Hyperblade's KP61 Racecar "BEAMS61"

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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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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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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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