FD Starter Upgrade How-To
 

Let me preface this by saying that my intention was not to fix a problem or correct an issue with the stock starter. I simply like the way it sounds when a rotary starts up quickly and crisply. On a trip to DGRR I heard many different cars start up, and the differences are vast. I understand that many factors contribute to this including battery health, battery placement, engine condition, engine management, etc etc. So, take this with a grain of salt if you will, and consider it a "cosmetic" modification more than anything else.

Are you using the stock FD starter with the stock trans? If so I have some info that may help you out. You can rebuild your starter to be a "super starter". I got the idea from R-Magic website where they sell a "high rpm" or "high torque" starter. I can't read it but there is a demo video. Scroll down to see the listing for the starter and here is the link for the video.

http://www.rmagic.jp/parts/engine/fd3s_engine/
So I did a bunch of research and brainstorming to see how they could have made this for an FD. I think they charge 350$ for it. I finally figured out how they might make them. The internals and motor housing are replaced with RX8 upgraded starter parts. The rx8 has three different versions of starters. You need the starter for 04-08 manual with the longer black motor case and 13 teeth. They are advertised as 2.0 KW or something on eBay. I got mine for 46$ shipped used after searching for awhile. All the rx8 starter parts transfer over to the FD starter "nose" or gear housing.
I'll let the pictures speak for themselves. Note that I did not take step by step pictures of the disassembly or re-assembly. But I will point out some tips that will help putting it back together.

Completely disassemble both starters
Attachment 546587

FD parts for reference
Attachment 546588

RX8 parts for reference
Attachment 546589


Note the size of the armature and windings in comparison
Attachment 546590
Attachment 546591

Finished starters. All parts swapped from one nose to the other.
Attachment 546592
Attachment 546593


Label for the RX8 starter
Attachment 546594

Reassembly notes:
Don't lose any parts. There is a single "ball" bearing between the armature tip and the planetary gear housing.
Take the time to clean and refurbish everything. New grease where needed at the planetary gears. Don't pack the housing full or it with cause excess rotational resistance.
Clean the commutator bars with fine emery paper and clean the grooves between the bars.

The difficult part of reassembly is the commutator and brush holder. Spread the brushes open and install the brush holder to the rear of the armature. Then place the rear motor "cap" over the brush holder and line up the screw holes for the brush holder. You can see where the brush holder wire lead grommet goes through the cap. Install the brush holder screws to hold it together. Then while holding it all together, slide down the stator(motor housing) into place on the brush holder cap. There are tabs that line everything up.
Now the motor part can be mated to to the already assembled planetary gearset/nose piece.

Nice! Comment so i can find it later:D

Awesome, ive searched many times for such an upgrade.

i looked through the parts catalog when i was shopping for my Rx8 starter, and i was a bit surprised that the original 04-06 starters are just FC/FD starters with a different nose, and the nose isn't that different either.

for the FAQ, there are a few different starters for the Rx8.

there is a 1.2kw starter, a 2.0kw starter and then an even larger one.

the 1.2 kw starter came on the 04-05 cars, the 2.0kw was installed in the 06-08 cars, and then the bigger one is 2009-2012.

there was also a service kit to upgrade the 04-05 cars under warranty, and the dealership that i worked at upgraded all the cars we could find, but most other dealerships seem to have not (because they are dumb, Mazda would have paid them to do it, so they didn't take free money)

in an Rx8 1.2 starter does 200-220rpm, and the 2.0 does 250-280rpm, and the 09 starter does ~300.

a little extra cranking rpm is really helpful in a renesis, especially when its hot.

Interesting, I'll definitely be doing this, thanks! :icon_tup:

Nice,

I was just researching this last week and ordered an RX8 2.0kw starter. Nice to see a quick write up.

I thought I was the only one who cared about the car sounding cool upon startup. I'll get to this eventually. Thanks! !

Ive been wanting to do this for ages,, my car has always been a bit of a slow starter (new battery,, new thicker gauge wire direct to starter motor, brand new starter motor). Its always started but just seemed a little lazy, Found an upgrade on ebay with 14 tooth motor for even faster cranking power,,, ill get on with this tommorow.. Brilliant!!

Nice write up. I've been working on doing this some time ago Just got side tracked with all the work I have going on in the shop right now. It definitely helps hot starts, especially in motors with some mileage/lower compression, or in looser clearance race motors. Also helps when deflooding a motor. I may start offering this to customers. It will be a complete starter rebuild and upgrade with a 1 year warranty. Would go nicely with my 140 amp alternators.

nice! new project!

After some more extensive research, I've learned that the newest model of RX8 starter is backwards compatible with the 04-08 cars. At first I thought it was not a viable option due to the different tooth count. I assumed that the change in drive pinion size would cause the mounting points to be slightly changed.

Attachment 546749

Actually this is not the case. Instead, the 14 tooth starter has the "offset" built into the design of the case and nose, so the mounting points are still the same.

