miata questions: budget boost build edition

Since the horrible death of my beloved 95 M edition last fall, I have been contemplating what I will replace it with. The short term answer is shifter kart, and they have been more wildly entertaining and so over my ability that it’s just funny.

I’ve decided that once the lawsuit from my wreck is settled I’d like another miata. My plan is to buy a cheap cheap version, rust free as possible, but I don’t care about mileage or even if the engine is blown. The goal would be for me to build a new boost friendly engine for it, as budget minded as possible. Mainly I want to do this because I’ve done lots of mechanic work but never built something up from scratch. I realize the stock engine ends runs into problems about the same time the trans does. I’ve heard the 6 speeds are stronger, but how much stronger?

Once done, the car would be used mainly for cruising around, monthly autox, and maybe a couple track days a year. I plan on doing all the cooling/reliability upgrades needed to make it as reliable as possible on the track. So what is a recipe if your starting with a bare block for a boost miata motor? I don’t have a specific HP or Torque goal in mind.

So what are the best bang for the buck? What can I pull from other cars to Frankenstein the best boost friendly motor together? When it get’s installed I’ll be doing a megasquirt 3 PNP.

Pistons? I’d assume lower compression to allow more boost

Rods?

Head? I thought I saw a listing of various head improvements and flow on flyin miata’s website, but I can’t find it now. What are the best bang for the buck improvements?

For cooling, I plan on doing the coolant re-route, oil cooler, all of Flyin Miata’s radiator/fan upgrades and hood vents.

icaneat50eggs wrote: So what are the best bang for the buck?

Probably an LS-X on a performance/$ scale, especially if you do the work yourself.

I need to know dis

Have you considered an ecotec swap? fairly cheap up front and go fast parts are even cheaper

H beam rods if you want more than 250ish hp and forget the 6speed, the 5speed is much better matched to boost. Thats ultra budget, if you want to spend more obviously get forged lower comp pistons then some head work.

I'm not very interested in the swaps. I've already checked the box for sticking an engine and trans somewhere it was never intended to go box on my bucket list. What I haven't done is assembled a whole engine.

Another question, on the 6 speed, if you swapped the rear end for one that's much higher, couldn't you space out the gearing? I've read about this somewhere but I can't find it now.

The factory 6 speed already has the highest (lowest numerical) rear gear ratio. So no.

I'd stick with a 1.8 motor over the 1.6. Transmission and bottom end are both good up to around 250 hp. The 1.8 gets you a beefier rear end and better brakes.

As far as actually sourcing the turbo and such? I'd like to know as well. The people with money always say "just get the FM2 kit and be done with it." It'd be more interesting to find the JY turbo from a XXX car and injectors from an RX8 etc etc to get where you want to be.

In reply to KyAllroad:

When i had my miata and was planning a similar build , i mapped out the rwd volvo turbo i just pulled off of my...volvo.. And it was perfect. It was a tdo4h-13g a 15g or 16t both from the fwd 5cyl volvos would be better for more umph but they all seemed perfect, hotside small enough for the sub 2.0 motors along with the cbv (bult in recirculate valve) made it even more perfect. You can find them all day long in the junkyards and they have the standard t3 flange so the ebay "tacotaco" cast iron $90 turbo manifold would have made it real easy. Oh and the 5cyl "flat flange" is easily welded to a 3in vband for simple exhaust instillation. If you wanted new screw that idea and blow money on a gtx28.

Edit:also injectors from a turbo dsm or t5/R volvo and front mount intercooler from a srt4 rounds out the junkyard package. Dont forget saving money by going with the rusefi insead of megasquirt!

My first suggestion is to go read up on miataturbo.net, a lot of your questions are answered there. Reading before posting though. :)

The highlights are:

• You want an NB head, although there are arguments for both the NB1 and NB2 heads.

• Chinese H-beam rods are cheap and seem to be strong, but not particularly light. Carillos are lighter, but more money.

• Supertech pistons are both cheap and fairly strong. If you want lots of boost go 8.5:1, if you want somewhat less you can do 9:1 to gain some spool. The thresholds obviously depend on what kind of gas you have available.

