How can I reduce ignition noise?

Electromagnetic Radio Frequency Interference (EMI or RFI) from the test engine’s ignition can be a major problem when trying to capture data via sensitive electronic instrument running adjacent to a high compression spark-ignition engine. EMI symptoms include bad dyno tach readings, erratic servo operation, Personal Computer lock-up, and holes or spikes in the captured data.

Interference worsens as the engine’s throttle is opened - this is due to the rise in spark voltage that accompanies any increase in cylinder pressure. Supercharging, turbocharging, and many race modifications that increase cylinder charging drive up ignition energy demands, often creating severe interference problems. As RPM increases (raising the EMI/RFI frequency) the number of interfering "pulses" generated goes up proportionally. The worst conditions often occur right around peak torque output (both cylinder pressures and RPMs are high) and the resulting EMI is often known to crash (blue screen) even a high quality PC running nearby.

Fortunately, there are steps that can be taken to reduce the interference at the source and also to harden the dynamometer's electronics and your PC from this ignition "noise." Taking one or more of the following preventive measures will generally allow testing of even the wildest combinations. EMI  problems are not in any way specific to the DYNOmite, so your ignition system’s manufacturer may have other suggestions you can follow.

1) Run all ground leads to either the engine’s battery (or block if no battery is in use) or to a clean common junction connected by a heavy-gauge ground cable to the engine’s battery. Ideally this battery's negative terminal and/or dynamometer's frame itself should be connected directly to a quality earth ground (e.g. buried large-diameter 8' copper ground rod) via a heavy-gauge wire (for a very low resistance connection). Avoid multiple ground points as this often creates a “ground loop” (where RFI can get onto the circuit).

CAUTION: Always hook up all the ground leads before hooking up any of the power leads for the DYNOmite data-acquisition module, its accessories, or the engine. Failure to follow this precaution can lead to circuit damage not covered under warranty!

2) Try using resistor sparkplugs (or caps) and also run graphite ignition cables (or genuine MAGNECOR brand Race Wires). These components tremendously reduce the level of RFI generated by the ignition. Subduing the noise at the source of generation is much more effective than chasing down every dyno harness lead that might be receiving these unwanted random signals.

CAUTION: Spiral wire wound “suppression” ignition cables are not nearly as effective (at reducing EMI) as true graphite core cables. The cheapest set of graphite wires will “out-suppress” the most expensive wound metallic wires. The only effective EMI suppression wires (other than the preferred graphite or carbon core) used in the high end automotive racing world are manufactured by MAGNECOR. For some straight talk about the pro's and con's of various type sparkplug wires, read "THE TRUTH ABOUT IGNITION WIRE CONDUCTORS" or "A Brief Overview of the Performance Aftermarket Ignition Wire Industry in the USA".

Tip: Keep an inexpensive set of graphite core cables in the dyno cell for troubleshooting problem ignitions. You don’t need expensive high temperature 8+ mm silicone jacket wires with high quality boots to survive on the dyno. Even installing just a graphite core coil lead may do the trick. New graphite cables will not reduce the engine’s power.

3) Keep the ignition wires (and coil wire) as short as practical and avoid routing the DYNOmite’s harness leads parallel or near to the ignition wires.

Tip: The EGT probes have extra shielding on them to allow operation near the ignition. Conversely, the Engine Temperature leads are quite sensitive to RFI, keep them away from the ignition if you can.

Tip: Temporarily iinstall braided metal shielding, such as Aeroquip stainless braid hose (grounded at one end to the engine block) over all the sparkplug (and coil) wiring. This trick was used on early Corvettes and many marine applications where the fiberglass engine cowling provided poor RFI suppression.

4) If EMI is interrupting communications between the DYNOmite Data Accusation Computer and your PC running DYNO-MAX (via a RS232 serial port connection) the use of Land Sea's special shielded and filtered cables may help. Symptoms include dropped data packets or random data spikes that worsen in intensity as the throttle is opened (increasing cylinder pressure and spark intensity). Avoid using USB adapters as they just add another point of EMI sensitivity - instead use a computer with built-in RS232 ports (or add an RS232 port bus card) so that there will be an uninterrupted grounded shield from the DYNOmite to the PC..

