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MG MGA - Performance: Alternator Vs Generator

Some of you will be aware from my thread about a month ago that I have converted to an alternator. Since then the engine has been running even more smoothly than before and I have the impression (gut feeling) that it is also putting out a bit of extra power.

Is it possible that the alternator is giving increased power into the coil, hence a stronger spark and improved combustion? The old generator was, I believe, the original although I did have it overhauled about 9 years ago.

Steve
Steve Gyles

Maybe the alternator is more efficient and makes less drag on the v-belt. I recall a highschool science class demonstration where we hand-cranked a small generator- then switched on a small light bulb.. The increased effort to crank was significant! The same conditions with an alternator created considerably less drag. I don't recall the "why" of the physics being demonsrated, but I changed my 65 Karman Ghia to an alternator soon thereafter. M
Marc Judson (2- 1978's)

Marc - Just the opposit is true, the alternator produces more drag or resistance to turning as the current supplied increases. This is why it is more important in a car with a alternator that the fan belt be kept tight, whereas the cars with a generator can be run with the fan belt running very slack. In fact, the generators on the T series MGs up through the early MGBs have to have a rather slack fan belt or there will be excessive wear on the rear bushing in the generator, which will result in the early demise of the generator. Cheers - Dave
David DuBois

Hi Steve

With this increased power maybe you'll get away from the lights quicker! Your probably running in a volt more, this could help the ignition and fuel pump performance

Terry
Terry Drinkwater

Even charging at 60amps, the electrical load is less than 1 horsepower. Even if the alternator were twice as efficient as the generator you are talking less than 1/2 horsepower difference, and your engines horsepower will vary much more than that just from changes in air temperature and humidity. Under normal daytime running, you will be using much less than 60amps, so the best case efficiency difference would be less than 0.1 horsepower.

As for the voltage, it is regulated at around 14 volts for either alternator or generator, so again during normal daytime running, there should be no difference between alternator and generator.
Jeff Schultz

Jeff

Many thanks most interesting. Maybe my generator was down a bit on poke because I am convinced there is a difference. The car is definately more lively. Terry's Coupe would now be left standing at the lights!

Steve
Steve Gyles

I have a friend who swears that her Mustang runs better after an oil change--sometimes it's more a matter of perception than reality.
R. L Carleen

R.L.,
I once saw a car where the oil had been neglected for so long that it got thinned out with gas and in turn would not run anymore because the hydraulic lifters would not pump up - so it is possible!
How's that for a run-on sentence!!
Todd C.
Todd C.

Steve - In your dreams !!


Regards
Terry
Terry Drinkwater

I worked on a car way back when where the owner never (read: NEVER EVER, EVER) changed the oil. He had 30,000 miles on the car, and when I went to pull the dipstick, all I found on the dipstick was gritty substance. Had to get the engine hot, change the oil, adding kerosene, run for about a half hour and change the oil again. He got lucky, the system never did block up anything. I've also seen new cars that needed a new engine because the leasee (not owner) never changed the oil, and at about 17,000 miles the engine gave out. He brought it to the dealership expecting a free replacement engine, but the oil filter was the original, and it was proven that he never changed the oil. So yes, oil changes can make the car run better.
mike parker

Couple years ago there was an article in Circle Track- (yes, i read it. those boys down south are NOT as dumb as they might have you believe. Alot of technology transfer between oval and road racing). Anyway, the point of the article was that an engine running an alternator made more horsepower than one running a total loss ignition system, since the coil was getting the designed 13.8 volts rather than less than 12 on the total loss ignition.

Steve's original statement may be valid. Alternator have a higher output, and at lower rpm, than a generator. A generator may be only just matching system drain at low rpm, I seem to recall my brother's mercury that did not meet simple demand until he was at 1500-2000 rpm, as evidenced by lower than 12 volts.

If Steve's alternator was marginal, he may well be seeing the advantage of better spark.

greg fast

A supporter! Thanks Greg. I am totally convinced my car is running better. The one factual point to date is the idle RPM has increased from 800 to 850 RPM. I am checking on fuel consumption but not holding my breath as I am having so much fun 'wellying' the throttle with the additional response that I am probably negating any gains in that area!

Steve
Steve Gyles

I also noticed a performance increase after converting my 1969 M.G. midget 1275 from Positive Earth 25 AMP Lucas generator to the Negative Earth Lucas 35 AMP Alternator (16ACR) fitted to 1970 Midgets. More current through the Ignition Coil at lower rpm translates into a higher spark at the low end, and at night the 1969 Generator actually was UNABLE TO KEEP MY "DRIVING LIGHTS" LIT UP ALL THE WAY!
wattswh1

This thread was discussed between 01/08/2005 and 06/08/2005

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