View Full Version : Forge DV
ibizacupra
27-01-2002, 22:21
Anyone know how the Forge DV operates?
Does the vacuum signal pull the piston up to vent, or is the spring pressure rated such that there is a balance between delivered boost pressure and vacuum signal to overcome and dump the excess boost.
What pressure level constitutes excess boost? (Vacuum signal only?)
thanks
Bill
I can see where you're coming from.
But I don't think they operate on a Balenced design. If this was the case, all the chipped cars would give spurious results, as unwanted pressure relief would occur :)!
As far as i'm aware, the vacuum is the only factor that pulls the piston up (open).
Cheers
TROG
(ADE)
I know an easy way to find out Bill, disconnect you vacuum line and plug it, then listen for the DV to open whilst driving, the vanes in a small turbo like ours should be able to easily handle the extra back pressure, just loads of lag between gearchanges
ibizacupra
27-01-2002, 23:55
Originally posted by ademason99
I can see where you're coming from.
But I don't think they operate on a Balenced design. If this was the case, all the chipped cars would give spurious results, as unwanted pressure relief would occur :)!
As far as i'm aware, the vacuum is the only factor that pulls the piston up (open).
Cheers
TROG
(ADE)
"All the chipped cars would give spurious results......"
the 19th seemed pretty erratic, even for like Oettinger cars.
i wonder..................
What pressure does the spring hold then? it must be balanced against the vacuum signal vs the boost trying to open the valve. 9(17psi is 17 pounds per square inch (approx the DV internal) after all)
Bill
ibizacupra
27-01-2002, 23:56
Originally posted by Mosser
I know an easy way to find out Bill, disconnect you vacuum line and plug it, then listen for the DV to open whilst driving, the vanes in a small turbo like ours should be able to easily handle the extra back pressure, just loads of lag between gearchanges
Good suggestion.
I'll look into this.
thank you
Bill
(Just posted this on another thread but this seems like a better place to post it)
What characteristics do you lot get with your Forge Dump Valves?
I was of the understanding that it was meant to keep the boost during gearchanges, but with my new boost gauge I have found that during gearchanges the boost drops off so quickly that I'm lucky if the boost gauge is showing any positive boost at all by the time I'm into the next gear!!!! Is this normal for a Forge Dump Valve???
Also, it makes a slight dump to atmosphere type sound which I didn't think you got from a recirc dump valve! Does it sound like a leak of some kind?
Thanks
Ben
If your boost gauge is plumbed into the inlet manifold then you wont see the boost staying up because you are after the throttle butterfly that shuts off the air supply to the engine, it is this butterfly closing that actually causes the backpressure!!,
You will always hear a slight whoosh when changing gear because it dumps into the airbox where you can hear it echoing around (sort of!) inside, if the noise is louder with the Forge DV then it is more efficient because it is dumping the air more quickly
Revo Mark
28-01-2002, 01:31
BenS1
Diverting the boost pressure via the DV,when you close the throttle is to stop the pressure backing up to the turbo and slowing the compressor wheel down to much! This inturn reduces the spool up time and lag when you get back on the throttle. So you won't have any positive pressure showing on your boost gauge whether it be fitted before or after the throttle body. once the recirc valve opens, as it basically leaks all the boost pressure back to the intake side of the turbo ( negative pressure), hence the hiss you hear as it fires all it's boost down the intake pipes.
Hope this helps.
regards
Mark APR
pstables
28-01-2002, 14:27
Is there any noticeable difference between The forge 006 and 007 dump valves? I'm considering a 007 in anodised black for obvious stealth reasons, but is the 006 a better item being a piston type rather than a diaphragm type?
Cheers,
Paul
Originally posted by ibizacupra
Anyone know how the Forge DV operates?
Does the vacuum signal pull the piston up to vent, or is the spring pressure rated such that there is a balance between delivered boost pressure and vacuum signal to overcome and dump the excess boost.
What pressure level constitutes excess boost? (Vacuum signal only?)
thanks
Bill
It's probably worth giving Forge aring. I spoke to them before I bought mine and they seemed very helpful. The springs can be changed for different ratings but I can't remember what they said now. I got mine from SJBsport and I remember John mentioning something about the spring rate, he might know something more.
Forge 01452 380999
Steve3961
28-01-2002, 22:38
Originally posted by ibizacupra
Anyone know how the Forge DV operates?
Does the vacuum signal pull the piston up to vent, or is the spring pressure rated such that there is a balance between delivered boost pressure and vacuum signal to overcome and dump the excess boost.
What pressure level constitutes excess boost? (Vacuum signal only?)
thanks
Bill
Very simple really, when the engine is under load it does bugger all, then when you release the throttle the vacuum in the inlet manifold opens the valve by means of sucking down the smallest hole and release's the pressure back into the inlet track.
It doesn't control boost in any other way.
There is no balance of presure & vacuum. They occur at diverent times.
Steve3961
28-01-2002, 22:55
Originally posted by BenS1
(Just posted this on another thread but this seems like a better place to post it)
What characteristics do you lot get with your Forge Dump Valves?
