It’s not something that comes around too often so when it does, believe you me, you’ll know it. What are we going on about? A build that transcends the highest levels of workmanship and components that you just have to take a moment to gather yourself after reading.
“The R-Core concept was a project of my own to exceed every aspect of the Type-R concept by Honda. I’ve made many mistakes over the years and finally I’m happy with the results. To put it simply, it’s very much a driver’s car. Nothing electronically assisted. Every force felt is felt raw. It’s like a very hardcore go-kart with a license plate. And so I named the concept R-CORE. The Core of the R and furthermore, R-CORE sounds a lot like HARDCORE.”
“My name is Lertsiri Boonmee and this is my ride based on the best front wheel drive handling car from Honda.”
Serious words from a serious man; and we can assure you, regarding a very serious build. Take our word for it when we say you’ll probably never come across a build like this till the last day you walk on this planet.
Lertsiri purchased this 1994 Integra in GSR form a decade after it rolled out the factory. Pledging his allegiance to the JDM gods, the first thing he did was carry out a front and rear end conversion with body parts from a 1998 JDM model.
Offerings made and deities pleased, he then kept it as it for a couple of years before switching to a shade of Imola Orange that was a factory colour for the NSX. Following that, Lertsiri placed the car on a diet by stripping the interior out and fitting a bolt-in roll-cage.
That wasn’t enough though and a while later, the car was back in the painters again for a matte black treatment. Killing two birds with one stone, Lertsiri decided that while the car was stripped of panels and parts for paint, it would be a splendid time to go to town with an angle grinder and take the weight loss to the next level.
Binned was the bolt-in cage, replaced instead by a comprehensive weld-in cage. Same goes for the heavy glass that were all tossed out in favour of Lexan. The icing on the VTEC cake? All the carnage the angle grinder carried out by cutting off all redundant steel bits and complemented by holes drilled all over the chassis to cut the poundage.
While the shell was undergoing its liposuction, it was also seam and spot welded for added strength and certain areas of the weld-in cage was tied to the shell with gussets. Gussets were also added to the rear floorplan to further reduce flexing.
If you’re wondering if the exotic weave of fibres makes an appearance with the theme heavily centred around weight reduction, you’d be spot on. The magnitude that it does however is something you simply cannot wrap your head around.
It wouldn’t surprise us if Lertsiri’s Integra contributed significantly to the carbon fibre industry’s bottom line that year.
The seats are custom bare carbon fibre pieces mounted on custom low-mount rails. Custom carbon fibre delete plates were also cut to cover out the door and hole that once housed the radio. The very same material was also custom formed into one-off cupholders and the bezel for the gauges.
If your eyes are besotted by the steering wheel, you have good taste. The wheel is a custom carbon fibre piece as well with a genuine, rarer-than-hen’s-teeth, horn button from a NSX Type-R.
It would probably be easier to list down the non CF bits. Those would comprise the S2000 start button and aluminium floorboards.
Oh, did we mention that he retained the air-conditioning in the car. It’s still street driven after all.
On the outside, the CF madness continues with a carbon fibre moulding of the JDM front and rear bumper, JDM Honda Access side and rear lower skirts, custom doors, custom roof skin, front fenders, front canards, Dogfight Pro lower lip spoiler, Nismo N1 R32 Skyline bumper intake vents, Aztec grille and headlight cover, J’s Racing driver side air duct, custom passenger side air duct, J’s Racing vented hood, custom diffuser and custom duck tail spoiler.
Yes, every single piece mentioned above is made of carbon fibre.
The Lexan side windows also have a NACA duct integrated with it while Spoon wiper downforce attachment, Mugen rear Airfoil with custom carbon fibre adjustable fin, clear Stanley side markers and Mugen front and rear tow hooks complete the exterior.
Lertsiri himself counts the roof skin as the crown jewel of his CF recipe as it lowered the centre of gravity tremendously for a marked improvement in handling.
It might not be unintentional but Lertsiri’s build seems heavily inspired by the wise words of Colin Chapman; “Simplify, then add lightness.”
With the shell prepped, the next step was the engine. A thirst for outrageous power that would never be quenched is something he didn’t suffer from. Instead, the goal was to build an engine with only the best bits and plenty of reliability.
The base of the powerplant would be a B20B block with a B16A head that had been bestowed with the port and polish treatment. Headwork consists of Toda C2 camshafts, Toda valve springs, Ferrea valve guides, titanium Crower retainers and Buddy Club P-1 lightweight valves. A set of 85mm CP high compression pistons attach to the crankshaft via Manley conrods to make up the bottom end.
Commanding the amount of air entering the engine is a custom billet 68mm throttle body with a Skunk2 throttle body intake heat shield gasket sandwiched between it and the intake manifold; itself separated from the engine by an intake manifold heat shield gasket to reduce heat transfer into the intake.
Feeding air into the intake is an air filter and carbon air intake chamber combo from J’s Racing. Fuelling is provided by 2JZ injectors fed by a Sard fuel rail which in turn is regulated by a Sard fuel pressure regulator.
Once ignited, the exhaust gases are led out by a custom 4-1 manifold, through a custom 2.5-inch titanium exhaust piping and finally vented after rumbling in a Spoon N1 muffler.
Auxiliary bits comprise a Toda oil pump gear, aluminium engine pulley, Mugen water temp sensor, Mugen water valve, J’s Racing engine stabiliser, polyurethane rear engine mounts and a power steering delete for that raw feel he set out to achieve.
