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MG MGF Technical - Poor damp start appears cured

You may remember I asked about damp start problems a few weeks ago... I had my plugs and leads changed at the weekend and the car is noticably improved. Cold/damp start problems appear (so far, touch wood) fixed and the engine runs so much more smoothly.
Champion plugs (dont know which ones) and Moss supplied performance leads.


A little info from magnecor ...

What is EMI, and why is it important to suppress it ?
EMI = electromagnetic interference

EMI from spark plug wires can cause erroneous signals to be sent to engine management systems and other on-board electronic devices used on both racing and street vehicles in the same manner as RFI (radio frequency interference) can cause unwanted signals to be heard on a radio receiver. Engine driveability problems ranging from intermittent missing to a dramatic loss of power can result when engine management computers receive signals from sensors that have been altered by EMI radiating from spark plug wires. This problem is most noticeable on modern street vehicles used for commuting where virtually every function of the vehicle's drive train is managed by a computer.
For many reasons, the effect of EMI on engine management computers is never predictable and, often, improper diagnosis for a driveability problem results in huge repair costs for a consumer because engine management sensors and other parts are replaced when all that was needed was a set of ignition wires capable of suppressing EMI (usually replaced as the last resort). As production vehicles age, engine management sensors, connectors and wiring deteriorate (and corrode) and become more susceptible to EMI radiated from spark plug wires not able to adequately suppress EMI. The problem is often exacerbated by replacing the original ignition system with a high-output system.

How much extra horsepower can I expect when I fit Magnecor Race Wires ?

Professional race engine preparers do not use Magnecor Race Wires to increase engine horsepower they use them to maintain full engine horsepower. Often, production vehicle owners comment that engine performance increased after they fitted Magnecor Race Wires, and most owners of modified vehicles find that horsepower increases during a dyno test however, in reality, performance increases because the engine's potential power was previously restrained by:
(1) Failing conductors in original equipment ignition wires;
(2) Failing conductors in aftermarket carbon conductor and European and Japanese spiral conductor ignition wires;
(3) Failing resistor-connectors on German ignition wires;
(4) Aftermarket spiral "low-resistance" and "super conductor" ignition wires interfering with the engine's electronics;
(5) So-called "built-in capacitor" ignition wires inducing too much available current to ground straps and interfering with the engine's electronics.
Despite what is published in advertisements and some vested interest magazine articles, no spark plug wires will generate or "install" additional horsepower. However, a decrease in horsepower will occur if the wires' conductors fail to conduct the spark energy needed to fire spark plug gaps, or EMI emitted from spark plug wires causes the engine management computer to react abnormally, or so much spark energy is lost into the ground straps of so-called "built-in capacitor" wires that little is left to fire the spark plug gaps see test in Circle Track Magazine (USA), May, 1996 issue. For these reasons, Magnecor Race Wires are used by many successful race teams and individuals all over the world to eliminate the risk of such events occurring.

Over the years, we have never ceased to be amazed how many people blame problems caused by spark plugs on the ignition wires. Ignition wires are nothing other than conductors of spark energy, and if the spark plug gaps are eroded or set too large, or a spark plug itself is defective for a variety of reasons, the energy conducted will be wasted. No spark plug lasts forever, and rarely, does any spark plug last as long as advertised, particularly if you want your engine to perform satisfactorily. Sometimes, spark plug problems can be disguised and postponed with stock wires, which provide suppression by reducing spark energy to the plugs, and sometimes spark plug problems can be made worse by Magnecor KV85 and R-100 wires designed to provide suppression without reducing spark energy from the coil (more so, with high-output ignitions). Unfortunately, all engines lose power if any or all spark plugs are not performing satisfactorily, no matter what ignition system or ignition wires are used.

Which spark plugs should I use with Magnecor Race Wires ?

