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DSG FPS Inconsistency/Build Thread

8718 Views 176 Replies 9 Participants Last post by  Leo Greer, 
mr. potatohead
Hey guys, I recently have been working on a DSG build, but I've run into either one or multiple problems depending on if they're related. My fps is inconsistent on semi, fluctuating between 380-360 fps. On full auto, fps is even worse. One day it was around 360, so not bad. But the next day it was in the 250-300 fps range, so I don't know what happened there. Full auto shot pattern literally looks like a shotgun spread, though at least it is feeding.
Here's my parts list:

-18:1 stock gear set with shs DSG gear and stock tappet plate (<11mm)
⁃ shs high strength polycarbonate piston (SS + SC)
⁃ Matrix silent piston head (aluminum)
⁃ ASG 30k boost
⁃ Gate titan mosfet (dsg setting)
⁃ Maxx Model CNC aluminum hopup (pro model)
⁃ G&G hopup bucking (cold-resistant)
⁃ Matrix CNC aluminum air seal nozzle (ground off <.25 mm)
⁃ Matrix silent cylinder head (aluminum)
⁃ m150 spring
⁃ 265 mm inner barrel
⁃ ported cylinder

DIY mods done:
⁃ AOE
⁃ Shimming
⁃ Tappet return spring -4 coils
⁃ Everything greased/lubed accordingly

***tested with 11.1 v 2200mah 25-30c lipo and .20 gram bbs***

Most of these parts, including the hopup, bucking, nozzle, and tappet plate were used in my 12:1 SSG build, which worked just fine. I had this same problem with the SSG build but solved it by grinding <.25 mm off of the nozzle which made my fps more consistent; when it did change it was +-10 fps. Still using these parts, but encountered the same problem again albeit worse. I had already cut 2 coils off my tappet return spring, and then did the tissue test. Paper was blown off, so I thought that my nozzle wasn't returning fast enough. I then cut off 2 more coils. Paper moved slightly after that (but still quite noticeable on auto). So in total there are at least 4 coils cut off my tappet return spring and I'm still having the tissue kinda pushed off. At this point I'm even considering that the nozzle might be a hair too short (thanks to me grinding a bit off), causing hopup compression issues.

Note: This is my first DSG build, so by far I don't know everything. Any help is appreciated.
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mr. potatohead
Guges Mk3 said:
I do think your nozzle is too short.

And burping pressure early is going to cause your FPS fluctuations.
Click to expand...
Yeah I was like no way there's 4 coils off and still have this problem. Imma order a new nozzle. Got some stock plastic ones lying around, but their seal is pretty bad.
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mr. potatohead
Guges Mk3 said:
Are you referring to the seal between nozzle and air tube from cylinder?
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Yes
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mr. potatohead
Guges Mk3 said:
Fluid Dynamics say that pressure loss via that direction is "irrelevant". Most people actually don't understand how "flow" moves.

All the top makers of AEG's know this and that is why their nozzles don't "seal". Krytac, Tokyo Marui, VFC...etc

Try is with any nozzle on hand...and see what you get.

O-Rings were used early on to address tolerance and alignment issue and not sealing issues...

There are so many things that are misconstrued in this sport....cough...bearing on spring guide and piston head...cough.
Click to expand...
All right so I cracked open my gb to swap the nozzle and found my tapppet return spring had snapped (most likely too much strain from the -4 coils). Changed the nozzle to a stock one and also changed the spring to a stock one (-2 coils). Chronoed my gun and fps was in the 360-340 range. I redid the tissue test and had the paper blown up. I'm guessing the spare tappet return spring I was forced to use is weaker, which is why the fps dropped and the gun's still leaking air. I don't know if I should just cut off another coil, or order another spring.

