Thoughts on Dump Valves
10 July 2001, 06:34 PM
#1
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A well covered subject, I know, but I have done some searching around and I still have a few questions.
Been thinking about putting a dump to atmos DV on my MY00 UK Scoob. I was thinking of using the Bailey Motorsport one, but I've had a chat with them and apparantly it is not so simple with the MY00 cars. The other alternative is the Forge version, which I know I can get from Scoobysport for around £120. Excluding the silly money jap versions - any other thoughts??
Cheers
Chris
[This message has been edited by Chris L (edited 10 July 2001).]
Been thinking about putting a dump to atmos DV on my MY00 UK Scoob. I was thinking of using the Bailey Motorsport one, but I've had a chat with them and apparantly it is not so simple with the MY00 cars. The other alternative is the Forge version, which I know I can get from Scoobysport for around £120. Excluding the silly money jap versions - any other thoughts??
Cheers
Chris
[This message has been edited by Chris L (edited 10 July 2001).]
10 July 2001, 07:28 PM
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Why bother, it beats me why people bother with toys like that. There are better ways to spend your money, or are you like a neighbour of mine (young lad with an escort turbo) who thinks the noise impresses people?
10 July 2001, 07:49 PM
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As Jim says they're are just for noise on the MY99/00 cars, as the standard item is huge and sufficient for quite a few ponies. But if you like the sound, that's another story.
WREXY.
WREXY.
10 July 2001, 09:18 PM
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Supposed to sound good,which IMOis a good enough reason - alternatively buy a full de-cat system and put an induction kit on - same noise and very cool!
Matt
Matt
10 July 2001, 09:30 PM
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I'm afraid I have to disagree with Jim and Wrexy. When I first got my Forge for my MY00, I didn't think it made much difference. A little while ago I took it off and immediately I noticed it just didn't boost up as quick as it did with the dump valve IMHO.
Regards
Steve
Regards
Steve
10 July 2001, 09:43 PM
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I have a bailey vent-to-atmosphere dump valve on my 95 WRX, and to be honest, I wish I hadn't bothered. Because of it venting to atmosphere, it can be difficult, particularly at motorway speeds, to come off of full throttle smoothly. As you lift off, the car almost lurches before power cuts fully with quite a jerk. I'm looking for a suitable recirculating one to replace it.
Leigh
[This message has been edited by Leigh (edited 10 July 2001).]
Leigh
[This message has been edited by Leigh (edited 10 July 2001).]
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10 July 2001, 10:41 PM
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I fitted a Forge dump to atmo to my MY99 (full decat SS) and instantly the car felt quicker, faster pickup. Turbo lag had almost gone.
Unfortunately the Forge isn't that loud with a decat SS but it does the job and keeps me smiling
DaveW
Unfortunately the Forge isn't that loud with a decat SS but it does the job and keeps me smiling
DaveW
10 July 2001, 10:48 PM
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Thanks guys for the comments - as you rightly point out - it IS my money and I choose to spend it as I wish. I'm well aware of the perceived benefits (or otherwise) and the noise issues. I have my reasons for doing this and I'm interested in peoples experiences with various makes. I already have a full de-cat system and I'm just 'tweaking' things at the moment - largely in the name of experimentation, rather than any serious attempt to massively increase boost pressure / spool up times etc etc.
Thanks for your input, keep 'em coming.
Cheers
Chris
Thanks for your input, keep 'em coming.
Cheers
Chris
11 July 2001, 08:36 AM
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Chris, I've just put a K&N induction kit on (and justified it to the other half 
- even more miraculous) and you get a bit of noise plus a fairly noticeable performance increase particularly, and this I find strange, in hot weather.
- even more miraculous) and you get a bit of noise plus a fairly noticeable performance increase particularly, and this I find strange, in hot weather.
11 July 2001, 10:04 AM
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Chris
I've got a forge (vent to atmosphere) for sale as from Friday (bought 2 months ago from SS) if that's the way you decide to go.
Reason - I have to use the APS BOV with their fmic which is finally being fitted on Friday
Rich.
I've got a forge (vent to atmosphere) for sale as from Friday (bought 2 months ago from SS) if that's the way you decide to go.
Reason - I have to use the APS BOV with their fmic which is finally being fitted on Friday
Rich.