I was of the understanding that it was meant to keep the boost during gearchanges, but with my new boost gauge I have found that during gearchanges the boost drops off so quickly that I'm lucky if the boost gauge is showing any positive boost at all by the time I'm into the next gear!!!! Is this normal for a Forge Dump Valve???
Also, it makes a slight dump to atmosphere type sound which I didn't think you got from a recirc dump valve! Does it sound like a leak of some kind?
Thanks
Ben
The turbo can't keep boosting in between gear changes as the would cause the engine to rev on its own, like keeping the throttle open!
A forge valve is meant to keep the turbo spinning not boosting in between gearchanges.
When you release the throttle and hear that noise you need to remember that boost is being recirculated in to a vacuum hence a whoosh sound.
hope this helps
:D
ibizacupra
28-01-2002, 23:38
Originally posted by Steve3961
Very simple really, when the engine is under load it does bugger all, then when you release the throttle the vacuum in the inlet manifold opens the valve by means of sucking down the smallest hole and release's the pressure back into the inlet track.
It doesn't control boost in any other way.
There is no balance of presure & vacuum. They occur at diverent times.
The spring fitted in the DV though must be of a certain rating to hold the piston shut on full boost. Otherwise you would get boost leak. The vacuum signal, by its very nature indicates closed throttle hence sucking the piston open, overcoming the springs spring rate to vent the excess boost.
Question is, how does this spring rate compare on modified cars, where Forge sell a standard DV. A friend of mine had a forge DV a few years ago, and its spring rate was to low that the DV opened during full boost. He ran a G60 mk1 Golf, and started with an advised Uno Turbo one (which leaked early), then an RS Turbo one (which also leaked early) and then a Cosworth one whcih worked. The differences being spring rates inside apparently.
I'll give Forge a call tomorrow. They are just up the road from me anyhow! which is handy. :D
regards
Bill
Steve3961
28-01-2002, 23:51
Originally posted by ibizacupra
The spring fitted in the DV though must be of a certain rating to hold the piston shut on full boost. Otherwise you would get boost leak. The vacuum signal, by its very nature indicates closed throttle hence sucking the piston open, overcoming the springs spring rate to vent the excess boost.
Question is, how does this spring rate compare on modified cars, where Forge sell a standard DV. A friend of mine had a forge DV a few years ago, and its spring rate was to low that the DV opened during full boost. He ran a G60 mk1 Golf, and started with an advised Uno Turbo one (which leaked early), then an RS Turbo one (which also leaked early) and then a Cosworth one whcih worked. The differences being spring rates inside apparently.
I'll give Forge a call tomorrow. They are just up the road from me anyhow! which is handy. :D
regards
Bill
I see your point Bill let me know what you find,
Any news on the RR yet? Am I on the list?
Interesting bill !!, my Forge DV006 leaks on full boost sometimes, it happens just after it has dumped and doesnt seem to shut properly, i assumed it was sticking and was going to take it apart for cleaning, but now i think maybe the spring rate is too low?? wot u think?
ibizacupra
29-01-2002, 00:12
Originally posted by Mosser
Interesting bill !!, my Forge DV006 leaks on full boost sometimes, it happens just after it has dumped and doesnt seem to shut properly, i assumed it was sticking and was going to take it apart for cleaning, but now i think maybe the spring rate is too low?? wot u think?
It needs to be checked I think, just in case its that simple.
i will call Forge tomorrow and ask anyway how they set them up and for what boost pressures etc.
I will post the reply and findings.
regards
Bill
I spoke to one of the guys at Forge at the Autosport show a couple of weeks ago. He advised me to open the DV and lightly grease the piston once every couple of months. Haven't done it yet and can't remember what grease he said to use either.
ibizacupra
29-01-2002, 21:44
i spoke to Forge today about their DV006.
They say it is rated for 2bar boost pressure.
I had a good look at my DV tonight and did a pressure test on it.
the design of it means the +ve boost pressure is behind the piston if anything and should help the spring keep it closed. The vacuum signal sucks the piston up enough (not much) to allow the boost to vent.
It was good to test the actual pressure it took to open the valve directly into the piston though. 18psi and it started to leak. Compare this to the 7psi it took for my standard bosch DV and you see its an improvement.
You can shim the internal spring to increase preload and hence effective seat loading.
One obervation though, was the piston seat (taper arrangement) was starting to show signs of bruising from the impact of the spring closing the DV shut hard repeatedly. I lapped in my seat to improve the seal.
The piston was also a bit sticky on pulling the vacuum (sucking through a pipe to actuate it manually) The piston showed some score marks which picked up on the 2 o-ring seals in the top chamber. It did not move easily and certainly was not smooth in operation. After much polishing of the piston OD, and lapping of the valve seat, it seemed better for it. I shimmed the DV piston to increase the seat load a little, and the retested seat pressure was then 25psi before leaking.
Back on the car and on the road, it seems quite crisp, but not stunningly different to drive at all. Audiobly it still dumps as before. Interestingly, the idle vacuum signal is now higher according to my boost guage, from -10psi to -12psi now. The seating and increased piston pressure seem to have improved what must have been a small vacuum leak.
