The Dr in Dr.John

Many Guzzisti will know of Dr.John Wittner and his influences on the Daytona sports model, leading to various successes in racing events.

Most will also no doubt be aware that his title stems from being a member of the dental profession, and I have often wondered what if, rather than spending what must have been hundreds of man hours designing cylinder heads, calculating ideal cam lobe angles and optimising fuel curves, that sometimes he just felt like getting a bottle of gas from his workplace, strapping it on and going for a burn.

I could say that it was this thought that was the motivation behind my own thinking but in truth the Dr.John-Dentist-Nitrous link only occured to me after the fact. In reality I have always wanted to try this particular method of power lunacy but never had the time/money/right machine/nerve. The choice about the 'right machine' I leave up to you dear reader, I finally found the rest.

What's all the Nitrous stuff then?

First of all Nitrous Oxide (N2O) is neither explosive nor even flammable, it is an oxidising agent. That is to say it a compound that readily releases oxygen molecules to promote combustion, on it's own it will not burn, not even a little bit.

The way nitrous works is in fact identical to the end result of turbo and superchargers and that is to cram more oxygen into the engine cylinder than the normal intake vacuum cycle will allow. All this extra oxygen allows more fuel to be squirted into the chamber and be of the correct mix to burn, producing more heat and pressure and therefore more power.

N2O has several big advantages over mechanical pumps.

• Mechanical devices compress atmospheric air, and when you compress a gas it heats up (turbochargers are esp. bad for this by their very nature of using exhaust gases to power them). All this extra heat entering the combustion chamber promotes detonation hence the use of intercoolers. Nitrous oxide however enters as a liquified gas and expands on leaving the injectors, and as a gas expands it's temperature drops thus inhibiting detonation.
• Another bonus relative to detonation pevention is that as the Oxygen molecules are released, Nitrogen is freed which acts as a buffer against the onset of detonation.
• For any given volume of additional gas introduced, N2O has 50% more available oxygen than atmospheric air.
• Cost and complexity. A basic nitrous set up will cost between £400 - £600 giving as much extra power as the jets fitted and your engine will safely allow (generally upto 50% over stock), it can be fitted in an afternoon with no major modifications to your stock engine. Try that with a turbo!

The big disadvantage is of course that the power only lasts as long as the bottle, but trust me on this, the benefits FAR outweigh this single limitation...

You may wish to read this FAQ on Holley® Performance's site, it is NOS products biased, but the facts hold true for any system.

The additional fuel required was supplied by fitting a 'T' into the LHS fuel feed from the tank, through an inline filter and into a standard NOS fuel pump before then attatching to the inlet of the fuel solenoid. A pressure guage was also fitted at this point.

Without doubt the biggest headache I had with the entire nitrous project was the fuelling. Losing fuel pressure whilst still injecting gas is probably the single biggest cause of catasrophic failure. Paranoia set in and I decided to fit a higher capacity pump and a fuel pressure switch. The bigger pump came from a GPz turbo, more than upto the job, too capable in fact. The pressure regulator I had to install to reduce the fuel pressure was a 'dead head' type and the pump was working against itself when the system was armed but off the gas, risking damage to the pump. The regulator was reconfigured to act as a relief valve rather than a restrictor, with a return line tapped into the top of the fuel tank. The regulator was again a NOS item and couldn't handle the flow the GPz pump was putting out so another was sourced from Highpower Systems in England, which although overpriced and oversized for a motorbike was at least able to give some semblance of control.

The next problem was air bubbles. No matter what I did I just could not get fuel to flow cleanly without either the pump cavitating or an air trap forming in the regulator causing the diaphram to resonate a very annoying squeal. Another problem was that the air bubbles were causing the fuel pressure cut-off switch to operate erratically. This switch is connectd to the solenoids to cut the gas delivery should there be any doubt that there is enough petrol to stop the mix from going too lean and into terminal meltdown (think cutting torch against pat of butter). Pumps cavitating, regulators squealing and solenoids rattling at a rate of knots...mmm...lovely, I think not.

