Your dyno sheet, before the dyno.
Grand River Racing Pro Engine puts the pipe, the head, the ignition, the intake wave dynamics, and the fuel system in one coupled model — then pulls it on a built-in dyno that computes power from real cylinder pressure. Design the combination, watch the waves work, read the curve. Live, in your browser, on any device you own.
THIS IS NOT A VIDEO. A 66.5 × 54 twin, pipe tuned at 10,500 — every point on these curves came out of the app's own solver: pipe pressure → trapped charge → burn → cylinder pressure → torque. 8,400 RPM — the pipe comes on. Watch the HP climb to the peak and fall off the cliff past 11,000 — that's the pipe off its tune. When the plugging wave arrives, the engine comes alive. The bottom trace shows exactly why.
Stop tuning parts. Start tuning the engine.
A two stroke is a complex gas-dynamic system. The intake wave draws the charge, the pipe decides what the cylinder traps, the chamber decides how it burns, the burn decides the torque. Pro Engine models the whole dynamic chain in one place, so every change you make anywhere shows up where it matters: on the curve.
Expansion chamber designer
The full pipe designer — header, three diffuser stages, belly, rev cone, stinger — with the pressure waves animated live as you build. The pipe's boundary (trapped pressure, residual gas, return temp, trapping efficiency) feeds everything downstream, at every RPM.
Combustion chamber designer
Bowls defined by depth gauge numbers, squish solved every quarter degree, MSV tracked against RPM with rod-stretch and piston-to-head clash warnings — plus the animated Live View that shows the jets working.
Built-in dyno simulation
Not a curve fit — a pressure calculation. The burn model integrates cylinder pressure through the cycle, friction comes off, and brake power and torque land on the chart, with weather correction and one honest calibration knob to match your real dyno.
The whole shop, one screen
Pull it before you build it
Brake power and torque vs RPM computed from real cylinder pressure — indicated work from the burn, friction subtracted, weather-corrected. Printable dyno chart included. Change a cone angle and re-pull in seconds.
The pipe drives the power
Trapped pressure, residual gas, returned-charge heat, and trapping efficiency flow from the pipe into the burn at every RPM — that's why the simulated curve has real two-stroke character, off-pipe softness and on-pipe hit included.
Engineer-level head design
Hemisphere, bathtub, and two-stage bowls from shop measurements, MSV solved against RPM with strain and clash warnings, band optimizer, and the animated squish Live View.
Timing from combustion physics
Wiebe burn model, MBT solver, detonation watch by octane, and safety-tiered advance limits for methanol, gasoline, and E-blends — with a printable advance chart for your ignition box.
Fuel the combination
Carb sizing analysis and recommendations, lambda targets across the map, and fuel-flow math tied to the same engine model that makes the power — so the jetting conversation starts from physics, not folklore.
The intake tract, simulated
The intake has its own resonance and pressure-wave dynamics — the same physics that makes the exhaust pipe work, applied to the intake side. Pro Engine models the intake wave, shows you it working, and lets you tune the intake system the same way you tune the pipe: watch the waves, see the trapped charge respond, dial the combination.
Browser-based, no install
Laptop at the bench, tablet at the dyno, phone at the track. No Windows requirement, no license tied to one hard drive. All updates included.
One coupled model beats a folder of calculators
The old way is a Windows pipe calculator here, a head spreadsheet there, a timing guess from a forum — each treating its part in isolation. Pro Engine is one physics model of the whole engine, with a dyno on the end of it.
