Surefire U2 Ultra Digital: Info and Mods?

I have been on the market for a reliable duty light. Was settled on a surefire fury (love a bright light) but I have came across a U2 from a friend for $60. Why is this U2 retail ($299) for more than a fury does with less lumens? And this light only goes to 100 lumens, where a fury at 500 for a little over $100. Just fill me in on what I am missing because you guys know lights! Since I am planning on purchasing the light, is there anything I can do to possibly modify the light to give me maybe a 100 more lumens? Any help would input and help would be much appreciated. Thanks and God Bless

The U2 has multimodes via the selector ring, which allows you to rapidly access any of the output levels. The pocket clip is very convenient for carry, although you might simply use a scabbard on your duty belt for any light you carry which would make the advantage of a clip moot.

To increase the U2 output, you need to be able to open the head, which is sealed using threadlock compound. Typically, application of lots of torque (e.g., via strap wrenches) and optionally heat (e.g., from a torch or a toaster oven) will break it loose. Once open, you remove the stock LED, and replace it with the LED of interest.

If you have one of the older U2s that uses a Luxeon III LED, then typical choices are the Cree MC-E or maybe the Cree MT-G2. See discussion here for a start.

If you have the newer U2 with the Seoul P4 LED, then a Cree XP-G2 or XM-L2 would be appropriate choices. See here for some shots of my U2 mod using an XP-G and the subsequently an XM-L.

The replacement LEDs will need shimming to put the LED die at the correct focus height in the reflector opening. Besides cracking the threadlocker, that is probably the key step in a good mod.

Justin, first off nice to meet you. Thank you for your information. I do not have the flashlight in hand at the current moment but will have it in the next few days, so I am not aware of how bright the light really is. With your mods, is the trouble worth the reward so to speak? This seems to be something that I would have to have someone do for me if it was done. I just read from surefire it has 100 lumens and I am not dogging 100 lumens by no mean but if you can get 150, 200, or even 500 for just a little more by making a mod, whos to say no..lol

How much does milky charge to mod?

dmitchell28 said:

How much does milky charge to mod?

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It depends on what he does to the light and what you want it to do. Scott, has been extremely busy lately with other projects and modding lights. I have 2 modded U2's from Scott, one with 2 sst-90's and one with 4 sscp4's and love them both. I highly recommend Scott and he does Excellent work, although you have to be patient on getting your light back. Hope this is of some help....Robert.

blackbalsam said:

It depends on what he does to the light and what you want it to do. Scott, has been extremely busy lately with other projects and modding lights. I have 2 modded U2's from Scott, one with 2 sst-90's and one with 4 sscp4's and love them both. I highly recommend Scott and he does Excellent work, although you have to be patient on getting your light back. Hope this is of some help....Robert.

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Definately helpful! I wrote him a message but as you said, he's busy so I haven't heard anything from him. I would hope he wouldn't have to do much. If it would cost too much I would just go ahead and buy a Surefire Fury. Wound be nice to be able to get slot out of this light tho, but I understand that sometimes you can't squeeze a bolder out of a toilet drain.

Not trying to turn this into a sale thread, but if you decide not to get that U2, I'll take it off your friends hands, if the serial number is preceded by a "B", and not an "A" (I can pay via PayPal or Money Order, whichever he prefers.)

Ok before asking about any mods on U2
Make sure you know which version you have
A. Lux V with boost circuit
B. SSC P4 with buck circuit

For A, the choice is very limited to 2S2P MC-E or XM-L Ez white, since Vout of driver is ~6V
For B, its much easier to do since it has a Vout of ~3.7V, you can swap a XM-L(popular choice), XP-G etc...

bstrickler said:

Not trying to turn this into a sale thread, but if you decide not to get that U2, I'll take it off your friends hands, if the serial number is preceded by a "B", and not an "A" (I can pay via PayPal or Money Order, whichever he prefers.)

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I understand completely. I will have the light in hand today..so I have already bought the light. I am at this point just hoping it is bright enough. My fingers are crossed for sure. i know its not going to be as bright as a Fury, but I dont really need it that bright, but a good 200 lumens wouldnt be bad either.

jh333233 said:

Ok before asking about any mods on U2
Make sure you know which version you have
A. Lux V with boost circuit
B. SSC P4 with buck circuit

For A, the choice is very limited to 2S2P MC-E or XM-L Ez white, since Vout of driver is ~6V
For B, its much easier to do since it has a Vout of ~3.7V, you can swap a XM-L(popular choice), XP-G etc...

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I will let you know asap tomorrow when I get my hands on the light. My luck its an A and it will cost a fortune to even try to make brighter.