• Don't cheap out on the manifold. All the cheap fabricated ones crack very quickly, the expensive fabricated ones will go farther but still crack. You'll give up a bit of power with a brand-name fabricated manifold, but gain a lot of reliability.

• Engine management is critical. If you don't have previous experience with tuning the engine, it's recommended to put the ECU in first, learn to tune a naturally aspirated car, then add the turbo.

• The turbo itself is comparatively unimportant. Figure out your power goal then pick a turbo that's the right size and fits the manifold you want to use.

• Cooling is critical if you're going to run it on track. You'll want a good multi-pass radiator (FM, 949, Trackspeed make good ones), a coolant re-route, and lots of airflow management. Removing the AC will help a lot in on-track cooling.

• On track you'll want significant brake upgrades.

• Assuming "mechanical empathy" a 5-speed will have a shortened life in the mid-200 rwhp range. It will be usable, but should be considered a consumable. A 6-speed will let you move that range higher by 50-100 rwhp. A lot of it depends on how you drive, and the grip level of the tires you use on the car. The 6-speed costs around a grand, and with a turbo you really want the 3.6:1 rear end ratio in the transmission. New, the gears are $600, plus a couple hundred more to put them in.

• If your power goal is below 350-400 at the wheels, a turbo is more cost-effective than an LS-X. Above that the GM motor transplant comes into its own.

You haven't said power goals, budget goals, or usage goals, so it is really hard to give recomendations.

If I was looking for solid street reliability and had a little money to spend, I'd buy the FM kit and bolt it to a nearly stock 1.8L, and target about 12 psi and 200 hp. Easy to bump it to 18 psi and 250 ho occasionally.

The stock engine is reasonably boost friendly. We run the Mumpkin at about 18 psi all the time and thrash on that 200K stock 1.6L. Making about 220 hp, with junkyard parts and dirt cheap, but I wouldn't trust it for street driving.

The Texas A&M car ran ethanol. With a 1.8L and a better tune, they were pushing 300 hp. Again, I wouldnt trust it for street driving.

Cooling is certainly an issue. All the normal recommendations, plus one that everyone forgets- the fans. The Miata has 2 separate fans- one for cooling, and 1 for AC. We rewired the AC fan to run with the coolant fan- doubled the air movement across the radiator. Solved all our cooling problems immediately. I've also never seen a Miata with decent fan shrouds (including intake gaskets to force air through the radiator).

For a daily street driver, I'd want to spend more and gain a bit of reliability. But the actual engine build?- I dunno... stock engine can handle a lot.

If you want 400 hp and reliability, you are out of the range of a Miata engine.

I've been on Miataturbo a ton, I've searched and read but honestly I trust the folks here more.
For the turbo system itself I fully plan on hitting the easy button and have Flyin Miata hook me up with the no electronics package. I've done megasquirt before, and have free dyno time to fine tune.

Power goals - 275-300 HP?
Budget - I don't know. I don't want to be cheap for the sake of cheap. I can afford to buy whatever, but this is kind of a personal challenge to see what I can build myself. I don't want to drive the price up needlessly

Performance goals. Drop kick the crap out of my dads s2000 in autocross is the baseline. If I can get to where I'm closer to the fastest locals guys at autocross it's even better.

In reply to icaneat50eggs:

I suggest you listen to Rex and Codrus. Skip the blowhards at Miataturbo.

I ran an FMII '95M as a dual purpose track/street for years and just sold it a couple of weeks ago. 10-11 PSI on a stock long block worked fine and provided plenty of shove. Any more boost would require more of everything (hard parts & cooling) for reliable track work. I still broke stuff, did a lot of upgrades and learned a lot about the necessary hardware & tuning over that time. Among other things, I'll add 10mm inconel studs to Codrus' must have list above. Feel free to PM me if you want more details or want to talk budget.

Good luck with the build!

The Mumpkin was getting in the top 6 or so at the events it attended prior to the challenge. It only got beat by some seriously prepped hardware. It placed second in the autocross at the challenge-to a turbo Miata. Unless your dad is into serious modifications to his S2000 you shouldn't have a problem beating him.

