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So after a lot of research on how racecar aero works, I started on the front splitter.

My goals are

  • Faster laptime (from more downforce)
  • Robust
  • Quick removal.
  • Cheap
  • Light

There are some Motorsport NZ Aero Regulation's that i have to meet, which are:




  • Height (min): bottom of wheel rims, 
  • Height (max): Top of wheel rims, 
  • Width (max): width of the bodywork, 
  • Length: spoiler shall not extend more than 200mm forward of the original bodywork. 


  • Height (min): bottom of wheel rims, 
  • Height (max): 100mm above the vehicle roofline (Sports Cars measured from the top of the full height windscreen), 
  • Width (max): width of the bodywork, 
  • Length: No more than 400mm rearward of the original bodywork

“Bodywork” means all the entirely suspended parts of the vehicle that are licked by the air
stream; and


So measuring the rims I have to keep at least 80mm clearance from the ground, and can't be wider then 1600mm total.

A lot of the other guys running starlets have already built splitters so it's great to see some examples. and get ideas.

This is a very quick 4age powered starlet.


More Info: http://www.themotorhood.com/themotorhood/2016/12/19/si-champs-spotlight-jamie-hodgins-kp61-starlet

And a Nissan 1.8 T powered starlet which is crazy fast when the boost is wound up.

But you do have to be careful about copying as that first starlet is trying to do a front diffuser (where the rear is higher then front), but it's venting into the wheel well, a high pressure zone, so it wouldn't actually be helping, and potentially is hurting rather then having just a flat floor. 

Most of the other starlet racers are using sheetmetal and are attaching it to the front aero dam. That doesn't work for me as i want it quick release I also want it more rigid.


So to make life simple for myself I have started with 4mm ply to use as a template (so i can make multiple for when I inevitably break one), this made life super simple to cut around the wheels.

So currently I've got this:


And it extends nicely to just past the steering rack.


And sticks out 140mm, which is larger then most, but I'm not going to do canards, so hoping this is about right considering i don't go over 200km/hr at the moment so i want it more effective at lower speeds.

I'm looking to add end plates to contain the higher pressure zone on the splitter, and also make sure theres no air getting to the tyre.

Haven't worked out mounting but am looking at Stainless Turnbuckles with the pins, but it's really going to depend on how flexible the final splitter ends up being.


I haven't decided on the final material, but currently contemplating 4mm ply with a fibreglass layer to give it strength, I don't want to to heavy, but you can't have it bending either so it's a balancing act.

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  • 1 year later...
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So as per normal, my best laid plans when to hell and i had other issues to sort out before the splitter.

Brake Cooling:

Brakes have been a continual pain, they are just getting to hot, it's not an issue in races as I'm running good pads, but it means the life span of the rotors and the pads is a lot less then they could be, and I keep going through piston seals.

So I made up some better cool air feeds, basically the air has no where else to go but through the disk, at the same time I went to a smaller hose diameter hose (2") which meant the whole thing didn't really work as I had planned.


Polycarbonate rear hatch:

Tried to get some weight out of the car to help the brakes, so went polycarbonate for the rear hatch.



This was enough to get me though the last club day and I won the overall Canterbury Car Club Championship and came 2nd in my class (1600-2000cc)

With the season over the intention was to get back to the splitter...

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Instead the radiator decided it was time to start leaking. So time to replace it, I had also been concerned that adding a splitter would trap heat in the engine bay (In hindsight this is correct and I would have cooked things).

I worked quite heavily on reducing the impact the radiator had on the aero by ducting the front and blanking off holes (with the overall goal of trying to keep the car still looking relatively normal...





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I also decided to vent it through the bonnet. This had a positive impact on air intake temperature dropping it by at least 10 degrees, which gave a noticeable boost in power.



Got cut down a bit...


The whole unit drops on to some pins and then has some clips at the top, so possible to remove in under a min.





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Finally! got round to finishing off the splitter, I ended up going with 12mm marine ply (the lightest i could find) which ended up being 12kg total.

I chose ply after looking at all the options, I wanted it quick release which meant it needs to be held up by the front and back with nothing in the middle. ACM was flexible and pretty heavy for the size you would need.


