dump valves

POE · Post by **POE** » Thu Mar 19, 2009 7:05 pm

hi, just a quick question about dumpvalves ,why do some recirc dump valve kits have adjustable springs for different pressure and what is the benefit?

martinholmesuk · Post by **martinholmesuk** » Thu Mar 19, 2009 9:27 pm

Well you don't want it to open under boost do you lol

reevio · Post by **reevio** » Sun Mar 29, 2009 8:40 pm

blunt and too the point

POE · Post by **POE** » Mon Mar 30, 2009 7:20 pm

yes ,but when you have 6 springs which is appropriate ,ive fitted the weekest of the springs and seems to do the job,i assume too strong a spring and it wont dump(pardon my english)

aibast · Post by **aibast** » Tue Mar 31, 2009 7:19 am

why did you but it on in the first place?

POE · Post by **POE** » Tue Mar 31, 2009 9:50 am

im running richmod and have read on forum that standard recirc valves dont last, what are the symptoms of dumpvalve not opening?

gltease · Post by **gltease** » Tue Mar 31, 2009 10:35 am

POE wrote:im running richmod and have read on forum that standard recirc valves dont last, what are the symptoms of dumpvalve not opening?

A constipated engine ??

aibast · Post by **aibast** » Wed Apr 01, 2009 5:32 am

get a VAG engine recirv valve. I'm running on that no problems. Its made from metall not platric costs pennies and is made to operate @ 1bar pressures.

Ps. I did kill my stock plastic by-pass with richmod out of controll (vacumehose to the boost controller broke)

POE · Post by **POE** » Wed Apr 01, 2009 1:05 pm

im using a forge motorsport recirc valve ,but came with 6 springs each of different strengths and am using weakest of springs ,feels about same pressure as original, if vacuum wasnt opening valve what boost reading would i get?

BLK_480 · Post by **BLK_480** » Sat Apr 11, 2009 6:12 am

Mine had really bad turbo lag between shifts and felt sloppy under steady accelleration (felt pretty strong under full throttle). I popped one of these in there:

and it's like a new car! Steady boost under all levels of throttle, a huge reduction in lag between shifts and it feels much stronger. I expect to see better fuel milage as well since the A/F mixture will be consistant.

POE · Post by **POE** » Sat Apr 11, 2009 6:38 pm

and assuming that the original dumpvalve diaphragm would weaken over the years,causing it to stop your boost levels getting up as they should do?????and dumping too early

Melvin480 · Post by **Melvin480** » Sun Apr 12, 2009 7:02 pm

The valve will not open due to pressure created by the turbo. The high pressure side of the valve (the original one) is at the side. This way the pressure can not push the valve open.

If the spring weakens then the valve will open at less vacuum in the inlet than at its orginal spring stiffness.

JohnTurbo · Post by **JohnTurbo** » Sun Apr 12, 2009 11:01 pm

The valve is actuated by a vaccum pipe from the manifold side of the throttle body. When the throttle is shut, a vaccum is made by the engines natural sucking motion.

So the valve without any spring would be on the point of opening precisely when the pressure was equal both sides of the throttle.

Its preferable to have it higher up the accelerator range than this....all you do by canging the spring is alter where that point is, to prevent the valve opening earlier or later than you'd like it too.

POE · Post by **POE** » Mon Apr 13, 2009 11:04 am

so we'll say that the valve is stuck solid what boost is created ? is it matter of waiting for ecu to kick (too much boost)? or is there no boost created ' sorry,but confusing me slightly .

BLK_480 · Post by **BLK_480** » Tue Apr 14, 2009 5:55 am

If the valve doesn't open boost will still be created but the excess won't be discharged when you come off the throttle. If you have the black plastic valve, it probably isn't funtioning properly. I've had that part on 3 cars now (My porsche, vw and now the 480) and all three of them leaked boost. To test it, take it out and blow into the side (boost port) no air should pass through the bottom port or the vacuum port. You can also check it by pushing the diaphram open from the bottom, while you're holding it open, cover the vacuum port with your finger. Release the diaphram and it should not close until you take your finger off the vacuum port.

POE · Post by **POE** » Tue Apr 14, 2009 7:25 pm

will there be danger of damaging engine in long run if left ?the dumpvalve thats fitted is a forge and i think is perfectly fine,a bit wary of the spring ive used is a bit stronger than standard,i was just wondering whether it is not opening as early as the standard plastic valve because of the higher pressure of the spring.

bkf_uk · Post by **bkf_uk** » Wed May 06, 2009 10:17 pm

I seem to remeber been told by rich that these forge valves are to be avoided at all cost.

When the stock valves give up they die in the open position and just allow boost to leak, therfore not killing the engine. on the other hand the forge ones die in the closed postion, not allowing the boost pressure to be dumped, this the kills the engine and the turbo.

From what i can gather the best dump valve to use is a 1.8 VAG one (i.e the ones in passat and a4 1.8 turbos)

I wasnt able to get one of these and use a bosch recirc valve from a saab 95 areo and it seems to work well.

Hope this is of help, and if im wrong im sure i will be corrected!

POE · Post by **POE** » Thu May 07, 2009 7:20 pm

would this cause you to overboost,are there any other symptoms of valve failing?and whats so different between forge and vag valves?

bkf_uk · Post by **bkf_uk** » Thu May 07, 2009 9:03 pm

I belive that forge failing would cause overboost. The main diffrences i think there are between the forge and the VAG valves are the way in which the diagphrams work, wouldnt realy know to be honest though, ive never botherd to look.

Ben Harris · Post by **Ben Harris** » Thu May 07, 2009 10:23 pm

I replaced mine with an Bosch dump/diverter valve from an Audi TT. Supposedly, it can handle 225BHP, which is much more than my 480 was making, even after a RichMod.

I bought it from here:
http://www.thettshop.com/search.asp?pro ... &site=main

If you so a search on the forum here for 710N (the end of the part number) you'll see that it gets quite a few recomendations.

Ben.