Dump valves for porsche turbos - an answer (long!)
Discussion
:type:
Okay, so i know the standard Bosch plastic dump valves are a bit crap and the diaphragms tend to leak very quickly.
They are the same as used in things like Audi TT's and Fiat Coupe's and those guys reckon they rarely last 10k miles before starting to give problems.
SO - i have researched every dump valve being used by the VAG lot in their SEAT/Audi/VW applications, and where i could find data also on 996tt and 944t applications.
The long and the short of it is that it seems the two most popular options (mainly for reliability) are the Bailey Motorsport DV30 and one of about three Forge Motorsport options. These are recirculating dump valves, so won't give you that "KSSSHHHH" noise everytime you let go of the throttle.
I have just received a pair of Forge FMCL007P which i have taken apart, checked out, and put back together. Very nice too.
If anyone else needs one or a pair (944t, 964t, 993tt, 996tt) i can let you know the cheapest place to order them since i did all the leg work already. They are then dispatched drect from Forge.
No association etc., just that i spent hours and hours trawling through data and websites and thought i'd save you guys some leg work.
Once i've fitted them i am expecting lag to be noticeably reduced on gearchanges, and maybe boost to be held slightly better in the higher gears (less leakage), but certainly not extra power. I have noticed a "flutter" noise on gear changes you see, that's why i think my diverter valves are knackered.
Sorry for the inordinately long post, but hopefully this will answer any mystery if anyone asks in future.
Blow off valve (BOV)
Dump valve
Recirculating valve
Bosch plastic closed loop diverter valve.
VS
:wavey:
Okay, so i know the standard Bosch plastic dump valves are a bit crap and the diaphragms tend to leak very quickly.
They are the same as used in things like Audi TT's and Fiat Coupe's and those guys reckon they rarely last 10k miles before starting to give problems.
SO - i have researched every dump valve being used by the VAG lot in their SEAT/Audi/VW applications, and where i could find data also on 996tt and 944t applications.
The long and the short of it is that it seems the two most popular options (mainly for reliability) are the Bailey Motorsport DV30 and one of about three Forge Motorsport options. These are recirculating dump valves, so won't give you that "KSSSHHHH" noise everytime you let go of the throttle.
I have just received a pair of Forge FMCL007P which i have taken apart, checked out, and put back together. Very nice too.
If anyone else needs one or a pair (944t, 964t, 993tt, 996tt) i can let you know the cheapest place to order them since i did all the leg work already. They are then dispatched drect from Forge.
No association etc., just that i spent hours and hours trawling through data and websites and thought i'd save you guys some leg work.
Once i've fitted them i am expecting lag to be noticeably reduced on gearchanges, and maybe boost to be held slightly better in the higher gears (less leakage), but certainly not extra power. I have noticed a "flutter" noise on gear changes you see, that's why i think my diverter valves are knackered.
Sorry for the inordinately long post, but hopefully this will answer any mystery if anyone asks in future.
Blow off valve (BOV)
Dump valve
Recirculating valve
Bosch plastic closed loop diverter valve.
VS
:wavey:
The main thing to look for is a nice billet design with piston rather than a diaphram.
I'll let the cat out and state i'd personally rather a dump valve than a recirc. What you have to remember is that you are recirculating boosted (i.e. hot) air and boost returns straigh away once back on the gas anyway...
I'll let the cat out and state i'd personally rather a dump valve than a recirc. What you have to remember is that you are recirculating boosted (i.e. hot) air and boost returns straigh away once back on the gas anyway...
Mods, if this is advertising then please remove post and i will e-mail people info as they ask for it.
Call 0870 755 1480 or email sales@monsterperformance.co.uk
Ask for Louise, and mention Pete/Porsche and she'll do you a deal on the price.
The dump valve i recommend is the Forge FMCL007P (in black or silver), and if you are running standard boost (between 0.6 and 0.9 bar) you will want the yellow spring, higher than this and you'll want the blue spring.
Remember, two turbos means two dump valves.
I may also write up and take photos when i change the dump valves on my 993tt - if so i will mention it on this thread when it's done.
VS
Call 0870 755 1480 or email sales@monsterperformance.co.uk
Ask for Louise, and mention Pete/Porsche and she'll do you a deal on the price.
The dump valve i recommend is the Forge FMCL007P (in black or silver), and if you are running standard boost (between 0.6 and 0.9 bar) you will want the yellow spring, higher than this and you'll want the blue spring.
Remember, two turbos means two dump valves.
I may also write up and take photos when i change the dump valves on my 993tt - if so i will mention it on this thread when it's done.
VS
ultra violent said:
I'll let the cat out and state i'd personally rather a dump valve than a recirc. What you have to remember is that you are recirculating boosted (i.e. hot) air and boost returns straigh away once back on the gas anyway...
Dumping to atmosphere screws with the fuelling on 993 and 996 turbos, because the air isn't recycled, so the ECU ends up overfuelling... (i looked into that for the same reason you mentioned!)