I also wanted it to be easy to replace if it got hit for mounting I went with Stainless Steel Turnbuckles (8mm Jaw Jaw) with 8mm tie rod ends (all sourced from AliExpress). 

Some minor grinding on the tie rod ends and making up the ali rear adjustable brackets, and I now have a really solid mount.

It's also adjustable in height and angle and takes my weight standing on the front.

The splitter is all quick release and I can install in about a min, which is great as the car won't fit on the trailer with it.





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Of course the first club day I had the splitter on and got punted off the track (first time for me).

From Behind:


I was very lucky, minimal damage all round, his wheel hit mine and the rear axle took the brunt, he then ran down the side of the car and hit the front splitter which protected the front of the car, I ended up with a couple of bent brackets and turnbuckles, but actual splitter was in pretty good nick.

Aero wise the splitter also had a major impact in high speed braking where i was getting huge weight transfer to the front and so the rears were locking, diffuser was now on the cards.

However I have dropped my PB from 1:37.187 to a 1.36:200

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Got that all repaired and going into the last race of the season had a few things to sort out.

Brakes were leaking at the rear still, so i pulled the calipers apart and found the seals were not the same size as the standard Toyota ones, really annoyed as they were done here in CHCH at great expense by a well known company.

While I was at it I replaced the front ones as well just to be safe as they looked like they were starting to leak as well.

I've had some 1mm Titanium brake pad backing plates made up for all the calipers which I'm hoping will protect the seals until I can replace the calipers all round with proper race ones.




Been a bit concerned going into Winter that if I have to race in the rain that I won't be able to see out of the windscreen due to fogging (I do run anti fog) so I hacked the original windscreen venting to take a feed from a bilge fan which will take hot air off the floor (above the exhaust).



Had the diff in to be checked after the hit it took, and have changed ratio from 4.3 to 4.5 so hoping that's going to give a nice boost at the end of the straight.

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And finally to balance out the splitter I created a diffuser, again out of 12mm ply as that was easiest (prototype for now), mounting was really tricky but got their in the end.

Have made some strakes for it and it's getting painted black to match splitter.




It's height and angle adjustable, and is again quick release as i'm guessing it won't fit on the trailer.

All ready to go for the last club day of the season Sun 5th May (Next weekend).

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Finished Version, just waiting on one mounting point to arrive.



Ended up sticking out further then what i was originally planning as I moved it back from the diff for clearance.

But shouldn't have a negative affect on the aero (opposite probably), and could still go out another 200mm within the rules! 

Can always cut it down later if needed

Only concern is it getting hit by another car, so painted the back red to stand out... 

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  • 4 months later...

So went out for a shakedown with a new diff of 4.5 from 4.3 and the car looking like this:


Some interesting results...

It's all very well talking about PB's but in reality while I may hit a time, i'm far from consistent, and repeating it is often a matter of luck (bit between teeth chasing a car etc).

So in the past i've always been around the 1.36:800 to 1.37:800 with the diffuser and splitter i was even more inconsistent and the laptimes were down, i just didn't feel comfortable with the car.

I had a very unnerving experience going through pothole (fast left hand 150kish turn) where the whole car nearly under steered off the track, I've never ever felt the car like that before.

So thinking being that the diffuser was working a little bit to well we pulled it off and just tried the splitter where i've felt I had an improvement in my times before.

So so, nothing really different, less understeer but laptimes were about the same. I think where i previously thought it gained an improvement was just me driving better.

So pulled off the splitter and just went back to basics, and did a 1.35.800, with consistent times between that and 1.36:500.

The new diff made a massive difference, the car is just on song now, and still accelerating well at the end of the straight.

So onto the last club day where i had a great day with my previous competition (Honda Integra DC5) unable to keep up:







I took out the overall championship again and also won my class for the first time.

So breaking it down, the diffuser is working really well, but the car isn't balanced with the diffuser on.

I've always been told a splitter adds one second a lap, i've never really felt that with mine, i've actually never felt a major difference in the front end.

So I don't think the splitter is doing it's job at the moment.

