The F series was born in 1999. But what if it were reimagined today—using modern materials, motorsport-level technology, and no compromises?

This post is a long time coming. Many of you know who I am, and you certainly know Urge Designs. What most don’t know is what we've been quietly building behind the scenes for the past few years: a complete reinvention of the F-series engine—the F25.

This project blends proven Honda architecture with cutting-edge engineering—borrowing from superbikes and applying techniques typically reserved for the highest levels of motorsport. Think Nikasil-style cylinder plating, exotic alloys, thermal barrier coatings, WPC finishing, and more. Every detail is scrutinized, every weakness addressed.

While steel sleeves are commonly used by many engine builders, performance is not the first thing that comes to mind—after all, they use it in your grandpa’s tractor. When all of the OEM FRM blocks are used past their service life, there will only be one answer for OEM-level reliability and performance: cylinder plating. And as of now, we’re the only company offering it for this platform.

Everything you’re about to see below has been backed by real-world testing and hard data. We’ve spent countless hours on the dyno, and hundreds more tearing engines down, inspecting, making changes, and retesting. The money invested into one-off components—custom velocity stacks, cams, and more—was spent purely to chase gains and validate theories. The current development engine has been running strong in a dedicated track car for nearly two years, living its life at 9000 rpm—with zero piston or ring changes.

Note: Everything I share here is based on my direct experience in development, testing, and implementation. All engineering data and technical specifications of Urge components are those of Urge Designs. If there are any discrepancies or technical questions, default to their published data.


What follows is a bit of a photo dump—snapshots of the process from early development to the latest prototypes, each with a bit of context. As with any serious R&D, this has been a cycle of problems, solutions, and constant iteration.

Posts will be broken up into focus areas of the powerplant. They may jump around a bit, but that’s intentional—to keep related components and processes grouped together for clarity and relevance.

Let’s get into it.

 

The heart begins with the block. One of the most significant changes is the replacement of Honda’s FRM liners with Nickel-Silicon Carbide (NSC) cylinder plating. This modern surface treatment increases cylinder wall hardness by 42% and improves the coefficient of friction by 20–30% over FRM. NSC is also fully serviceable—unlike FRM, which, despite having an OEM-specified process, rarely yields reliable results in practice. For that reason, I’ve never offered FRM boring at my shop; the margin for error is simply too high.

By moving to NSC rather than reverting to a steel liner, we’re able to run tighter piston-to-wall clearances—less than half of what’s required with a steel sleeve. This results in dramatically improved piston control, reduced skirt wear, and overall greater longevity under high-rpm abuse.

 

Within the block, you have the rotating assembly. This is what supports the power. Improvements over OEM components focus heavily on reducing both weight and friction. Reciprocating weight has been cut significantly--from 707g down to 471g--through an optimized piston design and the use of stronger connecting rod material, which allows for a more compact and lighter overall assembly.

The centerpiece of the rotating assembly is the C350 wrist pin--the highest quality pin I’ve ever worked with in any automotive application. Its strength and rigidity allow for a shorter piston and a longer rod, improving the rod-to-stroke ratio and reducing piston skirt side-loading--especially critical with the increased stroke of the crankshaft.

Friction has also been addressed through the use of WPC treatment on the pistons and all engine bearings, improving surface finish, durability, and overall mechanical efficiency.

Every piston, rod small end, and big end has been balanced to within 0.01 grams, ensuring the most efficient and smoothest-running engine possible, especially at sustained high RPM.

While the current Urge piston is a proven design, development is ongoing.
Below you’ll see a comparison of three pistons: Stock – Urge – Concept.

 

Moving onto the crankshaft--another area where drastic improvements have been made.

Recently released is a modified OEM Honda crankshaft that delivers something we’ve never had access to before: a 99mm stroke and the use of the original F-series rod journal size of 23.8mm.

Until now, builders had two options: commission a full custom crankshaft, or more commonly, repurpose a K-series crankshaft, which uses a narrower 19mm rod journal. The downside with the latter has always been long-term bearing durability--particularly under high cylinder pressures.

With the wider F-series bearing surface restored, we now have the ability to support much higher cylinder pressures without the added maintenance costs associated with accelerated rod bearing wear. This is especially beneficial in our race engine applications, where we routinely run significantly higher combustion pressures thanks to proper-grade fuel.

Additionally, with the use of bearing surface treatments, friction has been significantly reduced. In a controlled comparison between one of my OEM refresh builds and an Urge-spec build—with only the crankshaft installed and turning force measured--I recorded a 40% decrease in the torque required to rotate the crankshaft. The OEM setup required 10 in-lbs, while the treated bearing setup measured just 6 in-lbs. That’s real-world, quantifiable efficiency.

This crank bridges the gap between accessibility and performance in a way that hasn’t been possible--until now.

Below you’ll see three crankshafts, left to right:
Stock F22 – F25 – Lightened K24.

 

Moving onto the oiling system. All standard builds receive a ported oil pump--this increases flow, reduces cavitation, and helps control oil pressure fluctuations.

For higher-end applications, we use a Daily Engineering dry sump system. This eliminates windage in the crankcase by pulling oil out and storing it externally in a tank. It also applies vacuum to the crankcase, which reduces resistance on the pistons during their downward stroke--freeing up power and improving overall engine efficiency.