Thanks for the info - my valves seem to be working OK at the moment but nice to know that with a quick search on here I can get relevant info. if they need replacing.
Out of curiosity, I had a look at the selection of available recirc valves on the monsterperformance website, why did you not go for the next one after the ones that you purchased, i.e. the same thing but allegedly with "fast response"?
Out of curiosity, I had a look at the selection of available recirc valves on the monsterperformance website, why did you not go for the next one after the ones that you purchased, i.e. the same thing but allegedly with "fast response"?
Niels,
Mainly because, having spoken to the guys at Forge, they recommended the one i got as a direct replacement for the Bosch valve in size. Many of the DV's are larger.
Also, from the investigations other people have done, it seems that domed pistons are more reliable over longer periods of time than diaphragm types. I don't want to have to take the valves out every 6 months to clean them.
VS.
Mainly because, having spoken to the guys at Forge, they recommended the one i got as a direct replacement for the Bosch valve in size. Many of the DV's are larger.
Also, from the investigations other people have done, it seems that domed pistons are more reliable over longer periods of time than diaphragm types. I don't want to have to take the valves out every 6 months to clean them.
VS.
Got mine from Evo in the US.
www.evoms.com/p_996tt%20engine%20upgrades.htm
As for vent-to-air ie non-recirculating DVs, forget them, they are just to make extra noise and screw-up the mixture on MAF (mass-air-flow) equipped cars (the do work OK on manifold pressure cars eg MoTec). They are the reason why most modded Jap turbo cars run rich on gear-change and flame the exhausts, and also stall more often.
OK - thanks. Will be interested in how you get on with the fitting. Is this just intercooler & airbox removal giving access from above for the job, or up on stands and working blind lying on your back?
By the way, did you notice the "electronic dump valve" on their website? A clutch activated switch that makes a whooshing sound out of a little loudspeaker!
I can just imagine it at the traffic lights when the driver selects 1st at idle and the car goes whoosh in a very realistic manner!
By the way, did you notice the "electronic dump valve" on their website? A clutch activated switch that makes a whooshing sound out of a little loudspeaker!
I can just imagine it at the traffic lights when the driver selects 1st at idle and the car goes whoosh in a very realistic manner!
Well, it's done. They're fitted.
I started on the left hand side one, and couldn't see it after moving the blower motor over a bit, so decided to switch sides. Once i had taken the airbox off and gone in deep with a torch, i found the right hand one. Bu**er to get to. Then put that lot back together and guess where the left hand side one was... oh, i can feel it...
Suffice it to say, the engine was not cold so the engine bay was a sauna, and i was going slow to make sure i did it properly, and it took me 80 minutes (with one 5 minute drink stop).
I took photos at every major step, so if anyone wants them let me know and i'll throw together a word doc or something.
As to their effectiveness... my car is definitely faster! I'm shocked at how much difference there is, as i wasn't expecting to be able to feel it. The key is the time it takes to feel thrust again after a gearchange, which is now next-to-nothing! I'd never thought my car was "laggy" in between gears, but the change is fantastic! I reckon this would bring my 40-140 time down by a couple of seconds.
Very happy, and now with an even greater respect for the guys who work on these things for a living. Space really is an issue in that engine bay!
VS
I started on the left hand side one, and couldn't see it after moving the blower motor over a bit, so decided to switch sides. Once i had taken the airbox off and gone in deep with a torch, i found the right hand one. Bu**er to get to. Then put that lot back together and guess where the left hand side one was... oh, i can feel it...
Suffice it to say, the engine was not cold so the engine bay was a sauna, and i was going slow to make sure i did it properly, and it took me 80 minutes (with one 5 minute drink stop).
I took photos at every major step, so if anyone wants them let me know and i'll throw together a word doc or something.
As to their effectiveness... my car is definitely faster! I'm shocked at how much difference there is, as i wasn't expecting to be able to feel it. The key is the time it takes to feel thrust again after a gearchange, which is now next-to-nothing! I'd never thought my car was "laggy" in between gears, but the change is fantastic! I reckon this would bring my 40-140 time down by a couple of seconds.
Very happy, and now with an even greater respect for the guys who work on these things for a living. Space really is an issue in that engine bay!
VS
Martyn,
Already posted on Renn, but i have a similar install guide for the HID upgrade too:
www.verysideways.com/live/pages/hids.htm
Didn't need to do them on my TT cos it already had them.
Any use to you?
VS
Already posted on Renn, but i have a similar install guide for the HID upgrade too:
www.verysideways.com/live/pages/hids.htm
Didn't need to do them on my TT cos it already had them.
Any use to you?
VS
Hi Pete, great write up. How did you realise that your valves were knackered? Are there any tell tale signs or do they deteriorate gradually and most 993TT owners probably need to do this upgrade without realising? Also, one last question, using the Haynes manual 5 spanner of difficulty scale (5 being the hardest), how many spanners do you think this job is for a DIYer?
Thanks
Mark
Thanks
Mark
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