Ignition Timing: How It Works With Nitrous

Here at the office we frequently get calls about timing recommendations for various vehicles and configurations. Timing can be very confusing and frustrating for a lot of gearheads, so we wanted to go through and explain what timing is, how it affects performance, and why we need to adjust timing. This is the scientific definition of ignition timing:

Ignition Timing is the process of setting the angle relative to piston position and crankshaft angular velocity that a spark will occur in the combustion chamber near the end of the compression stroke.

To break it down in simpler terms, timing is setting where you want the spark to occur relative to piston position and speed.  Timing is referred to in degrees of angle before top dead center ( BTDC). To get the most power and efficiency out of an engine, the timing will need to be advanced. This is because from the moment that the spark occurs, it takes time for the fuel to ignite completely and begin expansion. When the timing is advanced, the spark will actually take place during the compression stroke before the combustion chamber reaches its smallest size, giving the fuel and oxygen time to begin expansion and push the piston down with greater force. If the spark occurs too early in the compressions stroke, it will expand against the piston that is still moving towards the end of the compression stroke, causing detonation (also known as pinging, or knocking). If the spark is too delayed (retarded), it will cause the maximum pressure of the cylinder to peak after the piston has traveled too far down the cylinder. If the spark occurs after top dead center (ATDC), you will lose significant power due to the gases not having enough time to expand and force the piston down.


Pictured above is the result of timing that is too advanced. The piston on the left failed due to detonation occurring over a period of time. With detonation, engine failure may not occur right away, rather taking numerous passes for the failure to occur. The spark plug pictured above shows signs of detonation occurring in that cylinder. We can tell by the small specks on the porcelain part of the plug. This is commonly called ‘peppering’, and is actually small pieces of aluminum from the piston or head.


One of the key points of tuning nitrous is setting the timing. When using nitrous or other power adders you have to ‘pull’ or retard the timing because peak cylinder pressure will occur earlier in the ignition cycle. This is because of added oxygen and fuel, which causes the mixture to burn at a much higher rate than a naturally aspirated engine; and peak cylinder pressure will occur much earlier in the cycle. When pulling timing we are trying to compensate for the accelerated burn of the mixture and we are trying to make the peak cylinder pressure occur at the same point it did while running naturally aspirated. If peak cylinder pressure occurs too early, it will cause detonation and parts failure. If peak cylinder pressure occurs too late in the cycle, it will cause lost power due to peak cylinder pressure occurring after the piston has already started going back down the cylinder.

Retarding your ignition timing with nitrous not only will help keep your engine safe from detonation and parts failure due to heat, but it will also help you get as much power as you can out of your nitrous system. Timing can be retarded multiple ways on almost all vehicles- through a tune or timing retard box, or by changing your ignition settings on your ignition control box. The ‘general rule of thumb’ for retarding your ignition for nitrous is pulling (or retarding) 2* for every 50 horsepower worth of nitrous you intend on spraying. However, that is not always correct as many engines have different timing requirements due to a variety of factors. The best way to find out if your timing is where it needs to be, or if it needs to be adjusted is to read the spark from a single pass.

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  1. Mark Woodruff
    August 2, 2018 at 12:47 pm — Reply

    This info is very informative.

    Any info you can offer would be better food for my brain.

    My ride, 84 Ford Ranger, Boss 351w, 427ci, 535 base hp, 250 shot sniper kit. MSD locked out at 32° at 4200 rpm IAW Ford Performance guidance. After reading your article I see that I should take out 10° or locked at 22°. I will never hold anyone responsible for my bad NOS/HP addiction lol. Just gathering data here. My buddy who runs nitrous already told me 26° for 150 shot. So this stands true along with your article. Thanky

    • Raymond Marabel
      March 2, 2020 at 4:22 pm — Reply

      Its 4 Degrees per 100 shot. You can safely run on up to 150 shot no retard. So 200 is 8 degrees 32-8=24 degrees

  2. Ray Hawkins
    June 21, 2019 at 7:09 pm — Reply

    Can I r***** the time I at the distributor for nitras or do I have to degree the Cam

  3. Ray Hawkins
    June 21, 2019 at 7:10 pm — Reply

    My question is do I have to degree the Cam or can I Retatrd the timing at the distributor for nitras

    • August 6, 2019 at 6:37 pm — Reply

      You retard timing via distributor, ignition box, or PCM tune.

  4. Mel Serrano
    April 2, 2020 at 8:29 pm — Reply

    Question: I have a vortech supercharged 302 engine with some after market mods like long tube headers,edelbrock manifold,bigger cam,ford racing alum. heads, 60lb injectors, SCT chip and it runs on alcohol methonal as well….I installed a zex nitrous wet kit 82023 with 75hp jet j stalled on it now…….the chart in the instructions reads 75 shot requires no timing retard, 100 shot requires 2* retard and the 125 shot requires 4* retard on the timing….now these instructions are for nitrous on a stock 302 engine….my question is what would be the required recommended specs for the timing retard on a modified engine like the one I have for the 75,100 and 125 shot jets ?

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