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Join Date: Dec 2002
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Running 80/100 watt bulbs ?

I put the Hella 80/100 watt bulbs in my new euro H4's.
Will this wattage be a problem if all I've done is the surco relay kit ?
All the wire and connectors are stock, just added the 2 relays.

Old 01-06-2005, 12:38 PM
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I'm running 80/100 watt bulbs in my Euro H4's. I ran new gauge wires(12's I think) fron the fuse block, to the relays, then from the relays to the lights. I was told it is recomended when running that high of a wattage bulb because the factory wiring will burn up.
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Old 01-06-2005, 12:41 PM
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I have been running 80/100w in my H4s with the same relay kit and stock wiring for about 8 mos without any problems. I have examined the wiring several times because of all the warnings people give here, and it looks as good as the day it came from the factory. I will probably upgrade it some day, but for the time being, it seems fine. My point is, unless your wiring is in bad shape to begin with, I don't think you need to rush out and immediately upgrade the wiring for 80/100w bulbs. I'm sure some will disagree with me.
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Old 01-06-2005, 12:54 PM
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I'll ditto not needing to upgrade your stock wiring for 80/100w lamps. Note that I said "need". Your stock wiring will support the larger wattage lamps as long as you use the relay kit. The weak link in the 911 headlamp system is the hi/low beam switch in the turn signal stalk and the long wiring run that gets the power from the battery, to the headlight switch, to the hi/low beam switch, then all the way back to the headlight fuses, and eventually to the headlights themselves. The proper use of relays, i.e. with the Sucro kit, will take care of 95% of the problem.

If you want all out performance, the installation of heavier gauge wire to the headlight buckets will lessen the voltage drop even more. The stock wiring has a voltage drop of around .2 volts at 100 watts and 12 volts.
David Dryden
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Old 01-06-2005, 01:24 PM
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Where do you get this Sucro/Surco Kit and what is the price?
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Old 01-06-2005, 03:54 PM
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Do a search under the name "Marcus Sucro" and you'll find it. 20.00 and your good to go!
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Old 01-06-2005, 04:30 PM
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Sorry to bring up an old thread, the search on thei subject gave me a headache.

I have a Sucro relay kit and I'm going to H4s soon and would like big bulbs. I really didn't know what to do. People say the stock wiring is fine with relays. Others say to get relays from D. Stern. Others say the stock wiring will go up in flames. Some say the bulb plugs will melt? If I do get the D. Stern kit, I'm not sure about the wiring sequence. Do I even need 80/100w bulbs with H4s? It is dark around here.

Man, all I want to do is see at night.

Sorry about the whining.
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Old 10-23-2005, 09:42 AM
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There is a lot of pontificating on this subject ... some not very accurate or factual

1. The control stalk [dimmer] switch is the weakest link in the entire headlamp circuit, and will fail repeatedly with stock H4 60/55 Watt bulbs.

2. The stock wiring [approx. 15 ga] is not optimal, but won't 'burn up' with 100/80 Watt bulbs! 12 ga wiring would be better if you are in the mood, and up for a completely new install with relays.

3. Four relays are the ultimate solution for best, redundant headlamp power. Even standard, off-the-shelf generic 30 Amp relays [such as what are in the Sucro kit] offer significant benefits in long-term reliability, but be SURE to carry a spare relay in the car ... no matter what relays you choose! Better choices in relay selection are available in 40 Amp, 50 Amp, and 70 Amp ratings, with obvious benefits for reliable night illumination without blackout incidents. The Sucro kit doesn't provide a spare relay, and the standard two relay installation is far from what I would recommend for reliable operation, yet many here feel it is OK and sing its' praise!

4. Kits are a compromise at best, and the best installations I have seen posted here on Pelican didn't use a kit at all ... just careful planning and ordering of a few select parts!
Warren Hall, Jr.

1973 911S Targa ... 'Annie'
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Old 10-23-2005, 10:11 AM
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skip the 80's and go straight for the 100's.... to keep it running smoothly, you should wire the relays w/ 12 gauge wire... it's more than enough but some go for overkill w/ 10 gauge. you also need to get quality bulb sockets. these eliminate direct wire connections to the bulb. instead, once the socket is hooked up to the wires, the bulb plugs right into the socket.

plenty of stuff about it here... try a search.... use RoninLB's name in the search too
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Old 10-23-2005, 10:12 AM
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I did the 12 ga. wire route with a kit from Daniel Stern. The kit included Bosch relays, Hella headlight sockets, fuse clips, etc. Here's the link to the thread.

Headlight Upgrade Pics
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Old 10-23-2005, 11:18 AM
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I installed the Sucro relay kit and Narva 80/100 watt bulbs about a year ago in my 83SC with US style H4's. To date no problems and I can see at night. I have started to experience some problems with my headlights going from low beam to high by themselves but I think my headlight stalk had already been degraded from years of use. I inspect the wiring from time to time and no visual defects.
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Old 10-23-2005, 11:27 AM
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I agree with Warren's comments above. BUT what you are getting with larger gauge wire is really a thicker chunk to make a good, low resistanc & mechanically sound connection with, NOT ANY significant reduction in resistance of the wiring. In previous posts I've exhorted people to look up the resistivity of the wire gauges and do the math. This time I'll do the math for everyone....

Assume you have already done smart things like put in a set of relays - 2 or 4 whatever floats your boat. Thus, the wire runs with any real current flow are about 2 ft. long or so. Also, the stock, metric sized wire is about 15 gauge (that is where Warren's use of 15 is coming from). Now make some conservative assumptions - use thinner wire for stock (16 gauge) so we can easily look up resistance in a table, and we'll use 10 foot runs for comparison (so I can be slovenly and just move the decimal pts over w/o having to do advanced mathematical operations like division):
for Cu wire at approx. 20 oC the resistance for 10 ft. of wire from any std. wire table is:
0.040 ohm for 16 gauge wire
0.016 ohm for 12 gauge wire

Now, who thinks that is important?

Changing the wire will force you to make new and likely cleaner & strong connections (the real adv.) - but 12 gauge is not needed - altho it won't hurt.
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Old 10-23-2005, 12:19 PM
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