On top of the performance benefits, the Daily pump adds to the bling factor, and includes a manual oil pressure adjustment--just a simple turn of a set screw.

 

Hours upon hours were spent on the dyno testing head port configurations, various camshaft profiles at different degrees, and multiple velocity stack lengths. This wasn’t just guesswork—it was structured testing with data driving every decision.

I’ve tested countless port configurations, including heads from well-known names like 4 Piston and other hand-ported setups. One conclusion has become crystal clear: if the entire port has been touched, it’s too big. The stock port is already borderline oversized for N/A applications. Just hogging it out kills velocity and hurts power.

Reshaping--not enlarging --is the key. Carefully refining the existing port shape to control airflow, not just volume, is where the real gains are. This principle holds true even with +1mm valves. On paper they might seem like an upgrade, but in naturally aspirated form, they reduce velocity and cost you power. They’re simply not needed.

We’ve even gone so far as to break into a coolant jacket during testing. You don’t know how far is too far until you go too far. That’s the level of R&D this project demands--and it’s how we’ve found the edge without crossing it in the final product.

One thing that’s been consistent throughout all this? The inconsistency of head castings. Combustion chamber volumes can vary by as much as 2cc from one chamber to the next--even in the same head. That seemingly small difference translates to a 0.4 compression ratio variance, which absolutely must be accounted for and corrected if you're aiming for precision and performance.

What we’re chasing isn’t flow bench bragging rights--it’s real power under the curve, throttle response, and consistency lap after lap.

 

Next up: the valvetrain.

There are a few good camshafts out there, but none of them are truly “plug and play.” Every cam needs to be properly degreed and dyno tested to determine where it actually makes power. Specs on paper mean nothing without real-world validation.

One thing that stood out with the Urge cam: the recommended centerline degree was exactly where it made peak power. That’s something I’ve never seen from another cam manufacturer. Maybe it's a coincidence, maybe it’s a sign of how dialed-in their development is--but it definitely caught my attention.

Testing is still ongoing. We're currently evaluating four different cam profiles, each with its own characteristics and tradeoffs.
Of course, it’s not just about what fits or what lifts. Every aspect needs to be checker--rocker clearance, retainer clearance, coil bind, and retainer-to-valve seal interference. All of it matters if you want reliability at high RPM and a powerband that doesn’t fall apart when you lean on it.

But with these improvements, the stock rocker arms have become a weak link. And it’s not just due to the more aggressive cam profiles. The rollers inside the rockers use simple needle bearings, which were never designed to be serviced--and they wear out. Honda never intended for these engines to run for decades under constant abuse, and now that the S2000 has been discontinued, OEM parts like rockers are getting harder to find. A single set of three from Honda will run you over $300.

To address this, I'm currently working on having new roller bearings manufactured from stronger alloys--so we can rebuild and restore these rockers instead of replacing them. This keeps the platform sustainable and reliable as we continue to push performance further.

 

How do we achieve a reliable 10,000 RPM with the F25?

Titanium.

Titanium valves paired with titanium retainers significantly reduce valvetrain mass - and that delivers two major benefits.

First, less mass = less stress on the rocker arms, which, as mentioned earlier, are already a known weak point at high RPM. Reducing load here extends component life and gives the rocker a fighting chance under the increased demands of a high-lift, high-speed valvetrain.

Second, lighter components mean better valve control. With less inertia to manage, the valve is less likely to float, allowing the engine to rev higher while staying stable and consistent -- exactly what you need when you're living at 9–10k RPM on track.

And because these are custom valves, we’re not just swapping material -- we're optimizing the design. This includes refining the stem-to-head transition, tweaking the fillet geometry, and making small but meaningful changes to improve flow characteristics and durability.

This isn't a catalog part. It's built for the purpose--and it's showing results.

Below are a few different designs and materials.
Note the weight differences--every gram counts at 10k RPM.

 

Super cool stuff. Glad to see continued development and a potential solution to the FRM liner. Larger bearings are always welcome too. Thanks for sharing.

I'm curious if you have any similar builds that you consider more streetable and what that would look like in terms of components and maintenance expectations.

 

Now stepping outside the engine — let’s talk intake.

We’re running individual throttle bodies (ITBs) on the F25, and not because they make the most top-end power. If you're chasing peak horsepower numbers alone, a well-designed plenum manifold will usually edge them out on the top end.

But that's not the whole story.

ITBs shine in the mid-range — and they shine hard. While our setup still makes over 300 horsepower up top, the gains in mid-range torque and throttle response with ITBs are simply unmatched. In real-world driving and track conditions, that midrange advantage far outweighs the slight top-end sacrifice. It’s a trade-off worth making.

We’ve tested nearly every configuration imaginable: long vs. short runners, different bellmouth shapes, varying diameters, and even a completely different ITB system with larger butterflies. The results?

The original oval-shaftless design continues to outperform everything else we’ve thrown at it. Clean airflow, minimal turbulence, and strong mid-range delivery — it just works.

New to the market: Drive-by-wire ITBs with a complete tuning solution. This opens the door for more precise throttle control, better integration with modern ECUs, and the foundation for future developments like active runner control.

On the to-do list: RPM-dependent variable-length runners.
This is a concept widely used in modern sportbike intakes, but rarely seen in the automotive aftermarket. There’s huge potential here to broaden the powerband without sacrificing top-end or mid-range. It’s not overly complex — just requires real testing and development, and we’re diving in.