I'm surprised SF still sells this light, especially at the price they want. I have an "A" series, which was pretty cool when I bought it ~7 years ago (?), but is old tech today. Sad to hear that mine is not so upgradeable.

dmitchell28 said:

I understand completely. I will have the light in hand today..so I have already bought the light. I am at this point just hoping it is bright enough. My fingers are crossed for sure. i know its not going to be as bright as a Fury, but I dont really need it that bright, but a good 200 lumens wouldnt be bad either.



I will let you know asap tomorrow when I get my hands on the light. My luck its an A and it will cost a fortune to even try to make brighter.

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Erm.. Sorry for misleading, my A and B doesnt really mean U2A or U2B, but just a notation, nothing to do with S/N
Btw you should say "unfortune" for having a Lux V modded, choice are very limited, boring is required to fit MC-E and i have no comment on XM-L Ez White, not familiar with it

jh333233 said:

Erm.. Sorry for misleading, my A and B doesnt really mean U2A or U2B, but just a notation, nothing to do with S/N

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Well, actually, from the SF U2's that I've seen, serials starting with 'A' have the luxeon emitter, those starting with 'B' have the SSC P4 emitter. A caveat I have mentioned earlier, some of the early luxeon bodies could take an 18650 cell with removal of a plastic sleeve so there was some swapping of bodies and heads by us CPF types.

To add to the confusion, the SSC P4 U2 was often called the U2A here on CPF since it was an updated model.

Vox Clamatis in Deserto said:

Well, actually, from the SF U2's that I've seen, serials starting with 'A' have the luxeon emitter, those starting with 'B' have the SSC P4 emitter. A caveat I have mentioned earlier, some of the early luxeon bodies could take an 18650 cell with removal of a plastic sleeve so there was some swapping of bodies and heads by us CPF types.

To add to the confusion, the SSC P4 U2 was often called the U2A here on CPF since it was an updated model.

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Didnt know that A/B-issue
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My 2nd hand U2(Lux V) didnt come with a sleeve and can accept 18650 directly, with 6 modes working fine
With golden chem coat
Tho sometimes it may not contact well at +ve spring as the tip of 18650 is too narrow(my bad)
BTW modding U2"A" with MC-E requires a slightly boring of reflector if i recall, but thats the only option besides EZ White

Well, I just got my light. I really love the light and tfe price I paid, no complaints! I do wish it was brighter, but awesome. It is the A model but in brand new shape. So modding might be out the window.

U2 is a good light if it has a higher lumen/watt
The boost circuit is great..
What a good disaster-prep light

jh333233 said:

U2 is a good light if it has a higher lumen/watt
The boost circuit is great..
What a good disaster-prep light

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How do you tel if it has the higher output?

dmitchell28 said:

How do you tel if it has the higher output?

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I meant higher efficiency, lumen per watt
Boost circuit + low output = uber battery leech which runs for weeks

jh333233 said:

I meant higher efficiency, lumen per watt
Boost circuit + low output = uber battery leech which runs for weeks

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I understand...I'm excited..it's my first true quality light. Big step up from my Coleman Maxfrom a few years ago. I still may buck up and buy a fury to blind someone lol

Honestly IMO i would go for the Fury,it's a great light,it's a very reasonable price & you do get 500 lumen of brilliant light with a good throw & lots of spill.You would save on all of the hassle as well.The U2 is a very good light but i'm guessing your needing the light for work duties si is there any point in going to all of the trouble of mods & hoping it will come back as good as you imagine in a decent time frame,when you can get a great light & have the all important warranty still intact as you haven't modified the light.Either way its just mu opinion & everyone will be different.

dmitchell28 said:

Justin, first off nice to meet you. Thank you for your information. I do not have the flashlight in hand at the current moment but will have it in the next few days, so I am not aware of how bright the light really is. With your mods, is the trouble worth the reward so to speak? This seems to be something that I would have to have someone do for me if it was done. I just read from surefire it has 100 lumens and I am not dogging 100 lumens by no mean but if you can get 150, 200, or even 500 for just a little more by making a mod, whos to say no..lol

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Now that you have the light, can you post a photo of the LED so that we can verify what you have? Put a digital camera in close-up or macro mode, turn off the flash, rest the light and camera to avoid blur, and snap the photo.

At least for my Seoul P4 U2, when I upgraded to an XM-L, the LED drew about 15% to 20% less wattage than the P4 while delivering probably 2.5X the emitter lumens. Also, the current draw/battery voltage to run the light in full regulation was such that 1x18650 probably could have met the requirements for a decent amount of time. With the stock P4, you'd have to deliver something like 4.5V, which means that 1xLi-ion can't ever reach full regulation.

Another nice thing about the P4 version of the U2 is that it works with 2x16340 Li-ion (and I would assume any other combination of 2xLi-ion such as 2xIMR18350). So you don't have to burn non-rechargeable cells anymore.