I’ve been working on adding an oil cooler to the Miata for a couple of weeks now. I purchased an oil filter sandwich plate that has a thermostat built in. After receiving the plate I quickly realized just how little room there is around the NA miata oil filter.
Here’s a photo from miataturbo.net that depicts the clearance issues at hand. On the left side of the photo you can see the NA’s starter support bracket. This bracket is by far, the most interfering when trying to install the sandwich plate.
You are able to remove the bracket from the starter, but my engineering sense kicked in! I knew that Mazda had to put the bracket there for a reason, and it worried me that using a part in a way that it was never designed could lead to failure. I quickly went to Google and searched to see if a different generation starters would bolt up to the NA without the bracket. Sure enough, I found that it’s very common to swap an NB starter into an NA. Not only does the NB starter get rid of the support bracket, but people also say it’s significantly lighter too.
I hit up eBay and found a used NB starter for $30 shipped.
Here’s a comparison photo of the two motors. My crusty NA starter is on the bottom, and the fancy new (to me) NB starter is on the top. You can see that Mazda extended the aluminum casing a bit more on the NB. I think this must be what allows them to get rid of the rear bracket without sacrificing support. After taking these photos, I now realize that the NB motor casing also appears to have a smaller diameter as well.
Both starters measured about 14 cm from the mating surface to the end of the motor case.
NA starter length.
NB starter length.
If anything, the NB starter is a few millimeters longer… I’m not that worried because I was mostly worried about the bracket getting in the way of the oil filter sandwich plate.
The last thing I wanted to compare before bolting the part back on to the car was weight savings. Keith Tanner from Flyin Miata claimed the NA weighed 9.8lbs and the NB weighed 6.0lbs.
Here are the numbers I got on my ancient bathroom scale.
NA weights ~7.5lbs.
NB weights ~4lbs.
I’m not sure how accurate these numbers are, but at least I seem to be getting the same ~3.5lbs weight savings that Keith and others claimed.
I went ahead and bolted the NB starter to the car. It definitely fits up with no issues like everyone says. You end up using only 2 bolts to hold it to the bell housing instead of the original 3, but hopefully that’s not too big of a deal.
The last thing I wanted to mention is that the NB starter does seem to spin slower, or maybe it produces less torque than the NA. I’m not 100% sure, but it definitely seemed to have a harder time cranking the car over. The slowness could be due to me running a $30 tractor battery, or it could just be how the starter was designed. I’ll have to feel it out for a little while. If cold starts become too difficult on the NB starter, I might end up going back to the NA starter and just risk running it without the support bracket. For now, I’ll call it a success!
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