
>
> Yes, but it will not compensate for the rest of the losses in the system.
> The fusible link is an example of only one of the voltage loss culprits.
> IIRC the remote sense is connected to the terminal on either the horn or
> fan relay. Both of these are after the fusible link.
>
> Yes a combiner will fix the isolator drop problem but not anything else
> like cables losses at a 150 or so amps.
>
> I think a installing a one wire alternator is looking for low voltage
> problems in several places on the coach.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
The 28SI has an "optional" remote sensing terminal available...

I had planned to utilize the remote sensing terminal using the factory wiring as I did not see any negatives to doing so...

However, since I do have the choice, are there any negatives to utilizing the remote sense terminal (other than redundancy) on a well designed
electrical system?
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
Ken Burton
> Yes, but it will not compensate for the rest of the losses in the system. The fusible link is an example of only one of the voltage loss
> culprits. IIRC the remote sense is connected to the terminal on either the horn or fan relay. Both of these are after the fusible link.
>
> Yes a combiner will fix the isolator drop problem but not anything else like cables losses at a 150 or so amps.
>
> I think a installing a one wire alternator is looking for low voltage problems in several places on the coach.

Ken Henderson
> All true, Ken, which is why I worded the comment as I did. However, he's indicated that he intends to replace the existing wiring with new,
> larger, conductors. He seems knowledgeable enough to correct those other voltage issues too. They're really not all that troublesome in a well
> maintained system -- witness the many millions of one-wire alternators running today.
>
> Ken H.

Hey Guys,

The last thing I really want to do is get between you two when you are throwing lightning bolts around, but you both just stepped into a mud hole that
has been a problem for me for years in the boat electrics business (now gone).

Problem, You are Both Correct (no surprise there), but so many do not understand is that the life of a 12VDC (nominal) system only about ~2VDC. Too
many unsuspecting owners look at the tables (like Ancor's) that say use this wire size for either (pick one) a 3% or a 10% voltage drop at X Amperes
for that distance.....
This is compounded by the fact (still a big issue in fiberglass boats) even more that they have only considered half of the circuit.

So, if you size for the 10% (1.2~1.5) loss, you are headed for a lot of stuff not working the way that they hoped. This is more of an issue than most
believe. One of the big hits is that it can make it near impossible to get a lead/acid battery to a 100%SOC.

What I have (had) to keep impressing the owners with when putting together a proposal is that while copper is expensive, you only have to buy it once.
If you don't buy it then, it will cost you forever....

It would be my contention that unless you plan to rewire the entire Alternator to Batteries part of the system that staying with a remote sense is
just about the only really good option. This is from personal (very personal) experience.

I really don't remember when it was, but we were in Louisiana when I noticed that the engine battery voltage was sagging. We did the standard
in-flight fix with the generator and I started looking for an auto electric shop. He was a good guy, but said it was too hot for him to deal with.
I'm a steam engineer, so I took it out and brought it in to him. He broke it down and put parts one specialized testers. The regulator was bad and
one of the diodes in the trio was not reading right. He noticed the part number of the regulator and remarked that it was for remote excitation. I
lost his context there. That was unfortunate. The regulator he put back in was a type for a passcar one wire. You might not expect the level of
irritation that was for the next two weeks and couple thousand miles. While it did beat no alternator, everything was a problem. I went so far as to
strap out the isolator to the engine bank and (it's a 73) leave the boost switch on a lot. When we got home, I got the right regulator.

The wire weights are different in the later coaches, but I still firmly believe that the remote sense is well worth the effort for a coach with
multiple banks and loads all over the place.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
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