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During my last rebuild I noticed the engine closing kit from Atkins had jumped in price from the last two sets I bought ($600-->$680). At first I assumed it was just inflation and was going to check out but decided to do my homework and see what was different.
As it turns out the price difference was due to the kit now using inconel side seal springs instead of their regular ones (ARE14 vs ARE84). I figured this out by comparing the parts list from my past orders. In the past years the ARE146 closing kit used to cover year ranges 86-95. Now it covers only 86-92 and a new kit, ARE148 with the inconel springs, was added to cover 93-95. Interestingly there is no drop down box to select which side seals springs you want for your build.
Has anybody had any experience with these inconel side seal springs and have any idea why they are now "standard"? I opted to just use the older ARE146 kit and save $80 even though it is no longer advertised as being applicable for the 92-95 year range.
For as long as I know the FD and FC side seal springs have been different from Mazda. FD part number is NF01-11-C17 and FC part number is N326-11-C17. FC part is like $2 each and FD part is like $8-10 each.
From what I remember Mazda made the FD side seal spring out of a more heat resistant steel so it will hold its shape better over time with the increased heat and HP the 13B-REW generates. Inconel would be a safe bet.
Don't know if you were looking at FC kits previously or if they were just using FC springs in the FD kit or something.
I would think it would be worth having the correct spring. It's hard to say what the long-term difference would be - they would probably be the same initially, but I would think the FC spring could go flat sooner, resulting in lower overall compression sooner. But, is that 20,000 miles, 100,000 miles?
Side seal springs don't do as much work as the apex seal springs do. The side seals stay pretty static as the rotor spins, the springs are just there to provide constant pressure.
I've seen FC springs actually break and migrate/bunch up next to the 'trailing' seal associated with the side seal after living a lot of their life at 9500 (E production). I've never seen that with comp or FD springs.
FD springs were inconel from the factory. They are significantly more heat resilient and I wouldn't use anything else in a turbo car. When ordering from Atkins, make sure to specify the fd inconel springs. This applies to all the seal springs. Atkins does a great job putting together rebuild kits for convenience but it wasn't always clear what the contents were, so make sure you specify what you want.
Last edited by IRPerformance; 11-30-18 at 12:14 PM.
Here are screenshots of my orders from 2016 and 2017 (lucky me - 1 rebuild per year including this one). It appears the kit was referred to as ARE346 per the line item and covers all years (although the details also list it also as ARE146 in the first pic). I bought the rebuild kits based on the recommendations on their site for year/make/model. That leaves some ambiguity as to what type of springs were being provided but I would guess "FC" springs based on the cost and kit bill of materials. Slim chance that all kits were being sold with Inconel springs.
In the kit there are the side seals in a separate bag/packet with FD OEM part number. At least that's how mine came with, but I picked them individually.
11-30-18, 09:28 AM
