Some questions I have is, should I keep the original Hella ballast or get new, should I keep 35 watt or move to 50 watt and how noticeable is the diffenerce?
I have been looking at both EvoX-R 2.0 and Morimoto mini D2S 4.0 bi-xenon but not sure what to get and what other parts I may need.
Any suggestions would be greatly appreciated!
I am abig fan of the DJ Auto lenses due to the solid build quality, fair price, and clear Euro corners. I am not much on an angel eye guy but if I had to choose I prefer the Orion V2s over the V4, why? because the real world output is about the same and with V2s have larger spaces between the LED chips so when not illuminated the appear more white where the V4s appear more yellow from all the LEDs. V2s are significantly cheaper too so it's an easy choice for me.
As for ballasts the Gen 3 Hellas which come stock on the E39 are arguably the best ballasts ever made with their solid output, fast warm up time, and juggernaut like reliability. In contrast aftermarket ballasts can offer higher wattages but have poor reliability and warm up speeds. The Hella ballasts to have a trick up their sleeves where they can be "boosted" to higher wattages by swapping some of the internal components. These mods not only increase the output but also the efficiency, so think of it like turbo charging the ballasts. I dug up a rough guide some Polish guy made on the process and have been building these boosted Hellas for the past few years, I have built probably 40-50 pairs at this point. They can be customized from 35w to 41.5, 43, 46, 48, 50, and 55w.
Here is a guide I made on the process, it's a big old and I have refined some things but this will cover the basics, if you have experience soldering you can tackle it yourself, if not then feel free to reach out to me.
For the sake of science I run 55w in my E39 to observe the long term effects of the increased wattage have on the projectors. HID bulbs emit heat and, more critically, UV light which can damage the chrome on the bowl of the projector so more power isn't always better and you want to take into consideration the type of bulb you use, the type of projector, and the frequency/duration of headlight use. If you are commuting 45min-1 hour each way in darkness and run aftermarket bulbs and projectors then I wouldn't recommend running very high wattages, stay around 43-46w. Quality OEM bulbs emit less UV light and can be ran at higher wattages same thing goes with quality OEM projectors, they usually have more robust chrome that the aftermarket projectors (although some aftermarket projectors have a warranty on their chrome for a few years, you don't want to it fail since that means re-opening the headlight, etc.)
On to projectors, there are lots of options that offer different light output so this is also something that should be given some consideration. If you drive at high speeds in rural areas with poor lighting then high beam and distance will be more important. More commonly people drive in or around cities where there are other cars on the road and the vehicle is making turns and cornering on winding roads so width will be much more important.
The E39 community always defaults to the Evo XR or Evo2 projectors since they based off the same gen Hella footprint and easier to retrofit and it receives and unwarranted amount of praise. The beam pattern of the Evos is REALLY narrow and the "hotspot" (peak light intensity in the center of the beam patter) is excellent but the rest of the beam pattern suffers. This projector is great for distance vision but it's output is like tunnel vision. There are many more well balanced Bi-xenon projectors out there offering nice high beams and much better low beams.
The halogen high beam bowls on the E39 are "good" and if a high beam isn't a big necessity for you then I would recommend skipping the Bi-Xenon projector retrofit in favor for a low-beam-only projector. They will offer far superior low beam performance, as good as it can get really. A proper HID low beam projector will outperform most of the modern LED headlights in terms of intensity and beam pattern.
So I would first reflect on how you use your headlights and think about the type of light output you need, from there you can get the projector to suit. I ALWAYS recommend OEM projectors, bulbs, and ballasts by default. Some aftermarket projectors are decent and there are some OEM projectors which are underwhelming but for bulbs there is no need to stray from OEM, their added performance and reliability are worth the price premium over aftermarket every time.
Here is a photo dump of examples. I first retrofitted Evo2s to give them a shot. Some OEM E39 housings will have goofy projector mounting posts and "bolting in" the Evo2 projectors can offer incorrect rotation which can be seen in my driver headlight.
This is the "light output" pic most people most which is close to a wall and the output looks great, nice sharp cutoff with good intensity.
Drop the exposure and you can see how concentrated the light output is 80% of the intensity is in the hotspot.
A greater distances you can better see the whole beam pattern, again centered intensity and the width it does have doesn't offer any intensity so it's not particularly useful.
I am a projector snob so the Evo2s drove me crazy and were removed after a couple weeks. I replaced them with a pair of Lexus RX-AFS low beam projectors with curved shields and E30 clear lenses. Mounting wasn't a bolt on affair like the Evos but with some forethought and creativity they found their new home.
Output of the RX-AFS projectors. Light is much more uniform and width reaches much wider I would guess about twice as wide (120 degree projection vs 60 degrees).
Here are a couple pics of my other personal build, different vehicle but you can fit these projectors into an E39. This IMO is the best of the best, quad projectors where one if dedicated low beam and one dedicated high beam. Low beams are Lexus SC430s with clear lenses w/ a boosted 46w Hella. High beam is a Morimoto D2S 4.0 modded for high beam only w/ 55w Hella. Photos are a little over exposed but the output is nothing short of amazing.
Notice the width in the 3rd photo, the SC430s offer insane width (I would guess 150-160 degrees) and nice intensity along the whole width. With this sort of width you look out your driver or passenger window and see light.
I will stop here but I can't stress enough that there are excellent projectors which can be had for very reasonable money, often cheaper than what the Morimoto projectors cost. I am happy to offer tailored feedback if you give me some info on your location, driving habits, lighting goals, etc.