DUMP VALVES, BLOW-OFF VALVES - OFFICIAL THREAD
26 July 2013, 12:22 PM
#93
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What they seem to be trying to say is that:
By using a recirc, the pressure remains in the system, just in a different place, therefore you don't need to pump up pressure all over again, cos it is still there. Which is sort of correct. How you prove the figures they claim, is rather open to discussion.
Competition turbo cars are all about trying to reduce lag by storing the pressure wherever they can. That will give better throttle response, assuming it works they way they expect it to.
Look at the start line of a rally and any modern rally car. They used to be sitting there revving the engine like crazy to be able to drop the clutch and power off the line. Now there is nothing happening at all until the start guy goes 5,4,3,2 and then they floor it and it instantly kicks in. That boost must be there somewhere.
David
By using a recirc, the pressure remains in the system, just in a different place, therefore you don't need to pump up pressure all over again, cos it is still there. Which is sort of correct. How you prove the figures they claim, is rather open to discussion.
Competition turbo cars are all about trying to reduce lag by storing the pressure wherever they can. That will give better throttle response, assuming it works they way they expect it to.
Look at the start line of a rally and any modern rally car. They used to be sitting there revving the engine like crazy to be able to drop the clutch and power off the line. Now there is nothing happening at all until the start guy goes 5,4,3,2 and then they floor it and it instantly kicks in. That boost must be there somewhere.
David
26 July 2013, 12:52 PM
#94
Scooby Regular
Thread Starter
What they seem to be trying to say is that:
By using a recirc, the pressure remains in the system, just in a different place, therefore you don't need to pump up pressure all over again, cos it is still there. Which is sort of correct. How you prove the figures they claim, is rather open to discussion.
Competition turbo cars are all about trying to reduce lag by storing the pressure wherever they can. That will give better throttle response, assuming it works they way they expect it to.
Look at the start line of a rally and any modern rally car. They used to be sitting there revving the engine like crazy to be able to drop the clutch and power off the line. Now there is nothing happening at all until the start guy goes 5,4,3,2 and then they floor it and it instantly kicks in. That boost must be there somewhere.
David
By using a recirc, the pressure remains in the system, just in a different place, therefore you don't need to pump up pressure all over again, cos it is still there. Which is sort of correct. How you prove the figures they claim, is rather open to discussion.
Competition turbo cars are all about trying to reduce lag by storing the pressure wherever they can. That will give better throttle response, assuming it works they way they expect it to.
Look at the start line of a rally and any modern rally car. They used to be sitting there revving the engine like crazy to be able to drop the clutch and power off the line. Now there is nothing happening at all until the start guy goes 5,4,3,2 and then they floor it and it instantly kicks in. That boost must be there somewhere.
David
If you were running a car with a VTA valve or a recirc that wasn't up to the pressure then running one of their uprated recirc valves would make a difference, in fact I would imagine it would make a huge difference going off your previous post about the lambda crapping itself lol.
But if I'm planning on fitting one of them to my Impreza Cosworth that runs 21psi or so I'm led to believe, then surely it won't make any difference whether the spring strength is 25psi rated (OEM) or 110psi (theirs) or 190psi (Perrin) ?
Last edited by thenewgalaxy; 26 July 2013 at 12:54 PM.
26 July 2013, 01:58 PM
#95
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This is what I had interpreted it as also, but to me it seems a little naughty.
If you were running a car with a VTA valve or a recirc that wasn't up to the pressure then running one of their uprated recirc valves would make a difference, in fact I would imagine it would make a huge difference going off your previous post about the lambda crapping itself lol.
But if I'm planning on fitting one of them to my Impreza Cosworth that runs 21psi or so I'm led to believe, then surely it won't make any difference whether the spring strength is 25psi rated (OEM) or 110psi (theirs) or 190psi (Perrin) ?
If you were running a car with a VTA valve or a recirc that wasn't up to the pressure then running one of their uprated recirc valves would make a difference, in fact I would imagine it would make a huge difference going off your previous post about the lambda crapping itself lol.
