I finally got all of the required stuff to do a full write up so here it is...

Adding a MOSFET and a 7.4v Lipo to a Tokyo Marui MP7 and Scorpion WITHOUT ANY EXTERNAL MODIFICATIONS!!!!!



ROF before and after numbers are coming soon, but I can tell you this...

There is no better electrical/battery upgrade for the price!! You can pay the $60 for the battery box upgrade but by then you could have done this upgrade 3 times and avoided having a nasty battery box on your gun.

On these guns you pull the trigger and "whack" a bb screams out! SO much damn fun!

List of what you need...

- 2 pairs of deans micro plugs(one for battery one for gearbox)($3)

- 2 feet of 18-16awg wire(skip the deans wet noodle though, too big for this application)($1)

- 1 BLADE CX2 Helicopter lipo battery.($10-$20)
*I used 10C 900mah batteries for this project although tenergy makes 25C 900mah ones!! I will have some soon!

- heat shrink tube pack ($2)

- IRL1404z n-channel mosfet($3)

- 1 100ohm resistor 1/4w($.02)

- 1 30K ohm resistor 1/4w($.02)


So you are looking at $25 dollars worth of parts. give or take $10 bux.

The easiest way to do this is to follow a few steps

1.) disasemble the gun
2.) locate and isolate the trigger switch
3.) install mosfet
4.) reassemble the gun

I know that sounds simple, but the reason I put it like that is, THERE IS NO DIFFERENCE IN DOING THIS THAN PUTTING A MOSFET ON ANY OTHER GUN.

The thing is, when you get to the trigger switch, it looks rather complicated, but really its not. You can remove all unused portions of it and leave some leads to your trigger contacts , and then it is business as usual.

First up is the Skorp.


Take down for this gun is retardedly simple so I won't go too in depth.

- remove this grub screw.


Pull out this pin!


- gun slides apart into two halves...


- remove this tiny screw near the hop up and remove plastic clip


- Bam! gun should look like this. Then disconnect the gearbox wires(spade connectors) and remove the two screws that hold the pistol grip on.


- CAREFULLY split the pistol grip apart! It is pinned and glued! (this is the hardest part.


- Remove the trigger switch assembly from the grip(two screws)


- remove the fuse by desoldering these.


- Remove this top plate( 2 screws)

- You should now see this. The trigger contacts are circled in RED so feel free to remove all excess coper plates to makes things easier to visualize.


- Here is how I did it...


- I put that aside for a moment and grabbed the gearbox. I replaced teh spade connectors with a deans micro plug. This is how the gear box will plug into the pistol grip from now on.


I then built a mosfet for this gun. I made a great guide on how to wire mosfets, so if you are confused please refer to it.

The only thing I did different was cut the heatsink down to save space. I also removed the drain pin and soldered the motor negative wire directly to the heatsink.
here it is...


here is a shot of the MOSFET. You can see how I used a piece of scrap copper to attach the motor negative to the heat sink.

The microplug I am holding will connect to the micro plug on the gearbox. Pay attention to POLARITY when soldering on your micro plugs.


- this diagram shows how I wired up the mosfet...


Trim any plastic you need to in the pistol grip to make room. Don't over do it though. If you are attempting this, then you are problably smart enough not to remove anything important.

I ran some 20awg wire from the triger contacts to the gate pin and the positive wire (see diagram)

I got a little excited and forgot to take pictures but here is how it should look...

You should have a micro plug on the battery...


A micro plug that goes to the gearbox(notice the trimmed plastic)


The gearbox should plug in like this now...


after that reassembly is a snap.

now for the Mp7...

The MP7...


Disassembly...

Remove two rear pins...


Remove this phillips screw and the charging handle spring...



Pull off back piece...


remove these plastic things...


disconnect the gearbox...


pull out the gearbox...


remove trigger/pin, the safety, and the lever above the trigger. These are easily removed with a proper sized punch(picture) or hex key.

Simply push out the retaining spring pin and pull them apart.