11 July 2001, 05:37 PM
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Chris,
I know you are not thinking about the Jap stuff but the HKS sqv is excellent. With the full decat flames are a nap if thats what you're after. Also has the benefit of different inserts being available to change the sound it makes.
Having said that I quite like the sound it makes as is.
If you buy another make and find you are growing a bit weary of the sound it has there's not alot you can do about it bar change to another type/ back to standard.
Alan
I know you are not thinking about the Jap stuff but the HKS sqv is excellent. With the full decat flames are a nap if thats what you're after. Also has the benefit of different inserts being available to change the sound it makes.
Having said that I quite like the sound it makes as is.
If you buy another make and find you are growing a bit weary of the sound it has there's not alot you can do about it bar change to another type/ back to standard.
Alan
11 July 2001, 05:44 PM
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I tried the Forge vent to atmos and found it not bad at all, it seemed to make some difference, but i cant quite put my finger on it. I have just changed to a HKS SQV and i can definateley say that it has made the car feel much more snappy, perhaps its holding boost between changes more efficentley. The sound may not be to everybodies taste, but i like it. By the way, its on a STI V5 Type R with lots of other mods
Paul
Paul
12 July 2001, 08:17 AM
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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by Jay m A:
<B>Admit it Chris, you want flames
Justin[/quote]
Damn, I've been found out
Cheers Rich - you have email mate.
Chris
<B>Admit it Chris, you want flames
Justin
[/quote]Damn, I've been found out
Cheers Rich - you have email mate.
Chris
12 July 2001, 10:28 AM
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After fitting you could be known as 'Chris (oh look me bumpers melted) L'.
Chris 'sneezing car' L
If you want it, go for it. I would like a listen after it's fitted.
Will it happen before the next meet?
P. (Evenings still iffy).
12 July 2001, 10:37 AM
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I have the Blitz blow off valve on mine and apart from the noise, which I love by the way and due to this alone won't go back to the stock item, noticed no difference in performance, hence my comments in my first post on this thread.
WREXY
WREXY
12 July 2001, 11:40 AM
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I thought dump to atmosphere valves had an adverse affect on turbo life expectancy.
I also though that from 98 onwards the standard item was perfectly adequate performance wise.
I have considered one purely for the audiovisual enhancement they provide.
Andrew...
I also though that from 98 onwards the standard item was perfectly adequate performance wise.
I have considered one purely for the audiovisual enhancement they provide.
Andrew...
12 July 2001, 01:01 PM
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Apart from causing your engine to run very rich (when venting) and hence producing exhaust flameouts, and the noise, is there anything else for or against a vent to atmosphere dump valve as opposed to a recirc one ?
I do like the idea of flames myself -novel way of getting rid of tailgaters
[This message has been edited by Eric Chadwick (edited 12 July 2001).]
I do like the idea of flames myself -novel way of getting rid of tailgaters
[This message has been edited by Eric Chadwick (edited 12 July 2001).]
12 July 2001, 02:13 PM
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[QUOTE]Originally posted by AndrewC:
[B]I thought dump to atmosphere valves had an adverse affect on turbo life expectancy.
I also though that from 98 onwards the standard item was perfectly adequate performance wise.
You do know what thought did, don't you?
[B]I thought dump to atmosphere valves had an adverse affect on turbo life expectancy.
I also though that from 98 onwards the standard item was perfectly adequate performance wise.
You do know what thought did, don't you?
12 July 2001, 02:34 PM
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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by Eric Chadwick:
<B>Apart from causing your engine to run very rich (when venting) and hence producing exhaust flameouts, and the noise, is there anything else for or against a vent to atmosphere dump valve as opposed to a recirc one ?[/quote]
Against is that when you come back on the throttle, the ECU is expecting the air that's been dumped to atmosphere to be still in the system, and therefore the fuelling strategy will be out - though it should be rich as it will fuel for the volume of air that has been dumped too.
Could someone please check my logic here? It would be unusual for me to be right twice in a day.
<B>Apart from causing your engine to run very rich (when venting) and hence producing exhaust flameouts, and the noise, is there anything else for or against a vent to atmosphere dump valve as opposed to a recirc one ?[/quote]
Against is that when you come back on the throttle, the ECU is expecting the air that's been dumped to atmosphere to be still in the system, and therefore the fuelling strategy will be out - though it should be rich as it will fuel for the volume of air that has been dumped too.
