[Guest]

I have inverted my recirv valve, and apart from the incredible noise
(I also have the HKS racing suction kit), the car definitely comes
on boost harder through gear changes......WICKED.

However, I have heard rumours that this may not be the safest mod
around.

My question is why ? Does anyone have a technical reason why this
mod should not be done , just that one of the UK's leading tuners
told me it is perfectly safe. I have been running witht the inverted
valve for a good 4000 hard miles, no probs at all.


Justin Foden

 

[Guest]

Basically, by reversing the recirc valve you are stopping it from functioning so the valve is always shut - I can give a detailed explanation but it is fairly confusing to write down!!. This gives compressor stall which can cause premature turbo wear and in extreme cases, the turbine to shatter.

IIRC R5 turbo's, Cossies and amp; RS turbo's don't come with any sort of recirc or dump valve as standard (if anyone know different please correct me on this one) so it could be this reasoning that your tuning company has basically told you to reverse it.

 

[Guest]

Thanks for answering.

Im not convinced though. When inverted, the valve is DEFINITELY working,
you can hear it chattering away when you change gear, it just makes
a different sound to the tshhhhhhhhhh when its the standard way up !

So, I shall carry on being inverted, and if my turbo blows, ill let y'all know

Unless some genius can give me a solid reason why I shouldnt.




Justin

 

[Guest]

Justin,

It's not the valve that's chattering, it's your turbo stalling. I had a friend with an R5 turbo about 6 years ago and he got the same sounds when sticking on a different air filter. The R5's come without any sort of recirc valve and the replacement filter bolted directly onto the turbo's compressor intake gave it that rally car chatter noise!.

To prove the valve isn't working, block off the recirc valve and see what difference it makes - I'm sure it will be exactly the same as what you're getting now.

 

[Guest]

doesn't actually seem to be affecting held boost when throttle is wide open in normal position

will give appearance of being faster as will reduce leak at part throttle

dataloging again

if you really want to bogie then fit a 3 port

later
andrew

 

[Guest]

BTW Cossies did have a recirculating dump valve as standard
- a little black plastic effort made by bosch I think?

 

[Guest]

Not that it really matters but the small turbo Escort Cossy (T25) had a dump valve built in to the turbo itself.

 

[Guest]

Looking at the icons, Yellow5 and Lightspeed are my long lost twin brothers.

 

[Guest]

Hi brother!!!!

 

[Guest]

questions...

why does the standard valve leak? Surely its just a spring acting on a plug type arrangement similar in principle to a radiator cap? I can see it leaking a tiddly bit but bugger all compared to total Turbo flow.

Given the spring/plug design when reversed it wont work at all. Therefore turbo compressor will surge. This is bad. Multilmillions are spent on compressors preventing surge. Turbo life will be severly limited.... DO NOT DO IT.... Or am I talking ###### (again)?

 

[Guest]

Oli,
The turbo will stall and not surge. This means that it will stop spinning and in some cases, spin in reverse. Repeated hitting of the compressor blades with a back pressure / flow may cause damage to both the blades and the bearings eventually.

Andy

 

[Guest]

Original Post:
why does the standard valve leak? Surely its just a spring acting on a plug type arrangement similar in principle to a radiator cap? I can see it leaking a tiddly bit but bugger all compared to total Turbo flow.

As I see it, the thermostat is a better analogy. The radiator cap is not designed to 'pass' during normal operation, only when operating conditions are well outside normal will it open. The thermostat however is designed to open and close during normal engine running, and as it approaches it's preset temperature it begins to creep open until fully open at the preset temperature. Substitute temperature for pressure and you have why the cheap OEM dump valve will leak.

Original Post:
Given the spring/plug design when reversed it wont work at all. Therefore turbo compressor will surge. This is bad.

The vacuum supplied from the intake plenum is sufficient to overcome the spring and open the valve, it just happens much more suddenly making smooth driving more difficult. Theres also the small matter of compressor stall but that has been explained elsewhere.

 

[Guest]

I will try and post a diagram of the normal and reversed dump valve, when you actually see how it works then it makes sense.
The only thing that is an unknown is whether the vacuum can open the reversed dump valve (due to boost pressure forcing it shut). If Chunky says it does then I believe him

 

[Guest]

ok,
Well it was Mark at MAD Developments that told me it was *PERFECTLY* safe,
and I have a LOT of respect for Marks opinion.

If Mark is on this list, can you set the record straight please ????


Justin

 

[Guest]

Presumably, if you reverse the valve and get compressor stall, the turbo will take longer to spool up when you get back on the gas i.e. more turbo lag than normal (with the valve in the normal position, I assume the turbo just slows down and is still spinning when you get back on the gas). If I'm right (unlikely ), then that's a bad thing. Someone please enlighten me!

 

[Guest]

If you read the very first post, I said by inverting your valve there is more Ooomph between
gear changes, this is not what id expect if my compressor was stalling.....



Justin

 

[Guest]

I think you are getting more oomph between gears because of the extra pressure build up, which would normally be dumped by the valve, and you are changing gear quick enough before the turbo stalls.

Just an idea.

 

[Guest]

HH6,
Hopefully these (very basic) diagrams explain what you mean. These have just been knocked up by me on Word in about 10 mins so don'y take the p!$$ too much please..... And I hope I can link to them correctly as well.

Andy

http://groups.yahoo.com/group/evo/files/Modded Inlet/BOVopn.doc

 

[Guest]

Yup, thats the way I see it although I always thought the vacuum would overcome the boost and open the valve anyway, now I'm not so sure. Is there any way to test this conclusively?

 

[Guest]

Chunky,
There has to be some way of working out what happens but a lot will depend upon the design and exact location of the plunger within the valve and the strength of the spring etc etc...
Seeing as how I'm a chemcial engineer and supposed to know about stuff like this (gas flow through pipes and valves etc...) I could probably come up with some complex equations that decide what happens but I recommend that the only way to conclusively test (and not put my engineering skills to the test !!) would be to put some form of airflow measuring device in the recirc line and then run the car and see if it measures any flow through the line when the valve is reversed.

Andy