13 hours ago, J.R. said:

I fitted a 35 watt (might have been 55) Ali-Express HID conversion and the light output was absolutely stunning.

 

However with the same alignment (done on MOT rig) as the halogens it was dazzling oncoming motorists, not all but one is one too many, I had to progressively drop the beam aim till Ino longer got flashed, it no longer lights up the road 2km ahead like a rally car but is still a million times better than the halogen bulbs.

 

This is what a lot of people don't understand, there is more to it than just the height of the cutoff.

 

Halogen bulbs have the filament in a certain position which gives the light output certain characteristics. The optics are precisely manufactured to project this light onto the road in a specific pattern and even the slightest change in the position of the bulb or the characteristics of the light from the bulb will change that pattern. If you look at a proper headlight alignment guide (the MoT one is probably a good example) it tells you how to adjust the headlights both vertically and laterally in order to give the correct pattern. Then, when used on the road, the headlights will provide the optimum illumination while driving, without the danger of dazzling oncoming traffic.

 

The issue with retrofitting HID/LED bulbs in a headlamp that has been designed for a H7 bulb for example is that the HID/LED will not have the same light characteristics as a H7 bulb and therefore the optics will create a beam pattern that can range from slightly less useful, to obviously incorrect. The way most people solve this is to simply adjust the beam height downwards until the hot spot is at approximately the same place it should be if the correct bulb was fitted. This is good because at least they mostly avoid blinding oncoming vehicles, but it also tends to mean that the actual light output is far less useful because you end up with 10-15 metres of road in front of the car lit up light super brightly but the road 100m ahead will have almost no light.

 

I know this all too well because in my youth I fitted some 55W LED bulbs to the dipped beams of a previous car. The lights looked awesome when you had them shining on a wall a few metres away or were driving in well lit areas but the first time I went out on a completely unlit road at night I realised it was dangerous because of how little light was going where I actually needed it. I got rid of them pretty quickly after this.

 

The overall problem until recently is that headlights have always been a compromise - they need to provide optimum illumination for the safety of the driver, but also need to avoid blinding other road users. Obviously with a bulb in a fixed position producing a single beam pattern, we ended up where we are now with dipped beams that have a sharp cut off but still perform relatively well. It's only now with the advent of sytems like AFS II and the even more advanced intelligent headlight systems that we have finally overcome this limitation because electronics can change the beam pattern constantly while driving depending on the speed, weather, traffic etc to give you the maximum light output without blinding other drivers.

I still think that I am in my youth but you can't be any more than a young adult to have fitted LED headlights "in your youth"

 

In my real youth 12v electrics and sealed beam headlights were the new thing, then Ford & Vauxhall brought out the Escort & Viva with oblong headlights, now that was something really new!!!!

 

The dipped beam light coverage from my adjusted downwards H7 HID conversion is somewhere between 15m and 2kmand a million times better than the standard set up, but then so were the 6v headlights on my split screen VW campers even with bad earths and a slipping generator drive belt.

Are you sure there wasn't something wrong with yours?? I am running Philips Whitevision Ultra H7 in my fl, and they are very good. I think they are pretty much the brightest and whitest road legal bulbs you can buy. I haven't even turned the voltage up to 100%, I think it's still at the default 92%.

9 hours ago, slow_nick said:

Are you sure there wasn't something wrong with yours?? I am running Philips Whitevision Ultra H7 in my fl, and they are very good. I think they are pretty much the brightest and whitest road legal bulbs you can buy. I haven't even turned the voltage up to 100%, I think it's still at the default 92%.

 

How do you turn up the voltage?

 

There's a option in VCDS under Central Electrics, I think it's called Headlight Dimming (Bulb Life Extension) or something along those lines. By default the voltage supplied to the headlights and tail lights is regulated to 12.6V even when the engine is running and alternator is outputting 13.8V or whatever. It's to prolong the life of the bulbs. you can adjust it between 12.3V and 13.6V or turn it off. Obviously a halogen bulb is just a filament with a fixed resistance and its power output will increase linearly with the voltage supplied to it, I'm not sure what voltage a 55W bulb is rated at but if it's 13.8V then it will probably only be producing 50W at 12.6V, in order words a 10% reduction of its design power.

Edited 24 June, 20205 yr by slow_nick

Power goes up in proportion to V-squared for a fixed resistance, so it's better than linear.

It's not a fixed resistance (nothing much is over the sort of temperature range a bulb filament experiences).

Interesting graph relating all the parameters - including lumens and lifetime - here 

http://www.lamptech.co.uk/Documents/IN Voltage.htm

Edited 25 June, 20205 yr by Wino

11 hours ago, slow_nick said:

There's a option in VCDS under Central Electrics, I think it's called Headlight Dimming (Bulb Life Extension) or something along those lines. By default the voltage supplied to the headlights and tail lights is regulated to 12.6V even when the engine is running and alternator is outputting 13.8V or whatever. It's to prolong the life of the bulbs. you can adjust it between 12.3V and 13.6V or turn it off. Obviously a halogen bulb is just a filament with a fixed resistance and its power output will increase linearly with the voltage supplied to it, I'm not sure what voltage a 55W bulb is rated at but if it's 13.8V then it will probably only be producing 50W at 12.6V, in order words a 10% reduction of its design power.

 

Thanks for that. I seem to remember the headlight voltage on mine was about 11.7v after some work was done on it. I checked it as the headlights had very poor output. I will check it again and have a look with VCDS.

Edited 25 June, 20205 yr by FatblokeVRS

7 hours ago, Wino said:

Power goes up in proportion to V-squared for a fixed resistance, so it's better than linear.

It's not a fixed resistance (nothing much is over the sort of temperature range a bulb filament experiences).

Interesting graph relating all the parameters - including lumens and lifetime - here 

http://www.lamptech.co.uk/Documents/IN Voltage.htm

 

Sorry yes you're right that's what I meant, linear was the wrong word, I meant proportional. I know the resistance changes with heat etc but for simplicity sake I think it's safe to assume the resistance will remain fairly constant over the voltage range that it is possible to drive the bulb with.

That link is interesting

Edited 25 June, 20205 yr by slow_nick

That link was a model of brevity and clarity that others should aspire to, especially the graph.

 

The "Hi guys!" influencers on Youtube or whatever they call themselves would make at least four 20+ minute videos to impart less information in a very unclear manner.