Denso Alternator Conversion

[Rupunzell]

It turns out the 74' needed an alternator as the one that came with the car was never working.. properly, the lack of an alternator light with the ignition switch on should have been more than a clue as problem.

Resulting in a dead battery.. A quick DVM check with a newly charged battery measured only 12.5V and dropping under load..

So, rather than getting the original Fiam alternator rebuilt or replace it with an later Bosch alternator.. I decided to install a Denso alternator from a Toyota Camry, Avalon, ES300. These are good units, reliable, durable, small, easily availiable and rated at 80 Amps, 14 volts running.

Here is the Denso Alternator next to a Marelli from a 79'.. This alternator is about the same size as the Bosch units used in later EFI cars.. Note the smaller size of the Denso -vs- Marelli.

The Denso pulley is a 6 groove flat belt, the X needs a 3/8" wide Vee belt.. So off came the pulley from the Marelli alternator for a trip on the lathe. The rear of the pulley has been relived similar to the stock Toyota pulley to clear the alternator body and set up the belt alignment. This clearance relief is tapered by 10 degrees from center about 0.10" deep x 1.30" on the ID.

The front pulley nut recess on the stock X pulley is not deep enough, so it is counter bored 0.20" deeper. And, the shaft hole gets enlarged to 0.670" to fit the Denso alternator shaft. Not shown is a 5/8", 0.125" thick SAE washer between the Denso alternator shaft/bearing to space the modified X vee belt pulley to get proper spacing and alternator body clearance.

Next, the stock lower alternator bracket is cut down from 72.3mm to 40mm initially on band saw to "rough in the cut" then finished in a mill. Note the corner re-entrant radius at the corner to prevent a corner crack from starting. The modified bracket is deburred and all sharp edges removed.

Here is the modified bracket painted and compared to a stock bracket. A FIAT twin cam head bolt is proper lenght and thread (M10x1.25) for the Denso alternator mount.

The top bracket consist of a support bar that mounts on the water pump housing and an adjuster bar and block.

The support bar raw made from 2024 aluminum bar stock. It has a 15 degree relief cut into it for the adjuster bar's rod end. The M8 bolt holes are 52mm center to center, M8 socket head bolts are 40mm long.

The adjuster bar is made from a 1/2"x 20tpi left hand threaded 4140 alloy steel threaded rod, ~3.5" long. One end has been drilled for 5/16"x24tpi right hand threaded rod end and the adjuster rod has been drilled from the other end to reduce thread engagement of the rod end side (it also lightens the part, HA!). A 1/2"x20 left hand jam nut held on by a 1/8" dia. x 3/4" long roll pin to allow turning of the adjuster bar. A jam nut lock the adjustment when set.

The block is 1018 steel, 1" x 1.2" x 0.75", The 0.75" side is threaded for 1/2"x20tpi left hand, and a 5/16"x24tpi threaded hole is for the top alternator mounting ear.

Here is the assembly mocked up before paint.

Same parts painted, front side.

The back side showing the 15 degree counter bore for the rod end bolt. This 15 degree counter bore is required to stop any bending force on the rod end bolt & nut.

Denso alternator and brackets installed in the X.. Top view:

Same, bottom view:

Same, end view:

Part two will be wiring up the Denso to the 74' electrical system.

:bla:
Bernice

 

[Black-Tooth]

Welp... Geez Bernice...

The adjusting bracket... If you look down from the front of the waterpump to the top bolt hole in the alternator... it appears a simple slotted swing arm could easily be fitted much like the GM conversion. Maybe a few washers for shims or Z'd for alignment.

Anyway... congrats on the conversion... it does make for a nice SMALL package though... which probably makes the adjuster you made even look more massive. HA!

 

[spiderrey]

Very nice

 

[Pete Whitstone]

Very nice work, Bernice

And well documented, too! Thanks for the write-up.

Pete

 

[bbrown]

Another great write-up...

Thanks for taking the time to write this up Bernice. It's stuff like this that keeps our cars going better and stronger as available parts disappear. Good detail here as well.

This is yet another choice for alternators outside the GM version.
Looks to be nearly double output of the original. Maybe doubling up on the output wire, (or the wire gauge) back to the battery would be appropriate as well.

