High Energy Ignition (HEI)

[DCUK Martin]

Compared to nearly every one of its North American contemporaries, DeLorean ignition specs are woefully out of date. Both coil voltage and spark plug gap more closely resemble 1971 practice than 1981 practice.

Once AGAIN, the voltage does not tell you the whole story. By widening your plug gap, you require a higher voltage to ionise the gases in the gap, but the energy transferred by the spark then depends on the sum of the current (the integral of the graph) the coil drew whilst charging.

And yet another sweeping statement about the age of the "practice". Show me spec on current production cars and their plug gaps from today? 0.7mm is still pretty vanilla flavoured AFAIK.

I haven't read your documentation, but a huge amount of work has gone into improving air-fuel mixing. This is one of the principle reasons behind fuel injection in the first place - more accurate delivery and better fuel atomisation, at which point you need less spark energy to produce a consistent flame front. I'm not an expert on this but it has just struck me that we're probably talking different requirements: With a carburetor, the engine is more likely to need extra spark energy (even though the carb'd PRVs natively used the same ignition as a stock DeLorean).

Bottom line: the ignition system used by DeLorean is quite badly matched to its lean mixing fuel system.

WRONG Working correctly, the DeLorean fuel system works at precise stochiometry (required for the 3-way catalyst to function correctly) unless the driver applies full throttle, at which point it runs rich.

[content22207]

And yet another sweeping statement about the age of the "practice". Show me spec on current production cars and their plug gaps from today? 0.7mm is still pretty vanilla flavoured AFAIK.

Do not compare a 1981 DeLorean to a 2011 model anything -- compare it to its contemporaries: http://dmctalk.org/showthread.php?14...ther-1981-Cars

Can you spot the cars running Bosch ignitions?

Face it: compared to nearly every other car new on a showroom floor in 1981, DeLorean ignition was woefully dated.

It hasn't improved with the passage of time.

Bill Robertson
#5939

[DCUK Martin]

Face it: compared to nearly every other car new on a showroom floor in 1981, DeLorean ignition was woefully dated.

"Woefully dated" is typical of your exaggerated soap-box antics. If it's reliable and does the job it was designed for, how can it possible be "woeful"?

You can't have it both ways. Either plug gap is a sign of how "modern" the ignition system is, or it isn't. The DeLorean is in line with contemporary european systems of the time (see the German manufacturers quoted in your list, and pointed out by the only reply on that thread) and is in a similar ballpark to modern systems now.

Face this: The DeLorean engine as designed is very reliable and does not suffer disproportionately from ignition system issues. Changing the ignition system is not going to give you any advantages over a properly working original system. You MAY see some advantages to HEI and larger plug gaps but only if you

a) are replacing worn out original components
b) i) have an existing problem which a hotter spark can help mask or
ii) a carburetor which doesn't achieve as good fuel-air mixing as fuel injection

[content22207]

Bullshit.

I will make two more spark gap comparison lists for you -- one for 1969, and one for 2010. That should settle the issue.

Quick Google search (complete lists will require some research on a parts house computer):
- 1969 Mustang with 250 I6: .024-.026"
- 2010 Mustang with 3.7 V6: .048-.052"

- 1969 Camaro with 230 I6: .035"
- 2010 Camaro with 3.6 V6: .043"

- 1969 Charger with 225 I6: .035"
- 2010 Charger with 2.7 V6: .050"

Notice the trend: from smaller gaps to larger gaps, fuel delivery method irrespective (larger gaps actually are on multiport injected engines).

Bill Robertson
#5939

[DCUK Martin]

Bullshit.

Which part?

You're now going against what you yourself said:

Do not compare a 1981 DeLorean to a 2011 model anything -- compare it to its contemporaries:

... and then you linked to a reference showing that its european contemporaries were much the same - you've conveniently ignored that salient point.

Seeing as you're so fond of repeating yourself, I'll join in:

The DeLorean engine as designed is very reliable and does not suffer disproportionately from ignition system issues. Changing the ignition system (on an original engine) is not going to give you any advantages over a properly working original system.

Quoting spark gaps in other cars is like judging their performance on the size of the wheels, it's meaningless.

[content22207]

Quoting spark gaps in other cars is like judging their performance on the size of the wheels, it's meaningless.

Society of Automotive Engineers Paper 720007, p. 60: "The conclusions reached as a result of this investigation are summarized below. Even though these conclusions are based on test results obtained with one basic engine, the trends observed should be similar to what would be expected of all modern engines."

Notice the trend: from smaller gaps to larger gaps, fuel delivery method irrespective (larger gaps actually are on multiport injected engines).

From the early 1970's onward, up to the present day, the trend has been larger plug gaps. .026" was very rare in 1981.

Bill Robertson
#5939

[content22207]

Show me spec on current production cars and their plug gaps from today? 0.7mm is still pretty vanilla flavoured AFAIK.

The largest selling car in Great Britain in 2010 was the Ford Fiesta. Spark plug gap: 1.3 mm (.051").

Bill Robertson
#5939

[content22207]

Spark plug gap on the Eagle Premier PRV: .030-.035".

Bill Robertson
#5939

[Ron]

50 pages, and "performance" still includes horsepower and emissions...

[content22207]

19 pages actually (48-66).

First page (48 ): authors define "performance" as cyclic combustion variations and emissions.

You have to actually READ the study....

Bill Robertson
#5939