Effect of nitrous/fuel mixture on power (historic document) new page www.nitrous.info

To main page

 

This shows the same two curves as before, but now in different colours, and a third (green) fuel rich curve.

1. The blue power curve shows the stock bike without the nitrous system in operation.
2. The red curve shows the same bike with the nitrous system set up with the correct or very slightly rich nitrous and fuel ratio. The extra 'richness' prevents detonation, and danger of burning the motor internals.
3. The green curve shows the same bike with the nitrous system set up fuel rich, to show the effect on the power curve, the system was operated earlier this time during the run at 6400rpm, and the richer mixture lowers the peak power produced, and gives a 'wiggly' looking curve. Power was still 180bhp however and set this rich it would be very safe to use on a daily basis with very little danger of engine damage. If the bottle is cold in winter for example, a similar thing happens as the pressure is lower in the bottle, but this time the rich mixture is caused by less Nitrous, rather than too much fuel so less power would be produced too.

 

Ideally you would set the Nitrous system up to be like the red curve (just a little too rich) on a hot day so that it will be safe on any other day even if not optimal. 

A full throttle 'plug chop' on nitrous, will also give a good idea if you have the mixture correct, if no dynamometer is available. Just run flat out through 3rd, 4th, 5th gear and then release the nitrous button hit the 'kill' switch and disengage the clutch and coast or brake to a halt without letting the motor turn over. When stopped pull out all the plugs, and look carefully at the outside ring - not the electrodes. It should be a nice tan colour with traces of black or spots of soot on it. No traces of soot or black means that there is no un-oxidised (excess) fuel present which means not enough fuel.. Nitrous is like oxygen, if you have too much with no fuel to 'use it up' it will burn your valves and pistons instead which is not good! Too much fuel will give less or no power increase or even misfiring but it will not damage your engine

Guide to mixture setting - Nitrous / Enrichment fuel ratio.
Run your engine at about 1/3 of maximum allowable rpm in neutral. Hold throttle very still. Now operate N20 system, and RPM should rise rapidly to close to rpm redline, and then after a second or so should drop back to around 2/3 max rpm and sound angry and be misfiring loads!  Make sure you try this test because it almost guarantees success first time! Then see below few lines and try again! 

Too much gas/not enough fuel and it will just rev sky high and not 'splutter' as it should. The opposite is also true, in that if too rich, it will rev up initially, and then die back to very low rpm or even stop. Adjust the size of the nitrous or fuel jet to compensate and try again until it sounds correct as above.

If you are using gravity feed on a motorcycle for eg without a pump, then the bit of 4mm tubing from the solenoid to the engine/distribution block effectively is your fuel jet. Non need be fitted at the fuel solenoid valve. This will provide the correct fueling for about 40 to 50 bhp extra. So fit a 40bhp nitrous jet to the nitrous solenoid and away you should go! but do the above test first!

If using a fuel pump and regulator, then set the regulator at 3, 5, or 10 psi as required. At 10 psi the correct fuel jet will be approx the same size as the nitrous jet used, whatever size this is.. At 5 psi you would need a jet about 1.3x bigger. At 3 psi try a jet about 1.5 times bigger to begin with. Then try the test at the beginning of this section to check you were right!

Superclean dynoroom at Quill-Racing A bike on one of my computerised dyno systems (my real business is building dynamometers!) ready to test - this one actually belongs to Andy at Quill race exhausts.

 

To main page