The Honda-Powered Silvia Touches Down

One of the key skills to hunting speed, is to get involved on the ground from the very moment that there’s even an idea being tossed around.

More often than not, these ideas rarely move beyond this stage. They forever remain as the product of big dreams without the ability to make them happen. We’re all guilty of this, myself included. What could have been

Some of these ideas do advance, and before you know it, things are happening at a much faster rate than you could have previously anticipated. Case in point: Stone Motorsport’s K-swapped S15 Silvia. When I first started with Speedhunters, we were always involved in some way of documenting builds from the ground up. There were often times where we even had a lot of input, too. Chris Rado‘s Scion tC, Vaughn Gittin Jr.’s RTR-X and  Darren McNamara’s DMAC-86, to name but a few.

Maybe the rapid advance of social media has relegated the idea of the build thread to the history books, and maybe this is a fruitless exercise, but part of me feels that there’s still value in documenting a build outside of character limits or with really small photographs on Instagram.

2018 Stone Motorsport K24 S15 Build by Paddy McGrath-13

I had to check, but it was September of last year when we last documented the progress of this particular tin-top racer. A lot has happened, but the ethos has remained the same. Chassis fabrication has been completed and the bare, caged shell has been painted.

When I visited – literally a few hours ago at time of writing – John Stone was quietly working on making the bodywork fit, before it’s removed and moulded so that spares can be made.

2018 Stone Motorsport K24 S15 Build by Paddy McGrath-14

So much has changed with the Silvia, that nothing really fits off the shelf anymore. This is the first time I’d seen the car on the floor, although it was only just about rolling in order to ensure the bodywork was correct. What struck me the most was how much lower it is than I expected.

The aim is to run the car in two trims; one for time attack and hillclimb with a comprehensive aerodynamics package to make the most of a slick tyre. This ‘go fast’ setup is estimated to weigh 940kgs (2,072lbs) wet, while the second drift setup (without the aero package or slicks, but with extra steering lock) has a sub-900kgs (1,984lbs) target weight.

John spoke about this being as about as low as they can go weight wise, without resorting to drastic – and expensive – measures. Instead, their focus has been about placing the weight that remains in the most optimal locations. For instance, the driver’s seat is fixed in place, with an adjustable steering wheel and pedals to suit the driver. The battery will be sunk into the passenger side floor. The engine bay has been extended back into the car, in order to move the dry sump tank back as far as possible.

2018 Stone Motorsport K24 S15 Build by Paddy McGrath-21

Regardless of what trim they run, the car will be Honda powered. At the moment, they’re using a K20 as a stand-in while they complete their K24. The masking tape, currently supporting the radiator, won’t be a permanent fixture on the car.

2018 Stone Motorsport K24 S15 Build by Paddy McGrath-18

A BorgWarner EFR 8374 will supply enough boost to produce around 550-600hp to the 2.4-litre motor, which hangs low on a custom equal-length manifold that they made in-house.

In case you’re wondering why they’ve chosen a longitudinally mounted K-series instead of a 2JZ or V8, it was a decision that was primarily based on weight. The K24 is approximately 100kgs (220lbs) lighter than the inline-six, and its smaller dimensions mean it can be positioned in a more advantageous location within the engine bay.

John told me that the K24 is slightly taller than the K20 (by 19mm), which they’ve allowed for but will require a custom valve cover to clear the underside of the bonnet.

2018 Stone Motorsport K24 S15 Build by Paddy McGrath-1
2018 Stone Motorsport K24 S15 Build by Paddy McGrath-11
2018 Stone Motorsport K24 S15 Build by Paddy McGrath-16
2018 Stone Motorsport K24 S15 Build by Paddy McGrath-20
2018 Stone Motorsport K24 S15 Build by Paddy McGrath-26

There’s still a while to go yet, and no doubt lots of further incremental improvements and decisions to be made. There will be problems and solutions, questions and answers all to come, while not to forget the creation and implementation of a full aero package, without the benefit of a wind tunnel or CFD modelling. Instead, John has taken it upon himself to study aerodynamics in order to get the basics right and work from there.

It’s not a car being built for world domination, but rather one that can be effective in various disciplines within Irish motorsport. While there’s no shortage of talent and ability involved with the car’s development, it isn’t an unlimited budget build either, which makes it more interesting for even the casual viewer.