As for incorrect tappet trimming, I can post a pic of my gb later. Maybe you guys can catch something else I haven't considered. I'm hesitant to grind down the front of the tappet plate because I'm afraid that the nozzle won't get pulled back far enough during the cycle, which could cause feeding issues.
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mr. potatohead
rm105 said:
Shouldn't need to touch the front of the tappet unless you've got some weird tolerance stacking going on. When I trim the tappet I open the gearbox, take the mainspring + tappet spring out, spin the gears by hand to manually pull the piston back, and adjust the tappet length such that it 'releases' when the piston is in contact with the last 1.5 - 2 teeth on the sector. Very small adjustments after that if feeding issues. If using active breaking on a neo motor might need to shape the bottom of the tappet slightly to avoid the opposite 'pickup' pin on the sector from crushing it.
Click to expand...
Thanks for that. I'll try it out when I get some time.
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mr. potatohead
Is trimming the tappet plate to <11mm the same thing as you mentioned, or is it a little different?
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mr. potatohead
Makes sense.
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mr. potatohead
So while adjusting my tappet fin, I noticed that my piston is pretty snug when the gb is closed and screwed up (as in it doesn't slide down the track). Is it supposed to be like that cuz last time I checked in my SSG build it was able to slide around pretty easily when the main spring was out.
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mr. potatohead
I think I'm gonna grind down the rails in the gb a bit. Weird cuz it worked in my SSG build with the same exact piston...
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mr. potatohead
Well 2 things:
1. It's too late lmao
2. The gb rails were the things sticking into the piston, so how would I modify the piston without weakening it? Just asking for the next time this happens haha.
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mr. potatohead
Will do. :)
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mr. potatohead
What does a homemade file look like lol? And yeah I did some adjustments with a dremel with a narrow grinding attachment so my piston slides around now. I will test it out today. I still suspect my tappet return spring is junk and isn't returning fast enough. If I cut another coil tho I bet it'll bust.
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mr. potatohead
5
Ok guys did a chrono test. Here's semi:
Corded phone Telephone Wood Office equipment Telephony
Tool Automotive lighting Wood Audio equipment Material property


Here's full auto:

Wood Audio equipment Sports equipment Gas Font
Audio equipment Gadget Electronic instrument Wood Material property



In semi it still seems really inaccurate...this was tested with .20 bbs (cheaper than the .25 tracer rounds I play with). Full auto is a wreck. Could the prob be with my tappet return spring (-3 coils)? It's literally a stock part from a lancer tactical I had lying around so it's weak garbage (maybe too stretchy still)...
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mr. potatohead
Inserted pics in wrong spots...fixed. Yeah dunno whats with FA...literally looks like a shotgun lmao
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mr. potatohead
3
Here's some pics of my gb. Ben and rm105, do u guys in particular have anything to say about my tappet plate? These are pics of tappet fully forward, and then drawn back when sector gear is on last couple teeth of piston. Would it hurt to trim more? I just need this fps to get consistent.
Motor vehicle Wood Auto part Gun accessory Cylinder
Motor vehicle Automotive tire Wheel Toy Automotive exterior


Also here's a pic of my janky tappet spring...I found a pretty short one I had lying around (better quality than the lancer stock part).
Wood Grey Automotive tire Font Flooring
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mr. potatohead
I have a few others...
Handwriting Office supplies Writing implement Font Pen

Blue one is shs (actually probably a similar one to ur pic) and I was using it but spring bent out the thing at the bottom...What if I just trimmed up to where the abrupt cut ends? Too much? If so, black tappet would probably be my next move but I've had it not pull back my nozzle enough in past SSG builds.
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mr. potatohead
Finger Font Office supplies Material property Office equipment
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mr. potatohead
Guges Mk3 said:
Was that an optical illusion or is it shorter?
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Lmao it's shorter; I trimmed a bit off of it once.
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mr. potatohead
Ben3721 said:
The sharp drop-off will break the tappet fin off the tappet eventually. It will also eat into it.

That tappet spring is too short. Only cut a couple coils off, too many and the spring weakens from being stretched and won't do its job as well anymore. It will also break sooner.
Click to expand...
Actually that's the busted one that broke cuz I took one too many off. I was wondering if I could use it still but I think I have my answer. Would trimming the sharp "cut in" piece off of the tappet plate be too much? According to your rough diagram, taking that whole part off would be the equivalent of taking all the green and purple off and them cutting a bit into the "yellow" section. Worst case I could see would be the nozzle kicking the bbs into the packing, but I could live with that...
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mr. potatohead
Originally was using probably the same one guges posted but busted the spring hook at the bottom...
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