I know there are a million better ways to get more power under the hood of a Miata, but for some reason the idea of a superlight naturally aspirated NA remains intriguing to me. Simplicity, purity, whatever you want to call it.
So, what's the recipe for a strong n/a 1.8? (Well, I'm guessing it doesn't stay 1.8L...) What kind of power figures can one expect to make without going totally nuts in terms of unobtanium rods and such? And how many cubic dollars will it take?
alex wrote: I know there are a million better ways to get more power under the hood of a Miata, but for some reason the idea of asuperlight naturally aspirated NA remains intriguing to me. Simplicity, purity, whatever you want to call it. So, what's the recipe for a strong n/a 1.8? (Well, I'm guessing it doesn't stay 1.8L...) What kind of power figures can one expect to make without going totally nuts in terms of unobtanium rods and such? And how many cubic dollars will it take?
Yea, either of the early engines are not exacly lightweights. Cast iron block does that for your. If you want superlight, the NC 2.0l is an aluminum block.
Ok- so that doesn't answer your real question...
I'm sure some of the more experienced guys will jump in here soon enough, but from what I've read, 150 hp is attainable on a stock VVT motor with bolt-ons and a very very very good tune. (I think 949 racing did something like that with their 95R). This is all doable without spending too much.
Also, look into the MSM intake cam, they're supposedly good for 5-7 hp.
If you open up the motor and run high compression, headwork, and (some say) ITB's, you should hit 170-180. But at that point, you'd be better off with a supercharger/turbo.
In reply to alex:
http://www.motoiq.com/projects/mazda/project_mazda_miatabusa.aspx
The 1.8 is a heavy pig and doesn't really respond to N/A mods that well. With a dedicated ECU, ITBs, Mazdaspeed high lift cams, higher compression (and octane), and an NB head you'll be lucky to see 170-180 whp. You can bore it out a little and install a stroker kit for a little more, but at that point you're $15k in the hole. A turbo will get you a reliable 250 whp for about $3.5 to $5k.
I should add, I like building motors. So tearing one down is kind of a plus for me. Spending metric dollars on weird parts that don't net a whole lot of power gain isn't a plus, however. If pistons/rods/crank are all that expensive to get more displacement out of it, I may be re-thinking this idea.
@alex, depends on what you call expensive but I have a set of pistons for a 1.8L NA motor at maximum overbore (85.5mm IIRC, 9:1 compression) that are taking up shelf space.
You could swap in a sweet, moderate (170hp) 4AGE 
Or if you want an n/a, high twisting, monster.. a 250+hp, 170 #/ft Loynings "tall block" (7AG).... 
On a side note... I know the Mazda head isn't the best for flow, but typical work on the bowls, and seats, a nice flowing 3 angle, as well as on the compression bumps should net you a nice improvement
This post. Emilio is using the '01-'05 VVT motor as his "base" here.
I've been slowly pitching a super-low-mile VVT motor into my '94, hoping to nail that 150 number when all is said and done...
Came here to post Emilio's post.
My plan is to build a VVT engine this winter. High comp pistons, +2mm overbore, headwork, cams, squaretop intake, full exhaust and an MS3x. Hoping for 165-175whp
K24 swap kit in the making....
just buy a wadded up RX-8 for a drivetrain donor.
alex wrote: I should add, I like building motors. So tearing one down is kind of a plus for me. Spending metric dollars on weird parts that don't net a whole lot of power gain isn't a plus, however. If pistons/rods/crank are all *that* expensive to get more displacement out of it, I may be re-thinking this idea.
A VVT head bolts right up to the lower compression 1.8L blocks, and gives a meaty torque bump if you happen to throw a turbo in the works. I may or may not be in the middle of doing this myself.
I once figured the expected weight savings for a BP with an aluminum block, using the percentage difference in weight between a bare iron LS block and a bare aluminum one. I think it came out to 15 lbs.
I've owned a 180 rwhp Miata motor with torque. We have another one at FM. They're a lot of fun. But they're not cheap. Emilio has a few secrets he doesn't always share, and he's digging deep into naturally aspirated power for the particular classes he races in.
The stroker kit mostly seems to fill in the bottom end, not add a lot to the headline peak power number. That's fine, it makes the motor a whole lot more driveable. But it's not cheap because there's no such thing as a mass-produced stroker crank for the BP. Only ones that are machined one at a time.
I'd be happy to sell parts to do this. But I have to admit that an S2000 engine swap might be an easier way to go...
In reply to Keith Tanner:
Have you guys measured a duratec, I mean mzr engine from an NC? I've never seen a direct comparison.
Keith Tanner wrote: I'd be happy to sell parts to do this. But I have to admit that an S2000 engine swap might be an easier way to go...
Is anyone out there commercially producing the parts to make this swap happen? I've seen a number of amateur swaps, ranging from hopelessly janky to pretty slick.
Swank Force One wrote: K24 swap kit in the making....
I really, really, really hope this develops. I'll be watching closely.
psteav wrote:Keith Tanner wrote: I'd be happy to sell parts to do this. But I have to admit that an S2000 engine swap might be an easier way to go...Is anyone out there commercially producing the parts to make this swap happen? I've seen a number of amateur swaps, ranging from hopelessly janky to pretty slick.
