Surefly SIM4P 4 Cylinder Impulse Coupled Magneto Replacement

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Part# 08-17074
MFR Model# SIM4P


Now approved for the replacement of both mechanical magnetos on most certified four- and six-cylinder Lycoming and Continental powered aircraft with dual SureFly Electonic Ignitions. Please review the Engine and Airframe STC's and installation instructions for further application information.

Note: Surefly strongly recommends the customer purchase a NEW slick-style harness and fresh spark plug set with every SureFly SIM.

The vast majority of 4-Cylinder applications will replace the impulse coupled magneto. 4.4 lbs.

SureFly is an FAA certified electronic (solid state) magneto replacement. The SureFly Ignition Module replaces one magneto - generally the left or impulse-coupled/starting magneto on most aircraft. 4 and 6-Cylinder models are available for Lycoming and Continental engines.

Replacing just one magneto eliminates magneto maintenance and cuts associated costs in half! Zero maintenance. Zero rebuilds. Zero overhauls. Most fixed-wing single engine aircraft can enable SureFly's advanced timing feature for improved cruise flight efficiency. Many other aircraft will be able to use the advanced timing feature as the FAA extends SureFly's Airframe STC AML.

In the Box

  • SureFly Ignition Module (SIM)
  • Power wire harness (84" long 14ga. wire with inline fuse holder, 10A fuse & ring terminals) If your battery is located in the tail of your aircraft, you will need to purchase a longer power wire.
  • Manifold pressure hose (36" long 1/8"ID x 1/4"OD high temp. rubber hose)
  • Engine STC paperwork
  • Airframe STC paperwork


For SureFly customers, 500 hours is simply not good enough. SureFly Ignition Modules provide operators a 2,400 hour operating service time. No inspections, no rebuilds, no overhauls. That prevents scheduling headaches and down time. That saves money. Period.

SureFly Ignition Modules have no mechanical parts that wear and all solid-state electronics. There's no need to disassemble a SIM like a magneto every 500 hours - which eliminates the chance of introducing a maintenance related failure.

SureFly Ignition Modules deliver a more consistent spark energy with higher accuracy than traditional magnetos. Variable timing advance provides SureFly customers real fuel savings. Low power consumption and light weight (up to 2 lbs. lighter than a Bendix magneto) make SureFly Ignition Modules light on fuel and light on the wallet too.

Better Starts
SureFly perfectly controls timing at TDC below 400 rpm which combined with longer spark dwell and the option to use wider gapped spark plugs, makes starting a breeze, greatly minimizing wear and tear on high performance starters and electrical systems.

SureFly Ignition Modules are hand built in Granbury, Texas almost entirely from components manufactured in Texas and Michigan. Designed, engineered, created and supported by the same team that brought you Sky-Tec starters and Plane-Power alternators, our approach to SureFly shares the same commitment, experience and passion for creating and bringing sensible, affordable solutions to the piston engine aviation market.

With the low cost of the units, combined with SureFly's potential fuel savings and low maintenance/replacement costs, there is simply no better value in magneto replacements for Lycoming and Continental engines.


  • Aviation spark plugs – gapped .016 to .036
  • Slick style harness – Shielded aviation harness
  • Input voltage 6-30 volts
  • Avg. Current @2700 500mA
  • Retards spark to TDC for starts
  • Up to 38 degrees Ignition advance – RPM & MP based
  • Hall Effect sensors provide velocity and position input
  • Manifold pressure sensor range – 6-74 inHg
  • Operational temp range -35 to 250 F
  • Minimum MTBF 2000 hrs
  • No interval inspections
  • RPM range 0-3500
  • Voltage to bridge .036 spark plug gap
  • Minimum 35mJ spark energy
  • 50mJ nominal energy


    Intelligent Timing Advance
  • For non-turbocharged engines, SureFly controls spark advance up to 38º before TDC as determined by manifold pressure and RPM (engine power setting). Each engine's base timing advance is read off the data plate and set into the SureFly Ignition Module or, "SIM" at installation. The timing advance schedule is hard set at the factory, when the SIM is manufactured, to provide the highest possible combustion efficiency.
    No Mechanical Points
  • Not only are points and condensers a point of failure in magneto ignitions, so are rotors and caps as they carbon track and provide alternate paths to ground as resistance builds in the system. That's why SureFly utilizes none of these antiquated technologies. SureFly components are all solid state and industrial-grade electronics.

