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The Myth Zone.

Ah, good catch, thank you. I will go back and correct that part.
Honestly I don't remember the exact page, it was some random free online dictionary.

As for the rest, :dunno: but if I'm not welcome here, for simply having some fun and taking part, "newbies..." , I can take a hint. There's a whole lot more internet out there.

And, I never said current was used in the wrong context, just that by current he meant amps, for clarity for other readers. It was clear that he knew current meant amps.

Peace.
 
Never said you weren't welcomed here, we welcome everyone .... even a guy who doesn't own a Chevy. :haha: Just asking to watch the tone. And good call on removing the last sentence and cleaning up the rest of your post. :waytogo:
 
AR_K5 said:
Myth:
Removing the battery from a car while the engine is running will fry the electronics in a modern day computerized car, and was only a safe test in older cars with points.

I just spoke with an ASE Certified Master Mechanic who retire from Toyota and now own his own shop. He said so long as you don't rev the engine, the car will remain running (so long as the alternator is working properly) and no damage will occur.

How an alternator works.
http://youtu.be/tiKH48EMgKE

The common "One Wire" alternator is a self exciting alternator and does not require an external power source to power the magnetic field. *note some of the very early alternators were not Self Exciting and did require an external power source (ie some charge in the battery) to function.
It is the job of the voltage regulator to keep the voltage within a usable range.
Myth Busted
Click to expand...

Sweet! You talked with one guy and did some internet research and have now PROVED something conclusively and without ANY DOUBTS! :doah:

Also fordum's explanation about constantly changing load is exactly how cars work, so do some more reading before questioning that.

Now I'm going to tell you about the "load dump" issue. This is not a theoretical problem - it's something auto makers design into every electrical component in the car, test for and validate for proper performance. Even if no numbnuts ever pulls the cable with the engine running, the connections to the battery can always get loose or corroded causing a similar condition (except repeatedly!). The alternator windings are large inductors and you can't change the current in an inductor instantaneously - that would require infinite energy. So if you're charging the battery at 40A and you disconnect the battery, the voltage will go high. It's not that it "might" or "could". It has to (V=L(dI/dt)). The voltage you see depends on a lot of factors, but the only real limit is the load dump suppression built into your alternator or a centralized suppression somewhere else in the car. Typically this is 40 or 50V and the pulse can last up to 1/2 a second, worst case. So theoretically your radio, ECM, etc. can take this kind of abuse, but in some conditions you can exceed their limits.

So moral of the story: disconnecting the battery when it it fully charged is probably OK if you have a good regulator and there isn't a lot of load. But DON'T pull the cable while the battery is still charging.

I have designed this kind of protection into automotive devices and I have designed tests that simulate the load dump for validation testing. I'm not just passing along hearsay.
 
It was expected of me and I followed through.
I posted a theory with a lot of evidence to back it up.

You posted your theory.
So where's the references or videos to back up your claim?
I've still yet to see a toasted car from simply removing the battery (and not shorting the cables).

Keep in mind this myth is about the engine at idle to test the alternator NOT for driving around with no battery. (Surely nobody would jump start their car and run the engine WOT while unhooking the battery)
 
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shady said:
Open headers is fine. But No headers or manifolds (bare heads)will IIRC.
Click to expand...

Running an engine lean causes issues. That's it. Backpressure reduces the need for fuel (by restricting flow, which any exhaust system does, just to varying degrees) and thus once the restriction is removed the engine goes lean.

There are two myths here I believe, one that you need backpressure under certain conditions, which is false when talking about anything other than negative backpressure EGR valve operation, the other being that the valves exposure to ambient air is the issue. With exhaust being ~1200* coming out of the cylinder, "cold air" isn't ever hitting the valve.
 
The open header, no back pressure is a big pet peeve of mine too.
 
my Camaro sounded AWESOME on the way to the exhaust shop running nothing but bare stock cast manifolds :D
 
lived through the 4 mile beating just fine:thumb:
 
Exhaust valves can warp after an engine was run with open headers or too little back pressure,thats why drag racers stuff rags in the zoomie pipes after a hard run down the track....personally I've never seen one warp,but I guess it is plausible--they claim the cold air reaching the valve can cause it to cool too rapidly and warp...
I've run all kinds of engines from one lungers to cars and trucks with no muffler or exhaust pipes after the manifolds and haven't had any burnt valves..yet!..
 
Based on personal experience, I'd wager a fair number of hobby racers have poor comprehension of how an engine actually works. I would not take their actions as being rooted in science. Definitely not lumping all together, there are many who simply drop a block off at a machine shop with a grab bag of parts and say "put it together". Cam selection, RPM range, gearing, head flow, compression, head gasket thickness, are nothing they really concern themselves with...I want a race cam, I hear vortec heads are good, so put this motor together for me. Dunno, don't care what chamber size really is, deck height, lift, or compressed gasket thickness, they don't mean much.

Proper exhaust will actually make more power over open exhaust, that's one reason racers don't run open exhaust. Can't think of any internal combustion engine racing that intentionally creates backpressure outside of any rules requirements for noise reduction, etc., and the noise reduction components provide minimal benefit at best, in an attempt to NOT hurt exhaust flow.

The guys who go fast, have engines last a season, and win, are the ones who don't limit themselves to myths that others believe, and don't put together an engine with the cheapest parts available. You can tell the racers who actually take the time to put together a good engine.
 
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