Nevermind, I'll just hand it to you.
The only way you can make it worthwhile is to run completly on H (without the gasoline), and that's a tall order. Gasoline is massively energy-dense material and you are going to be hard-pressed to find something that can compete with it.
In order for you to be driving down the road laughing at me in my primitive gasoline powered Supra, your hydrogen fuel must offer the power, vehicle range, convenience, and affordability that everyone takes for granted with gasoline.
This places tough requirements on the vehicular hydrogen-storage system. One kilogram of hydrogen provides about the same chemical energy (142 MJ) as 1 gal of gasoline (131 MJ). Factoring in the greater efficiency of PEMs, we need to store about 1 kg of hydrogen for every 2 gal of gasoline on a similar internal-combustion-engine vehicle. It is estimated that the entire onboard hydrogen fuel system—which includes the weight and volume of the hydrogen and its required fuel-delivery support such as the tank, pipes, pumps, and heat exchangers—must provide a volumetric energy density of at least 6 MJ/l and a gravimetric energy density of at least 6 MJ/kg energy equivalent of hydrogen to be even close. We will need about double those values to completely replace gasoline internal-combustion engines at any reasonable level of performance.
The hydrogen density, calculated from the weight and volume of the hydrogen alone (hydrogen basis) must be considerably higher to compensate for the weight and volume of the support hardware. Similarly, incorporating a hydride into an onboard storage system will substantially reduce its effective hydrogen density. There is no rule of thumb for the degree of reduction; it depends on the choice of storage medium and the required system design.
Compressed gaseous storage is closest to technical feasibility and is fundamentally appealing because of its familiarity and conceptual simplicity. The major difficulty with compressed hydrogen is its volume. One kilogram of hydrogen stored in common laboratory gas cylinders at 2,200 psi occupies 91.2 l (1.6 MJ/l, hydrogen basis—the effective energy density in a storage system will be substantially lower). For comparison, a mere 8.2 l of gasoline carries the same energy. Hydrogen tanks of 5,000 and 10,000 psi are being developed, but even at 10,000 psi, the volume of hydrogen is 27 l/kg (5.3 MJ/l, hydrogen basis).
At high pressures, deviations from the ideal gas law are large. The hydrogen gas density at 10,000 psi is only two-thirds that of an ideal gas. Doubling the pressure to 20,000 psi, if that were technically feasible, would increase the gas density by only about 50%. High-pressure tanks are complex structures containing multiple layers for hydrogen confinement, rupture strength, and impact resistance. High-pressure storage is most appealing for large vehicles, such as buses, which have more available space—on the roof, for example. I'm not sure where you plan to store your 20' long hydrogen cell on your Supra? Maybe a trailer?
Demonstration fuel-cell vehicles have been built using liquid-hydrogen storage. Here, the volumetric situation is somewhat improved compared to compressed gas because liquid hydrogen occupies about 14 l/kg (10 MJ/l, hydrogen basis). But hydrogen vaporizes at –253 °C, which necessitates an exotic superinsulated cryogenic tank. Inevitably, heat leaking into the tank will produce serious boil-off, and the tank will begin to empty itself in days in undriven vehicles. Liquid hydrogen seems best suited to fleet applications, where vehicles return nightly to a central station for refueling. Advanced tank designs may extend the boil-off period to perhaps a few weeks. Proposals that combine high-pressure and cryogenic capabilities in a single tank design could also mitigate boil-off.
Also, there is a large energy penalty for hydrogen compression (equal to 10% of the energy content of the gas compressed) or liquefaction (30%). Although this affects the storage economics, it does not impact the on-board storage system because the penalty is paid before the hydrogen is delivered to the vehicle.
Simply put, you aren't going to run your Supra on hydrogen anytime soon. And the gas density power requirements problems don't go away even if you are just trying to create a hydrogen rich intake system. Remember an engine is an AIR pump. You are OXIDIZING fuel. You want to displace the o2 with a new fuel (H). It's not going to work the way you think and the simple mathematics don't work out.