| GRAND RIVER RACING PRO ENGINE | PIPE / HEAD CALCULATORS | FULL ENGINE SIMULATORS | |
|---|---|---|---|
| PLATFORM | Any browser — laptop, tablet, phone, no install | Windows — licensed to one machine | Windows — licensed to one machine |
| SCOPE | Pipe + head + ignition + fuel + dyno — one coupled model | One part at a time, treated in isolation | Full engine — steep learning curve, no head design |
| PIPE WAVE ANIMATION | Live pressure waves animated against the crank, all 7 sections | Static numbers only | No pipe-wave visualization |
| PIPE ↔ ENGINE COUPLING | Pipe pEPC, residual gas, return temp & trapping eff feed the burn at every RPM | Pipe sized in isolation — no combustion link | Varies — often uncoupled |
| SQUISH & MSV | Solved every ¼° with rod-stretch correction, clash warnings, animated Live View | Single static MSV number | No head design module |
| CHAMBER DESIGNER | Hemisphere, bathtub, two-stage — input depth-gauge numbers, get mill coordinates | Limited or none | None |
| SQUISH BAND OPTIMIZER | Sweeps geometry to hit a target MSV window automatically | None | None |
| DYNO SIMULATION | Pressure-based brake HP & torque — real two-stroke powerband dip included, printable | None | Yes — curve fit, not pressure-based |
| CALIBRATION HONESTY | One visible BMEP trim knob — match your real dyno, see the number move | — | Dozens of buried coefficients |
| IGNITION & TIMING | Wiebe burn, MBT solver, detonation watch, printable advance curve for your box | None | Varies |
| FUEL MODELS | Methanol, gasoline, E-blend slider to E85 — fuel-specific burn properties throughout | Limited or none | Varies |
| CARB & FUEL OUTPUT | Carb sizing recommendations, lambda schedule, fuel-flow from the same engine model | None | Varies |
| MACHINING OUTPUT | X/Y coordinate table from the split line — take it straight to the mill | Dimensions only — no coordinate table | None |
| INTAKE WAVE DYNAMICS | Intake resonance and pressure-wave simulation — included in Pro Engine | None | None |
| INTAKE DESIGN OUTPUT | Animated intake waves, tuned-length solver, charge effect on the dyno | None | None |
| UPDATES | Instant — always the latest version, no installs | Versioned installs | Versioned installs |
Comparison reflects the typical feature set of established Windows-based two-stroke tools and engine simulation packages as published by their vendors. Verify current versions before purchase.
Built for engineers. Priced for builders.
Design the pipe and the head as one combination, verify the curve before you cut metal, and hand the customer a printed dyno chart with the build sheet. That closes work.
Weather moved, fuel changed, class rules tightened — re-pull the virtual dyno in seconds and see what the combination wants, before you burn passes finding out the hard way.
One tool for the whole engine conversation: cones, chamber, timing, carb, curve. Quote it, prove it, build it, print it. We're a shop too — that's why it exists.
One license. The whole engine.
Less than one dyno day. Less than one wrong pipe. Yours forever — intake module included when it lands.
- Complete pipe designer with live wave animation
- Complete chamber designer with squish Live View
- Built-in dyno — pressure-based HP & torque, printable
- Ignition module with printable advance curve
- Fuel & carb analysis with lambda targets
- Intake resonance & pressure wave dynamics module
- Runs on laptop, tablet, and phone — all updates included
Instant license by email. Questions first? Call the shop — (616) 755-3101.
Straight answers
How does the dyno simulation work?
The pipe model sets the trapped charge at each RPM — pressure, temperature, dilution, trapping efficiency. The combustion model burns that charge in your actual chamber and integrates cylinder pressure through the cycle to get indicated work. Friction comes off, weather correction applies, and brake power and torque go on the chart. One visible calibration trim lets you match your real dyno — and tells you exactly how far the raw physics landed from it.
I already own Weeks Pro Pipe or Pro Head. What happens?
Pro Engine contains both designers, coupled. Your existing designs carry over — the pipe side reads Weeks Pro Pipe exports directly. Call the shop about upgrade options for existing license holders.
What do I need to run it?
A web browser. Laptop, desktop, tablet, or phone — Windows, Mac, iPhone, Android. Nothing to install, and your license isn't chained to one computer's hard drive.
Will it work for my engine?
If it's a two-stroke with an expansion chamber, yes — kart, motocross, snowmobile, drag, vintage, watercraft. Methanol, gasoline, and E-blends are all modeled.
What does the intake wave module do?
The intake tract has its own resonance and pressure-wave dynamics — the same physics that makes the exhaust pipe work, applied to the intake side. Pro Engine models the intake wave so you can design and tune the intake the same way you tune the pipe: watch the waves animate, see the effect on trapped charge, and dial the whole breathing combination from intake bell to stinger.
Is this a subscription?
No. One payment, one license, updates included — the intake module too.
Who's behind it?
Grand River Racing — a competition powersports engine building shop with 30+ years across drag racing, motocross, hill climb, and sled racing. Every model in the app answers to our own dyno and our own time slips first.