Could someone please check my logic here? It would be unusual for me to be right twice in a day.
12 July 2001, 03:14 PM
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Some people have told me that dump to atmosphere DV can cause lumpy idling. I don't have first hand experience so I can't comment.
I have a Forge recirculating dump valve. Why??
Well if you take off the standard one blow off valve, and try to compress the spring by hand, you'll find it goes easily! Try that with a Forge one! I though my fingers would break before the DV would give!
Also I'm running more boost pressure than the standard one is designed to cope with.
Any downsides?? No flames!
Andy
I have a Forge recirculating dump valve. Why??
Well if you take off the standard one blow off valve, and try to compress the spring by hand, you'll find it goes easily! Try that with a Forge one! I though my fingers would break before the DV would give!
Also I'm running more boost pressure than the standard one is designed to cope with.
Any downsides?? No flames!
Andy
12 July 2001, 07:42 PM
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Andy
The standard dump valve is not only held shut by the spring but also by the boost pressure being applied to the piston on the top of the valve.
The fact that the spring is softer than on the forge is not relevent.
Also people seem to think that if you up the boost you need to uprate the dump valve because the extra pressure will push the valve open.
This is not true.I agree that when on boost the pressure does try to push the valve open but as mentioned above the same pressure is applied to the piston on the top of the valve.
This piston has a larger surface area and so will always exert a stronger closing force than the opening force.What this means is that the increased boost actually makes the valve seal better than before.
People also seem to think that a dumpvalve is fitted to improve performance,it isn't,it is there to reduce the maximum pressure that the turbo and intercooler/pipework are subject to thus improving their life and the cars longterm reliability.
I can understand that people want to fit a dump to atmosphere D/V so they get flames and the noise but I don't understand why people change to an aftermarket recirc type?.
What does puzzle me is the effect of fitting a front mount intercooler because now there is far more pressurised air in the system to be dumped(maybe three or four times the volume of a standard car)Where does all this air go?,can a standard dump valve flow this much air?I doubt it!.
Andy
The standard dump valve is not only held shut by the spring but also by the boost pressure being applied to the piston on the top of the valve.
The fact that the spring is softer than on the forge is not relevent.
Also people seem to think that if you up the boost you need to uprate the dump valve because the extra pressure will push the valve open.
This is not true.I agree that when on boost the pressure does try to push the valve open but as mentioned above the same pressure is applied to the piston on the top of the valve.
This piston has a larger surface area and so will always exert a stronger closing force than the opening force.What this means is that the increased boost actually makes the valve seal better than before.
People also seem to think that a dumpvalve is fitted to improve performance,it isn't,it is there to reduce the maximum pressure that the turbo and intercooler/pipework are subject to thus improving their life and the cars longterm reliability.
I can understand that people want to fit a dump to atmosphere D/V so they get flames and the noise but I don't understand why people change to an aftermarket recirc type?.
What does puzzle me is the effect of fitting a front mount intercooler because now there is far more pressurised air in the system to be dumped(maybe three or four times the volume of a standard car)Where does all this air go?,can a standard dump valve flow this much air?I doubt it!.
Andy
12 July 2001, 10:12 PM
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I've just dabbled a wee bit with the stock BOV, and a Forge atmo one....found a few interesting characteristics.
1. My stock BOV doesn't like 18 psi. It started to release boost, but just on 3rd gear... 
2. The Forge one seems to cause some idle problems, ISC value on the link changes all the time...and since the link is kinda static this makes it a MAJOR pain in the nether regions to get idle stable...at set value.
I've spoken with Forge today, and they're a bit puzzled as well, we're suspecting a faulty o-ring, they're sending me a "maintenance kit"...I will let you hear what I find out.
In the meantime...stay *away* from atmo BOV's, go for a recirc one...trust me.
/J
1. My stock BOV doesn't like 18 psi.
It started to release boost, but just on 3rd gear... 2. The Forge one seems to cause some idle problems, ISC value on the link changes all the time...and since the link is kinda static this makes it a MAJOR pain in the nether regions to get idle stable...at set value.
I've spoken with Forge today, and they're a bit puzzled as well, we're suspecting a faulty o-ring, they're sending me a "maintenance kit"...I will let you hear what I find out.
In the meantime...stay *away* from atmo BOV's, go for a recirc one...trust me.