All that ammo would be wasted if it wasn’t governed by a solid plan and to address that, an Apexi Power FC allowed fine-tuning of the fuelling and ignition. The commander was also given an upgrade with a brighter OLED display.
Sending the 252 horsepower and 231Nm of torque to the front wheels is the Integra DC2 Type-R transmission spinning straight cut gears. Not only are they stronger to cope with the extra power, the gears also give out that invigorating “whirring” sound associated with racecars.
A custom 4.929 final drive ratio is a shot in the arm for acceleration while a Cusco Super O.S clutch and flywheel reduce slippage.
By now, the car was beginning to handle like a go-kart courtesy of the weight loss but Lertsiri wasn’t going to neglect the suspension area. Anchoring it are a set of Mugen Showa five-way adjustable Low Down suspension and from the name itself, you know it’s something special.
Bracing up the chassis are J-Sport fender braces, front and rear Spoon lower tie bar, Ultra Racing three-point undercarriage triangulation bar, EM Racing aluminium trunk floor bar, EM Racing aluminium C-pillar bar, Function 7 rear bracing, front and rear Carbing strut bars, front room bar and a front traction control bar.
Keeping with the exotic theme are a pair of Mugen billet aluminium Group A racing spec extended control arm with ball joints. Further adding adjustability to the alignment geometry are Function 7 billet aluminium control arms and a Mugen aluminium anti-roll bar relocator.
Stopping wouldn’t be an issue now with the car weighing almost nothing but that doesn’t mean that braking should be neglected. Spoon monoblock front calipers bite on Mugen slotted rotors with Spoon brake pads up front. For the rear, Integra Type-R DC5 rear calipers, slotted rotors and Endless brake pads get the job done. Shoring up consistency are APP front and rear stainless steel brake hoses and a Cusco master cylinder brace. The ABS has also been deleted in the quest for that raw, unadulterated sensation behind the wheel.
Honda owners are notorious for hunting down rare, obscure wheels for their rides and Lertsiri is no different. He sourced a set of 16-inch Mugen MF10 wheels with a width of 7JJ and an offset of +43. Wrapping them are Yokohama Advan Neova AD08R in a 225-45-16 size.
Builds like these are something you come across every three or four blue moons, perhaps even less. Forget the finances involved, the sheer effort in getting things done and sourcing for the rare parts alone would have sent most owners down the ricer path.
Not Lertsiri though, he’s a special one. He wanted something hardcore and he achieved something better, the R-Core.
Car – Honda Integra GSR 1994
Engine Mods – B20B Vtec, 85mm CP high compression pistons, Manley conrods, Toda C2 camshafts, Toda valve springs, Toda oil pump gear, Ferrea valve guides, titanium Crower retainers, Buddy Club P-1 lightweight valves, port + polish + honed B16A head, custom 4-1 titanium exhaust manifold, 2JZ fuel injectors, Sard fuel rail, Sard fuel pressure regulator, custom billet aluminium 68mm throttle body, Skunk 2 throttle body intake heat shield gasket, J’s Racing carbon air intake chamber + J’s Racing air filter, intake manifold heat shield gasket, aluminium engine pulley, custom titanium 2.5-inch exhaust, Spoon N1 muffler, Mugen water temp sensor, Mugen water valve, J’s Racing engine stabiliser, polyurethane rear engine mounts, power steering delete
Transmission – Integra DC2 Type R straight cut gears, custom 4.929 final drive ratio, Cusco Super O.S clutch and flywheel, solid ball joint transmission mount
Electronics – Apexi Power FC + new upgraded commander with OLED display
Brakes – Spoon Monoblock front calipers + Mugen slotted rotors + Spoon brake pads, Integra Type-R DC5 rear calipers + slotted rotors + Endless brake pads, APP front and rear stainless steel brake hoses, Cusco master cylinder brace, ABS delete
Suspension & Chassis – Weight reduction, seam + spot welding, welded-in roll-cage + gussets, rear floorpan gussets, Mugen Showa five-way adjustable Low Down suspension, J-Sport fender braces, front and rear Spoon lower tie bar, Ultra Racing three-point undercarriage triangulation bar, EM Racing aluminium trunk floor bar, EM Racing aluminium C-pillar bar, front and rear Carbing strut bars, front room bar Mugen billet aluminium Group A racing spec extended control arm + ball joints, front traction control bar, Function 7 billet aluminium control arm, Function 7 rear bracing, Mugen aluminium anti-roll bar relocator
Wheels & Tyres – Mugen MF10 16×7 +43 wheels, Yokohama Advan Neova AD08R 225-45-16 tyres
Interior Mods – Custom bare carbon fibre seats, custom low-mount seat rails, custom carbon fibre steering wheel + NSX Type-R horn button, S2000 start button, aluminium floor boards, custom carbon fibre delete plates for door and radio, custom carbon fibre cupholders, custom carbon fibre gauge bezel, functional air-conditioning
Exterior Mods – Carbon fibre JDM front and rear bumper + JDM Honda Access side and rear lower skirts + custom doors + custom roof skin + front fenders + front canards + Dogfight Pro lower lip spoiler + Nismo N1 R32 Skyline bumper intake vents + Aztec grille/headlight cover + J’s Racing driver side air duct + custom passenger side air duct + J’s Racing vented hood + custom diffuser + custom duck tail spoiler, Lexan side and rear window + NACA duct, Spoon wiper downforce attachment, Mugen rear Airfoil + custom carbon fibre adjustable fin, clear Stanley side markers, Mugen front and rear tow hook
Power – 252hp@9000rpm, 231Nm@6400rpm