Mazdaspeeding's 2012 ~400whp engine rebuild

So I've owned my 2012 Mazdaspeed3 since it was brand new. I did a bunch of little "stage 1" type things right off the bat like rear motor mount, short ram intake, hpfp internals, Cobb AP +OTS tune, stainless steel brake lines, shifter bushings + short shift plate. It was very reliable for about 130,000 miles. I had just replaced the suspension with Bilstein B6's when I developed rod knock due to low oil and now I'm planning an executing a rebuild with a ~400whp power target in mind.

I've got ~$10,000 to make stuff happen here and get my speed3 back on the road. While the engine is disassembled for the rebuild, I also plan to replace the clutch and fix the second gear pop out problem. I think I'm going to add a CST4 turbo with the EWG setup, a corksport intake manifold with additional fuel rail, an ETS TMIC and also replace the motor mounts. I don't want the car to be very loud at idle or around town, so I intend to replace the downpipe but keep the exhaust stock past that. I'll also fix some things like replacing the skid plate I lost, swapping sway bar bushings and getting new tires. I'll keep it updated as I intend to start ordering parts this upcoming week and having the car back together within the next 2-3 months at most.

 

Welcome, and great to see!

I'm a huge sucker for the Focus ST Manifold, since all-in you are half the price of the Corksport IM, and it should work perfectly at your power levels. You just need to modify the FMIC piping a bit to make it work - you can see that on my build thread if you are interested.

I would also look at a CST5 or BNRS4 if you want to hit 400 without really working the turbo too hard, and it's a pretty insignificant cost difference.

 

Welcome! I have the CST4, and it will top out at 400. CST5 is where you may want to look. I have my motor in rebuild status, both CS manifolds, CS FMIC and TB, 3.5" intake, CST4 IWG, CPE DP, CS 3" exhaust. I am hoping for 400. No port injection, E85, or meth. Just a 93 tune.

 

The corksport intake manifold has no provision for mounting a tmic fyi

Edit. I am wrong

 

Good catch.

 

This is good to know. Although the info below about the intercooler is new for me and I'm going to have to do some thinking.

I want to keep the car as a daily so I'm thinking a CST5 might be just a bit "too big" and I'll probably just have to revise my power goals.

Now this is exactly the kind of information I needed. I'll look more into the FMIC options and other intake manifolds maybe.

 

If I revise my power goals to ~350hp-375hp I wouldn't need extra fueling so the intake manifold becomes less of a worry to begin with.

My philosophy for this rebuild is just making everything as good as it can be while staying (mostly) within OEM packaging and the realm of "bolt-ons". I'd like another 100k miles out of this car with proper care hopefully.

I'd initially thought about keeping the cost down and just doing the engine rebuild w/ forged internals, the clutch/transmission fixes and swapping the K04 for like a S3/CST3 for reliability more than anything else. But tbh, I want the EWG for the novelty factor more than anything else. That's what's pulling me to the CST4 over the BNRs or the CST3

 

I think it does...I also think its the only one that will accept TMIC.

Also, from the CS FAQ section...
Will this fit with a TMIC set up?

Asked by Aleksandar | 09/13/2021, 12:03 PM | 1 answer(s)
Yes it will.

Answered by Brian Bernier | 09/15/2021, 03:49 PM

 

Shit I stand corrected

 

If you're going built motor and big turbo your car deserves a FMIC, it is a noticeable and appreciable drop in BAT, especially if you are using it as a daily.

 

Not necessarily or necessary @Enki

 

I know Enki will die on this hill

 

If you're running a built motor and big turbo and a higher % of ethanol your car doesn't care if it has a FMIC or a TMIC. Vash made 550 wheel with a TMIC, and I made about 380 with no intercooler at all (but did have WMI).

Edit:
The CS intake mani does have TMIC mounting provisions but if you're going to use a TMIC with PI you may need to run the stubby injectors; this is one thing I've not tested yet. I'm also not sure *which* TMICs you can run with the rail in place, though the CS TMIC would probably work out since it's quite thin and sits a bit higher than, say, a CPE (which is what Vash ran).

Side note number 2: The bigger the turbo the more efficiently it can make boost. Running a 500 WHP turbo at 400 WHP with a TMIC may actually be a good compromise, as the turbo outlet temps into the TMIC should be lower (depending on where on the map you are).

 

also the shitty ebay cores and lack of ducting to the fmic that everyone seems to end up with are easily worse than an upgraded tmic

 

I'd definitely buy a quality IC and absolutely abhor ebay.

So far, I don't ever plan on going past ~500whp, my mechanic is recommending a mostly stock bottom end with upgraded head studs and bolts. At most I want to do a CST4 turbo with full supporting mods. I'll almost certainly do the manifolds and full 3"+ intake and exhaust

 

I realized my intake is actually only the 2.5" inch Corksport intake and I'm debating how far I want to go with 3" vs 3.5' and having to move the battery

 

If you plan on going bigger turbo later, get a 3.5". No reason not to, and gives you a whiff of more topend on the baby K.

 

I plan on going to the CST4 and no further. Beyond that I'll just optimize the car and I'll probably buy a second car in the next year or two but I won't get rid of the speed.

I just don't see the point in a 500+ hp FWD car but that's just me. I'd build the car for AWD before I'd swap a bigger turbo on personally.

 

You can tune per gear, ya know. And softer compounds can for sure hook that.

 

As far as the clutch goes, I've been pointed to South Bend or Xclutch. I'm leaning Xclutch but I'm not sure if I should spring for the street plus over the street. They say peak tq holding in the street is ~440 and I don't think the CST4 can really top that but I'm not sure if the extra overhead of the plus would be worth it.