Alternator Upgrade Effect on Emissions?

[goloch]

I'm planning on doing the Bosch/Saturn alternator upgrade on my 71B. Anyone have any idea if the alternator swap will help or hurt emissions based on a change in engine load?

 

[Nunyas]

erm... i don't think it'll effect the emissions much, if at all. The load it places on the engine should be small enough that the idle (if it changes) can be corrected with less than a 1/8 turn of the idle screw...

 

[dklawson]

I'd certainly agree with that. There should be no significant change on the emissions at idle.

I have a question for you though. Does NJ perform emissions tests on 1971 cars? For years our cutoff date was 1975 and I believe we've now started a 25 year old rolling limit. I don't think you need to have anything older than 1980 emissions tested here this year. They would probably do a visual inspection though to make sure all the correct parts are in place.

 

[goloch]

If I were to register the car as an historic vehicle it would be exempt from emissions; however, I would be restricted to less than 3k miles per year and wouldn't be able to drive at night so that's not an option. In order to register as a regular-use vehicle, it has to pass emissions and safety inspection. The good news is that the requirements are scaled for older vehicles so it's not impossible. The bad news is that this car's ignition and carbs were a disaster and it was 12.5x over the legal limit for hydrocarbons back in October - 6200 measured against 500 allowed. Hence my trying to squeak out every improvement I can without resorting to reinstallation of the air pump (removed by PO).

 

[703MGB]

I failed to see how you are going to pass the emission test without the air pump!
That thing was put in place to deliver oxygen to exhaust gas in order to consume un-burned hydrocarbons.

 

[Radford]

Oh, these cars will pass without the air pump. I had a TR8 here in GA that had to pass (we're exempt after 25 years). Took it to my mechanic's shop and detuned to pass. The car was barely running and just made enough power to pass, but it did. No rails, no pump, no filters.

 

[goloch]

I've heard similar stories about detuning B's dating back as far as the mid-70's. My principal had a 69ish GT that he had to tune down to barely running to pass in 1975! That's what I'll be banking on after I get everything cleaned up and back together in the next few days.

 

[MattP]

I've been considering the same upgrade as I need a new alternator. My hold off has been whether or not you need to upgrade the fuses to handle the higher output. Anybody know about that?

 

[SilentUnicorn]

changing the fuse ratings shouldnt be needed. alltho why not put in new ones of the correct ratings at the same time?

mark

 

[MattP]

I was planning on that anyhoo. I hope to spend my next 4 day weekend under the hood ect. I just got the car a bit ago and want to do a tune-up, oil change and a few other of the maintenance things when I install the new alternator, kind of zeroing out the car so I have a base of reference for my maintenance schedule. Just a thing of mine. I do it with any used car I buy.

 

[danmas]

[ QUOTE ]
My hold off has been whether or not you need to upgrade the fuses to handle the higher output. Anybody know about that?

[/ QUOTE ]

Matt,

Your new alternator will have no higher output than the one you replaced, it'll just have it at a lower RPM. The output of the alternator is determined by the load, nothing else (assuming the alternator isn't overloaded). If you don't change the load, you'll not change the output.

As for fuses, they are there for one reason and one reason only - to protect the wire. Unless you increase the size of the wiring, DO NOT increase the size of the fuses.

 

[MattP]

[ QUOTE ]


Your new alternator will have no higher output than the one you replaced, it'll just have it at a lower RPM. The output of the alternator is determined by the load, nothing else (assuming the alternator isn't overloaded). If you don't change the load, you'll not change the output.

As for fuses, they are there for one reason and one reason only - to protect the wire. Unless you increase the size of the wiring, DO NOT increase the size of the fuses.

[/ QUOTE ]

Thank you! Electricity has always been a bit confusing to me. Your explaination cleared up a lot. I probably will upgrade now.

 

[goloch]

Just to add to danmas' point, changing the fuse ratings could actually be catastrophic depending on what you change. Fuses are rated based on the device at the end of the wire, not the power source. I would however heed Mark's advice and make sure that all of the fuses are of the correct type and rating while messing around with the alternator. Generally speaking, whenever I run a power line in any vehicle I make sure that it is fused independently of wherever I draw the power from. Better to blow the $1.50 fuse than the $$$$ device at the end of the line.

 

[Nunyas]

the cars can certianly be detuned to pass smog... that's basically what happened in my case. While I DO have the air pump and the air rail, the pump was not functional (I didn't know for sure until relatively recently). I had to tune it so lean that it barely moved under it's own power... Since I'm in Cali and need to keep it I'm planning on getting another pump, I suppose I'll check the air rail for blockages while I'm changing the pump too.

