Plug-N-Play Standalone Engine Management System

MegaSquirt PNP Frequently Asked Questions

What makes the MSPNP2 better than the Gen 1?

For starters, we've based it on the more powerful MS2 processor, which allows for over 100 times more precise injector pulse width, more sophisticated idle and boost control, and many other upgrades over the MS1.  Instead of two injector output channels like the original MSPNP, the Gen 2 has up to four, allowing for sequential injection on four cylinder engines and semi-sequential injection on engines with more cylinders (exactly how many are enabled depends on the application).  We've also added built in det cans to let you listen to your knock sensor, and some other new circuits as well.

Why do some vehicles have an MSPNP2 model and others have the MSPNP Pro?

The MSPNP Pro was introduced to tackle the challenges that some vehicles present such as an increased quantity of sequential fuel and ignition channels, VVT, alternator control, etc.  The MSPNP Pro isn't designed to supersede the MSPNP2, but complement the lineup.  So why not design MSPNP Pro models for all the cars in your lineup? Simply to keep the cost down for you.  The MSPNP Pro carries a higher price tag due to its complexity, and many vehicles simply don't require the extra I/O and capabilities that comprise the MSPNP Pro.  In those cases, the MSPNP2 performs equally as well on these particular platforms.

Does the MSPNP allow tuning in real time?

Yes! You have complete control over your fuel and spark tables, and changes to those take effect immediately. You can tune it while it's on a dyno or while the car is running around a track - although if' you're tuning it at Road Atlanta, we recommend wrapping up your tune changes by the end of the back straight, as tuning while going through that chicane before the Suzuki Bridge and then plunging into Turn 12 like a roller coaster can be distracting.

Do people really ask about tuning from the passenger seat while running around Road Atlanta?

Sorry, that's only happened once. We'll try to stick to more common questions from now on.

Can I remove my mass air flow sensor or vane air flow meter using an MSPNP?

Yes. The MSPNP has a built in MAP sensor, letting you run speed density. This means it has no need of a mass air flow sensor, and you can replace yours with a length of straight pipe if you're so inclined.  We've often seen a measureable horsepower gain from this on a dyno, particularly if you have a vane style air flow meter.

You said the MSPNP runs speed density. Does it support other load modes?

Yes. It is possible to set it to use a mass air flow meter, although you will need to generate a calibration curve for your MAF - there's an internal switch that swaps the MAP sensor input for the factory load sensor. It also allows alpha-N operation (using a throttle position sensor for fueling) or even blends of alpha-N and speed density. The software has a special ITB mode that uses the MAP sensor at low throttle / high vacuum and switches to the TPS at high throttle / low vacuum, for those using independent throttle bodies.

Do I need to make any changes to my wiring or sensors to run an MSPNP?

MSPNPs can run a car with all stock sensors and its built in MAP sensor, but there are a couple times we strongly recommend sensor changes:

  1. If your car is not equipped from the factory with an IAT (intake air temperature) sensor, the MSPNP will default to a fixed air temperature correction value. We recommend adding an IAT sensor to compensate for changes in air temperature.

  2. On turbo cars, we recommend using a post-intercooler IAT sensor, which often isn't present from the factory.  This lets the ECU measure the effectiveness of your intercooler better.  Factory turbo cars sometimes appeared to have their ECU set up to measure the air temperature upstream of the turbo and estimate the final air temperature based on the behavior of the factory turbo and intercooler - a method that is easy to throw off with intercooler or turbo upgrades.  And most naturally aspirated cars that have been converted to turbo did not have a sensor layout intended to accommodate the extra temperature and pressure.

  3. A wideband oxygen sensor system can help make tuning easier.

  4. As above, removing the mass air flow sensor often results in more horsepower.

  5. Cars that do not have a potentiometer type throttle position sensor have the option of switching to one to allow for alpha-N fueling and other optional features.  You don't have to switch the TPS, but we give you that option.

If any wiring changes are required to run a stock car, they're usually very minor, such as removing a fuse.  No current MSPNPs require any wire cutting or splicing.  Even installing an IAT sensor can be done with no changes to the stock wiring.

How much boost can I run with an MSPNP?

All of it. The MSPNP has a 4 bar MAP sensor as standard equipment, which can read up to 44 psi.  In the unlikely event that is not enough, it is possible to use an external MAP sensor that reads higher. As long as your fuel system can supply enough fuel and your engine is tough enough to handle it, you can tune for it with the MSPNP.

Can I have two maps in it? Like one for power and one for fuel economy?

The MSPNP has a switch input to allow switching between two fuel and ignition tables.  However, we have generally found that a good tuner can produce a table that gets both maximum power and good fuel consumption, so we don't recommend trying to create separate power and economy maps.  Good uses for this feature include a pump gas and high octane race gas map, one map for wide open exhaust and a second for tracks that require a muffler, or switching to the second map when a nitrous system is active in order to pull timing and add fuel.

Is the MSPNP emissions legal? Does it return OBD2 codes?

The MSPNP is sold for competition use on race tracks, autocross, drag strips, off road courses, and things that otherwise don't get driven on public roads.  Although a correctly tuned MSPNP is capable of relatively low tailpipe readings, a badly tuned one can send emissions through the roof.  Consequently, installing one on a street car does not meet Federal emissions rules.  The MSPNP also does not return OBD2 codes, either.  If you have to return your race car to street duty, you've got to unplug the MSPNP and go back to the stock ECU to stay street legal.

If you're outside the USA, you'll have to check your local laws.  Other countries are sometimes more lenient.

Where are MSPNPs made?

The case and PCBs are made in the USA, and all assembly work is done in the USA as well.  The connectors, transistors, and other electronic components come from all over the world, so they can be advertised as "Assembled in USA" but not "Made in USA."

I have a question the FAQ doesn't answer.

No problem. Send our tech department an email and we'll get back to you soon with an answer.  If it's a common enough question, we'll add it to the FAQ.





The MegaSquirtPNP, as with any programmable engine management system, may not
be legal for use on pollution controlled vehicles and is therefore produced and sold for off road/race use only. Check federal/local laws.

MegaSquirtPNP, MSPNP, MegaSquirt PNP, and MS PNP, are trademarks of Hoffmann Innovations, Inc d/b/a