Sam Elassar

ok i have got the dawe fitted on my evo 7. and every thing is dandy. however in 4th or 5th gear when floored the boosts goes 20psi (which is what it is set at) then when it reachs 3500-4000 revs to goes down to 18-19psi for few hundred revs and back up again?

does anyone get that? due to the position of the turbo it does not run the usual short piping you can achieve with the subaru so the pipe to and from the dawe are around 2/3 of a meter i suppose. is not that right johns

sam

Cosie Convert

Sam

I believe john added stability by enlarging the bleed hole on the Dawes. I run with a 2mm bleed and the boost is rock solid.

I think the critical pipe to retain a short run on is the pipe from dawes to wastegate. You may be able to reposition it to achieve this ?

cc

Sam Elassar

i can make the pipes a little shorter but not by that much really. the area is very tight for access on the EVO7. ask john (t-uk) i think he spent over 30 mins just trying to remove the turbo and wastegate hoses!!!!!!

if increase the hole won't that reduce the spool up time? i am not really interested in getting it to spool slower.

sam

Cosie Convert

Increasing the bleed hole will not change spool up time, what it does is stops the 'over correction' of the boost pressure.

ie as the boost rises, when it approaches set point the dawes opens and allows the pressure to open the wastegate, the bleed off stops it opening too far and dropping boost.

It should help in your case, where the small bleed may struggle to vent the extra length of pipe quickly enough.

cc

Sam Elassar

will try that soon and see how it goes.

cheers for the input

sam

mutant_matt

CC,

Enlarging the bleed hole on the Dawes does two things

1) Primarily, it "stablises" boost fluctuations when on Boost
2) This has the effect of reducing the spool up speed slightly (which also helps part throttle "smoothness"

Matt

P.S. John banks seems to have become the "Dawes Scooby Guru" so it may be worth double checking with him....

T-uk

I think that it may be the length of the pipes,try shortening them as I did not feel that you needed to drill the hole out with yours.

by the way,my knuckles are healing nicely

john banks

Sam - I did notice this effect when we were out in your car.

If the hose lengths were too long there would be a big overshoot which does not happen as you car does peak and (eventually stabilise) at the same level - 20PSI.

The way the Dawes works is to be closed until near target boost and then over the last few PSI it gradually opens until equilibrium. A larger bleed hole and the same overall boost level will ever so slightly slow that last bit of spool up - damping it a little more. It also seems to benefit as I reckon the ball will not be oscillating like it could with a smaller bleed - since you are over target boost it will just stay open enough with the bleed to hopefully keep the ball in a steady position and make your boost smooth.

This is all conjecture - you have to try it on your car, but I would see what it is like with that bleeder valve you have first so you can decide how much to drill. Should not affect your peak power for the rolling road day

If you want to try the bleeder put a T-piece in the line that goes to the wastegate JUST AFTER the Dawes (this will be next to it and most accessible on your car). Off the side port of the T-piece attach your valve from Falkland Performance. Screw it all the way shut to start with - can blow through to check and it is clockwise. Then gradually open it up say one turn at a time. You will need to gradually unscrew the Dawes (to make it longer) to compensate. This will change the damping of your spool up and maybe make it smoother. Try it and see, and then you can judge how much to drill the Dawes. If you want me to have a look on Sunday I can bring a portable drill and miniature drill set to give you a hand if you bring the valve and t-piece with you.

Regarding the valve - the adjustment works in one direction only (supposedly). When you look at the side with the diagram on it, the left hand side should be nearest the T-piece and the right hand side venting to atmosphere (you can remove the brass fitting from this side). However, the valve edges could scratch some of your pipework so go easy how you mount it.

Hope this is as clear as mud and I am not telling you the obvious.

[Edited by john banks - 1/18/2002 10:18:50 AM]

Sam Elassar

cheers guys.

john i will phone you on saturday sometime if that is ok with you. john (t-uk) you have done very well mate i would not have done it with out you.

sam

john banks

That is fine Sam.

Sam Elassar

add a bleed valve, in the same side as the original bleed hole on the dawe.
and now the boost is as flat as a pancake

boosting and holding 20psi in 4th geari get around 0.5-1psi more boost in 5th gear though and maybe 19.5psi in 3rd.


cheers guys

sam

john banks

Sounds excellent Sam.

My EBC is on the car and working OK considering I have not fiddled with the settings much yet. I'll see how good I get is by the end of today - I might run with it or the Dawes tomorrow.