Ignition Timing And Nitrous - Edelbrock 70003 Installation Manual

6.0

Ignition Timing and Nitrous

Because we are oxidizing the air/fuel mix going into the engine when nitrous oxide is used, we must pay close attention to
the ignition timing profile. Remember, "nitrous" oxygen is more dense than "atmospheric" oxygen and resulting in an
accelerated burn rate of your fuel.
In anticipation of the quicker burn time, you must retard the timing of the ignition system when using nitrous oxide. The
more power we try to make, the more timing in degrees we must remove from the timing profile. This is not in total advance
but the time in which we bring timing in (the advance curve).
This is why all nitrous users are so concerned with evidence of detonation. The accelerated burn rate of the air/fuel charge
can cause severe detonation without a "nitrous" ignition strategy. A timing profile that is accelerated and a total timing
number retarded will keep you from experiencing catastrophic engine damage.
The general rule of nitrous use ignition timing should be to retard the "total" advance number approximately 2 degrees for
every 50 HP increase when using nitrous oxide. It is always best to start with your engines best total timing (without nitrous)
and reduce total timing from there. Use an initial timing retard setting that is at least 2-4 degrees more retarded than you
expect to be the best setting for your application. All stated timing adjustments listed in jet maps is where the motor being
tested worked best.
When using aftermarket ignition components and/or systems, it would be advisable to contact the manufacturer for
information on using their components with a nitrous system. It is always better to be very conservative in your timing
approach and tune towards an optimum timing setting.
Example:
Ignition timing without Nitrous Oxide
100 HP increase from Nitrous Oxide
Initial safety margin
Total timing with Nitrous Oxide
Suggestions on How To Perform Accurate and Repeatable Tests with a Nitrous Vehicle:
1. Testing should be done on a dyno. Never street race - always obey all traffic laws.
2. Always test with your vehicle when up to normal operating temperatures and operating conditions.
3. Ensure all vehicle systems and components are adjusted to proper settings (tire pressures, oil levels, coolant levels,
etc.).
4. Always verify fuel pressures and nitrous pressures are the same, every time you test the vehicle. Different
pressures will always yield different results.
5. Use all of your senses to determine how your vehicle is operating. Listen for detonation, watch your gauges, smell
for strange odors, etc.
©2004 Edelbrock Corporation
Brochure No. 63-0190 - DC/mc
38 degrees "total"
2 degrees "retard"
2 degrees "retard"
34 degrees "total"
Testing Checklist
Page 23 of 28
Rev. 03/04
Catalog #70003 & #70004