    The result is zero maintenance, zero overhauls, no rebuilds, and no maintenance costs whatsoever! Nothing to wear. Nothing to maintain. Run it to 2,400 hours of SIM operation.



View the latest eligibility chart at Application Guide

If any of the following items apply to your installation, please call SureFly at 817-373-5161 before proceeding with the purchase or installation of a SureFly Ignition Module:
  1. Your aircraft tachometer is one of the following:
    1. Horizon,
    2. Electronics International,
    3. EFIS or Engine Monitor that requires magneto P lead inputs,
    4. EFIS or Engine Monitor that requires a 0-5 volt square wave input,
  2. Your aircraft has more than one engine,
  3. Your aircraft has an existing electronic ignition,
  4. Your aircraft has one of the following STC’s:
    1. Western Skyways Turbo STC,
    2. Auto Fuel STC.
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Since acquiring/installing/flying 10 hours with the Surefly magneto in my PA38 112 Piper Tomahawk O-235 Lycoming engine. Ive seen smoother performance levels in EGT and CHT as per my JPI700. Now saving 1.5 GPH in Fuel flow with leaning properly on average. Im using fine wire plugs all around, which are recommended. To achieve the most efficient and effective use of the technology that Surefly magneto brings to the table.

January 19, 2024

Very happy so far. Relatively easy install, easier starts and much easier hot starts. I’m also seeing about .5-.8 GPH better in a Mooney M20E with an IO-360 at cruise. Also cooler CHTs.

Kirk A Verified Purchase


September 20, 2023

The Surefly SIM4P is a great way to upgrade to electronic ignition without the fuss of using automotive spark plugs and having to replace your harnesses. Ive been so impressed with my SIM 4N on the right side, Ive decided to upgrade to dual EI with the SIM 4P on the left side. Dont forget to order a standard magneto gear as you wont be needing the Impulse Coupling for this installation.

Mike E Verified Purchase


August 8, 2023

The future!

Jacques H Verified Purchase


June 24, 2023

Installed a 24 volt Surefly on an 0-235-L2C on the right side of the engine. During unboxing of the componets, I was unimpressed with the 14GA wire and $1.99 fuse holder with a 10 amp fuse that was Critical to the operation of the Magneto. So, I am going to be dependent on a 10 amp fuse between me an a critical component required to keep my engine running. Not to mention a 1 amp continues drain on the battey while parked. Surfly recommends a battery minder to maintain the battery while not in use, other wise you have about 30 days till the battery is dead. The Surefly was installed as per their instructions, then test run. During the test run the Surefly Stumbled, then during the mag check it was found that the Slick Mag was not working, we shut down the engine, changed the bad slick mag with a brand new one. During second runup/test the Surefly mag tested bad and the engine was running on the slick mag. We shut down the engine, checked the fuse on the Surfly to find it blown, we changed the fuse on the Surfly and retested. During retesting the Surfly was dead and the Slick mag was functioning normaly. The SureFly was removed, boxed in orginal boxing and sent back. To date Aircraft Spruce has refused to issue a refund since it was installed, the Surefly was not working is clearly defective however, they have refused to process a refund.

Marvin M Verified Purchase


May 21, 2023

Easy install. Great engine starts. Very smooth engine now. Will see if the fuel burn improves.

Norman S Verified Purchase


May 20, 2023

If you have a fuel injected engine and it is hard to start, this will fix the issue! The prop only makes 2 revolutions and engine is running. Burns 1/2 gallon hour less at same power setting. Best money I have spent on my Arrow.

