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Hi guys, I am looking at a possibility of dropping either engine into my 89 Miata.

I'm leaning more towards the SR20DET as it seems to be the cheaper option and less hassle as the k20a is still relatively new.

Also has anyone had any trouble or heard of people registering it to the VicRoads, as I want a track ready road car.
I only want to ideally spend nothing over 5k for the full conversion and hopefully have it register ready.

Put yourself in my shoes, what would you do?
Thanks in advance for the feedback.

What size are your shoes (and how deep are your pockets).

Others can answer the Vic question, however a quick search of the forum will show that what you are asking for will be 'difficult'.

What is the problem with using a BP engine anyway? They can make good horsepower using forced induction on stock internals.

A total dream due to the $5K budget. You will blow $2k for an Engineering Cert (not doing any mods) and Emissions testing.
Go the turbo route on a BP engine - your budget fits easily.

just the Honda custom sump or dry sump will cost you more than the $5k. There's a lot more to them. Get a second job and buy my setup. Selling for $20k and it's a $20k discount on what it cost me.

Also SR20 seem cheap but at wrecker prices they far from reliable.

What kind of times are you getting in a stock car? Are you anywhere near the better club level drivers? If not, do that first, then come back.

Or is your theory to throw $5k at a billion-ty kilowatts so that you can become fast?

Guys, don't scare him off!

I had dreams of dropping in a K but ended up going down a different route. The costs for any conversion end up being a lot more than you first expect. My spreadsheet of costs for a K20z1 conversion ended up over the $10k mark and that was with a high Aussie dollar at the time and with myself doing all the work as well as some fabrication. It's really not realistic for anyone in Australia to achieve cheaply which is a shame given how nice a MX5 would be with a well built K20. I think realistically the cheapest you could achieve would be $12-15k.

As for the SR20DET, once again the costs add up. You might be able to get one in for your $5k budget if you can find a cheap secondhand kit as well as a good secondhand engine. You'll need an Ecu and wiring, exhaust, better cooling, plus a lot of time to get it to work. It's not really an easy undertaking unless your familiar with engine swaps or familiar with MX5s. If you don't have either experience it's going to be big task.

If your 1.6 is in good condition, look at the various turbo kits available. You can get up to 250hp with a good setup and the 1.6 is pretty much already built to slap on a turbo. If your 1.6 engine is a bit old, then you can look at doing a 1.8 swap. Either way you'll learn heaps about your car and how it works.

A MX5 doesn't need massive power to be fast... speed is all in the handling and being nice and light. A 1.6 with a turbo will get you in heaps of trouble as it... Even a 1.8 is a good upgrade, especially with a few easy bolt on upgrades, like a CAI and extractors / exhaust.

Would be cheaper to buy a 180SX or 200SX.

Madjak has pretty much summed
Up the sr20 swap. I looked into it but just the sump is $2000
Plus the age of these engine is getting on.
You need custom tailshaft wiring and lot of other bits

K20 is a poor choice of a k24 for a start. Almost impossible to feed it enough oil at the higher revs where a k24 doesn't rev as high and needs less oil.

That said.... No way your going to come close to a k swap at 5k.

Track read car? Have you got the following
- race seat
- harness
- roll bar
- decent suspension
- good rotors and pads
- 1.8 or better brakes.
- track wheels and tires
- limited slip diff
- helmet

If not - there's a couple of k you need to spend before you can think about an engine swap.


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sailaholic wrote:K20 is a poor choice of a k24 for a start. Almost impossible to feed it enough oil at the higher revs where a k24 doesn't rev as high and needs less oil.

Off topic, but I'd do a K20 over a K24 for a track car.
1) you can run in the under 2000cc class
2) it's more happy to rev than the K24 so it suits my driving style and IMO a MX5
3) You can remove the VTEC (race cams) run a higher flow oil pump and get them reving to over 9500rpm with over 250HP pretty easily... This combination in a MX5 would be a class winner I think (may as well chuck in a quaife sequential too whilst your at it)

For street use / autocross then yes, K24

Mine is the K20A head on the K24 with a compression bump and upgraded CAMs
300+ bhp on 98 Octane, a few more hiding with E85.

all the K24 Frankensteins at 8000 go straight past the K20 revving out to 9000 and beyond.

Don't worry about classes, once you go cross make it's typically a prototype only classification.

Even in outright class, if you're in the 2000-4000 class you're up against some serious competition with forced induction, like fully developed Evos and WRXs as well as supercharged lotuses etc... really the MX5 can't win regardless of power as the competition has more power, aero, brakes and less weight. Under 2000 you stand some chance of actually being competitive since its basically it's a n/a class. I'm not that far off the under 2000cc outright class in most events as it is.

Personally, I'd stick with a K20, but that depends entirely on the motorsport you do.

Can you put a B3 bottom end in an NA8 and turbocharge it to stay under 2L?

In an outright class you can do whatever. Run a space frame, fiberglass panels etc. Some of the quicker cars in my series run supercharged Hayabusa engines. I think if you were going to the trouble of using a B3 bottom end you may as well use something else entirely though.