> Nitrous with Turbochargers: Using Nitrous Oxide with a turbocharged engine. Why & how it works.

Nitrous Oxide and Turbochargers

Why ever would you want to, or need to?
There are lots of very good reasons for adding Nitrous Oxide Injection to a turbo car or to a turbo motorcycle.

Apart from more power, how would you like FULL BOOST at any RPM? Maximum power from the second you push the pedal?  No waiting just go.

Just to get more power you can, even with a small road car sized turbo, usually turn up the boost to a degree to get a little more but the problem is that there will still be that bit at low revs where there is no boost and you wait. Its called lag and its horrible.

If you want really big power you need to fit a bigger turbo, as a small one that boosts at sensible revs is very restrictive and inefficient at high power outputs. It kind of gets in its own way!

Now you have an even bigger hole at the bottom end and even more horrible lag. Nitrous can completely eliminate this. I mean gone! Completely! Full boost from the moment you floor it.

You fit it because:

1) Because it totally removes all turbo lag - completely!  Full power/boost from idle RPM's upwards! Stand on the gas and GO! The nitrous initially provides the go, but this makes a lot of exhaust gas that spins the turbo up fast! Sudden boost too! from almost no revs.

2) Because if used as a "turbo lag remover" the nitrous is automatically turned off as soon as boost is achieved via a manifold pressure switch, so the bottle lasts AGES!

3) Because PEAK power can be drastically improved - if used normally (on all the time @ full throttle) rather than just to eliminate the turbo lag.

4) Because the charge cooling effect gives a measure of safety and prevents detonation, meaning higher turbo boost pressures can be used.

5) Because it means a much bigger turbo can be used!  The turbo is the limiting factor for higher power outputs since if its small enough to come on boost at say 3000 rpm, it is already restrictive in size at full power... See number 1 again...

6) MORE power than expected is usually obtained on turbocharged vehicles, because it also improves charge density, and boost levels at the same time.

7) Because its easy to fit! Your fuel injected car already has the required 3 port regulator for the fuel, and its a simple matter of tapping into this fuel line and fitting a nitrous/fuel injector AFTER the intercooler and preferably as soon after the throttle body as possible.  This way the correct psi above intake pressure is already taken care of by the existing fuel system.

For option 1 to work as a boost lag elimination device you need to also fit a simple pressure switch, (a cheap one would be an old oil pressure type switch), that switches the Nitrous off as soon as it sees say 2/3 of your normal boost level. Say 8 to 10 PSI.

In short - Turbo cars and bikes are crying out for Nitrous Oxide! It improves them in all the areas that they are weak. Gives the same effect as simply having a larger engine! 

Details...

Fuel Injected & Intercooled or Road going Fuel Injected Turbo Cars
Most of the above will be running 3 bar (3 bar above manifold pressure or whatever the manufacturer chose) fuel pressure to the injectors. Because the fuel pressure on these types of systems is regulated to be 3 bar or 45 PSI above the manifold pressure you can just fit the system as if it was not a turbo car or bike. You will automatically get an increase in fuel pressure as the Turbos boost level increases. So at 1 bar boost you will actually have 4 bar of pressure in the fuel system.  This is because of the use of a compensated 3 port regulator as standard. So unless its been modified by increasing fuel pressure to suit other tuning work, jet as for a stock 3 bar or whatever your car is set to (see chart) fuel system. Start with small power levels!

Blow through carb systems - some bikes, early turbo cars, aftermarket conversions, metro turbos...
These are a little strange and usually a bit overly complex as even the manufacturers ones were a bit on the "bodged" together side! But basically they all used a carb with as float, that needed feeding with fuel at around 3 to 5 PSI pressure ABOVE manifold pressure. Because for the carb to work properly its float bowl must be at the same pressure as the inlet manifold. The float chambers breather pipe is connected to the inlet manifold. Now for the fuel to feed into the carb at the correct 3 to 5 PSI above this boost pressure they too must use a high pressure pump, and a 3 port regulator. This COULD be used to feed your nitrous systems fuel supply too since it maintains a few PSI above Boost level at all times. But only for small amounts of Nitrous. For larger doses its unlikely that the pump fitted will have enough capacity spare.

So in this case you will need a pump capable of enough flow @ max boost pressure, plus the pressure you choose to run your nitrous enrichment fuel at. For e.g., You need 1 BAR boost, (15PSI) plus say 10PSI working pressure plus 10 percent at least. And a 3 port regulator, set to 10PSI and connected to the inlet tract after the turbo.

Draw Through and obviously Non Intercooled Applications - Mr Turbo systems on bikes, all out race vehicles, home designed systems etc.
Treat these as a simple carb low pressure system if the point of injection is after the carb, before the turbo! Easiest, and it works fine. Use simple pump / regulator, or gravity feed fuel.

If its to be injected after the turbo, then you will need to arrange your setup as for a blow through system with compensated regulator.

*Technically the term NOS is incorrect as this refers to an specific company (called Nitrous Oxide Systems, in the US)