Critique my Mod Path for 200whp
 

Hey guys, my name is Will, I bought my first miata (MY 1990) in November and need your help laying out my mod path.

Usage:

• daily driver. I have a backup car, but I prefer not to use it.
• occasional track day (once/month). I'm not looking to be competitive. I just want to enjoy the car, get "decent" times, and drive home from the track with the car in one piece.

Goals/Requirements:

• 200 whp on 91
• 230 whp on e85
• broad powerband
• well-rounded
• stock driveability (AC, cold start, etc.)
• MUST BE RELIABLE

Below is a list of mods that I plan to purchase. The mods are grouped into steps. Each step will be executed all at once, which means every item in each step will be purchased and installed (nearly) simultaneously. If you think anything should be added, deleted, or rearranged, please let me know. Simple replacement maintenance items (timing belt, spark plugs, etc.) have been omitted. Oh, and the mods listed in blue are what I've already bought.

Step 1: essentials

• 1.6 long nose crank
• roll bar
• helmet
• bucket seat
• aluminum undertray
• steering wheel, hub

Step 2: handling, brakes

• coilovers (ST suspensions)
• 15x8 wheels
• 205/50 tires
• pads, rotors, fluid
• sway bars (what are good front/rear diameters to start out with?)
• FM butterfly brace

Step 3: pre-turbo mods

• Megasquirt 3
• Toyota COPS
• variable TPS
• injectors
• coolant reroute
• wideband

Step 4: drivetrain

• 3.9 torsen conversion
• upgraded clutch

Step 5: TURBO!

• T3 churbo
• FM or BEGI cast iron manifold
• inconel studs
• DIY downpipe
• ebay intercooler, DIY piping
• aluminum radiator
• lines, fittings, etc.

Anything I should change? For example, should I opt for 15x9s and 225s? Any handling mods I should add? Sway bars? Bushings? Let me know! And thanks!

A few things, first off take my advice with a grain of salt im a noob. But im a well read miataturbo noob, which makes me an expert in most forums =P. Seeing as you want a ebay cast iron manifold im guessing you have a 1.6.

Move upgraded clutch to before you install the turbo it wont last and its pointless to put it off.
Second, why do you want an ebay turbo/manifold. Even if its cast it wont hold up for more than a year or two at most with a track day every month. This of course depends on how hard you beat on it. (the manifold not your....) Seriously just do a used FM/Begi manifold combo with a used sr20 turbo that you can rebuild.

Third IDK wtf St Suspensions is but if your serious about tracking every single month then get Xida's from 949.

Fourth Make sure you have searched this forum can be brutal to the noobs

Edit* omfg i had a dumb. You need the inconel turbo studs from Trackspeed engineering to keep your shit from falling apart.

Iconel studs won't help you when the manifold itself falls apart.

Forgot about inconel studs. Added that to the list.

At first I was hesitant about the ebay manifold, but I haven't heard of any first-hand reports of failures. The only reviews I've read were positive. Am I missing something here? I don't mind forking out another $200 for a BEGI cast manifold if the ebay one is junk, but I don't see any reason to think that.

If I get a BEGI manifold I'll need a t25 churbo instead. Is the one BEGI sells the only tried and proven option?

ST suspensions is owned by KW. The coilovers they offer are supposed to be a galvanized-steel-bodied-or-something version of the KW v1. A basic setup, fixed dampening.

I've heard the sr20 turbo is a terrible match for the 1.6. Apparently the turbine housing is too big? Or is there another version I've missed?

I thought the ebay cast B6 T3 manifold was supposed to be pretty decent.

It is as long as you don't track the car hard.

OP. Stop eating cum and read Underdog's build thread. Use Braineack's old turbo.

https://www.miataturbo.net/attachmen...823_165942-jpg

they work if you don't track the car.
it might crack if you do

Thanks. That's enough to convince me. Guess I'll be dropping in a BEGI manifold. Doing research on t25 options now.

Might as well swap steps 4 and 5. I'm not sure you'd really need COPS.

I'd say clutch is a must if you intend to turbo the 1.6 at all, I dont think my 1.6 with a 14b was anywhere near 200 and it destroyed a clutch with general driving. I'd move it up a bit on the list, that way it can be nice and broke in as well.

I agree that if "1.6l long nose" means you're swapping in a different, fresher motor (which since it's a '90/short nose is probably the case), that would be the time to install the clutch kit.

If you're doing a coolant reroute along with a few other things, you could consider moving the engine swap to further down on the list where the MS3 and other bits are. It'll give you the chance to install the clutch kit and parts of the reroute on the back of the head while they're more easily accessed.