But if I'm planning on fitting one of them to my Impreza Cosworth that runs 21psi or so I'm led to believe, then surely it won't make any difference whether the spring strength is 25psi rated (OEM) or 110psi (theirs) or 190psi (Perrin) ?
26 July 2013, 02:45 PM
#96
Scooby Regular
Thread Starter
I can just imagine the hypothetical conversation between the parts
MAF "Righto Lamdba, there's all your air "
DV "Nrrrrgh"
Lambda: "Woohoo I'm getting high"
Turbo "whoosh"
DV "I eat raw ox liver three times a day"
MAF "Lambda's acting drunk again"
Turbo "flutter"
Pistons "ARRRRGH!"
26 July 2013, 03:19 PM
#97
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Well put Sir. You're getting the hang of this.
The old motor racing adage was.
When I hit 2 bar of boost the rev counter read £8000.00
The old motor racing adage was.
When I hit 2 bar of boost the rev counter read £8000.00
02 August 2013, 11:10 AM
#99
Scooby Regular
Thread Starter
Okay so this morning someone started a new dump valve thread, this time asking where to get them.
I think I now know why people hate dump valves so much.
It is because the people that want to fit them and make loud noises generally have the attitude to match.
I will be updating the front page with some suppliers of dump valve kits after I have searched through the existing threads of which I know there are hundreds.
It is because the people that want to fit them and make loud noises generally have the attitude to match.
I will be updating the front page with some suppliers of dump valve kits after I have searched through the existing threads of which I know there are hundreds.
02 August 2013, 12:09 PM
#100
Scooby Regular
[My 2 p]
So my experience of VTA was in the Blue Oval RST world "back in the day", and I never heard of any failures due to VTAs, or any lag, misbehaving, or poor running come to think of it either. One would assume that's due to the Bosch KE Jetronic MFI system. Even then, I didn't like VTA's much.
Based upon that, I would imagine that since engine technology and fuel injection systems have changed, the tolerances have become less in terms of loss of air/fuel, and modern ECU's don't like the imprecision?
One could speculate that older turbos were "weaker" in construction, and releasing pressure off of a MAP based system on high boost with a VTA was the fastest way to save the Turbo vanes, note: that's pure speculation on my part.
Although there's no empirical evidence of VTA's on Modern MAF based fuel setups killing engines, is it really worth the risk? Especially for those of us behind the wheel of 2.5 non-forged motors. Personally, I won't move away from the stock item unless there's an immediate reason to do so, (I.e. 25psi+, Standard Re-circ failure, or forging with intent to go over 25psi in the future), and even then it would be a re-circ, simply because I don't like the sound of VTA's.
Then again, I don't like rap music either, but that's not to say that no-one should listen to it... As long as they're out of my earshot!
[/My 2 p]
So my experience of VTA was in the Blue Oval RST world "back in the day", and I never heard of any failures due to VTAs, or any lag, misbehaving, or poor running come to think of it either. One would assume that's due to the Bosch KE Jetronic MFI system. Even then, I didn't like VTA's much.
Based upon that, I would imagine that since engine technology and fuel injection systems have changed, the tolerances have become less in terms of loss of air/fuel, and modern ECU's don't like the imprecision?
One could speculate that older turbos were "weaker" in construction, and releasing pressure off of a MAP based system on high boost with a VTA was the fastest way to save the Turbo vanes, note: that's pure speculation on my part.
Although there's no empirical evidence of VTA's on Modern MAF based fuel setups killing engines, is it really worth the risk? Especially for those of us behind the wheel of 2.5 non-forged motors. Personally, I won't move away from the stock item unless there's an immediate reason to do so, (I.e. 25psi+, Standard Re-circ failure, or forging with intent to go over 25psi in the future), and even then it would be a re-circ, simply because I don't like the sound of VTA's.
Then again, I don't like rap music either, but that's not to say that no-one should listen to it... As long as they're out of my earshot!
[/My 2 p]
Last edited by Frenchwood; 02 August 2013 at 12:11 PM.
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