[fredio54]

Yesterday I was lucky enough to receive my holset safely and VERY well packed in from the US of A. Its in near new condition having done under 1000miles of service in its former dodge. The lack of use shows too, people ask if its new or 2nd hand. its not obvious. especially now that i've cleaned off the small amount of soot in the hot side.

plans for this are ($ dependent) :
ceramic coat the exhaust housing
weld closed the wastegate hole (22mm hole is too small)
figure out if i can use the built in solenoid for boost control with an external wastegate, and remove it if not.
clock both housings such that the drain is on the bottom in service

Today after finding out how small the wastegate is inside it, i wandered down the road, and bought myself a nice waaaaa leeeeeeeeeeee chinese super duper tial rip off 44mm vband wastegate.

this thing is slightly rough from its chinese nature, but nothing the dremel and precision angle grinder and arm could not fix. the diaphram is a nice silicone one with fibre reinforcing. the ally looks nice n shiny on the outside, but is just die cast in reality, and as such, has some air pockets in it that you can find when you look around.

the cast iron exhaust section of it was machined slightly off centre from the molding line, so i ported it down to match the vband adapter. i also smoothed down the casting seams on the outside, and the step around the valve head such that it looks the part when coated ( if i can afford it) and flows nicely when it needs to :-)

it comes with a spring of unknown tension, so i applied 3.9kg to it, and it went from 104 free length to 99 with that load applied, it is one BIG spring.

in the housing it is compressed down to 41.3 + 16.8 - 8.7 mm = 49.4mm

from 104 with our 1.282 kg per mm spring rate gives ( 104 - 49.4 ) * 1.282
70kg (no wonder i had issues even with longer bolts getting it apart nicely)
the exposed diameter of the head of the valve is 39.5mm

39.5 / 2 = 19.75 / 25.4 = 0.77756 inches squared and times PI is = 1.9 square inches

another 21.5 mm of spring needs to be compressed with 27.56kg of pressure

the effective diaphram is about 73.6mm in diameter

73.6/2/25.4 = squared times PI = 6.6 square inches

now, if we combine the two areas it gives 8.5 square inches with 70kg * 2.2 for pounds = 154 / 8.5 = 18.2 psi

hmmm, i guess thats a rough calc, but it seems high. using electronic boost control, that can be made higher, but not lower. of course, i'm assuming that the exhaust pressure = the intake pressure, perhaps sick could comment on these calcs etc...

fred.