K20 mx5

[madjak]

Hi guys,

I'm looking to fit a k20 motor into my MX5. I can now get all the conversions parts from the US. I'm looking for clean, free reving N/A power for use on a track / sprints. I'm not familiar with honda engine so here's a few noob questions:

1) Where to buy a K20 motor. Seems there aren't many in the classifieds etc. Can you import them or are there other sources in Australia? I'm looking for just a long block, so no transmission, exhaust, IM.

The K20 will bolt up to the stock transmission which is good for a max of 250HP. So I'm looking for an engine with around 230-240HP. Now the IM won't fit into the car so I was actually looking at ITBs or fitting a S2000 IM. so my next question is:

2) what should I actually look for in terms of getting to 230 HP. K20a, K20a2, K20z1 etc all look to get around 200HP as stock, so is any preferred for minor tweaks? Would ITB's and ECU be enough to get it one to my 230HP target?

3) instead of doing all this myself, should I just get a built motor? ie spend more now to save later.

4) Revs, Revs, Revs... I like them, so what upgrades would be best? Lightened rods, rockers, better valve springs, cams, Kpro?

cheers

edit: and I don't want to fit a K24 motor. I want to stay in the under 2000cc class.

[EKVTIR-T]

getting an engine,you could buy a removed motor from one of the tuning shops,they sometimes pop up for sale but its a big gamble on the motors health as some on this forum have found out

a better way is buying a damaged donor car with the k20 like integra type R or S and civic type R

230hp is easy with basic bolt ons and tune,no need for ITB really

and exactly how high do you wish to rev? that also depends on your gear ratios and where you want to be


btw which mx5 chassis? NA I assume?

[mocchi]

you have a budget?

[Chernoby1]

Not related to the engine, but i would be worried about the gearbox taking "250 hp". HP doesnt really break boxes so much as torque does and youd be surprised at the amount of torque that can come out of these engines (~200nm).

Getting your hands on A k20 isnt the cheapest of endevours so i would personally recommend a destroked H22a (aka an F20b)

[madjak]

Yes NA... Gearing I'm not exactly sure how that will all work with the existing gearbox, 4.3:1 diff and 15" rims.

The reason for the ITB's is to fit into the engine bay. Seams a nice way to get around the IM issues (standard intake would be through the firewall at the rear of the engine). Alternatively, I can get an adapter to fit a S2000 intake which would sit correctly. I like the idea of the ITB's as it's not going to be driven much on the street.

Can you get halfcut imports or would I need to look for a write-off locally?

[madjak]

If the transmission can't take the power, remember the mx5 is pretty light and I am a gentle driver (or try to be), I can put a 6 speed MX5 box in which will take more power. At this stage, I'm trying to keep costs manageable to start with, and then upgrade later, which is why the K20 is a good starting point. Eventually it would be nice to get 280+ HP but thats later down the track.

Costs will start to build up, thats really why I'm posting now to get an idea of the engine costs. I know everything else I need and it's not going to be cheap.

[u mad?]

i have a jdm k20a ( higher comp, better cam) for sale atm, if buyer falls through i will pm you

[madjak]

For comparison, my stock 1.6l mx5 motor will only get around 130hp so this will be a substantial upgrade. Turbo upgrades will get the little 1.6 engine up to around 240-250 at which point things will start to fail, like the rods, or the gearbox.

It may be that the first stage is just the stock engine, then look at options for more power / revs later.

A stock K20a / K20a2 your looking at 7,500rpm ish, maybe 8000 with an ECU, is that right?

[lolmclol]

http://www.k20a.org/forum/showthread.php?t=112309

do it OP

[madjak]

http://www.k20a.org/forum/showthread.php?t=112309

do it OP

Yes that is the kit... however there would need to be a few mods to that to fit it into a RHD car. Power Steering and exhaust don't fit.

[Stevil]

Well I dont see turbo mx5 gearboxes failing with normal abuse so a K20 is hardly going to change things. whats ya location Madjak, what classes r u thinkin of competing in should you do the swap ?

[madjak]

Well I dont see turbo mx5 gearboxes failing with normal abuse so a K20 is hardly going to change things. whats ya location Madjak, what classes r u thinkin of competing in should you do the swap ?
I'm in Perth and currently doing club track and hill climb events as well as a speed series.

