LED Headlights: Hiw Many Watts?
 

get the highest W you can, but even with LED lights you should add a Rennbay headlight relay harness to get full voltage at the bulbs.

Get the Hella E-code housings instead. With a relay harness and you'll have plenty of lumens.

I think that's true for most cases, but the exception would be (some) of the LED bulbs that are designed for use in an H4 housing. Done properly, they make use of reflectors and lenses to give the proper beam. There's a great thread with evaluations of different bulbs on the 928 forum somewhere...

The Rennbay is a nice high end setup but not exactly economical by any means for wire and relays. This sort of upgrade is not limited to Porsches, there are also other options for headlight relay harnesses at a fraction of the price if you do a google search. Just sharing as an FYI.

most of the ones i find on the internet for $30-80 or whatever dollars use smaller wires than the Rennbay kit which sort of defeats the purpose.

headlights use a lot of power, especially if you up the wattage...the $30 harnesses might be a little improvement but not as good as the real deal.

LED headlights should draw way less current and IMO should not require an upgraded wiring harness. I put 'em in my VFR and they drew 1A each vs 3A or more for a stock H4. The over-wattage H4s probably draw close to 10A each.

LEDs can be voltage sensitive sometimes, the stock 944 wiring harness might put 10V at the H4 plugs.
Running a Rennbay harness gives you 12-13V plus higher amp capacity, but yes LEDs will take much less W overall.

MAGK944 - Not trying to rock the boat or stir things up, we may have to agree to disagree on it, but I guess to me "only $165" is not a phrase that goes together for me in this instance. It is quite a bit of $ for some relays, fuses and wires. Wire gauge aside as V2 mentions, I have a hard time swallowing paying $165 +shipping for something that can be had for 1/6-1/2 that amount on a premade universal style kit. I fully believe the Rennbay is an outstanding harness, probably nothing better available anywhere, and it is likely the perfect solution for a great many people.

Rennbay is not the only solution is all I am trying to share, I want to make sure people know there are more economical alternatives. Even upgrading to a lesser harness is a smart move just as a way to limit risk of overloading 30yr old wiring and switches and causing a fire. I would rather have someone read this thread, find out there are cheaper alternatives and use one to upgrade light output and safety than never do it because they cannot afford the premium package Rennbay harness. We all like to buy the best, but $100, $50, $25 more over the course of a project, those little bit more expenditures on each item add up and at the end you are at that $3-4K range to get a 944 back on the road when you can shop around and spend half that and have a vehicle that is fun and reliable by doing a little more work yourself. I think most owners (at least here on this forum) with one of these cars is likely a tinkerer and spending 10min extra time to tuck a longer wiring harness away nicely imho is more than worth $100+ savings. Heck that $100 almost covers the E4 housings part of the upgrade, and now the driver has much better light output which is beneficial for everyone on the road.

V2, that is a very good point about wire diameter and definitely worth people keeping in mind when they are shopping to do this upgrade.

I ordered a harness kit off of Amazon for $20 that is aimed at Jeeps and Toyota trucks, but still uses the same connectors. I'm modifying it a little to suit my needs but the wire size is plenty big to give me a minimal voltage drop. The most benefit is saving on all the little connectors you need to buy. For the price of one relay, I have an entire harness with relays already made that I can substitute parts in if needed. The Rennbay one looks very well built so if you have the budget, go for it.

The real benefit of any of these harnesses is using a relay to avoid having your headlight current pass through the switch in the dash. This will reduce your voltage drop an order of magnitude more than any change in wire gauge. There will be a benefit of larger wire cross-section, but if you calculate the difference in voltage drop it is fractions of a volt. For instance, going from 14AWG to 12AWG will be a difference of 0.09V for a 5A load (about how much a 55W bulb would draw). Of course, the higher wattage you choose, the higher the current draw so this number will increase, but a few quick measurements and calculations will show you exactly how much benefit you can realize.