As said earlier, bad idea. With alternator not working my car runs like a pig. Not enough voltage to ignite the spark plugs.

I think you have your logic wrong: The alternator savings are minute anyway. Your alternator will draw next to no power if your battery is fully charged.

You'd gain more performance from removing your passenger and rear seats, honestly

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Lillee - 1969 Morris Mini K

We are talking race cars here - no passenger seats, light weight (expensive) battery, etc. Keeping weight down and getting every last bit of HP out of the drivetrain is important.

In my case it will not be feasible to run with no alternator as this vehicle will run electric fuel & water pumps and thermo fans, with no ability to recharge between runs on most hillclimbs.

For a daily driver mini I would still recommend one of these Denso alternators as they are cheap, reliable, compact, light and efficient.
Internal fan alternators are lighter and more efficient than external fan units.

The newer (2000- ) ones have Segment Conductors and are 20% lighter and 50% more output. There are also an abundance of used ones that can be picked up cheaply from 20A Kubota engines to 100A units off EL Falcons that can be scrounged for $40

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Too many cars, and too little time.

OK sorry for a race car, I still honestly think (besides weight) the amount of lost power running an alternator has got to be a unmeasureably small. What you eat at breakfast before the race would have more bearing on performance than running with or without an alternator surely. Unless your alternator was seized or something...

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Lillee - 1969 Morris Mini K

12 volts*5 amps=0.060Kw * 1.44(?Kw to hp)=0.07 HP
there's mechanical losses from the belt however which might add up, but you need it for the water pump. If you put in a lecky pump to remove that, then you would need an alternator

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

It's a shame you can't get small permanent magnet alternators (yet), to improve the efficiency. 55% for a typical automotive alternator is pretty poor. A quick search finds you can actually buy new replacement rotors to suit AC Delco alternators, aimed mostly at the home alternative energy market: http://www.windbluepower.com/Permanent_Magnet_Alternator_Rotor_Fits_Delco_10SI_p/pma-rot.htm

For my purpose, I'll just stick with a Suzuki alternator
Rough max. consumption:
2A for EWP
7A Thermo fans
15A Engine management & ignition
10A fuel pump
Total 34A peak in theory, but probably only about 20A in practice as things like the thermo fans will not be running while the EMS is under peak load.

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Too many cars, and too little time.

There's changes in the wind with other motors as well. Brushless DC motors run at about twice the efficiency of brushed series wound motors (like you find in thermo fans, heater motors, etc).

Is that efficiency includeing the mechanical losses from the belt?

Still with those numbers and the efficiency included, that adds up to 0.32 Horsepower when running at 20 amps. Peak load at 34 Amps will drag 0.55 HP.

(Oh, 1kW = 1.34HP...not 1.44 oops)

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

No, not including belt losses. The permanent magnet technology, and the price that they pump them out of China, will no doubt filter into more automotive use.

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Too many cars, and too little time.

If you're looking at this presumably you've removed your other seats!!! I disagree, many alternators have a fan built-in, so you've got that, then the belt friction. If you have an EWP and don't need an alternator then you can remove the whole belt assembly.

People are right in saying that without an alternator, the car running voltage with a new, charged battery will drop from to 12 - 12.6v, depending on the battery (With an alternator above 3000 rpm you will get between 13.7 - 14v). This will drop off as the battery is depleted, when you race. Every car with spark plugs uses electricity, although the mini doesn't use much.

The central issue is, without a solid 12v voltage and/or decent current, at 8000 rpms you may missfire due to running voltage - THIS will be more detrimental to your track times than any alternator slowing you down.

The solution you are looking for is an accuvolt. http://www.jacobselectronics.com.au/audioaccuvolt.htm

This is a step-up voltage regulator. It will maintain a variable voltage (within a range) to a set voltage. This is the only way I know of to remove the alternator, yet maintain set voltage (eg 13.5 - 14v) throughout the race. At $800 - probably not worth it.

P.S. if anyone has some exact model numbers for compatible nippon denso alternators, can you send 'em to me? Been hunting for some for a while.

The step up regulator is interesting Simon, but yes it is out of my price range. If money was no object I'd get a Magneti Marinelli A45 L permanent magnet alternator - 13.5V 20A from only 750g

The Suzuki Swift Gti alternator part numbers are:
Suzuki: 31400 - 60B1 1
Nipon Denso: 100211 - 6600
These run the multi ribbed belt, so you'd have to change the pulley to suit the mini V belt.

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Too many cars, and too little time.

I used to work on Formula Pacific cars running a Ford BDA motor (BDG?) and they didn't run an alternator and they revved to 11,000 (or 12,000 on a good day)
If you forgot to charge the battery overnight you were in trouble though! They would start to misfire at the end of the longest straight and eventually the misfire would start earlier on the straight.
It was the electric fuel pump not keeping up with the demand.
The ignition system would still work long after the fuel pump slowed down.

At a Bathurst 12 hour in the 90s I was working on a Suzuki Swift GTI and the alternator packed up very early in the race so we had to keep changing the battery to keep it running. When it was running low it would start to miss under brakes as the draw from the brake lights would kill the power to the injectors.
I wanted the pull out the brake light globes but was over-ruled by the drivers. (one is the current CAMS president)

I see that some of you guys have done some rough calcs. but if you were to measure the HP dragged out of the engine it would be in the order of 5 to 8 HP. One item that was not taken in to consideration in your calcs is the pulley sizes. I used to recondition alternators and dynomos and test them. I made my own test bench and started off with a 0.75 HP Motor (same pulley size as the harmonic balancer) and kept upping the size. In the end I was using a 7.5 kW motor (2 pole - 2880 RMP) to run the standard Lucas 15 ACR & 16 ACR up to full 35 Amp Output.

The Dynomos we used to 'motor' to test.

The Alternator will withstand being disconnected from the battery while running - it's an old wives tale that it will do damage.

But, it will only sap HP if there is load on the electrical system. The HP required just to keep the battery on float is very small and there would be more HP absorbed in the drive belt than the alternator.

So to answer your original question, yes it is fesible and yes it will give you a HP boost.

albeit very tiny on a race motor?

Cheers GT,

Simon K was the unlucky recipient of a blown reg unit only a month or two ago due to reconnection of the alternator while the engine was running, so I wouldn't make a habit of reconnecting them.

I am intersted in the testing however, there's no replacement for the cold hard facts. Did you get any idea what was sapping the energy at the time you were doing the bench tests? The energy consumed is 1700% greater than the energy output (using those figures) which is not very efficient at all...

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

The way that the regulators and alternators are designed you won't have problems disconnecting them, unless......a component in the system was damged or on the way out. Poor Battery Charger operation is one cause of this.

You never hear of an alternator dieing when a cell in the battery becomes high resistance, which is the same as disconnecting it when operating.

The reason for the apparent inefficency is related to the pulley size, the power factor that the alternator itself (not the complete unit, but the AC part of the alternator) actually runs at and the harmonics within caused by the rectifier and it's own losses on top of that. The losses from the harmonics compound as the unit is loaded (i'm sure that you've heard some alternators 'sing')

Run your alternator at 100% load and see how long the drive belt lasts.

Apologies, other losses that I neglected to include are eddie currents in the laminations and other iron losses.