Power curve s200

[ray7]

Hi all. I am a new owner of an AA S200 mk3 I have bought this second hand and when I got it it was over powered. I have solved that problem but now the power curve seems a bit steep. I set it up last night so I was getting 11 ft/lb but had run the pressure down to about 120 bar. Today I filled it to 190 bar and put it back on the chrono and it was doing 8.7 ft/lb this went up as I kept testing until after 5 mags and at 140 bar it was back to 11.1 ft/lb.
I have heard that the s200 has quite a big curve but is this big normal?

Ray

[Raj]

No it isnt .... at least it doesnt need to be

From what you have described, it looks like the main spring is set up quite tight. This gives you a lot of power ... more than is legal in the UK. You then need to bring it to legal limits by choking the power down with the venturi. This will result in the peak of the curve shifting to the kind of bar pressure you have described.

Here is an analogy that will help you ... hopefully. Think of the main spring as the accelerator on a car. The venturi is the brake. The 12 lbs. legal limit is your speed limit for the road. You can throttle the car till it produces a lot of power ... and speed. You can then press your brake to bring this excessive speed down to legal limit. Now you are driving with one foot on the accelerator and one foot on the brake to stop your car from setting off the speed camera You wont get many miles/gallon driving like this = poor shot count ?

What I found works best is setting the main spring to about 11.7 ft.lbs with the venturi all the way out ... and then choking it back with the venturi to get to a comfortable 11.3 or thereabouts. Dont ask me why but you do need both - the accelerator and the brake to get the best mpg out of your car (S200). The trick is to reduce that essential braking down to a minimum. Give that a try and let us know how it worked out

[ray7]

Thanks Raj for the reply. It looks like the former owner put an FAC spring in I did order a standard spring but they sent the wrong item and I am waiting for a replacement. So what I have done is take 3 coils off the spring, unscrewed the venturi for no restriction. The hammer screw is now giving 11.1 ft/lb at 140 bar at 1 3/4 turns in from flush with the venturi still turned out for no restriction. So should I screw the hammer screw in a bit more and adjust with the venturi and if so at what pressure?

Ray

[Raj]

Hi Ray
Really sorry I am not sure how an FAC spring with three coils cut off will behave compared to a normal spring with all the coils in pace
Once you have the right spring, my experience tells me that it is best to set the power with the venturi fully open to about 11.7 ft.lbs. Then choke it down with the venturi to get it down to about 11.2 - 11.3 ft.lbs. I found that this is the best way to get max. shot count and min. spike in the power curve.

On the other hand, if you set the main spring alone to give you 11.3 ft lbs and leave the venturi fully open, you may find that the shot to shot consistency varies. This is because the power curve is entirely dictated by the dynamics between the force of the main spring and the back pressure of the air in the cylinder trying to close the firing valve shut.
Let us know how you get along with these parameters.

[ray7]

Thanks Raj. I will leave it as it is until the new spring arrives and just fill to 160 bar. When the new spring arrives I will do as you suggest and let you know how it goes.

Ray

[ray7]

Unexpectedly the new spring arrived today. The spring that was in was the same length before I took the 3 coils off but much stronger, even with 3 coils off it took a lot of effort to get in but the new one went in easy.

Set the hammer at 11.8 ft/lb and then turned it down to 10.8 ft/lb with the venturi. Now at 190 bar it started at 9.28 ft/lb to a max of 11.38 ft/lb on the 7th mag and back down to 10.26 ft/lb after 90 shots and was down to 100 bar.

When I go to the club on Monday I am going to see what the grouping and POI are like from the start of the 4th mag that gave 10.42 ft/lb to the end of the 8th mag that was still giving 10.97 ft/lb.

Another problem I found was that the venturi screw was that loose every time it was fired it opened a little, it now has a bit of loctite on it and I have ordered a blanking screw to replace the anti tamper that the former owner had removed.

Thanks Raj for your help. I can`t understand why people have to push the power up that far.

Ray

[Raj]

Looks like a result