C4Scott

How do you tell what light type it is between the all the "H" types. I have just purchased a stock 91 S4.

Alan

How is the beam pattern? - specifically have you checked how good the horizontal cut off is now? compared to with incandescents - also how is the comparison between low & high beam now?

Alan

Alan

8" vs 7" - size and presence of chromed (plastic) trim ring around the lens

Genuine Bosch H4's (ROW) all say H4 embossed right in the middle of the lens and also say BOSCH at the bottom and do not say "DOT" anywhere. They also have smooth front lens surfaces. They may (or not) have a bubble at the top of the lens so the driver can see if it is illuminated when driving.

Genuine Bosch H5's (87-94 USA) also say BOSCH and have 3 protruding aiming nipples on the front lens surface (makes them difficult to wash with a sponge) - the lens surface also has DOT embossed on it

Genuine lenses are glass - plastic lenses are not good. Aftermarket cheap options abound - and they are generally rubbish. Lamps from Hella, Cibie that are ecode can also be very good - often these may be H4's in 7" sizes - they may need to be adapted to the stock lens mounts. Good manufacturers are proud to put their names on their products... usually H4 lamps will say so somewhere on the lens.

Note that Bosch lamps designed for a 928 come with the lens carrier, adjusters & bulb connector/seals (they just bolt in - no messing) - if you buy other lenses you may need to find/fabricate/ adapt all these items

Cheap deals on ebay are usually for.... cheap crap... YMMV...

Alan

Ducman82

Cut off pattern is crisper. the beam pattern for H/L are about the same but much more sharper. tonight I'm going to hang the sheet and draw the lines again, and i will take a few pics.

here is what an 8 inch H4 looks like.

C4Scott

Alan,

Many thanks for the information.


Scott

Bill Ball

I have a cheap eBay HID setup in my 8" H4s - the horizontal low beam cut off and flare-up to the right is quite similar to a stock H4 bulb, so I use the same basic low beam aiming targets (flare-up point centered horizontally and down 3" at 25'). Like stock H4 bulbs, which are painted on the end to block direct forward output, the HID bulbs came with a reflecting shroud over the front. Strangley enough, when I removed the shroud on one side, it made almost no difference in the low beam pattern.

Mine is a pivoting bulb, so provides high beam as well as low. High beam is much higher and further down the road, basically lighting up the entire landscape way down the road. I don't know an aiming spec for high beam. I know the basic law in CA is no high beams within 500 feet of an oncoming car or 300 feet of a car in front of you, but I have always gone to low beam far before that. I've not had any indication that the HIDs in my H4s are bothering anyone.

As you have indicated, H4s are a major improvement over H5s, and higher wattage halogens (e.g., 80/100 "off-road" bulbs) are another step up, although, as you've said, they can stress the stock wiring. HIDS, even these technically incorrect HIDS adapted to fit H4 bulb mounts, are a remarkable improvement. The beam pattern is very acceptable.

Some kind of "true" HID headlamp assembly that could be made to fit and look good in our headlamp openings would be ideal. Some have tried to go down that path (Paul Jager was working on a molded bubble and bucket for the opening to would accomodate an OE projector lamp system, but abandoned that 4 or 5 years ago), but nothing cosmetically acceptable has appeared.

Ducman82

here is what the back of that kit looks like installed. it moves the bulb in/out for the high low function. it also had a shroud on it, but being there is a reflector lick shroud in the housing already, i opted to remove it.

andy-gts

resurrecting a thread,,,are the h4 lights able to illuminate the high hiway signs over major interstates or do they cast their beams too low...been thinking of h4 upgrade!!

LT Texan

Sean, question on an old post.

Is that 13.19v on the plug without the actual bulb illuminated (ie, unplugged) or with the bulb plugged in and on?

Ducman82

They shows the signs just fine.

Ducman82

In fact I have hid lights now. You an see the signs start to light up about a mile out! :-)

Alan

Genuine H4s with stock (ROW) bulbs illuminate overhead highway signs very well... quite unlike most DOT patterns, also highway side signs low and high (to the right)... Better coverage to the sides down low for turning in the pitch dark also. They work better in fog for this reason - easier to see kerbs

IMO they are all round better - in every single respect - by a wide margin. DOT lenses are absolute crap by comparison - the Porsche engineer responsible for lighting must have been crying over what the DOT required to be downgraded for the USA cars.

Alan

Fabio421

There is another new fangled option available these days. One of our fellow Rennlisters installed them the other day. I don't want to spill the beans but I'm hoping he will pop in with some details.

Ducman82

^^^ i know i know!!!! ^^^^ he he he

SeanR

Bulb illuminated, tested at the back of the plug.

I know right? (hate that saying, but fits here)

Waiting on the trim rings. Maybe today/tomorrow.