AEG shoots at 0.5J on 11.1v battery, but 1.1j on 7.4v. Why?

[Vendivorex]

Hi all, 

Just a quick one as I really can't figure this out. 

So today on site, while my AEG was being chrono'd, it came out too hot at 1.3J (my site limit is 1.14J. It had an m120 spring inside, so I quickly changed the Spring to a 110. 

When I came back, there was a significant power drop to 0.5J. I couldn't work it out at all and decided to use my back up rifle. When I got home I had a look on my own chrono and got the same result, yet when I swapped the batteries over (from 11.1v to 7.4v) the power jumped back up to 1.1J.

The batteries have the same ampage and C output, so I am stumped. Any ideas why the power drop using 11.1v? Both batteries were fully charged.

 

[ak2m4]

short inner barrel? battery voltage shouldn't affect J

 

[Speedbird_666]

Pure guess:

Tappet timing.

The nozzle is not returning forward fast enough for the next cycle of the gears causing a huge airleak around the hop unit. Lower voltage battery means that the gears are rotating slower to complete the firing cycle giving the nozzle time to seat itself in the hop unit before the piston (thus air) is released.

It's become a common issue on KWA guns but in theory could apply to other manufacturers.

You can test by turning the gun upside down and placing a small square of tissue over the hop unit feed inlet. if the tissue is blown upwards when firing on an 11.1, yet not (or to a much lesser extent) on a 7.4, there's a good chance that could be your issue. If that's the case, make sure that the you remove any sector gear delay chips, replace your tappet spring and make sure your tappet is lubed on the rails, moving freely and in good condition.

I'm sure others will chip in with alternate possibilities.

 

[Vendivorex]

I think this is totally right! It is a KWA rifle as well!! 

Thank you so much, you are a star and spot on.

 

[Rogerborg]

Wow, every day is a learning day.

 

[Speedbird_666]

I think this is totally right! It is a KWA rifle as well!! 

Thank you so much, you are a star and spot on.

Negative Airsoft has had to deal with a stack of KWA's with low power on 11.1v LiPos. There's a video on his Patreon with the 'fix' for the problem.

You will need to add a bushing onto the Tappet spring guide to increase the spring tension, and you might also have to cut the tappet fin down (DSG style) so it will release earlier in the firing cycle to get nozzle moving forward earlier. If you cut the fin down - remove the delayer chip as well.

View attachment 105482

View attachment 105481

I intend to do the same mods on my my KWA once I notice any kind of power drop.

I take no credit for the info above - if this helps you fix your gun - please consider signing up to Negative Airsoft's Patreon for a fiver a month, even just for one month. There's loads of information in his longer-form videos that you won't see in his standard youtube releases.