In reply to MrJoshua:

Well... autocross is much more about driving and suspension then it is about engine or power. A built engine in a stock Miata chassis with a inexperienced driver will not beat a sorted S2000.

The Mumpkin had a well sorted suspension and a good driver, in spite of it's power limitations.

icaneat50eggs wrote: I've been on Miataturbo a ton, I've searched and read but honestly I trust the folks here more. For the turbo system itself I fully plan on hitting the easy button and have Flyin Miata hook me up with the no electronics package. I've done megasquirt before, and have free dyno time to fine tune. Power goals - 275-300 HP? Budget - I don't know. I don't want to be cheap for the sake of cheap. I can afford to buy whatever, but this is kind of a personal challenge to see what I can build myself. I don't want to drive the price up needlessly Performance goals. Drop kick the crap out of my dads s2000 in autocross is the baseline. If I can get to where I'm closer to the fastest locals guys at autocross it's even better.

I like these goals.

275-300 is aggressive for street reliability, but attainable with the boost turned up on track.

SVreX wrote: In reply to MrJoshua: Well... autocross is much more about driving and suspension then it is about engine or power. A built engine in a stock Miata chassis with a inexperienced driver will not beat a sorted S2000. The Mumpkin had a well sorted suspension and a good driver, in spite of it's power limitations.

Indeed, power is only one part of the equation. Few cars have a chance of beating a well sorted S2000, no matter the prep level. A well prepped powerful Miata does.

Well yes, and at that point what level of prep are we discussing? If his S2000 is B Street and your Miata is SSM your PAX is gonna be tough. Since Miatai respond primarily to playing to their strengths however, it's the handling prep that makes them so absurdly fast in CSP trim.

Get the car sorted out first with Hoosiers and suspension and then bump the power. 300 whp may be more than you really need anyway.

As far as miataturbo.net goes, you don't have to post to get useful information by reading various threads on there. :)

If autox is one of your primary goals then it will probably influence your choice of turbo. The big power turbos (3071s, for example) generally have significantly poorer spool up than a smaller one (2554, 2560), and the additional top end power will be hard to take advantage of on a small course. The cheap Garrett knockoffs from various Chinese manufacturers that are all over ebay are also not a great choice for this application, because they tend to have lousy spool response.

Inconel mounting hardware for the manifold-to-turbo is the right choice, but my preference is for 8mm studs, not 10. Going from 8mm to 10mm is a significant increase in PITA-ness (you need to re-drill and re-tap the manifold, for example, and there's a lot less clearance for installing stuff) and in my experience the 8mm studs are enough.

An FM2 no-electronics kit is a great starting point. I have essentially that on my car at this point (albeit an FM2R using the external wastegate on a 2863), with an MS3 computer and some id1000s. I will say that I'm not a fan of the ceramic catalytic converter that's in their current 3" exhaust system, though. It's got substantially more back pressure than the metal core cat that they used to sell (which, unfortunately, had longevity issue), and it really shows.

KyAllroad wrote: 300 whp may be more than you really need anyway.

Does not compute!

icaneat50eggs wrote: Another question, on the 6 speed, if you swapped the rear end for one that's much higher, couldn't you space out the gearing? I've read about this somewhere but I can't find it now.

I've heard about this. You use the 3.63:1 ring & pinion. Basically 1-5 are a touch tighter than a 5/4.30 and then you have additional overdrive with 6th. Unfortunately the 3.63 Torsen is super rare, (MSM only, I believe) so there goes "budget"

Mine has the 5 speed (97) with a 4.3 torsen diff out of a 99. It helps acceleration but man is it busy on the highway! Good autocross setup though.

In reply to KyAllroad:

I also have the 5-speed with the 4.30 VLSD and a 1.6L. Definitely kind of buzzy on the highway but also agree that it's great on the autocross. I hit 2nd gear and never touch the shifter again. Plus on the highway you never need to shift down for overtakes, you are always right in the powerband