Finally. The top vacuum pipe connection is too large really for the factory pipe. It has to stretch so far it tears it outer fabric binding. It goes on eventually, but it is being tortured.
Bill
Blimey bill !!, you've been busy with your DV !!,
I am going to have to read and reread your post a few times to make sure it sinks in as to what you did, then i will take my DV off for a while and put my bosch one back for a while whilst i work on it!!, what sort of lapping paste did you use?, are ther different grades?, also, by polishing the piston, doesnt that actually reduce its diameter? which will make it a looser fit?,
I am going to nip down now and remove my DV to have a look !!
ibizacupra
29-01-2002, 22:39
Originally posted by Mosser
Blimey bill !!, you've been busy with your DV !!,
I am going to have to read and reread your post a few times to make sure it sinks in as to what you did, then i will take my DV off for a while and put my bosch one back for a while whilst i work on it!!, what sort of lapping paste did you use?, are ther different grades?, also, by polishing the piston, doesnt that actually reduce its diameter? which will make it a looser fit?,
I am going to nip down now and remove my DV to have a look !!
I initially used fine lapping compound but this was still to aggressive, so I resorted to Autosolve Chrome polish, which was much smoother, but took much longer.
I also used Autosolve to polish out the scratches on the pistons OD. It did help make the operation smoother, but it still is'nt as easy as I would want it. It feels almost like the piston almost goes beyond the 2nd o-ring seal on full extension (DV closed) and tries to pitch slightly, causing a slight binding before it centres itself and moves (jerkily) back into the chamber. The O-rings are quite a hard shore-hardness, and they almost feel like the roll over in their grooves instead of sliding over the pistons OD.
regards
Bill
Cheers bill, do you think greasing the piston might help it slide easier as Dreamer said?,
Just went down to take my DV out and realised i am driving Amethysts loan car!!!, so cant get my DV, Doh!!!
ibizacupra
30-01-2002, 00:16
Originally posted by Mosser
Cheers bill, do you think greasing the piston might help it slide easier as Dreamer said?,
Just went down to take my DV out and realised i am driving Amethysts loan car!!!, so cant get my DV, Doh!!!
Been there done that.
It was already well greased, bu I wiped that off and regreased.
Driving Amethysts loan car - lol... I thought you would have notived that :D
Bill
Graham said that as i was borrowing the 1.4 beezer it is unlikely that i will get done for speeding, and he wasnt kidding!!:D
:)
Er, Bill.... would your observations likely resolt in a problem if not corrected? I know where the dump valve is and what it does but as for taking it off and sorting it out I wouldn't have a clue!!!
Cheers
Ben
ibizacupra
30-01-2002, 00:28
Originally posted by BenS1
:)
Er, Bill.... would your observations likely resolt in a problem if not corrected? I know where the dump valve is and what it does but as for taking it off and sorting it out I wouldn't have a clue!!!
Cheers
Ben
I don't think so, unless yours is sticking, which is unlikely.
You would know by the lag you get whether you have a problem.
regards
Bill
Originally posted by BenS1
:)
Er, Bill.... would your observations likely resolt in a problem if not corrected? I know where the dump valve is and what it does but as for taking it off and sorting it out I wouldn't have a clue!!!
Cheers
Ben
Don't Forge give a lifetime guarentee on the DVs antway so any problems should be covered.
Bill
What about using silicone grease, I've always found this is much better for piston type applications in industry and when O rings are involved it tends to keep them soft. Excellent stuff for many applications, I even used a bit to stop a squeek in the dash.
ibizacupra
30-01-2002, 13:55
Originally posted by whelme
Don't Forge give a lifetime guarentee on the DVs antway so any problems should be covered.
Bill
What about using silicone grease, I've always found this is much better for piston type applications in industry and when O rings are involved it tends to keep them soft. Excellent stuff for many applications, I even used a bit to stop a squeek in the dash.
I did consider silicon grease for the same reaons, however I have read that MAF and or Lambda problems can occur when silicon is present. The vacuum line will suck and release during operation so I guess there is a sligth "potential" for cross over.
I just used moly grease and a bit of engine oil.
The o-rings and piston are a bit jerky though in operation, and the piston is allowed to float a bit, which seems to be part of the sticktion I have found. When it goes out of square tot he bore it binds slightly.
Not huge binding, but not smooth either.
I think they do carry a lifetime warranty.
Bill
I am currently cleaning and lapping in my DV, took some pictures of the insides incase anyone is interested as to what they look like!!
Bloody hell, is that all there is to a dump valve?
How the hell did Bosch manage to make something that simple so unreliable???
Ben
Those Forge DV's any good I'm looking for a decent unit with a decent sound (without sounding like I'm competing in a group N welsh forest stage!)
Sausage
Originally posted by sausage
Those Forge DV's any good I'm looking for a decent unit with a decent sound (without sounding like I'm competing in a group N welsh forest stage!)
Sausage
The valves are great but you don't really get any noise as they are recirculating valves as opposed to atmospheric dump valves which are not recommended on these engines.
Cheers whelm, function over form, like it!
Sausage