Alternator upgrade on a race car

[edbaus]

Hi,

I have been using an early alternator with an external regulator. Now I have a late model housing and a rebuilt alternator.

What I know is that:

I need to hook up a constant battery power to B+

I need to hook up a ground wire or strap to D-

The question I have is that D+ usually needs to go to the alternator bulb on the dash. I have no intensions of using a bulb.

Is the D+ wire the one that needs to be hooked up to switched power and I should run it through the electrical shut off switch?

Thanks

Ed

[Grady Clay]

Ed,

What year, model and class? What kind of events?

If you don’t install the alternator warning light, how are you going to tell if there is a broken fan belt?

Installing the correct wiring for the shutoff switch is critical. All the track organizations require the engine to be running and then turned off with the emergency switch. Incorrect wiring will immediately fry the alternator. There have been numerous threads on this subject.

Best,
Grady

[edbaus]

OK, Yes, I reallize I need to run A wire through the shutoff. I need to know if this it the wire that should. Bad wording on the original post.

This is an existing race car that I built 6 years ago and has passed tech for the shutoff switch. What I need to know is this how this wire should be run.

The treads I have found have not helped in a completly ground up from scratch application.

No, I am not running a light. I have a light for over temp.

PCA GT4s, NASA GTS4, and SCCA ITE.

Thanks

Ed

[Grady Clay]

Ed,

An over temperature sensor, even on a cylinder head, is way too late. I encourage you to use the regular alternator light.

Do you use a Factory wiring harness or did you build your own?

My SCCA GT2 914-6 doesn’t normally use an alternator. I have an empty housing to support the bearings and shaft for the fan. All the electrics run off the largest Interstate automotive battery. I have a little Honda 600W generator to recharge between sessions.

I address the fan belt failure warning with a small adjustable air pressure switch (a 908 part) plumbed to the fan shroud. I use a bright yellow trailer running light on the instrument panel.

The oil pressure warning light uses an adjustable oil pressure switch (a 917 part) set to about 40 psi. There is a red trailer light on the instrument panel. When hot, the light comes on below about 4500 RPM. Since the engine is at 6500-8300 all the time, it never should come on during track time except cool-off.

I also have two safety cut-off switches. The normal one is on the cowl with the “E” decal. There is a second alongside the shifter that I can easily reach with my belts on. My theory is I might be in a situation where I didn’t want to release the belts but would want to use a master safety shut-off (injury, car on its side or top.) Same for the fire system.

I’ll help you with some Pelican searching. I’m pretty sure this has been addressed in depth.

Best,
Grady

[edbaus]

I do not have any of the factory wiring left. Everything is custom.

The gages that I use have a programable low oil, high temp trigger that I run to large lights on the dash.

I have been thinking about doing the same thing on the cut off switch. I have mine probably in the exact same place and I too have to dump the belts to get to it. Or, I had thought about running a cable to it so that I can turn it off from inside.

Any help on the searches would be appreciated.

Really wanted to get the new motor fired up this weekend, but it seems like the little stuff is getting in my way. Changing too many things at once.

Thanks

Ed

[Grady Clay]

Ed,

My first search produced 68 threads here:
http://forums.pelicanparts.com/search.php?action=showresults&searchid=1884376&sortby=lastpost&sortorder=descending


Here are a few good ones from the first page (of 3 pages):
roadside kill switch install help??

How to wire a 4 poll kill switch

Race Kill Switch problem

Hope this helps.


I still think you will have a problem if the fan belt fails. There isn’t any way you can use the oil temperature to catch the failure without damaging the engine. Envision that the belt comes off at redline after a long pull in 4th. You then shift into 5th for another long pull. You are at high speed so the front cooler is getting a lot of air which slows the oil temperature rise. With no cooling air going across the heads and cylinders the temperature of those parts and more rise exceedingly fast under full power. I’ll speculate serious damage can occur in as little as 2-3 seconds.

I agree that an adjustable switch to warn of high oil temperature is useful. With today’s electronic a rate-of-rise feature would also be useful. I would position that sensor on the engine oil out pipe in hopes that a failing bearing over temperature (or rate-of-rise) could be detected in time to not do more damage.

I like to continue using the Factory gauge. Driving many 911s over many years, you develop a “sense” where you don’t have to study the gauge. In fact I use the one from a ’68 where the range of the indication is 140-280F. It is much more sensitive than the later 120-300+F versions.



Your question:
“The question I have is that D+ usually needs to go to the alternator bulb on the dash. I have no intensions of using a bulb.

Is the D+ wire the one that needs to be hooked up to switched power and I should run it through the electrical shut off switch?”

One side of the charge indicator light is connected to D+ at the alternator, the other side of the light goes to switched 12V. Clearly you should not connect D+ directly to switched 12V power.

The later wiring diagrams (with the integral regulator) don’t show the internal circuit for the 3Ø alternator or the regulator. Based on the earlier version, the charge indicator light is out during normal running because it has 12V on both sides of the bulb (zero difference). When you first turn the key ON, the bulb gets switched 12V on one side and ground through the regulator so the bulb lights. When the alternator comes up to speed, that ground is replaced with 12V via D+ and the light goes out.

What I don’t know for sure is if you can simply not connect anything to D+. If that were to cause a problem then every failed charge indicator bulb would cause the problem. Unlikely.


Please post some images.

Best,
Grady

[Early_S_Man]

Ed,

If you don't hook up the D+/61 lead to a source of +12 Volts ... the field winding won't get any pre-excitation current, and the alternator won't develop any Voltage output.

Grady's points about the belt failure warning nature of the alternator warning lamp are very good ... and I agree 100 percent! By the time your overtemp warning lamp comes on ... your heads and cylinders will have been cooking without cooling air for 5 - 10 minutes or more!