I would basically go into an outright (closed body) under 2000cc class in the speed series, which puts my up against some pretty quick cars. I currently run against AE86 and Lotus which makes it hard to compete. I really don't know how the mazda would perform with a K20, though I suspect it would be pretty fast. Light, low and able to get the power down quickly out of the corners. The turboed 220HP ones put down some pretty good times, and I think the NA K20 would be more drivable.

Currently the car is road registered so I would probably try and keep that subject to getting all the right approvals.

[curtis265]

Interestin - subbed. Any reason why Honda K series?

[madjak]

Interestin - subbed. Any reason why Honda K series?

Seems to be a good match for the car. High powered light engine around the same size that can get good clean power with a nice sound. There are other Honda motors I suppose, but this kit makes it easy to fit a K20 / K24 without doing all the hard work getting it to fit. There are lots of nice bolt on upgrades to the engine and lots of info out there on how to get power out of them.

[stndrd]

Good to see some guys in Oz are looking into these recently released conversions.

I have a JDM K20A & a K20Z1 with Z4 pistons and a JDM cylinder head/cams for sale if you are interested

[SHOGUNOVDDRK]

http://www.k20a.org/forum/showthread.php?t=112309

do it OP

http://www.k20a.org/forum/images/smilies/xwtf.jpg.pagespeed.ic.tIjnbNHVa0.jpg

[thomwootton19]

Dude buy a dc2r motor

[SHOGUNOVDDRK]

Dude buy a dc2r motor

Engine spins the wrong way iirc and he can't adapt an mx5 box to it.

Go hard OP, we'd like a build thread here also.

[curtis265]

Why would you B when you can K if it's already going to be custom work?

[madjak]

I actually have access to a cheap K20A3... I know they aren't ideal, but what can be done to them that's cost effective and will bring the power up to the 200-220 hp mark? Or are they really not worth looking at? Are there items that I can install on a K20a3 that I can reuse later on better base. Things like flashing the ECU to a honda k-pro, cams etc.

I was thinking I could build the car and get it running the the K20A3, whilst I source and build a higher power K20a motor. Given the cost of this build I think I would probably look to get a little more power out of the engine than I was originally planning. I may as well go the whole hog if I'm going to do this. I've already sourced a 6 speed box for the mazda which I'm going to put into it for this year. The 6 speeds can handle mode torque / power so it will be more suitable when I do the engine conversion.

[u mad?]

k20a3 are fukin shit. might be ok while you source/build another engine though. not worth trying to get power out of.

Those mx5 6 speed are the same as the rx8 gearbox if im not mistaken, seem to be good for around 400 or so hp.

[PHO]

K20a3 is a potato.

[hondapop]

Hook it up to an alloy V8. There's sure to be a yank that's done it.

[madjak]

Hook it up to an alloy V8. There's sure to be a yank that's done it.

here is the link to the V8 Conversions http://www.flyinmiata.com/V8/ and they are actually quite common. I have run against a few V8's in my little 1.6 and I'm only a few seconds off their track times. It's hard to get everything balanced with a V8 in such a small chassis.

So it's not really my thing. If I want power I'd turbo a 1.8l Mx5 engine... but I prefer drive-ability of NA over turboed power any day.

[madjak]

K20a3 is a potato. What about these killer vtech builds? Putting the exhaust rocker on the intake to remove the vtech and using a2 cams. They seam to get 200hp out of a a3 pretty easy. Though there are a few that have grenaded by the sounds of it.

[dorikin]

Here you go

http://www.k20a.org/forum/showthread.php?t=112309

[RenzokukenJ]

Subbed for Perth and kswap feel

[chez00]

The gearboxes are actually pretty good strength-wise - their main downfall is the (single) synchros causing crunches, particularly 3rd. This comes down to driver sympathy though - there are fixes but can be fairly expensive. I reckon you'll be fine with a natural K in front of it. There are lots of final drive options available too for the MX5 which are shared with the s2000. Go for it!

[lilthug]

k20a3 are fukin shit. might be ok while you source/build another engine though. not worth trying to get power out of.

Those mx5 6 speed are the same as the rx8 gearbox if im not mistaken, seem to be good for around 400 or so hp.

from what ive been told

same as 6 speed s15 200sx boxes

please correct me if this info is wrong

[chez00]

Yeah the 6 speeds are pretty similar between the mx5, silvia and rx8. The OP would have a 5 speed in the na though I think.

[plohl]

You have to get a rhd sub frame from v8 roadster and fab up engine mounts yourself as the subframes magic will be selling are lhd specfic.