The rollbar, bucket seat, etc. really don't have much to do with an engine swap, and since you said everything in each step will be installed simultaneously.....I'd move the FM butterfly brace up to the first group since you already have it, and move the engine swap down. You'll probably have the seats and console out for the roll bar install, since it gives you more room to move around. With the seats out, you're just a carpet pull away from getting access to install the butterfly brace.

Definitely get some sways, that was the biggest improvement I've felt suspension wise.

And as other have said, move 949's 1.6 clutch higher up on the list.

The t25 is a GREAT match on the 1.6. Great spool and capable (albeit barely) of 200hp. If you do go that route, fine a genuine Garrett off an sr20 and rebuild it following the directions here with a gopopshop.com rebuild kit. There was one for sale recently for $100. Might still be there.

As for the manifold, that cracked one is genesplicer's. He raped the shit out of it for two seasons of racing iirc, and it finally cracked. Id be perfectly comfortable using it for daily driving and a first turbo setup. With inconel of course.

If you decide not to however, I'd instead use FM's DIY package. They've got a great manifold and better shipping times than begi.

If you're swapping the motor, why on earth would you put another 1.6 in there? Is it required by class rules or something?

--Ian

Check out the build thread for my Silver car. Uber-reliable (have more than 30K turbo'd and go to the track several times a month). I'm really happy with it.

Specific thoughts on your list:

What's an aluminum underpanel? If you're talking about an undertray, keep in mind that the stock undertray does a great sealing job and they cost ~$60 from Mazda. Make sure any replacement seals the radiator as well or better.

Just because you have a LNC, don't be lulled into a state of complacency on keeping tabs on the crank bolt. LNC can suffer the same issue. Use Loktite there and carefully torque it.

You'll probably find that you'll need engine mounts. Use the Mazdaspeeds. Also, do your clutch when you swap the engine.

Those butterfly braces are kind of heavy and are a pain to fit on the 90-93s because of exhaust clearance. They also make doing maintenance on the bottom of the car a pain. Definitely do the frame rail reinforcements though. They do a good job of protecting the car when you go off track.

If you want real stiffening, look into door bars.

I'd put the Torsen into this list. You've done your homework.

Do invest in a known-good exhaust manifold. BEGI or FM. I've got a Greddy with relief cuts and have no complaints.

You'll definitely want at least a 2.5" exhaust and, if you can get away with it, a test pipe.

Add an RB front sway bar with a brace kit. 949 end links. I'd stay with rubber bushings on a DD.

Thanks for all the replies!

I should've mentioned this earlier, but aside for the butterfly brace, everything I already have (the items in blue) is already installed. So yeah, the long nose crank is already in there. The last owner replaced the engine, for whatever reason, with one from a 93. Which is why I'm not dropping in a 1.8.

Steps 4 and 5 have been flipped.

Sway bars have been added, but what diameters are a good start? The ones I have now are 22mm front, 19mm rear. Is that stock?

It seems Braineack is very well respected on here and in this post he says otherwise. Am I missing something here? I admit I know absolutely nothing about Nissans, so maybe there are different versions in duscussion? Here is a list of stock turbos that I found on the 240 forums. When you say "sr20 t25," which of these are you referring to?

Hornetball, you brought up a lot of good points but I'll have to respond to them later.

I would think strongly about spending any money on parts that are not compatible between a 1.6 and a 1.8. Anything you can do to a 1.6 you can do to a 1.8, but those 200ccs of displacement will always make the 1.8 faster. The more money you spend now on parts that don't swap, the harder it'll be to upgrade later, when you realize you want those 200ccs and the better-flowing NB heads. :)

--Ian

To be specific, the part that doesn't swap is the exhaust manifold. Usually, the downpipe and hot-side intercooler piping won't swap either because the exhaust manifold locates the turbo.

I agree on the thing about spending money on the one-six. Only invest baller money on stuff that can be shared between 1.6 and 1.8. (injectors, megasquirt, exhaust)

You see 1.6 parts for sale from time for time on here. If you see BEGI or FM cast manifolds for sale for a 1.6 drop the cash. If you have any intention of upgrading later i'd even be willing to go greddy if you can get it (with downpipe) for a reasonable price. They might be fine but they have weird downpipe routing and the older manifolds tend to crack. YMMV.

I am torn on your power goals though. Part of me feels like you shouldn't need e85 to hit 230hp if you have a turbo that will support it. But then, I don't know 1.6's at all.

FM's sway package is the easiest and a great price at $200 for both. Although RB's hollow 1.125 bar and the Mazdaspeed 14mm bar is 949's choice. $450 for their package with end links.


