more indepth AFC modifcation, and tuning....

[DTanklage]

never mind...the tst springs finally showed up today

already had the other mods done and man, putting the medium spring in my 913 pump really helped me get it right

barely smokes and boost is up 8 psi

i did port the ex housing some more this week also tho

so maybe that is contributing a little to the extra boost

all i did was grind the foot til 7/8 of the angle was gone, flip the washers, ground both sides of the barrel (just to be sure), and put the med spring in

the wheel is all the way forward, smoke screw is all the way reward, no plate, and i put the housing all the way forward

was gonna put shop air to it and get it so it was juszt touching the lever while holding the throttle wide open but got antzie n just bolted it on there

it smokes less than it did since i first started messin with it and hauls ass so what would be gained by moving the housing back to the exact correct position?

and how would that affect the spring rate? cuz how ever much i move it rearward i would have to move the smoke screw forward same amount in order to be at the same starting point i am now. and that would effectively change the spring rate, right?

i am done screwin with it - think all i can do from here is mess it up anyways

lol

 

[White Knight]

how about the area of the diaphram ?

thanks, don

I'll work on the installed height tomorrow, I forgot to measure that tonight. The diaphragm is roughly 55mm in diameter on the inside of the rear cover. Its rounded and sloped so its hard to measure accurately. The washers are 40mm OD but that's insignificant.

The stock housing/arm seems capable of 15mm of travel if everything is prefect, but 10-15mm seems more attainable. Washer interference seems to become an issue.

F=P*A and F=-kx would work to get you spring rates needed. It will be more accurate once you know the installed and free standing hieght.

and how would that affect the spring rate? cuz how ever much i move it rearward i would have to move the smoke screw forward same amount in order to be at the same starting point i am now. and that would effectively change the spring rate, right?

i am done screwin with it - think all i can do from here is mess it up anyways

lol

By moving the smoke screw you are just increasing the x measurement. The spring rate is the same regardless. You just have to factor that extra initial force in the negative x direction in when you do your calculations.

If someone knows of a good source for springs, this math could be very helpful in picking springs.