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MG Midget and Sprite Technical - Dumb Ignition Question...

I hate to sound like a complete moron since I'm doing the car myself, but what exactly is the difference between an electronic distributor and a standard one? Is there any system that completely replaces a distributor? (I'm thinking no... but please enlighten me) Where do the various coils come into play? The reason I ask is the vacuum advance on mine busted off being moved over the last 14 years, and I'm wondering if it'll be an issue if I upgrade...or do I need it...or can I replace the whole system with something mordern...or...?!?!?!? ARGH!

Car electrical/emissions stymies me...

Chris
'75 midget 1500

C
Chris Elkerton

Chris, electronic ones do away with the points and condenser of the regular or standard type of transmission.

There is no system I am aware of that replaces a distributor on our cars but I could be wrong.

The different coils are designed to operate on a given voltage but accept a higher one to provide a "hotter" spark to ignite the fuel mixture. Once the car is running, they drop to the operating voltage. Some operate on a 12 volt basis all the time depending on the car type.

The vacuum advance moves the time the spark ignites depending on the speed of the engine. This is known as timing. An engine at idle fires at one set of degrees and advances as the engine advances in speed.
Clive Reddin 76 Midget

there is an after market dist. less system called a mega-jolt...it reads the gaps in the driveshaft pully with an optical lens....common on Z-tek engines...pretty cool several on here have done it....

Anyway,,,,call around to the local chain parts stores, you would be surprised the differance in cost for a rebuilt dist....I got mine several years ago for $80 at autozone.


if yoou want something with some zip...mallory makes a duel point dist and you can get pertonix chips for it....not sure what else is avialable for the 1500 maybe a 123 aldon, of even pertonix themshelves


prop
Prop

I think the closest you can get to your goal would be using an ignition box like MSD with a crank trigger. You would still need the distributor but it's only function would be to direct the spark to the correct cylinder, the internals would be removed & no longer a factor.

As far as the broken vacuum advance, a good speed / performance shop should be able to change the springs & adjust the centrifugal weights in the distributor to modify the advance curve so you can do away with the vacuum advance. I did this 30+ years ago on my Sprite Mk IV - 1275 & it worked great. Much more predictable & tunable.
Mike G

Funny you should mention that mike,

On the 1275...there was a 2 year period here in the USA, I think 69 & 70 where they made the lucas dist with a mechaniccal advance instead of a vacume advance.


prop
Prop

Hey Prop,

Mine was a '69 with both the mechanical & vacuum which is what allowed me to re-curve the mechanical advance & do away with the vacuum.

BTW - We were answering at the same time again - Spooky, huh?
Mike G

Check this out:

http://www.theautochannel.com/autoparts/ignitionbestmg/itemu7970_42401_8.html
Mike G

Hey chris

Your in luck...Got 10 bucks???

http://cgi.ebay.com/ebaymotors/_Car-Truck-Parts-Accessories__MG-Midget-and-TR-Spitfire1500-Distributer-GC-NR_W0QQitemZ120262510204QQadnZCarQ20Q26Q20TruckQ20PartsQ20Q26Q20AccessoriesQQadiZ2865QQcmdZViewItem?hash=item120262510204&

prop
Prop

Thats a great price mike....Ive seen those for around $300 usa.

was your dist for a 1275 that you had modified....69 Im guessing so


I got a mallory duel point dist. but is dependent on points because its got vacume advance....Im going to put it in my new hi-performance engine....which Im hoping next year to build at this point....still collecting parts for it.

Im surprised at the qulity differance between the lucas and the mallory....night and day...makes the lucas look like a toy.

I was thinking about taking it to a race shop in st. louis and having it redone for machanical advance that way I can do electronic ignition from pertronix...I dont know, maybe not.

prop
Prop

Where was my head at? I was writing about distributors and wrote transmission in my post!! Must be because I used the word "standard" and that threw me off. (lol)
Clive Reddin 76 Midget

There are a number of systems we use that do away with the distributor entirely and use wasted spark coils, and thus use no dizzy rotor arm or all that clat.
The systems range in price from a few pence for a DIY fixed up systems from bits of modern cars, to £500 for a complete aftermarket set up.

Like all modern ignition systems they require a sensor on a trigger disc to determine the rotation of the engine and a processor to look at throttle position and decide when to spark.

I use the Alpha system on my car now.
Bob England

BTW hows that working for you Bob?
Finding it any better than the old dissy?
Bob T

I really happy with it at the moment just need to sort out the rev counter issue.
I have remapped it on the rolling road yesterday and it is running as sweet as a nut.
I did have another problem originally which was a bad miss at 4500 RPM. The car felt like it ran into a brick wall. In 1st to 3rd I had enough power to drive through it, but in 4th and 5th that became my rev limit. By chance and hope I re-routed the crank sensor cable away from the alternator and the problem seems to have disappeared.

Also I am only getting about 25 to the gallon, perhaps the SU is not quite as economical as my weber was!!!! :-))

Or more likely it is as a result of I am very rarely in a gear much above 3rd and at full throttle.
you gotta laugh aint ya!!!!
Bob (robert) Midget Turbo

Hey Clive,

I just figured you must have known something I didnt....lol.

But you have to admit...the idea of a carb having a type of transmission is an intreging idea


If it was hooked up to the butterfly...and the butterfly actully spun at a high speed instead of fliped back and forth to meter the air and fuel combo...making it more mixed...you could make the air/fuel more broken up at lower rev. and more atomized at higher rev. with a carb. transmission...you could even have the carb tran run a throttle shaft insert to make it longer and narrower for more torque at lower revs. and shorter and wider at the higher end for stablity and fuel econ0my....


So your in-advertant thought makes for so cool madification ideas.....you dont mind if I throw that idea in to my modifacation idea book do you


prop
Prop

Prop, be my guest at whatever brain storm I may have inadvertantly set off.
Clive Reddin 76 Midget

This thread was discussed on 17/05/2008

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