/J
13 July 2001, 08:59 AM
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From Forge Motorsport
SecretAgentMan
I am sorry that you have this problem, and that this is an isolated incident.I will do my best to make this right for you.
FYI
The Forge valve will not cause any MAF or idle problems , we have had no problems with " flame outs " and would not reccommend fitting a valve to obtain this effect.
The reason we offer a recirc valve is because we have had many instances of the OEM valve failing , this is expensive to replace at £ 250.00 a time .
The Forge valve is servicealble and guaranteed for life !!
This valve also has a larger internal diameter that allows you to release more air between gear changes , giving you a better turbo response.
We now supply this valve to many main dealers.
If anybody with a Forge valve that has any problems , please contact me.
SecretAgentMan
I am sorry that you have this problem, and that this is an isolated incident.I will do my best to make this right for you.
FYI
The Forge valve will not cause any MAF or idle problems , we have had no problems with " flame outs " and would not reccommend fitting a valve to obtain this effect.
The reason we offer a recirc valve is because we have had many instances of the OEM valve failing , this is expensive to replace at £ 250.00 a time .
The Forge valve is servicealble and guaranteed for life !!
This valve also has a larger internal diameter that allows you to release more air between gear changes , giving you a better turbo response.
We now supply this valve to many main dealers.
If anybody with a Forge valve that has any problems , please contact me.
13 July 2001, 09:35 AM
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Peter,
Welcome to the board - it's great to have suppliers provide their input.
Thanks for explaining why go for a replacement item, particularly to replace a failed unit with a better manufactured product at a better price!
One question regarding your statement that you can dump more air between gear changes (bear with me I: for a recirc valve, is air dumped into a closed loop system? If it is, how would fitting a replacement valve allow more air to be dumped as the volume of the system would remain the same.
I hope you see where I'm coming from on this one. Does the forge system include larger pipework to allow more air to be retained in the system? Or does this not matter?
Thanks in advance,
Nick.
Welcome to the board - it's great to have suppliers provide their input.
Thanks for explaining why go for a replacement item, particularly to replace a failed unit with a better manufactured product at a better price!
One question regarding your statement that you can dump more air between gear changes (bear with me I: for a recirc valve, is air dumped into a closed loop system? If it is, how would fitting a replacement valve allow more air to be dumped as the volume of the system would remain the same.
I hope you see where I'm coming from on this one. Does the forge system include larger pipework to allow more air to be retained in the system? Or does this not matter?
Thanks in advance,
Nick.
13 July 2001, 09:43 AM
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Welcome Peter!
It'll be interesting to see what happens when the bov gets some new seals.
I've done some further testing today, and it seems better if I give it a bit of stick, driving in econo-mode seems to enhance my particular problem.
Cheers
/Jerry
It'll be interesting to see what happens when the bov gets some new seals.
I've done some further testing today, and it seems better if I give it a bit of stick, driving in econo-mode seems to enhance my particular problem.
Cheers
/Jerry
13 July 2001, 09:59 AM
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The recirculating ones vent back into the inlet after the MAF, hence the problem that occurs with *some* cars and *some* atmo BOV's...yo're letting metered air out of the system, air that the ECU is aware of, which makes the car run rich, the ecu detects this and leans the mixture out.
Imagine this scenario...full chat 2:nd gear, liftoff, full chat 3:rd gear...the BOV releases air on the gearchange, the car runs rich, the ecu leans out, you get back on the loud pedal, and the car runs lean for a split second, when you get on boost.
This is bad on some cars, not on others.
I have to add to this that I had *NO* problems at all with the stock ECU and the atmo Forge BOV, my idle phenomenon is a bit strange...
Either the JECS ecu is so fast and adaptive I didn't notice that the idle stepper motor was adjusting continuosly, or the BOV has just started to leak on the vacuum side.
/J
Imagine this scenario...full chat 2:nd gear, liftoff, full chat 3:rd gear...the BOV releases air on the gearchange, the car runs rich, the ecu leans out, you get back on the loud pedal, and the car runs lean for a split second, when you get on boost.
This is bad on some cars, not on others.
I have to add to this that I had *NO* problems at all with the stock ECU and the atmo Forge BOV, my idle phenomenon is a bit strange...
Either the JECS ecu is so fast and adaptive I didn't notice that the idle stepper motor was adjusting continuosly, or the BOV has just started to leak on the vacuum side.
/J