Maybe the build thread isn’t dead just yet?

Paddy McGrath
Instagram: pmcgphotos
Twitter: pmcgphotos



Add comment

E-mail is already registered on the site. Please use the Login form or enter another.

You entered an incorrect username or password

Sorry, you must be logged in to post a comment.


by Oldest
by Best by Newest by Oldest

Amazing build, btw anyone know what happen to Chris Rado? So much success and suddenly he's gone. He had a pretty mad Scion.


He's around, He's the owner of Global Time Attack


That rat's nest of a intake manifold, what in the world? Seems like a 90deg bend would do the trick just fine :P

Personally not a fan of time attack/tube chassi's cars, they seem too... sterile to me, a complete lack of character. The other side of the coin, of course, is that you have a car (more like a chassi with body panels on it) built for one single task.


I hope you are trolling, you can literally see the chassis and the turbo hanging off the exhaust manifold...


Exhaust manifold, K series are "reversed" compare to D/B/H series, in a fwd the intake is facing the radiator.

Awesome build by the way, K swap everything why not


That's an exhaust manifold and it's a full chassis car :)


I love the color of the cage and how it pairs with the white paint and the black seat, it looks so sick, keep up the gnarly work guys!


So he needed a light weight 2.0L engine? good thing Honda came to the rescue. they never would have found a Nissan variant.


To be fair, there's a pretty significant difference in reliability between a 600hp SR and a 600hp K24. I say that as someone with a serious soft spot for the SR, too.


That masking tape fitting seems shaving a lot of height, are you sure it's not permanent?
Imprezas and lancers are living examples that a 4 cylinders engine is capable with more than enough power so there is no need for extra weight while trying to achieve very considerable power/weight ratio.
The cage color is perfect combined with the white exterior, hope they keep it like this (it escalated to be the best on my list using white exterior winning over dark orange).


The white is only the colour of the bare panels, the whole car will be painted the same colour as the roof.


Should look amazing and executed in a perfect way, since the cage painting is perfect so sure no shortcuts on the outside. That color (i can't guess but seems something "blackish") is mean and may be better for track scars, dust, rubber from tyres,... but as a personal taste i wish it was kept white.


What kind of wheels are those? i really like them


AVA Avant-Garde HE215s


I believe those are Nismo LMGT rims made by Rays.


I love how it looks, bigger wheels & sit much slower... reminded me of GT300 S15!


Very nice build, but I have one question: why go with an K series instead of an SR? Where are the advantages?


The K is a much newer and more efficient engine using v-tec and variable cam on the intake, this combined with the larger displacement will mean a much earlier spool on the turbo and a wide torque curve. Driveability is key on this car as it going to be used in hillclimb here in Ireland where response is more important than peak power figures.


The K-series is also a decade newer and made by one of the best OEM engine designers. It really is an amazing piece of engineering.


I've asked John to detail his reasons, but my understanding is that the K-series will be more reliable for their target power figure. The idea of a 600hp SR20 both excites and terrifies me at the same time.


Interesting project for sure. Most of the s-chassis time attack cars have SR's with VE heads pushing 600+. VET for sure, a regular Sr wouldn't be worth it at that point.


Built K24 probably has better power/weight figure than built SRs. I'm no expert though.


Original: 2.0l
Now: 2.4l

Still an upgrade, though.

Also, this is another build that screams "today's cars are boring" aside from new Trust demo car.


It might be only 400cc in the difference, but with mild work it can be expanded to 2.5-litres which is the same as an RB25 or a 1JZ, but with two less cylinders and a lot less weight.


Pretty much every engine makes more sense than a 2JZ from a performance stand point. They are one of the heaviest "performance" engines out there and offer no substantial gains over other engines that are both lighter, more compact and can be cheaper to build to equivalent power levels.

Lol @ the comment below with the guy saying tube frame cars are sterile and lack character. If it goes fast and wins: job done.


Body looks so good!


Interesting. Can't wait to see it in action, looks fun.


Bodykit going into production?


A guy named Toli in Australia has a turbo K20A S13. Stock motor with 200,000km+ from its life in an Accord, combined with a GT3071, made 250rwkw on 6psi with a powerband from 3500-8500rpm. Hard to argue with, despite spastics complaining about its "low" power output.

Chris Kreschollek

Johnny Tran does it again. Props.