I'm guessing the issue is the bonnet vent, I've now got a straight path from the top of the splitter through the radiator and out the bonnet. I think this is stopping a high pressure zone from forming on the top of the splitter.



So i'm looking at changing the flow of air into the bottom of the radiators to create that high pressure zone.


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So I've been getting sick of rebuilding my front calipers regularly as they have been getting to hot.

After the last club day of the season, the disks were again to hot and so had significant micro cracking and was only a matter of time before the cracked through again.

I've also had major issues with pad knock back and stub axles cracking from the forces, also bearing life is an issue.

So time to put a big upgrade into motion.

I had decided to replace the front calipers and disks once and for all and to do it right.

I was running Wilwood calipers with a Toyota Yaris disk (254 x 20mm) machined to fit.

I went with AP CP4567 calipers with a 267 x 25.4mm ap disk on a bell (directionally vaned) which is pretty much the biggest i can get in 13" rims without going to another setup which is like twice as expensive.

The setup is what's used on rally Escorts and is the Monte Carlo version rather then the forest version.

The idea is the wider the disk the more heat capacity it has. Also bigger diameter helps the caliper leverage.

I went with the AP's as I wanted a proper motorsport caliper with decent seals, knock back springs and pad availability.


I could have made it fit the Starlet stubs axles, but i've had issues with them cracking and with the areo load i plan, i was even more worried about them.

So I decided to upgrade to AE86 front stub axles, which meant new suspension, but did let me buy a "bolt on" kit for the brakes.

Oh and also a new pedal box as I need different master cylinder sizes for front vs rear.

So begins a long process...

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Fitting a pedal box in a starlet is a bitch of a job at the best of times, but add in an existing roll cage to work around and it becomes a nightmare...

Frankly I would not have attempted this without @Snoozin and @sheepers posting their detailed write up of what they had to do to create one for Snoozin's starlet.


So a massive thank you to them for sharing their process!

Rather then go the normal route of using a Wilwood box, I went for Tilton as I needed to be able to adjust the pedal positions vertically as I had very little room to move the pedal box around, 
I also wanted to replace the throttle pedal at the same time so I could eventually Heel and Toe if I wanted to.

So start with working out the only position the pedal box can go in to clear the firewall, tunnel, steering shaft, bulkhead and cage (get oh so lucky it actually fits)...

Get the position right for all 3 pedals:

Lots of cutting and fiddling later and a bracket is tacked up:

Realise you can't actually get it out now... so adjust slightly and you end up with this...



Needed to hook up the brake lights, so used a micro switch which goes to a relay, nice and simple and allows adjustment if required.

Since I was changing the throttle pedal, it was no longer a direct pull through the bulk head, so had to make a cam up to translate the movement, this took a bit of thinking to get the right movement in relation to the throttle bodies so it was linear the whole way.

Work out that the reservoirs absolutely need to be remote mounted, start buying gold plated fittings to make it work:

Reservoirs mounted and plumped in:

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  • 7 months later...

Been a while since I've updated this.

Decided to do a cold airbox around the existing filter.


Made no difference to intake temperatures, still up around 40 degrees, i suspect it's heat soak through to the filter plate where the sensor is mounted.


I've been struggling with keeping the rear brake temperatures down, and it's been meaning the front have been doing more work and they started getting a bit hot and micro cracking.

Also into the hairpin which is where the brakes are the hottest the car just hasn't felt like it's slowing as fast as it should considering the weight, which I picked was the rears going to hot and losing the friction.

Before they become full cracks in the rotors I had to sort the rear out to relieve the strain on the front, some new AP Racing rear brakes, same calipers as the front just 20mm wide instead of 25mm, with full vented 2 piece rotors were fitted.

It's a very tight fit behind the rear wheels so they are slightly smaller in diameter than the front.


Thankfully that's finally got all the temperatures sorted, and both front and rear are now way down, so that's finally solved that issue, don't let anyone tell you the rear brakes do nothing on the track...


I've been struggling with the new suspension.

Changing so much at once made things hard to diagnosis some of the issues.

I have now added a rear sway bar which has certainly helped in keeping the nose down now and helping with the turn in.


However the car has been shuddering under braking and had no grip, tried softening everything still didn't help.