Carefully remove the trigger switch block from the rear...


FIND THE TRIGGER CONTACTS!(circled in red)


Add the gate wires (one goes to the positive wire one goes to the gate pin on the mosfet)


Wire in the mosfet as usual. Once again I put a micro plug on the gearbox, on both ends of the mosfet wire, and on the battery

Here is how the gearbox will attach to the mosfet wires again...


reassemble...


One major thing to remember is to measure the wire correctly. This is the trickiest part of it all.
Try assembling the mosfet, the gearbox, and the battery together and see if they are long enough(short enough) to fit inside of the gun body


the only hint of what lurks inside...


finished

electrical guide...

http://www.airsoftforum.com/board/Aeg-Elec...de-t104376.html

I love you man. too bad I don't have ANY skill doing this

GoLgo, You F'in rawk!

I'm forwarding this to my guys right now. I want this in my M93R so bad my guts hurt!

This is the ULTIMATE guide of guides, and it needs to be pinned ASAP

This is an incredible guide GoLgo, I am sure you will help not only me, but so many other people by doing this for the community. Thank you so much

Awesome guide man. Read the whole thing. I am really impressed at your soldering abilities. How do you solder wires that small?

Hell, I have trouble saudering deans..

You may have just convinced me to pick up a Well Skorpion. Can you add the lipo battery and deans without installing the mosfet? The mosfet install looks too hard for me...

You can definitely add the lipo and deans without the mosfet. That would make it all much simpler. JUst solder the wire leads from the original battery tabs and add teh connector. It all fits in the fine.

Sweet, I'll probably do that. Thanks for the guide, and it definately needs to be pinned.

A guy on arnie's said that he did the CX2 battery only, and teh gun held up for 20k+ rounds. So it is definitly doable.

Now that I have a bit more time to write and delve into this topic a bit more (I was in a rush earlier but I couldn't leave without saying thank you) I have a few questions:

1) Is there any specific Lipo that you would recommend to use in modifying my MP7? I have looked at a few on airsoft sites but they are all pretty expensive and I have heard there are better places to buy the batteries.

2) Can I do this modification without fear of ruining my internals or harming the longevity of my gun? I would love to do this, because the trigger response seems to be a vast improvement along with the rate of fire but If I can only put a few thousand rounds through the gun after doing this then I don't really even see the point of doing this in the first place.

3) Finally I was considering upgrading the spring, how would that play into the equation? I am sorry for being so new to the sport and modifications and I hate to be annoying with all of my questions but I just want to learn as much as I can so I can hopefully be a help to others later on and save myself some money if I can.

Oh and thank you again for posting this guide, I have been hoping someone would do this for a while.

A guy at arnies added the blade cx2 battery and nothing else to his gun and he claimed it lasted 20k+ rounds. SO the short answer is, This can be done reliably. EVen without the mosfet. But with airsoft guns you never know.

You can get blade CX2 heli batteries from ebay for $35 for 2, or common cx2 800mah batteries for $10-$15 at nearly any online hobby shop.

Upgrading the spring would definitely help prevent premature piston engagement, but with added stress on the piston. If you do the spring, get a nineball piston and a nineball bearing set to go with it. Then your gun would be strong as hell.

Do you know what went wrong with the gun after those 20 thousand rounds for him? Because it would be a shame if the gears bit the dust or something with the lack of replacement parts. Thank you so much again, I really appreciate your help with all of this.

he actually didn't mention that it failed, he said he used it for 20K rounds and then rewired it with a mosfet. I guess I can ask him.

This has totally inspired me to do this as my next project. Do you think you could fit an AB fet in there? I have an extra one I made laying around and was wondering. I can't actually see the room inside the grip because I don't get the gun till moday.

Oh and golgo, where did you get that silencer? That thing looks perfect on there.

This post has been edited by j_king: Aug 29 2008, 08:48 PM

An AB fet can fit, but it will take some measuring /planning.

The silencer is a copy of the first factory slim suppressor 150.