Nice work!

 

[glenegan]

Great engineering!

Your projects are always so ingenious!

Cheers,

Glen

 

[lookforjoe]

Superlative Work!!!

..Nice detailed explanation & photo guide, too!

Think I'll probably just go with a 90's Volvo/Bosch 100A, since I have ready access to same :grin:

 

[eflexter]

NEAT!

I'm a fan of mods that increase reliability. So was Fiat when they replaced the entire electrical system with a Bosch replacement.

I'd like to see more of these thoughtful mods documented here using this one as a guide.

Fast is nice, but getting home is more important to me.

 

[kmead]

..Nice detailed explanation & photo guide, too!

Think I'll probably just go with a 90's Volvo/Bosch 100A, since I have ready access to same :grin:

I think we need to find a new name for your car's brand, FIvo, VolAT or something. Nice job bringing another Euro maker's parts into your car.

 

[kmead]

Thanks for the excellent write up, a great modification. There are a raft of small, light weight Japanese alternators out there.

Have you ever looked at the way the A2 VW Golfs offered adjustment? They have a simple quadrant with a section of gear teeth welded on to create a rack. The clamp bolt for the alternator passes through a hex headed bushing with a gear on it.

To adjust it you loosen the clamp bolt, apply a wrench on the hex head of the bushing to adjust the tension and then tighten the clamp bolt. Its very simple, positive and can be applied to most any alternator.

This is a pic of the bushing and clamp bolt (side view)

Front view facing the alternator.

 

[Rupunzell]

Not just Denso or other Japanese, the new Bosch Alternators are just as miniature and reliable, durable and a quality part.

The rack and pinion adjuster is also found on some Japanese cars like Mazda. Only problem with any adjuster like this, over tightening the belt is easy to do.

Bernice

Thanks for the excellent write up, a great modification. There are a raft of small, light weight Japanese alternators out there.

Have you ever looked at the way the A2 VW Golfs offered adjustment? They have a simple quadrant with a section of gear teeth welded on to create a rack. The clamp bolt for the alternator passes through a hex headed bushing with a gear on it.

To adjust it you loosen the clamp bolt, apply a wrench on the hex head of the bushing to adjust the tension and then tighten the clamp bolt. Its very simple, positive and can be applied to most any alternator.

 

[Rupunzell]

Well,

FIAT sorta had a hand in the x1/9, but it really was a Bertone offering and in this designs later years of production, Bosch replaced Marelli electrics.

Fact is, the early x1/9 electricals were not bad at all, they were wrecked by the US federally mandated requirements such as seat belt inter-locks and buzzers and seat switches and etc.. Fact is, most cars from the 70's were equally bad due to Fed Nanny policies that were poorly conceived but politically proper for that era.

I'll post some of this festival of electrical fun in part two of this project.

Most of the electrical problem in later x1/9 are usually due to the frying to a-cinder big brown wire connector or poor ground connections. Most of the electrical components are reliable.. even now that most are over 20 years old.

Bernice

I'm a fan of mods that increase reliability. So was Fiat when they replaced the entire electrical system with a Bosch replacement.

I'd like to see more of these thoughtful mods documented here using this one as a guide.

Fast is nice, but getting home is more important to me.

 

[Rupunzell]

Well thanks Bob and everyone..

There is more than one way to solve a problem.. Me being not very attached to originality, origin of parts used or etc.. is likely to come up with stuff like this..

BTW, one of the to do items is to convert the 74' instrument cluster lighting to LEDs and installing digital volt meter.. ala Bob's not a tungsten filament to be found any where on the X1/9 idea.

I'll post part two as time permits. The Denso alternator is currently working fine.

Bernice

Thanks for taking the time to write this up Bernice. It's stuff like this that keeps our cars going better and stronger as available parts disappear. Good detail here as well.

This is yet another choice for alternators outside the GM version.
Looks to be nearly double output of the original. Maybe doubling up on the output wire, (or the wire gauge) back to the battery would be appropriate as well.

Nice work!

 

[kmead]

... Only problem with any adjuster like this, over tightening the belt is easy to do.

Bernice

Yeah, its always hard to account for the loose nut holding the wrench. One hopes that is something most of us have a handle on by now