Turns out the valving and pressure in the shocks is way to hard i.e SuperTourer figures (for a car that's significantly lighter), not sure what's gone on there, but getting revalved now, waiting on the lock down to end to get them back.

But I've decided it's time to move on to Evolution 4 of this build.

  • Evo 1: Street Car with 4AGE
  • Evo 2: Race Car with 4AGE
  • Evo 3: Street Car with 3SGE
  • Evo 3.5 Race Car with 3SGE
  • Evo 4: Race Car with ???
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Now interestingly enough a certain someone 


 had some interesting comments on this engine in 2007 on another forum. and than went onto have a long discussion about the merits vs the BEAMS :D 


I think that the ??? engine is brilliant.

Better than the beams engine IMO.

If there's anything that ??? knows how to do, it's build awesome NA engines. :)


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So as has been guessed it's a Honda K20a Euro R motor (Basically same as Type R, but more on that later.)

These only come in fwd layout, so obviously that's going to make things challenging.

They came in the following cars

So Why Change?
The 3SGE Beams Blacktop is a good engine, it's been very reliable and I've had no issues, however when you look around there is very few of them around the world which means the aftermarket support is limited and there are very few experts with them.

CelicaRA and Harris Engineering (Previously Lyn Rodgers) being the main ones who have any experience modifying them significantly, the older 3SGE engines have a lot more support.

Being RWD already they are cheaper than putting a K20a in and if you keep them internally stock they are a pretty good package for a lot of cars, but they are a cast block so weigh a lot more than an aluminum one.

I wanted a little bit more power.
I wanted to remove weight from the car.
I wanted better aftermarket support.
I wanted to keep the engine internally standard for now for reliability.
I wanted easy availability of them.

Why K20a vs F20c?

The F20c is hard to get and not cheap. Honda took what they learnt from the F20c and made the K20a so it's a better engine, and also more supported.

Why K20a vs K24

Need to keep in the under 2L class.

Why is there such a large aftermarket support for the K20a/K24?

The USA, Honda produce so many cars for them and they made ones which feature a detuned variation of the K20a which means all the companies got stuck in producing performance parts, and as the engines are so similar it's basically a massive parts bin of bolt on parts.

Why Euro R version?

Ideally (will explain later) you would go for the FD2 version as that's the best by a little bit, however as these are newer they are much harder to find. DC5 ones would be next on the list but they are also very popular so hard to find.
The Euro R version however is relatively easy to get.

The Euro R is slightly different, it runs a different ratio gearbox with different mounts and wasn't produced for the USA, so makes support for it just a little bit trickier with some items.
It has balance shafts in the sump attached to the oil pump, and the ports on the head are supposedly slightly smaller (might be a good thing) (but where manifold bolts up is the same), the head water outlets are slightly different design.
However pistons, cams, valves, water pump, cam cover, pretty much everything else is the same.

You can think of the Euro R K20a as being a K20a Block but with a K24 head, but running all K20a Type R internals. Being it's similar to a K24 head that means you can take advantage of all the K24 parts available, while still using K20a Type R parts for everything else.

It's not a major but does have an impact on some things. e.g if you need to do anything with the sump (which you should baffle) you need to get rid of those balance shafts, luckily this is just a case of bolting a oil pump kit from an FD2 on (which many stores sell).

The ECU is also not tune able unlike the other versions, for me that was a non issue as i will be using an aftermarket one.

It also runs the best intake manifold out of all the K20's (RBC) which everyone wants to bolt on to there K20's for more power.
The Conversion Package

So after looking around I decided to go for a Euro R complete engine conversion package from Strong Hondas Auckland, they were great to deal with and I ended up getting one with 112'000k's, was completely hassle free, and would have had a warranty if not for it going in a racecar.

So for $3,390.00 incl delivered to CHCH I got the following.

Gearbox (with LSD)
O2 Sensors
Gauge Cluster
Driveshafts + Intermediate Shaft
Shift Lever + Cables
Engine Loom + Body Loom
Clutch Pedal + Master Cylinder
Brake Pedal
Flywheel + Clutch (worn)
Intake manifold + throttle body
All sensors except Air Intake Sensor.
Misc Cooling Hoses

Obviously that's a lot of money, but if you were doing a conversion into another Honda that is a bloody bargin for everything you get.