This is a difficult question to answer, and is in fact one of our most frequently asked questions, but in general you can use any spark plugs with Magnecor Race Wires. On a full race engine, spark plugs specifically designed for racing should be chosen. A decision as to which type and brand should be made only after investigating which spark plug is used by other competitors racing engines and vehicles similar to yours. You might find it easier to get this information from spark plug suppliers, although experimentation will always be necessary.
On production vehicles used exclusively on the street in standard tune, often the vehicle manufacturer's original spark plugs are a good choice, except where a double platinum version is available which is a better choice. Always use resistor spark plugs if the vehicle manufacturer specifies them, as the resistance is there to not only to help reduce RFI, but also to extend the life of spark plugs by reducing tip erosion.
Unless you know someone with an identical vehicle who can vouch for spark plugs that are heavily promoted and promise extra horsepower and fuel mileage, it's best to avoid them, as these spark plugs rarely fulfill the claims made and always, you will be paying more in the price for the promotion that makes you think you need them than the cost to manufacture the actual spark plugs!
After fitting a high-output ignition most people are tempted to widen spark plug gaps, and although the latest aftermarket ignition systems can easily cope with the extra voltage necessary to jump the larger gap, often the smaller diameter spark plugs used in most recent street engines will cause an engine misfire (usually at high RPM) after a few miles because the spark tends to track down the coating formed from combustion on the center electrode insulator in preference to crossing the widened spark plug gap. Also, wider-gap spark plugs will wear out prematurely. Owners of some modified street cars have found differences in acceleration response by altering spark plug gaps, but generally, if Magnecor Race Wires are used, the best response will be attained with a standard gap. Again, experimentation is always necessary.
If you are experiencing problems finding a suitable spark plug for your modified production engine, you should try spark plugs such as those made by Torque Master <> (who also make plugs for full race engines) if you don't want to be constantly changing spark plugs. Most people we encounter using this style of plug find them useful for this purpose.

Because of the huge variety of different brand spark plugs currently available, care needs to taken to ensure the spark plugs you use to replace worn out plugs are identical in proportion. This is particularly important if your engine uses multi-part extension type spark plug connectors with top seals that need to fit flush with the valve cover. You need to ensure that the height of each spark plug from the gasket seal to the top of the spark plug is identical to the original factory spark plugs, if you think the height of the plugs you are about to fit are different to that of the originals, please contact us before ordering. We have seen spark plugs, sold as aftermarket replacement and/or performance plugs, that can be up to 5mm taller (top seals will be pushed up) and 5mm or more shorter (spark plug wires may not properly engage spark plugs).

Magnecor Race Wires for German other European engines completely eliminate the need for resistor-connectors, and owners will notice a difference in engine response with Magnecor Race Wires. Although we are always pleased to hear our wires made such a difference, particularly on Porsche, BMW and Volkswagen engines, we must admit it's not necessarily all because Magnecor Race Wires increased the engine's response and efficiency, as it's more likely some of the improvement emanated from the elimination of the original style of ignition wires that reduced the spark energy available to the spark plugs to provide suppression.
Occasionally, consumers who have their German vehicle's regular maintenance performed by the dealer are advised their Magnecor ignition wires don't have the same resistance as the original wires, and sometimes the dealer justifies the re-installation of the ridiculously expensive limited-life original style resistor-connector ignition wires with this statement. Be assured that Magnecor ignition wires do provide the resistance needed by the ignition system and without a reduction in spark energy! Magnecor has sold tens of thousands or more wire sets over the last 21 years to replace resistor-connector style ignition wires on BMW, Mercedes, Porsche and Volkswagen and other European vehicles.


Very interesting but largely superfluous information that I feel is an attempt to sell more products and justify a higher price for it.

What they conveniently failt to mention is that most of the improvements that will be seen with be due to the replacement of old and now below spec parts with new. If the comparison is between new and new then the differences will be very, very much smaller and in most cases discernable only by the use of accurate measuring information.

EMI is a problem with systems usually only when and sensor wires are in close proximity to the HT circuit, then the problems can be interesting, but rarely do they reach such intrusive situations.

Roger Parker

This thread was discussed between 14/11/2000 and 18/11/2000

MG MGF Technical index

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