Tip: In extreme cases fiber-optic RS232 serial "cabling" is available. Such hook-ups use a converter at each end that translates the normal hard-wired connection into a light signal that runs along the fiber optic link. However, be sure to select models that do not require power from the PC or DYNOmite RS232 signal to operate! If you go fiber optic, order 100' long leads so that you can run one test with the PC far away from your engine - if the problems go away during the remote test, its your PC (so jump to suggestion #7 below).

5) Modern computers have gotten lighter and less expensive - and plastic housings are part of the reason. Unfortunately, plastic offers much less EMI shielding that the heavy metal cases used for early PCs. Toady, even many of the most expensive model PCs and laptops are very poorly "hardened" against the levels of EMI present near a spark ignition engine. If you can, try a few other models (or brands) to find the most robust computer.

6) Most modern PCs are no longer grounded via their power cords or chargers. In certain cases running a large gauge (#12 or 10) wire to ground the PCs case helps - try it both ways. Moving a problem PC further away from the engine is always a good idea. Sometimes, simply reorienting  the position of the PC (rotating it 90 degrees), moving the angle of the power cord, etc. may uncover a less sensitive position (just as moving a radio's antenna effects its ability to pick up a weak station).

7) Place your PC and monitor inside an EMI shielded enclosure to harden it against the interference. You do not necessarily need a $6,000 military specification EMI housing - something like the DYNOmite RFI/EMI Shielded PC Cabinet should do the trick.

Maybe it's not ignition noise!

Here is a question, and our suggestions, regarding one user's problem we received several months ago:
“Sometimes my laptop’s screen freezes up in the middle of a long hard pull on our Harley motors. This only seems to happen when I am both recording and have the throttle wide open. As soon as I back off the power, the screen comes alive again. I believe it’s RFI, but why does this only happen while I am recording?”

Your computer is probably sitting close to those engines. Laptops and newer PCs feature some of the lightest (per gigabyte) hard-disk drives ever made. This is great for reducing travel weight, but not so good for shielding their sensitive innards against the noise inside a working dyno cell. Under the extremely noisy conditions typical during a WOT pull, many new hard-disks refuse to transfer data – which, of course, is actually better than recording erroneous data.

So what happens to your real-time data? All personal computers provide solid-state (memory) buffers, where data queues up while waiting for the physical drive to respond (to XP’s write requests). Unfortunately, the buffers are small, intended to handle only short (one or two second) periods of drive unavailability. Once its buffers fill, Windows must sit and wait for the hard-disk to respond again.

If your dyno pull is fairly short (e.g. a quick inertia only test), the drive buffers may be large enough to temporarily store all the real-time data. Once the noise subsides, the drive catches up and so there is no problem. However, during your longer full-throttle pulls the disk buffers fill to capacity and Windows hangs – patiently waiting for more room of the disk drive’s “loading dock.” During that period the PC’s screen appears frozen.

What can you do if your personal computer is a victim of this problem? Here are a few easy solutions:

Solution #1) Replace your old mechanical hard-disk with a modern SSD (solid-state drive) unit. These non-magnetic units rely on the latest flash-memory technology. Any new SSD will be more robust when it comes to dealing with the conditions in a dynamometer bay compared to a conventional disk-drive. For examples of top-notch SSD offerings, check out Samsung or Toshiba units.

Solution #2) A similar solution is to use a Fast USB (2.0 specification) “thumb drive” to install your DYNO-MAX 2000 installation onto (instead of putting it on the PC’s hard-disk). These USB interface devices are less expensive, but slower, than an SSD unit. Note: Your computer may not support the latest USB 2.0 specification. If it does not, do not bother trying to use the slower 1.1 specification thumb drives!

Solution #3) Install“RAM disk” software to create a virtual disk drive in the PC’s memory. Be sure to use a software package that provides write caching and includes automatic data synchronization with a physical copy on the PC. One, of many, such products can be found at www.everstrike.com/ramdisk and offers a free trial.

Solution #4) Avoid the noise. Buy, or build, an industrial enclosure for the PC. Or, if practical, move the PC (hard-disk) farther away.

Solution #5) If you have over $5,000 to spend on a noise-hardened military-grade laptop, check out www.ruggednotebooks.com. Once you chose to go this route, be sure to specify their solid state drive and additional RFI/EMI hardening options!