Scott S Verified Purchase


April 21, 2023

Im extremely happy with the performance improvement from the SureFly ignition. Startup is a dream. IT will pay for itself by keeping me from replacing starters so often. This unit is installed on a Piper Cherokee with 0-320 and is used in a flight school. I was replacing starters too often during the cold weather. Startups are fast and easy now. This is the second one I have installed on an aircraft and happy with both of them.

Datchair L Verified Purchase


February 14, 2023

Installed on O-200 engine. runs smoother, climbs better and there is about 50 rpm gain at full power. K. Petrov

Konstantin P Verified Purchase


May 21, 2022

Impressed with the completeness of the kit. Everything needed for a straight swap from the old magneto is in the box, including screws, washers, 20g wire, crimp terminals, placards etc. Even more impressed with the performance of the Surefly ignition. Cold or hot, my 0-320 now starts like a car. Subjectively, it seems smoother with a little more power, even on the fixed timing setting. Looking forward to using the variable timing option in due course. Very happy.

Malcolm K Verified Purchase


April 26, 2022


Please note, Aircraft Spruce Canada's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce Canada assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Mooney utilizes the shower of sparks system and does not have an impulse coupler. Would I buy the Sim4p or the Sim4N?

A Shower of Sparks system would be replaced by a SIM4N. As a side note, that is a Bendix magneto and will require the installer to change the spark plug harness with one that mates to a Slick magneto. All SureFly units mate with Slick style harnesses.

Q: Regarding the Surefly: Do you need to change spark plugs or still use the aviation ones? How do you save fuel with this?

Per Surefly: With any of the SureFly units we recommend the owner stay with whatever plugs are approved for that aircraft. They work just fine with auto plugs in the experimental world, so the unit itself doesn't care. Fuel savings are dependent on the aircraft and the operator. Lots of variables there. In general, we might expect some savings when running lean of peak at cruise. The biggest advantages are NO MAINTENANCE and easier starting.

Q: So I do have a Horizon electronic tach which I really like as it shows the performance of both mags. So if I use this to replace one Mag , how will it interface with my Horizon tachometer? Thanks

Horizon Tach is supported via the Tach 2

Q: Is there a Horizon tach fix yet?

Horizon tach is supported via the Tach 2.

Q: Do you have to replace both magnetos on Lycoming engines when installing a SureFly SIMP4P?

No, you do not.

Q: Can you replace both mags with the sureflys?


Q: Is everything shown in the Hardware Kit drawing included with the Surefly SIM4P unit?

Looking at the Hardware Kit drawing: Everything that is a dotted outline is not included. The remainder of the items listed are either already on the SIM4P or in the installation bag that comes with the SIM4P.

Q: What slick harness would I need to order? I would be replacing my bendix mag with the surefly.

This will depend on your engine make and model, spark plug barrel size, and if you are replacing the left or right mag. With this info, use the slick by champion application chart to select the harness needed for that application.

Q: slick makes different harnesses for my engine based on the model of the magneto. telling me to use their chart does not help. what model slick magneto does surefly copy?

When using the Slick by Champion Harness application chart, you will need to first select 5/8 or 3/4 barrel, then find your engine, Slick mag model, then left or right harness. Example: 5/8" barrel plugs, Lyc O-360-A1A, narrow deck. The first three columns of the mag models are for Slick, and this application has an "X" for the M4006 harness kit, left is M2983 and right is M2984. If you replaced your right mag you would want the M2984 harness, or if you did the left, you would want the M2983, or if you replaced both then order the kit M4006.

Q: Lycoming in the process of releasing engines with the surefly mag. Its my understanding that an engineering change was made on the surefly to upgade/change the bearings to comply with Lycoming reliability requirements. My question is, did surefly make this change across the board to all there products or just the ones that Lycoming will be using?

The units are identical except for color and some difference in the firmware. Bearings and all the mechanical parts are identical.

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