So after I sold off things I didn't need, the engine is currently owing me $981.73...

And I'm still to sell:
Gauge Cluster
Engine Loom + Body Loom
Throttle body

That's a pretty good starting price, but I have to buy conversion parts so they will add up quickly...

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So having picked the engine/gearbox it was now a case of bolting them together.

This is relatively easy, all you need is an adapter plate, and an off the shelf flywheel to suit.

So what you are looking for is K2F as a search term as it's a pretty common conversion.

I ended up going with a JSPFab adapter plate as they were half the price of everything else once landed, had all the hardware and had good instructions.


They were great to deal with.

To fit I needed to clearance the adapter plate to the head (for k24's you don't need to do this as the block is taller), I chose to clearance the head vs the adapter as the top of the adapter is free floating on the engine so I wanted as much strength in the plate so the gearbox didn't move around.

A little bit of chopping some unused bits of the head and it fits great.



This keeps the engines 15 degree right hand lean.

Next was the flywheel, the most common one found in many stores was the ClutchMasters FW-K2F-AL


It weighs about 4.5kg, and has a replaceable friction surface which is awesome (no need to resurface), it also came with all the clutch plate bolts.

This allows any standard S2000 clutch to bolt up, which gives a lot of options, the downside is S2000 clutches are more expensive than say a K Series.

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Next up was the oiling.

The K20a from the Accord Euro R runs balance shafts off the oil pump in the sump.

These are to reduce vibration at lower revs, the Integra and Civic versions don't have these so it's safe to remove them (or just buy an Integra/Civic engine to begin with...).

The downside is they take up a huge amount of space in the sump, they sap power(supposedly about 9whp) and they weigh 5.3kg alone!





So it's a win to remove them all round.

Luckily you can raid the Honda parts bin, so the standard thing to do is to buy an Civic FD2 kit to replace them, it comes with a new oil pump, oil chain, oil chain guide and windage plate.

So many stores sell these kits as the K24 engines also have them, so it's a pretty easy change.

One thing is that the K20a oil pumps are known to not be great over 9000rpm, so a lot of stores are now porting the oil pumps which frees up a little bit of power and makes them safe to 10,000 rpm.

I ended up going with one of these kits as it ended up cheaper than a stock kit, one thing to note is the K24 engines and the Euro R version of the K20a need the housing of the oil pump modified for clearancing, it's nothing major and the kit i brought already had it done.

I brought the kit from kmodperformance with it being the K24a2 version which bolted straight up.


Now that frees up a lot of space!






Now a few might be wondering how i'm going to fit it in the car even with that sump.

The plan is to put the steering rack on the front of the engine cross member (escort like) narrow the cross member and position the engine entirely behind the cross member or as far back as we can get it.

There are a few challenges with this as I have a roll cage bar going through the dash, so would like to not have to alter that and it may put the gear lever quite a wee way back, but will deal with that later. It has some big advantages however, obviously the position is great from a weight balance point of view, but it also allows me to run escort style anti dive bars (tied from bottom arms BACK to chassis), which make a huge difference in braking.



Yes there is going to be a lot of chopping.


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Now that's what I'm doing, however if you wanted to run it over the cross member you might consider the following kit from K Miata.



Or a Ktuned Steel Oil Pan and chop it up.


Or a Moroso Pan


However be very careful as the standard cast aluminium oil pan has the bottom 2 bolts for the gearbox.



And also this massive brace back to the bottom of the very solid pan.



Replacing the pan with one of the above means you can't bolt the gearbox at one of it's highest stress points, i.e it want's to separate right at that point.

Basically your going to fuck your main bearings with the forces on it.

So that's out for me, if I need to I will cut up the existing pan.

In terms of baffling, I have some pics of a Spoon K20 sump baffle, and @Roman  did a great write up on improving the BEAMS sump to match the TRD version which I saved, so a combination of both should work out well.

Main thing is stopping the oil freely going up the oil chain under braking.

Here's a standard sump, which is just a dumb design:



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