Tune, Startup and Tweaking

Consider this the basics. For anything beyond the basics I would recommend you check out the links section for various forums and do your own research or contact a professional.

In this section you will find a BRIEF outline of the following:

  • Tune
  • Fuel (AFR)
  • Plugs

The first thing you will probably want to do is remove timing before you spray. Either it needs to be removed from your tune with something like HPtuners or you can remove it on the fly with a timing retard device.

The four timing removal methods I considered were:

Lingenfelter LNC-002 - This is nice device although costly. It plugs into your coil pack harness and alters timing at the coils. The benefit of this is it alters only the timing and no chance of changing anything else. The downside is the ECM does not know what the resulting timing is. In the last generation (002) Lingenfelter has added an analog output from the device that creates a timing reduction signal. This can be fed back to your software (HPtuners or EFIlive) to show the amount of timing being pulled.

Harris "The interface" - This is a nice controller that uses the IAT circuit to pull timing. The instructions have procedures for those using stock as well as modified IAT tables. The timing retard is secondary function as its primary use is to alter fueling automatically by using the MAF circuit. As an example instead of tweaking your fuel jet in your N20 nozzle/plate the interface skews the fueling from the MAF/injectors to create the desired AFR in the overall (N20 + OEM) system. This is cheaper than the Lingenfelter and does more.

The unknown about using IAT devices on this platform is I don't think anyone can say for sure what high IATs do to other areas of the tune. It's commonly thought that high IATs will alter your fueling as well as other possible changes. So take this under consideration when choosing this type of device.

Simple Resistor Mod - This is the cheapest method of pulling timing excluding changing your tune. All it requires is paralleling a resistor across your IAT (thermistor) or switching in a resistor in its place. This is normally done with a small relay and switch or allowing your controller to do it for you. Once again the only downside to this type of circuit is the unknowns of what happens when you change IAT values. Click here for a resistance vs temp chart.

Changing the Tune - Cheapest, easiest and most control/effective method if you have tuning software. This will give you ultimate control over your timing. The downside is you need to switch tunes back and forth or drive around on a lazy (less performance) tune and mileage often suffers slightly.

When installing my switch panel I added a switch for timing. My Maximizer 2 will do this automatically when armed and in retrospect this might be a better solution as it eliminates the potential to forget to flip the switch.

A GENERAL RULE of thumb is to remove around 2 degrees of timing per 50 HP shot of nitrous. So the following applies:

50 HP - 2 degrees removal
75 HP - 3 degrees removal
100 HP - 4 degrees removal
125 HP - 5 degrees removal
150 HP - 6 degrees removal


Most kits are going to come safely jetted. The general consensus is to shoot for AFR of 11 to 11.5. However this is just a starting point and reading your plugs is the proper way to tune fueling.


A colder plug will be required for N20. BR7EF is a popular plug for this application.


After double checking all your hose connections to make sure they are tight using soapy water and verifying your wiring I think its a good idea to bring things up slow. I would start off with the smallest jetting you have available and depending on the complexity of your window switch/controller spray the system briefly a couple times just to make sure solenoids work and it fires when you expected it to.

In my case I have a lot of control with the Maximizer 2 so I created a config file and told it to spray only in second gear at WOT and just from 4500-5000 RPMs.

I jetted the plate for 100hp (as small as mine goes), pulled about 5 degrees timing and connected HPtuners (with wideband) to my notebook and made a short blast. The first attempt roared right past 4500 RPMs in second gear and felt like nothing happened. In review I noticed my tachometer in the Maximizer software was reading 450-500 RPMs when the truck was actually idling about 900. The manual says to set the timing multiplier to /4 for an 8 cylinder when it fact it really needed to be set to /2. This means my engine would have to reach 9000 RPM before it started to spray!

So I changed the setting and verified the engine speed was the same in the Maximizer software as the truck was indicating. After this I made a short blast and there was no question it fired this time because the truck lunged forward when it hit 4500 in second gear and fell off when it reached 5000.

I reviewed the HPtuners scan to make sure it was clean of KR and the AFR was in a safe zone. From there I created a new config file where I told the truck to spray 50% at 3800 RPM and ramp up to 100% by 4100 RPM in first gear and spray 100% through all three gears. Checked the log and once again pretty clean of KR and AFR stayed consistent through the 1/4 mile run.

Back to garage and check all connections including electrical, plumbing and make sure nothing physically came loose.

Video of Maximizer 2 software from above run here


I am not going into great detail here. Check the links section for more information.

Read your Plugs ! Great article here

More info coming soon.....

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