Yeah, he likes the t3. I've never used it myself. I just like the cheapness of a genuine Garrett turbo. It spools incredibly quickly and still makes 200hp. Not enough for some on this forum, but it is for me. It's really just a choice you'll have to make.

I am going the sr20 t25 route as well... but I come from the 240sx world, then got an RX-7, then a Miata...

Basically there was 3 different variants of the sr20 engine.

• s13 sr20
• s14 sr20
• s15 sr20

Generally it goes that the s13's came with t25. S14 came with t28 journal bearing. S15 came with t28 ball bearing.

The power kind of scales with that too.

t25<t28<t28bb

So if you go the t25 route, and you end up wanting more power later on, you can always just find an s14 or s15 turbo, or any of the other T2 turbo's(gt2871r .64 ar) without having to get a new manifold. That would be plenty of power for a 1.6 build IMO.

A *19* mm rear? I've never seen a rear sway bar that big on a Miata, and I suspect a 22/19 combination would unbalance the car to the point where it would do a complete spin pulling into your driveway.

22 sounds like a stock front bar (not sure what the NA 1.6s had), I think stock rear was 11mm.

FM's package is a solid 1" front and a 5/8" (15.8mm) rear, and IMHO that's too loose. Note that that's less front bar and more rear bar than the 949 setup. If you want to approximate that balance with cheaper parts, an FM front with a 12mm (99 sport) rear is probably close.

--Ian

Hornetball:
I'll definitely check out your build thread. Sounds like you've got the winning formula I'm looking for.

Here is a pic of my undertray:
https://www.miataturbo.net/attachmen...ine=1393994634
I only had a few hours to make it, with limited tools, so it doesn't look very pretty (it's not even complete, so I'll figure out a way to secure it in the rear, don't worry) but I think it seals fine.

Mazdaspeed engine mounts need to be replaced every so often, don't they? Would you still recommend them in spite of that? I was thinking of getting ones with stiffer (poly or something) bushings.

Door Bars:
Did some reading on door bars and they definitely look worth it. Something I haven't been able to get a clear answer on, though. Do door bars negate the benefit of the butterfly brace? Should I just keep the frame rails and sell the butterfly brace when I get door bars?

About the 1.6 vs. 1.8 topic:
I'm seriously torn on this subject. Will need to think about it some more, but I definitely do see the logic in it.

Sway Bars:
Thanks for the suggestions, and going into detail regarding the measurements. The "norm" is definitely different on Subarus so I would've never guessed a balanced setup would consist in such thin rear bars. I'll look into the brands you guys suggested.
I could've sworn the rear one was 19mm, but I could be wrong. Will measure them again over the weekend (when I have access to measuring tools).

Curly and Carbon:
So do you guys disagree with Braineack then, regarding the suitability (or lack thereof) of the size of the sr20 t25 turbine housing? It definitely looks laggy on that dyno sheet he posted. Peak power output doesn't seem to be his complaint. It's spool, which you've claimed is good.

If you aren't worried about classing, I think the Frame Rails are worth it just from being able to slide the jack under the car and lift it.

It also helps protect them if you make a mistake like this:

https://www.miataturbo.net/attachmen...ine=1394024993

Dumped it off around 55 or so? Just kept my foot in it and drove it back on track.

This is all that happened and when I later removed them the frame was barely touched.

https://www.miataturbo.net/attachmen...ine=1394024993

I know it's an easy place to save some of the budget but I'd hate to see you pick up an eBay intercooler. :facepalm:

Let me know when you get to that point. Our smaller unit is a direct bolt-on. You'll likely eat up the money you saved on an intercooler trying to get an eBay unit mounted.

(Same installation procedure on the NA)
https://www.miataturbo.net/attachmen...ine=1394030244

Basically, if you keep your HP target at around 200HP and use good engine management, you should have a reliable car. You are far from breaking stuff at that level.

On the undertray, make sure the radiator is sealed to the mouth. There should not be a gap on the side of the radiator to let air around it. That is the challenge with fabricating an undertray from a flat piece.

As for the picture of the scraped up frame rail, +1000. That's exactly why I have them. You should see some of the curbing at MSR-C.

If you add door bars along with a roll bar, sell the butterfly IMHO.

I would recommend safety wire on the turbo fasteners when you complete the install. The nuts would back themselves off from the sustained high RPMs leading to a massive exhaust leak.

I'd recommend TSE stud kit for the turbo fasteners. Nothing to do with sustained high RPM, everything to do with temperature.

There's a nice picture in my Silver build thread of what happens when you use steel connectors and try to keep it together with safety wire. It will stay together at least, but it won't be sealed. Get the TSE stud kit and it's set and forget.