Dump valve issues...

[pyromaniac_yeti]

I'm fully aware that im going to get called all the names under the sun for this, but here goes...

The 1.5TD recived a 2nd hand forge twin piston dumpvalve.

Vac connection goes from the servo side of the one way valve, into the solenoid, out into DV.

Boost connection goes from a T on the manifold and connects to the solenoid.

DV is a twin piston forge jobbie. It has been stripped, regreased, cleaned and rebuilt more times in the past week than i've had hot meals...and i eat a LOT. It moves VERY VERY smoothly.

Vac pipes i have changed all through over three different sets, no change, same with the boost lines. no change.

No boost leakage, full 17PSI boost.

Microswitch connected on throttle stop, when pedal released switch clicks and valve opens. pedal pressed valve drops...both almost instantly, slightly slower on the upwards.

Whenever i drive the car setup as such, no "ppssst" noise.

HOWEVER,

Should i drive the car with the microswitch in my hand, run it along the road at anything above (at a guess) 5psi ish, and press the microswitch before lifting, "PSSSHT".

As far as i can make out, the boost is gone before such times as the valve opens.

I have tried:

Two different solenoids
Copper grease on the seals
Diesel oil on the seals
General purpose grease on the seals
WD40 on the seals
Replacing the vac tubing throuought
Replacing all jubilee clips
trimming one coil off the mainspring
Removing all spacers from mainspring
Trying one spacer at a time on the mainspring


Grease and a new solenoid helped a great deal with the valve opening, however im now at a loss. Perhaps the forge DV has too big a piston for the 1.5TD's vac pump to move quickly? Perhaps the seals are shot (when i push the piston all the way up and put my finger over the vac/boost hose inlet, it slides down to about the halfway point and then very very very slowly drops to the fully closed position, however doesnt propperly shut till i let my finger off)??

Im fully aware that the main cause of said problem is my inner steak & kidney lock opener trying to get out, and that it was a **** idea to start with, however this should in theory work perfectly!

Any help would be much appreciated! :thumb:

EDIT: I'm not sure if this would have any effect whatsoever on the engine, however one of the downpipe bolts decided it diddent like life anymore and i've yet to replace it.

[pyromaniac_yeti]

Judging by the amount of views and lack of comments i'm guessing everyones as stumped as i am! lol

[Jack]

Thats because everyone wants to see a wikidy bo DV, but when they see technical yak, they get bored lol

Does the vac line have good, er, vacuum? As in, if you run the engine with the vac pipe in your hand and kick the revs, do you get suction?

I've got a Forge DV on the Celica, it does have a habit of sticking when cold. But its dirty as feck lol

[mowgli]

i'm guessing it isn't reaching enough pressure to do anything.... which, on a diesel, if i'm thinking right, is quite likely.

[pyromaniac_yeti]

Very much leak free - tested everything a million times!

Wants a new DV then with the smallest possible piston....bailey or something like that & the old one flogging on.

This said, if i can make it all work propperly then theres some potential money to be made from £10 of scrapyard parts!! £120 for a fecking "proper" kit on ebay!

[Balley]

Maybe its just not working because when you let your foot of to make the switch work there isn't enough boost pressure as the very thirsty cylinders have already sucked it all in.

I know with mine the second you let the foot off the pressure drops to nothing. So as there is no throttle flap the pressure can't store it self.. why not fit and in line throttle body like new modern diesels..would work with out the switch then to as it would actually make a vacuum... This is how series three land rovers used to fill the Servo any way.. and it will be a for engine braking... wouldn't be hard to make either!

[windfreek]

Perhaps the forge DV has too big a piston for the 1.5TD's vac pump to move quickly?
the problem isnt vac, its pressure differential for one side of the BOV to the other side of the BOV, the only way you can easily replicate this is as Balley said, with a throttle body to create the pressure differance, as you let off the butterfly closes, the pistons continue to draw in and create a vacuum to that greater of the boost on the piston side of the BOV and as the air is desperate to escape from the intercooler and pipework to equalise itself to the outside world if finds a weak point in the BOV and as the vacum has now lifted the primary spring within the BOV the rusultant pressure can move the piston out of the way and escape.


Perhaps the seals are shot (when i push the piston all the way up and put my finger over the vac/boost hose inlet, it slides down to about the halfway point and then very very very slowly drops to the fully closed position, however doesnt propperly shut till i let my finger off)??

thats because in a normal turbo system when you press the accelerator again, the butterfly will open up and allow the turbo pressure into the vac line to force the piston shut again to retain boost, as with your finger over the vac port the piston is still trying to draw outside air in thru past your finger and it slowly leaks back in, hence the slow movement

ideally you will need a big IC and oversized pipework in which to "store" the boost and a throttle body and a very heavy right foot!

[mowgli]

people, its a diesel, it is built for low end grunt... a DV is designed to lose boost to reduce low end grunt on a petrol.........for traction...

i think it will be fighting a losing battle trying to adapt petrol gear for a diesel.

[Jack]

I'd have said a DV would increase low end power, after gear changes. Plus it protects the turbo from trying to compress against a closed throttle plate which is probably more important for road cars (i.e. prolonging turbo life), which is why they're not fitted to diesels as that problem doesn't really apply on them

Its doable, as the cav had a DV on it prior to me purchasing it. But I told the potato to pull it off lol. IIRC it was kinda like an EDV, with a microswitch on the accelerator or something - I've got all the bits still, but as I didn't see how it was on the car I've got no idea whats what and haven't really paid much attention to figuring out how it worked... lol