Jump to content


Fitting A Smaller, Lighter Alternator On A Z22Se

  • Please log in to reply
5 replies to this topic

#1 blackoctagon



  • Pip
  • 93 posts
  • Gender:Male
  • Location:Lothian

Posted 06 June 2020 - 02:10 PM

I recently was looking at the TOCA engines from Swindon Powertrain in another thread (http://www.vx220.org...d/#entry1987364)

One thing led to another and I decided to reduce some static and roating mass by looking at alternators (http://www.vx220.org...00a-alternator/ )

That thing led to another thing, and in the photos below you will see how to mount a Corsa 1.3 CDTI 90A alternator.
I am aware this is not as far-out as buying a small Denso racing unit, or a 50A off an old Daihatsu etc., and that will be for another day, but you can get these alternators on ebay for £20, so I felt it was worth the try.

This is a Denso manufactured unit and it seems that 1.2 petrol Corsas had a 70A version with more conventional radial mounts. It can be made to fit and they are around £20 on ebay and I did get one to try, but I had another idea.

I had seen a member on here had relocated his alternator to the aircon location to fit a supercharger. While he may (or may not) have done it for expediency in supercharging, it has the nice effect of putting a roughly 5kg mass around 130mm lower in the chassis. I will also show that it can also allow you to remove the heavy pulley tensioner and have a direct belt.

There is one major downside to this method - you need to modify the unused lower aircon on the sump (see below).

First up is to weight the new part:
5.2kg. That includes a rather heavy one-way alternator pulley which with only the crank driving the alternator I elected to swap for a new lighter aluminium one.

This is the part:
as mentioned it is in the same family as the 1.2 Corsa 70A.

Here are the comparisons with the z22se 100A unit:




The z22se 100A unit is just shy of 138mm across (there is double parallax error in the photo, but thats the measurement):

The CDTi 90A unit is 120mm across (slightly less parralax error in this shot)

If you are not familiar with OAPs/clutched pulleys they need a special 33 spline tool to get them off. £4 on ebay.

What is now going to be shown is mounting a 1.3 CDTi alternator in the position of the aircon pump that VX220s don't have (it was maybe an option - I do not know).

Modification 1 - Remove the dowel and grind the upper, outer alternator mount flush to the webbing:


This picture shows the original 100A alternator mountinG bosses:

These are the aircon bosses we will pick up on to mount the 90A:

#2 blackoctagon



  • Pip
  • 93 posts
  • Gender:Male
  • Location:Lothian

Posted 06 June 2020 - 02:14 PM

This is how you would offer up the 90A for fitting:

This shows the 100A lower, inner mount being picked up by a temporary bracket I made:

And a top view, during bracket development:

The bracket will look like this:
It is made, for now, from solid aluminium - I intend to make something nicer when i build my good engine.
The red-outlined one was the original before I realised I needed to use the 100A lower, inner mount. Dont copy that one.

Pre-lightening front case:

Rear case (there is virtually nothing to take off this one):

Lightened and reassembled 90A with it's aluminium pulley:

Comparison of Blackoctagon super-turbo-gti-Evo1 100A and super-turbo-gti-Evo1 90A

Weight of s-t-g-e1 90A:
Only a saving of around 0.4kg, and most of that is in the pulley, but as a % it's not bad.

The final unit in-situ:

Bracket details:


And to prevent chaffing relocate the water pipe by inverting it's P-Clip and runing the hose a bit higher to give the alternator room to rock under accel/deceleration:


The belt I used is a Gates Powergrip 5pk803 (5 rib, 803mm inner length, £8 on ebay)). For reference the 100A and tensioner use a 5pk880.
You need a plastic flat bladed tool to help it on, but the tension (and this photo was taken after 5 minutes of idling) is spot on. I would neither want it looser or tighter.

This is what you have to do to the sump aircon boss to get the lower mount of the bracket to fit:
I have a sump thread in prepartion, so i'll show it there.

This is the clearance you get above the lower wishbone front mount:
Again some parallax error in the photo means it may look tight, but it is not. Plentyl of rocking room, unless your fore and aft engine mounts are shot.

The factory wiring just needs past the dipstick tube re-routed and there is no strain in the positive or the plug cables.
It all works, good alignment between pulleys in the horizontal and vertical and making it's 14.3V on Ophttps://sendvid.com/90kfogor-Com.

Here are some walkaround (technically crawlaround) videos:
Vid 1 https://sendvid.com/hikl2318
Vid 2 https://sendvid.com/90kfogor

Edited by blackoctagon, 06 June 2020 - 02:20 PM.

#3 blackoctagon



  • Pip
  • 93 posts
  • Gender:Male
  • Location:Lothian

Posted 06 June 2020 - 02:24 PM

Some bonus weight saving pictures:

You lose this:
z22se sprung belt tensioner:

You lose this:
880mm belt:

But you have to put this on:
803mm belt:

#4 Arno


    Need to get Out More

  • PipPipPipPip
  • 1,210 posts
  • Gender:Male
  • Location:Netherlands

Posted 07 June 2020 - 11:05 AM

Neat  thumbsup


Amps of the unit should be plenty in the VX/Speedster.


Most alternators used in the Elises (Rover and Toyota) are between 80-90 Amp. K20A Honda conversions also run alternators that give around 85A.


I suspect you could even drop to a 70-80A unit without noticing too much issues. The 100/120A in the VX really is overkill unless you want that bangin' bass!  :D


BTW.. For the belt you could also look if there's a suitable Stretch-Fit type available:




Never need readjusting of tension.


Bye, Arno.

#5 FLD



  • PipPipPipPipPipPipPipPip
  • 13,526 posts
  • Gender:Male
  • Location:Near nantwich
  • Interests:Tugging my todger.

Posted 08 June 2020 - 09:11 AM

Fantastic job.

#6 blackoctagon



  • Pip
  • 93 posts
  • Gender:Male
  • Location:Lothian

Posted 13 June 2020 - 05:42 PM

I have the 70A 1.2 Corsa on the bench today to rebuild and put up for sale, but it's packaging is deifferent due to the radial mounts.
I never got the chance to see if the rotor of the 70A was lighter than the 90A when I did have them both together, but if the experience of the 100A vs 120A can be applied here then it's likely the two rotors are the same and the stator coils and magnets are what gives the 20A difference.

From looking at it (no measurements), and knowing they are from the same parts family from Denso, the stator from the 70A could be put in the 90A casing. That would, if the lesson from the 100A vs 120A comparison holds true, reduce some static mass.
It would be a cheap way to get a slight further reduction in alternator mass, but for me my next evolution will be a noticibly lighter Denso alternator, rather than a 70A/90A hybrid.

I've put 90 miles on the Powergrip belt now and the tension is still okay, but i'd probably recommend a stretch belt to anyone else doing it.

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users