LOL the Skorpion gearbox is so small. But wow, the rof on that... That actually scared me a bit. Not gonna lie.

Why is this topic not pinned yet?

It has to be one of the best AEP advances since the AEP itself!!!

I have to agree with you. This is a truly epic guide. but... you may want to put a warning in the guide to install at least metal bushings before running a 7.4v lipo.

1: I gotta get me a scorpion....

2: DO NOT get a stock E-Flite CX2 battery. There are much cheaper and better ones available.

You can score a 950Mah Thunder Power for $19-22, You can score a Common Sense 850-900Mah for $14-19, or a MaxAmps 850Mah *10C pack for $19-22. Just look around, if you can't find one PM me.

Here is an audio analysis of ROF

Top line LiPo MP7 18RPS!!
Middle line STOCK MP7 13 RPS(full charge)
bottom line LiPo SKORPION 20-21RPS!!



Also Me and Opsic66 came up with a pretty good list of TM SMG sized lipos. I will post it soon.

That would be awesome. I've already got the skorpion and everything else except the battery. That list will be very helpful!

wow I feel really stupid I put up a tread 20 min ago asking if it could be done

I wanted a Skorpion and I wanted the externals to look exactly like you have it. It's a nice gun and this is a great write up, so thanks.

I friggin' love your Scorpion. Makes me want one now.

You, sir, are amazing! I am in awe at your soldering jobs. I suck so bad at soldering (tried to solder some stuff on electronic boards on paintball guns when I played paintball back in the day, and have tried on several things recently) and I suck!

VERY nice guide! I'm sure it shoots pretty amazing now. I don't have the guts to do this to mine when you get it to me, but I might end up trying this in the future when I work up the courage and practice soldering on something else. Definitely deserves pinning! ...how do you think of these things...

I am now going to call you: GoLgo...master of the AEP

I am pinning this...

I am going to do this to my MP7 ASAP. That is friggin insane!

Thanks for posting all of this.

I got started on this project last night. It's actually easier than it looks. I'm going to try to fit an AB mosfet in there, as It does have room (if you remove the fuse housing). I'm going to finish it tonight if I have the time. Will post back with results.

Awesome, I'd like to see how it turned out for you as well. Post a link if you make a new thread.

I finished the project and was able to get an AB mosfet in there.

...but there's a problem. I seem to have lost semi-auto. It shoots in full auto in both semi and auto modes. Everything seems to be fine otherwise.

Does anyone know what the problem might be? I think it has an external cutoff lever, which seems to be working but I can't be sure.

That's awesome that you got AB in there. '

There is a metal lever with a pin that extends outside of the mechbox. After that, there is a series of plastic peices that interface with that pin and transmit the motion of the pinned lever to the trigger block. Something between the switchblock and the mechbox must be jacked up..

here's what I did:


now here's my problem:


The two levers that are screwed together...one pushes the trigger switch up to the contacts, the other is the cutoff lever.
When assembled together, the cutoff lever moves when engaged in full auto and stays put in semi. I think that cutoff lever is supposed to be triggered in semi after one shot, but it's currently not moving.

Can someone tell if I'm missing something, or have something assembled improperly? Everything looks OK.

If anyone has a manual for either a TM or Well Scorpion, can you please scan the diagram and post it?

Thanks.

Anyone think this can be done with the G18c, M93R, or the USP??

OK. I think I found the problem. The little lever that extends out of the gearbox needs to trigger the cutoff lever, but it's not making contact. I think there's a piece or two missing that connects them. I think I found it (or part of it)?

Anyone know what this is, and how it's installed? The notch fits the little lever that extends out of the gearbox, but I can't seem to figure out how it fits to trigger the cutoff lever.

I'm such a Newbie!! I figured it out. That piece just sits in place.

It now works perfectly. I will post a video of it in action later.

This post has been edited by govtcheez: Sep 13 2008, 03:30 PM

Hey I just found that exact piece and where exactly does it go? I have the exact same problem. I just finished it up this morning and its full auto on both.