 

[goloch]

Good to hear. Carbs are off the car for a good cleaning and possible rebuild before heading back to inspection at the end of the week (Spring Break is a wonderful thing; I highly recommend teaching to anyone interested in having a fantastically rewarding career AND a week off to work on their LBC in the early spring. /ubbthreads/images/graemlins/smile.gif).

The nice thing about NJ inspection is that since it's been privatized the employees have no clue what an MG is, let alone what emissions control equipment it should have. When I went (and failed miserably) in October, the rather young inspection worker was more interested in the set of new Brembo rotors I had purchased for the front discs than anything else.

 

[dklawson]

Upgrading the fuses is not required when putting in an alternator. Your car's electric motors and lights aren't going to draw any more power than they did before. However, what is necessary is running an additional HEAVY gauge wire from the alternator to a position like the hot side of the starter solenoid. The old wiring to the battery wasn't designed to carry that much current. The old C40 generators only produced 22 Amps while alternators produce significantly more.

Another thing to consider when you do this conversion is that it will allow you to use halogen headlamps. If you switch to halogens though, consider putting a relay panel in place to operate your new headlights. The halogens draw more power than the sealed beams and you don't want to put more power through those 25+ year old Lucas switches in the dash.

 

[danmas]

[ QUOTE ]
Fuses are rated based on the device at the end of the wire, not the power source.

[/ QUOTE ]

Gabe,

With all due respect, I disagree with you. The wire is sized to handle the load of the end device, and the fuse is then sized to protect the wire. A fuse cannot protect the end device. If there is a short on the wire, the voltage/current to the end device will drop, doing no damage to the end device. If the end device faults, then it is already destroyed, and the fuse can't help. The only possible source of excess voltage to any device in the car is a failed alternator regulator, which will generally allow only 18 volts or so, which will usually cause no damage to any device, but the excess current from this most likely won't blow a fuse anyway. 18 volts is only a 22% increase, and most fuses aren't sized that closely.

 

[goloch]

Speaking outside of the specifics of car electrical wiring and looking at circuits in general, the purpose of a fuse is to protect expensive components from excessive current with a dispensible, inexpensive part. This excess current can either be as a result of a surge from the power source or by an increased draw from a component. The wiring run from the power source to the device must be of a sufficient gauge (lower number = thicker wire) to handle more than the maximum expected current draw from the device, a common practice in automotive and most general wiring to prevent melting of insulation and a subsequent short in the result of a current overload situation. The fuse rating is then determined such that the fuse will blow at an amperage lower than that at which the wire melts or the device is damaged, but greater than the reasonable expected maximum power draw from the device.

In the case of automotive circuits, the power source is an alternator so a surge would be limited by the mechanical ability of the alternator to generate power. However, depending on the tolerance of the device, a potential 30% increase in voltage generated by a change from 13.8 volts to 18 volts and subsequent change in power (Ohm's Law: power = voltage*current) *could* be enough to overload a device. If there were to be a current surge from the alternator the fuse would blow in response to the excessive current thereby saving the device from damage caused by the surge. On the other end should a device develop a short, even assuming that the device itself is destroyed, a fuse will prevent an increased draw on the alternator through the low resistance circuit and save the alternator from damage.

 

[dklawson]

Regarding fuses...
When I was in high-school many, many years ago the local British car repair/parts shop had a fake sales poster on the wall. It pushed "New Lucas No-Blow Fuses". They had taped a series of 1" lengths of copper tubing to the board.

I do not wish to contradict or compete with any of the statements in previous posts. I will add one more serious fuse comment. Fuses are rated by (and blow in response to) current. Yes... they often have a voltage rating. However, the voltage rating is there to indicate how high a voltage can be present as the fuse blows before an arc is drawn and maintained inside the fuse. In other words, if you have a 10 Amp, 120 VAC fuse and you install it in a 240 VAC circuit, you stand a chance that IF it blows, an arc may be maintained inside the blown fuse... continuing current flow. Also, it's much harder to develop high-current DC switch gear. AC arcs are somewhat self-extinguishing because of the sine wave... DC just keeps flowing. Next time you pick up a switch at the hardware store, notice that it will have both AC and DC Amp ratings and the DC rating will be substantially lower.

 

[goloch]

See now that part I never knew. Most of my fuse work has been dealing with automotive or amateur radio applications so I've never dealt with anything other than 12 VDC. I'll be sure to file that away for later use.