Why aren't miata engines so good for all-motor power?
 

When people build Hondas they make these high revving stroker engines with cams and such, and make ridiculous amounts of n/a power, but usually when people want fast miatas they put a turbo on it, else they do a K swap. What makes Honda engines different? How much power can you make from a miata n/a?
​​​Not sure if this is the right thread. But i was thinking about this lately. Considering buying a Honda just for the experience and fun tuning something different.

Crank support and head design which allows for more air to get to the engine, mostly.

Wut?

I really enjoy messing with my miata and want to work on a K engine. I think it would be fun.

Madjak has a thread in this same subforum in which he makes 220whp out of a BP with all sorts of goodies. I *think* it's a 1.9L. So double the original WHP the car came with. Is that the kind of thing you're talking about?

Now if you just wanna play with a K engine, then go right ahead.

Mostly because you can build a solid low lag turbo miata for less effort than trying to make the same power na. If I wanted NA power I'd not choose a shitty sounding honda engine and put in a light v6/v8 for both require plenty of effort.

This.

Melody,

165whp on E85 is about the limit for cost effective power. N/A BP's don't make serious power without huge cams. Even then a junkyard K24a2 will embarrass it. The funny thing is that N/A power is all cams. You can put a stupid huge set of cams in a bone stock BP4W with nothing more than stiff valve springs and make 185whp on E85..briefly. Madjaks engine is highly developed and just matches the junkyard K24A2 with a header. The difference is the K24 will last like 200hrs.

We have put together maybe a dozen 150-170whp BP track cars in the last 12 years. Only one 8500rpm, 200whp, ITB 2.0L. That car was fun but made no sense in any context.

Then there are turbo BP's. The current record is something like 650whp in a drag motor. But 400whp track builds that have 50+hrs on them are almost commonplace. That full race 400whp BP cost only 2-3k more than a K swapped anything. That the 400whp BP can just about be ordered off a website or two and just bolted together furthers it's position as the preferred option.

There is a reason this forum is named so.

50 hours?

Dammit!

Why do I keep turning up the power if it is shortening the life of my engine so much? This is supposed to be fun and cheap, haha. Maybe I'll stay with 330.

That's not a hard number. That also assumes 50 hours at max power. I think a dry-sump motor with Billet crank and Billet main bearing caps could be built to last longer.

I've always been puzzled by people who, absent any rules-limitations, elect to build insane naturally-aspirated engines.

If you're doing it just for the sake of doing it, then I can respect that. That's Hackaday.com kind of stuff.

But if your goal is to wind up with a car that's daily-driver-friendly yet also insanely fun when you have some open pavement in front of you, and you're working with a 4 cyl chassis, then it just makes no sense to ignore forced induction.

Yeah I know hahaha I looked up MadJaks miata that thing is absolutely wild and probably totally undriveable. Thats why my car is a turbo. I'm not trying to make something like that necessarily, I just think the concept is interesting because miata tuning and Honda tuning are just completely different fields, and I was recently watching some videos on the origins of Spoon, and saw a guy who has like a 700 horsepower n/a k24. I think its just so fascinating and something I want to try when i get more time and money.

Spoon? Their annual tuner and r&d budget is probably more than the cost of a large house.

https://cimg8.ibsrv.net/gimg/www.mia...80547209c8.gif

Ive seen some K series bored and stroked way out so theyre like 2.6L or more, running methanol, making ~500hp. Theyre also drag racing grenades Id imagine.

But to the OP, this tells the whole story:

BP:
https://www.miataturbo.net/attachmen...eadcompare.jpg

B16:
https://www.miataturbo.net/attachmen...e-dsc00704.jpg

K20A flows better stock than a race ported B16 head. This is why they make big power so effortlessly. All you have to do is build it to support the RPM, throw wild cam profiles at it, and you get all the power.

It was an economy engine designed in the 80s.

mindblown.png

I've seen those photos before. Something about them has always bothered me, and I just figured it out.

In the Honda cutaway, the slice has been made right through the middle of the vale-guide bores. This means that the ports have been sectioned at their widest point, presupposing that they are roughly circular and also co-planar with the valve stem.

In the Mazda cutaway, you can't see any of the valve-guide bores. This suggests that the cut is not through the center of the ports.

Or, put visually:

https://cimg2.ibsrv.net/gimg/www.mia...e64f9a0eb0.png


I'm not disagreeing that the port design in the Mazda BP-series heads is sub-optimal, but those photos seem disingenuous to me.

I noticed the same thing. It definitely makes the BP ports look smaller than they are. The shape is very obviously worse though.

The BP just doesnt breathe well and takes too much work to get it to do so in N/A form. 80s technology

The K series engines are modern and breathe very well and they dont mind higher RPM they are designed for it. Modern Technology

OP's next question:
why aren't Miata's so good at transporting a family of 8?
why aren't Miata's so good at being a pickup truck?

stay tuned folks, this is gonna be a real gripper :D