Attachment 546750

What I'm trying to get at here, is that the largest and baddest starter may also be an option on our cars. I have purchased one and once I get it in hand I will get some measurements and more detailed pictures.

Attachment 546751

I didn't mention it before, but the main reason you can't use the RX8 starter as a direct drop in replacement, is the pinion protrusion length. It does not extend out as far as the FD starter. This would translate to not engaging the ring gear enough or maybe at all. By my estimation the difference in length is 8-10mm. In the 13 tooth version it turns out this is easy to correct by using the FD nose with all other parts from the RX8. When you have the two aluminum castings side by side, the similarities are remarkable. It almost looks like the only thing they changed is the pinion position relative to the mounting pad. One neat thing is that they added a needle roller bearing to the pinion snout support in the 8 starter and the FD has a bronze bushing. I couldn't figure an easy way to move it to the FD housing.
You can see the 14 tooth model has an exposed pinion design. Meaning swapping out the housings and other parts probably will not work. I'll take some more exact measurements on the pinion extension and see how it compares to the stock unit. I have a feeling that one machining operation on a lathe to remove a bit of the mounting pad would bring the starter in towards the ring gear just enough.

Another thing I want to mention is that I have only bench tested the upgrade starter I put together. My car is no where near ready to install it. I have some mild concern regarding the higher power starter. The oem starter should be drawing around 100-120 amps of current. The larger motor and windings of the 8 starter should draw 160-180 amps.
Please make sure your wiring is up to par before putting a bigger starter on. Make sure your ground and power connections are clean and tight.

Sorry for the novel

This is interesting, I am adding this to the mile long list of mods needed on my FD for spring.

i don't think anyone is bored enough to think of this stuff, but that makes perfect sense, the FD bellhousing is longer due to the pull type clutch. the Rx8 went back to the T2 style clutch, literally in fact.

If you put an RX-8 starter in an fd as is the gear protrudes too far and it will grind as you try to start it.

^Incorrect.

RX-8 starter gear does not protrude far enough to reach the flywheel when mounted on an FD trans.

This is one of those things that would be awesome to have, but I'd never have time to do myself with the backlog of car work on my plate (similar to LED tails)... an upgrade/service would be very cool.

P

As I recall the one I had only contacted the front side of the flywheel closest to the motor. Since it wasn't engaging properly the teeth were slipping. Could see the wear pattern on the gear. This was a number of years ago and I was doing this at like 4am so I may have it mixed up. Either way it doesn't work as is.

This looks like an awesome upgrade.

Before doing this however, anyone who thinks they have cranking speed issues should try a direct fresh large wire at least 2ga from the battery to the starter.

I've had a 2ga battery relocation, running up to the factory fuse box, and down through the factory harness crank at what I thought was a decent speed. Switched to a 2/0 gauge wire direct to the starter and was blown away by the increase in speed!

Got the new starter in hand and looks like it can be made to work. The pinion extension on both RX8 starters measures out to 54mm and the RX7 starter comes out to 60 mm. Difference of 6mm, which can be milled off the mounting flange(16mm thick) to make the starter engage the ring gear. I will be adding a brace of sorts between the trans case and the rear of the starter. This should help compensate for weakening the mounting flange. My machinist(brother) is going to cut it for me over the thanksgiving holiday.
Other note of interest is that the motor assembly is the same as the 13 tooth starter.
Here are some pics

The lineup
Attachment 547154

Remove solenoid (impact screwdriver)
Attachment 547155

Remove case bolts
Attachment 547156

Separate motor assy
Attachment 547157

Slide off stator
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Remove end cap
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Carefully slide off brush holder
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Reduction gear assy
Attachment 547161

Slide out rubber part and metal oval underneath
Attachment 547162

Remove rubber seal/insulator and planetary gears
Attachment 547163

See pinion offset in housing
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Rough marking of material removal.
Attachment 547165


I'll post more pics on the pinion disassembly later and update after the housing flange is machined.

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I have couple of old Rx8 supposed to be "upgraded" starter core sitting around, was thinking to return them to get a few more new starters. but after seeing this hmm, maybe I should try to rebuild and swap 1 of them into fd casing to see how this works cuz I have been thinking about this for quite a while.

Now after seeing this post, I am gonna try it in a few days and see what sup.

Looks like Banzai Racing started offering a new 2.0 Kw starter for the FD! Hmmm wonder where they got the idea for that huh? Looks like the price is pretty good for one already put together with all new internals, for someone who doesn't want to play around with building their own....
Good job guys !

We have actually been working on the starter for some time now

Awesome, pretty sure I will be buying one of these. Can you comment on the parts used? Are the non FD parts OEM mazda rx-8 parts, a reputable reman like bosch or some other brand?

Starter mod works great! I was wondering why the rx-8 when it started it didn't sound like an rx-7... now I know why!