There's someone who recently started work on a K-series swap kit. Apparently the K-series is even cooler than the F-series in the S2000.
Original thread, plus the MiataTurbo hyenas take on it.
alfadriver wrote: In reply to Keith Tanner: Have you guys measured a duratec, I mean mzr engine from an NC? I've never seen a direct comparison.
Nope. Don't have any available right now, but I'll try to get a good apples-to-apples comparison at some point.
Sorry, I don't speak Honda Alphabet. K-series is one of the relatively new versions, I assume? Obviously it's not one of the reverse rotation jobs. The pictures look promising, as long as it fits under the hood with the oil pan as high as it looks in those pictures it may turn out well. It'll be interesting to see what the final cost will be on it as well. Should be a fair bit less than the V8s because you can keep everything stock behind the clutch, but of course you're also not looking at 400 lb-ft 
It's funny - I get a lot of phone calls about oddball swaps. Everyone wants to be the second person. It's gotta be different (those LS swaps are soo played out, plus the car is a nose-heavy understeering pig) but they don't want to deal with the problem solving.
Keith Tanner wrote: Sorry, I don't speak Honda Alphabet. K-series is one of the relatively new versions, I assume? Obviously it's not one of the reverse rotation jobs. The pictures look promising, as long as it fits under the hood with the oil pan as high as it looks in those pictures it may turn out well. It'll be interesting to see what the final cost will be on it as well. Should be a fair bit less than the V8s because you can keep everything stock behind the clutch, but of course you're also not looking at 400 lb-ft
I don't speak Honda either. IIRC, Ks are in the RSX, CRV, and TSX? And then there's the Lego-like mix-and-match of this head plus that block to unlock the magic...
Interesting swap, though the builder seems awfully flip about moving the steering rack forward 4". I am not a suspension engineer, but that seems like a mighty big change to me.
Most of the power from simple BP builds comes from cams. Good porting will bump intake port flow from around 204cfm to 230cfm at stock valve lifts. BP's don't need or want much compression until you have big cams. We have experimented with CR's from stock to are-you-insane and found the best overall results with modest 10.5:1~11.0:1 ratios.
Rods, pistons, dual valve springs,ACL bearings etc, just allow the thing to survive being spun to 8k. No significant power gains from those parts.
+1 O/S valves are a good idea if you port it. If you aren't porting/deshrouding, don't waste time/money on O/S valves.
The 99-00 Miata have the BP4W (non VVT) head casting. Swapping the standard BP4W intake cam for the slightly bigger BP5A cam from the 04-05 turbo model is a few more cheap and simple hp.
The 01-05 Miata has the BP6D VVT head. The cams are shorter duration than the BP4W so peak power is often a few hp less than an identical BP4W build. The difference is the BP6D has the potential for a more torque below 5500rpm.
A typical street car build around our shop and the baseline SuperMiata spec series race motor is a junkyard USDM 10.0:1 BP6D engine, I/H/E/ECU on CA91 pump gas (like coors only weaker) that will net around 145-150whp and last almost 100 race hours if fresh. It'll tolerate over revs to the high 7's a few times but that's about it. Overrev to 8500 once and you bend all the intake valves a teeny bit. Run the forged internals, dual valve springs, a good damper and you have a near bombproof setup. for less than $4K if yo build it yourself.
Emilio, What cam companies have you been looking at, or have you experimented only with the factory cams?
<- Is looking at a "low buck" 1.6 build, and would love to see 150hp, but knows it's going to take a lot of work, and experimentation. I'm also class limited to 1.6L
tpwalsh wrote: Emilio, What cam companies have you been looking at, or have you experimented only with the factory cams? <- Is looking at a "low buck" 1.6 build, and would love to see 150hp, but knows it's going to take a lot of work, and experimentation. I'm also class limited to 1.6L
OEM or Integral Cams, now out of business. Megacycle in California bought Integrals designs. They're a bit frustrating to deal with but you can still get those cam designs.
I was just reading this thread, I think this is a cool recipe to start with:
http://clubroadster.net/vb_forum/59-irtb-individual-runner-throttle-bodies/81194-my-172whp-n-engine-stock-bottom-end-no-porting.html
Emilio700 wrote:tpwalsh wrote: Emilio, What cam companies have you been looking at, or have you experimented only with the factory cams? <- Is looking at a "low buck" 1.6 build, and would love to see 150hp, but knows it's going to take a lot of work, and experimentation. I'm also class limited to 1.6LOEM or Integral Cams, now out of business. Megacycle in California bought Integrals designs. They're a bit frustrating to deal with but you can still get those cam designs.
Ahh ok. Btw thanks for all the work you've shared with the commuity. It really helps.
alex wrote: Spending metric dollars on weird parts that don't net a whole lot of power gain isn't a plus, however.
Well that's too bad because you just described the process of getting big power gains out of a N/A motor
Seriously you go N/A if you want rock solid reliability and modest power gains. If you want serious power without spending even more serious dollars...you need boost.
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