90 replies to this topic

[Rockoz]

Fan Belt squeeling could be just due to extra load on alternator.

[FastEHHolden]

Was this latest effort just using the conventional points setup, with original resistance wire powering both coils etc?

Yes.

[FastEHHolden]

When i had it on my EH (425 Impco gas mixer, YT head, mild sort of cam, extractors....your average warmed up 6) it definately had a noticeable effect when you connect and disconnect the 2nd coil whilst the engine was running.....on this HQ (bog stock 202 on petrol) there wasn't a great deal of difference..only those I mentioned a couple of posts ago...and I haven't done another run to work in it to work out the economy.

As i said..the only way i think it will make a difference will be to put it back on the EH...but even then YT head and cam are gone...just a stock 202 with the gas gear on it now...but I think gas was the reason for the change in idle speed...I know the 425 runs very rich and I am confident that an increase in spark voltage caused it to pick up.

Edited by FastEHHolden, 05 March 2009 - 06:27 PM.

[VitcLJ]

Well, have had deep and meaningful discussions on this subject over the last few days, have a theory as to why it works.

With two primaries connected in parallel you need twice the current in the circuit (logical right?) this means twice the power (P=VI) that is Power equals Volts by Current.

You can't destroy energy.

When the transistor (this was originally about HEI) switches off (or points open) there is a sudden collapse of the magnetic fields in both coils inducing a rising voltage into both the primaries and the secondaries, as the one with the plug connected actually sparks it acts as though there is a short circuit on the secondary secondary current flows .

This means that the primary of this firing coil looses any inductance it did have and wants to drop immediately to zero volts (it basically stuffs all its energy into the seconday current).

As the second parallel coil hasnt fired the energy stored in its field produces a current in the primary of the firing coil. (the primary at this time has a voltage of several hundred volts across it and sees the short circuit on the primary of the firing coil).

This primary current from the second coil into the firing coil causes the spark time to be lengthened giving a hotter spark and thus probably better combustion under some circumstances. (Apparently it can improve the burn rate because it lights up more of the swirling gas in the cylinder giving a better wave front this gets a bit esoteric and I really cant be stuffed following it up I believe them)



Theory says that if both coils are the same you will get at most 1 - 1/2 times theoriginal spark power. the other is dissipated in the windings of the two coils resistance.

This is a simplified version as there is actually a lot more going on as far as the theorry goes. (heavy Maths )

the voltage across the secondary of the second coil should, if the same coils are used, not be higher than the secondary voltage of the firing coil..


All I can say is SORRY fellas i didn't believe it originally but thanks, I have learnt a lot from this (including how much simplistic bullshit exists on the internet about auto ignition).
Theoretically it does make sense.

however there are still downsides.
Whether you are using HEI or points you need to provide twice the rated current through the points or the main transistor. This will shorten the life of either of these devices.

the firing coil will get hotter, Plugs will take a beating! wiring will get hotter. Points will burn out quicker.
HEI modules may be taken beyond their safe ratings and fail quicker.

If your ignition system is up to scratch for your comp ratio and fuel type /mixture then the only difference should be noticed at high revs due to the faster time constant. (the higher the comp ratio the hotter the spark needs to be to fire it)

you could probably get the same result by bypassing the ballast resistor and run the resistive coil at full battery volts.

all in all a good learning exercise when I get the time I may just set up a system and do some experimentation and see exactly what the gains are in the electrical sense.

[VitcLJ]

torbirdie : not at all the first theory still applies at high revs.

This theory gives the reason for the apparent benifit at low revs. both apply!

Consensus reached was that it will make the gains when the original ignition is not up to firing the mixture fully.

You will always get the rise time benefit but it really only affects higher rev ranges. (thus the use in the Jag V12)

So for the VOLVO (Arghh) it probably had a crappy ignition system (matching the car in my opinion)(please guys its my opinion don't throw buns Please!!).

for the Eh comp ratio and mixture coupled with gas as a fuel probably lit up better with this system.

The f@@D in the article probably higher comp ratio, rich mixture, lit up better.

[77_LX_HATCH]

VitcLJ, that makes a lot of sense, after nearly completed my ad dip in electronics (whilst doing an apprenticeship), you have hit the nail on the head. Have done a lot of previous work on transformers, and what you are saying is correct!

As for FastEH, i reckon that the 'hotter' spark would cause the gas to ignite better.

I think i'll have to try another old coil in parallel with the 202 kingswood on gas!

But do agree that removing the ballast resistor or resistance wire would produce the same affect. (in points system).

Cheers

Mike

[FastEHHolden]

So...if I am reading this right...the ideas expressed in the scanned magazine article are correct?

[FastEHHolden]

its only that high when the car is running...you need to use the "12 volt" coil for your 13.8 volt system.

[FastEHHolden]

you should run the 12 volt and not the 9 volt coil....one that isn't for use with a resister. The 12 v coil is built to handle the system voltage.

[VitcLJ]

12 volts is only the nominal terminal volts for the battery. The lead acid battery is rated at 2 volts per cell but is in reality 2.22volts per cell for a fully charged unit. A well charged modern battery will be between 13.2 and 14 volts. 13.8 volts sounds about right, a good modern altenator will run about 14.2 volts at the altenator terminal.
If you read the fine print for bench supplies for car operated equipment they normally run at 13.4 or 13.8 volts to simulate a fully charged or charging battery.

The elecrtonic ignition is designed to run at anywhere from 4.0 to 16 volts from my research work on this thread.

Just as an aside some ignition modules actually limit the current that can be drawn, which means that the increase in spark energy may be somewhat less in theory, than that of an unlimited system (points).

I am some what amazed at how complicated it all gets when you start really probing this subject.

Also how little information is available in an easily read format.
I basically had to find out what the silicon devices in the modules were to get the operational principles nutted out.
Please dont ask I don't think I can type fast enough to finish before Xmas 2012.

[micklx]

The thing I have learnt through this thread is that unless I can get my six spinning to 12,000 rpm, I shouldn't have a problem with the H.E.I with 1 coil?

If you connect your tacho to both coils - who knows, you might see 12,000 rpm....