It turned out the solution was to relocate the pump from the space below the tank where the airbox had resided, to a much lower position beside the starter motor. This, and some fiddling with the delivery hoses, sorted it. I went back to the smaller pump, removing the regulator and tank return line which were now no longer required.

A steady 6psi is now produced with only a slight dip on initial operation, not a worry at the settings I currently run at, but I may try a bypass regulator again in the future.

Gas Supply

The nitrous bottle is a 2.5lb item mounted to a strut that was fitted as a factory recall due to subframe weakness (bet you never thought Guzzis and Hayabusas had something in common). True it's more 'in your face' than 'wolf in sheeps clothing', but the amount of looks and double takes the bike gets is incredible. Generally this is followed by the uttering of "You've done WHAT? To a GUZZI?". I do plan on secreting some smaller bottles about the bikes person at a later date.

From the bottle valve and through an inline filter, a braided hose carries the liquified gas directly to the nitrous solenoid fitted beside the fuel item on the RHS of the bike just below the seat where the rear shock top mounting bolt is.

Brass tees fitted to the outlet of each solenoid have microbore lines routed to the injectors screwed into the cast carburettor mounts on the cylinder head.The jets which control the mixture are also here, at the ends of the microbore where the fittings screw onto the injector. I chose to use NOS Fogger 2 injectors which claim to give a better mix and slightly softer 'hit' (or is just marketing bullsh*t).

Electrics

A separate wiring loom was built for the nitrous system enclosed in the blue convoluted tubing visible in some of the photographs.

The best way to describe the system is probably to go through the process of operating the nitrous injection.

A feed from the battery passes through a small fusebox located under the riders seat, from here a cable is run to an aircraft style toggle switch fitted to the top of the front fairing on the LHS of the fuel tank. When operated this switch performs two functions. The first is to activate the main system relay which starts the fuel pump and also feeds power to the Fire switch. The second function is to change the function of the horn button to be the Fire button. The horn button lever has been enlarged by attaching a piece of shaped aluminium. The change from horn to fire was accomplished by tapping into the wires as they went to the horn itself rather than trying to rewire the inside of the bar assembly.

A microswitch was attatched to the RHS carb (now moved to LHS carb and sits inboard) via a fabricated bracket and operates when the throttle is wide open (WOT). When the fire switch is pressed the signal passes through the WOT switch (if closed) then through the fuel pressure switch. This switch ensures that the nitrous oxide will only be injected if there is sufficient fuel pressure (else bye bye pistons). From there the signal reaches the solenoid relays, once these operate the progressive controller computer feeds power from another fused source and opens the valves thus allowing gas and pressurised fuel to pass down to the injectors, mix, enter the combustion process and YEEHAAAA!!!

The progressive controller pulses the solenoids to gradually build up the amount of mix being delivered. This allows larger HP jets to be used without the sudden surge of power damaging the engine. It is adjustable for delay before activating after the fire switch is pressed, time to reach maximum power and amount of power to start from.

There is scope for additional control such as a rev switch to ensure that the system will only operate above a set rpm (usually about 3000).

Final Setup

The system was first tested uing the smallest jets, 17HP (BTW the quoted horsepower/jet-size is the theoretical maximum gain, actual additional horsepower will depend on many factors). This produced results that though not wrenching my arms out of their sockets, did give some extra 'push'. 30HP jets were installed and there is now no mistaking the extra surge in power. I will leave it at this setting for the moment before moving upto 50HP jets. That is probably be the maximum the engine can take with the bike in its present form, we shall see what happens in the future....

This was my first experience with Nitrous Oxide and I was not disappointed.
If you are reading this and either have knowledge and experience to share or like me just feel like giving it a try and the madder the final project the better (I used a Moto Guzzi fer crisssakes!!) then please feel free to get in touch. Jet powered roller skates anyone?