The difference is the steering rack mounts are located different laterally between lhd and rhd.

Using an s2k manifold will be much cheaper than itbs.

You'll need a custom exhaust made to clear the steering rack.

I did a lot of research into this when the k20a thread first popped up. It was looking close to 15k for the conversion with myself doing the labour but paying for the required fabrication.

good luck with it man!

There is an nb mx5 being done by byp at the moment as far as I know.

[dove grey 64]

F20c not even considered?
V8 isn't an option, wants to stick to under 2l class guys

[Stevil]

here ya go Madjak, K24 allready on the go in Sydney, custom Subframe and motor already in ! B-)

http://madmick3006.com/ahngallery/upload/files/2014-03/09a3bbde.jpg

[plohl]

^Got any more info on the sub frame?

[Stevil]

what like this lol !!

http://madmick3006.com/ahngallery/upload/files/2014-03/eb43c62e.jpg

[plohl]

Haha yeah. Like that. It looks pretty fimilar! Haha

[EKVTIR-T]

damn that mx5 must be awesome with the k24

do want

[Vvvtec]

Ask byp for test drive

[EKVTIR-T]

is it a customer car or workshop car?

[Vvvtec]

Evil kestevil should have some more infos

[Stevil]

lol they are recent pics, manifold to be made up, relocate fuel lines etc, I'll update as it progresses B-)

[plohl]

Awesome

[EKVTIR-T]

lol they are recent pics, manifold to be made up, relocate fuel lines etc, I'll update as it progresses B-)if they sort out a conversion kit for audm, will be ballin

opens up another avenue for aussie kswaps

[madjak]

Nice work there Stevil! Don't suppose you want to make me a copy of that subframe? How is the clearance with the power steering?

I had been thinking it wouldn't be that hard to make up a custom subframe. Extractors aren't that hard either the tricky bit is getting all the lengths right for performance especially for N/a.

I'm waiting atm as I plan to run the full season this year as is. I'm focusing on chassis setup with the aim of starting collecting parts for my build towards the end of the year. This will give me time to build the car and hopefully by then someone will release a RHD subframe.

I have just depowered my steering rack and i'm going to install a six speed box so my power targets can raise a liitle. So k20a(2) it is...

whats the going price for a K20a, K20a2, k20z1?

[plohl]

^sounds awesome man! Keen to see how you go with it.

The subframe Stevil posted looks like the v8roadster one. IIRC A few people have looked at building custom ones before, but unless you can fab it'll end up costing more than buying one. Lucky7 Racing have also got a subframe out now for 13b conversions. Subframe would also be dependent on how you're going to do the sump, or visa versa.

I have a solidworks file with the front and rear suspension geometry somewhere if you want that. Although I don't think it includes the anti-dive incorporated into the top pick up, and it's an unknown source so not sure of it's accuracy.

[Stevil]

Madjak I wish it was my car ! Thou I'm considering putting a K series into another mazda B-) ! Lol ....

[YZFr1]

Just wondering, how much does it cost to put a k20a in an mx5?
Also, Is it alot more $ than a k20a in a ek civic?

[RenzokukenJ]

Pm Vvvtec and TbM, they have done both

[madjak]

I ended up going for a fully built n/a 1.8 mazda engine in my car. Nothing compared to a K20 but then I am running in a production class at the moment.

Later in the year I'm putting a Rotrex on the engine which should bring the power levels up a bit.

In terms of K20 / K24 in an MX5, costs really range from around $7k upwards depending on how much stuff you want to make yourself. Still it's not bad, given you can purchase a fairly tidy NA6 for $3-4k. The total package I believe would make a very nice road / race car with good balance and power.

[YZFr1]

Pm Vvvtec and TbM, they have done both

sadly, no reply

[YZFr1]

I ended up going for a fully built n/a 1.8 mazda engine in my car. Nothing compared to a K20 but then I am running in a production class at the moment.

Later in the year I'm putting a Rotrex on the engine which should bring the power levels up a bit.

In terms of K20 / K24 in an MX5, costs really range from around $7k upwards depending on how much stuff you want to make yourself. Still it's not bad, given you can purchase a fairly tidy NA6 for $3-4k. The total package I believe would make a very nice road / race car with good balance and power.

oh i see

[carayan]

byp has done it, but they're a bit ehhhhhhhhhh

if u got money, any workshop worth their salt could do it