Wasn't sure whether to post here or in the ask a tech section but it's a very general query.

I don't know too much about them, my mate has one on his R5 and was ultimatley the reason the std turbo blew up!

Is it possible to get them for modern cars (ie a Fab vRS) or do the ECUs regulate pressure so would they one be pointless.

Could be wrong, but I don't think it's possible on the Fabia as the ECU controls the boost. I know it was possible on the old Scooby, but you'd also have to budget for some guages so you had a bit of warning if things weren't quite right!

Chris

Wasn't sure whether to post here or in the ask a tech section but it's a very general query.

I don't know too much about them' date=' my mate has one on his R5 and was ultimatley the reason the std turbo blew up!

Is it possible to get them for modern cars (ie a Fab vRS) or do the ECUs regulate pressure so would they one be pointless.[/quote']

Hi

The problem with aftermarket dump valves is that they drop air out of the system without the engine management knowing. This can lead to bursts of overfuelling, resulting in premature engine wear (bore washing). Not too sure what the situation would be in a diesel, but cannot see a benefit from fitting a dump valve. At best, you could have a plume of smoke evey time you backed off the throttle enough to open the valve, and at worst you could seriously phase the drive by wire system in the Fabia, possibly poisoning the CAT prematurely.

Chris

bleed valve and dump valve are two different things

Not too sure what the situation would be in a diesel, but cannot see a benefit from fitting a dump valve. At best, you could have a plume of smoke evey time you backed off the throttle enough to open the valve, and at worst you could seriously phase the drive by wire system in the Fabia, possibly poisoning the CAT prematurely.

There's no dump valve on a diesel (much to the vRS boys dissapointment )..... delroy is talking about a bleed valve which increases the turbo's boost pressure

Chris

Well actually there are some dump valves but they are only for that ssssst sound, they dont serve the purpose like on petrol engines.

Well actually there are some dump valves but they are only for that ssssst sound, they dont serve the purpose like on petrol engines.

only ones operated by electricity for about

For what it's worth, i wouldn't bother with a bleed valve at all. Too many of my mates cars have blown using these primative "performance devices".

As for dump valves, it would just attract the wrong sort of attention in my view.

bleed valve and dump valve are two different things

Hi

Not too sure what you are referring to with the term bleed valve? Anyone care to explain?

Chris

I'm not sure how they work but they can be used to increase the boost the turbo is running.

A dump valve doesn't increase the boost they just allow the turbo to be kept spinning during closed-throttle conditions and therefore, theoretically enable full-boost to be achieved sooner.

Not too sure what you are referring to with the term bleed valve? Anyone care to explain?

Something like this I believe....

Chris

Something like this I believe....

Chris

It is a hole in the wastegate actuating sensor circuit (or a fault / bodge as it would be known in the trade). If I remember correctly, Essex boys used to fit a restrictor and vent into the wastegate actuator pipe of early Ford turbo cars so the wastegate did not open as early. Touble was that the resrtiction would introduce a delay into wastegate actuation. Often the boost would go further than the ignition retardation could handle and pinking would be rife.

I tuned a Metro Turbo (worst car in the world? Dont get me started) with a similar degree of finesse when the wastegate actuator hose blew off one day.

Personally, for the frankly bargain cost of a remap, I would do any prospective warming up of the engine "properly" and avoid the potential hassles that introducing sensor fooling leaks could cause.

Chris

Hi

Not too sure what you are referring to with the term bleed valve? Anyone care to explain?

Chris

There are two different devices which do the same job really, only one of which is correctly called a 'bleed' valve. The other is a manual boost controller.

A bleed valve sits in the pipework to the wastegate and by way of a threaded taper allows a proportion of the air passing through to 'bleed' away to atmosphere. this allows the ecu to believe it's sending, say, 1 bar of pressure to open the wastegate, but the wastegate may remain shut as on the other side of the bleed valve there is only say 0.8 bar. Modern ECUs will detect the fact that too much boost is being generated and often shut down or go into a 'limp' mode, rendering a 'bleed' valve much less worthwhile. Work well on 'old' turbo cars though (petrol or diesel)

A Manual Boost Controller does the same job, in a different way. It allows the wastegate to open very quickly, but also keeps it firmly shut until boost pressure reaches the preset level. It would normally use a sprung ball or flap to hold back the pressure in the wastegate pipe until it reaches the 'cracking' pressure of the valve, at which point it 'cracks' open, and pressure hits the wastegate actuator. As soon as it falls, the MBC closes, which can lead to an 'on, off, on, off' wastegate operation, resulting in boost spikes. However, properly employed a good quality MBC can work very well on certain vehicles (most notably in my experience the Rover 2.0 T16 turbo engines)

There are two different devices which do the same job really' date=' only one of which is correctly called a 'bleed' valve. The other is a manual boost controller.

A bleed valve sits in the pipework to the wastegate and by way of a threaded taper allows a proportion of the air passing through to 'bleed' away to atmosphere. this allows the ecu to believe it's sending, say, 1 bar of pressure to open the wastegate, but the wastegate may remain shut as on the other side of the bleed valve there is only say 0.8 bar. Modern ECUs will detect the fact that too much boost is being generated and often shut down or go into a 'limp' mode, rendering a 'bleed' valve much less worthwhile. Work well on 'old' turbo cars though (petrol or diesel)

A Manual Boost Controller does the same job, in a different way. It allows the wastegate to open very quickly, but also keeps it firmly shut until boost pressure reaches the preset level. It would normally use a sprung ball or flap to hold back the pressure in the wastegate pipe until it reaches the 'cracking' pressure of the valve, at which point it 'cracks' open, and pressure hits the wastegate actuator. As soon as it falls, the MBC closes, which can lead to an 'on, off, on, off' wastegate operation, resulting in boost spikes. However, properly employed a good quality MBC can work very well on certain vehicles (most notably in my experience the Rover 2.0 T16 turbo engines)[/quote']

The manual boost controller I am familiar with. The devices I have seen are inserted into the wastegate actuator pipe in manual analogue systems and pop the wastegate open when boost gets to the desired level, in the same way as the manufacturers ECU controlled ones do now. As you say, the problem with aftermarket ones is the propensity to produce dropouts and surges in boost.

Surely doing it the electronic way with rolling road for feedback is the best way to go. These manual add ons where always sort of effective, but more folks blew up than had success. I remeber when my dads mate had Cosworth Sapphires, he used to blow em up on a regular basis trying to get the Cozzie to go as fast as the old mans 24V Senator.

If I understand correctly, the vRS turbo is a variable geometry unit, so I would imagine this (bleed valve) kind of device causing more harm than good.

Chris

Bleed valves can cause nasty boost spikes aswell as they arent controlled, seen many a turbo shat itself over this, mainly on R5's and RS Turbos.

Whoooooosh - BANG rather than the nice noises you'd want then

I'd prefer a remap over this type of thing ANY day. Much more controlled, safety still built-in, and more gentle on the hardware

I thought it was the other way round.. I've read a lot of people have used these MBC's to control the spiking the original boost control system makes (n75 valve). Correct me if I'm wrong though.. :confused: at least there are a lot of people around the net who have installed a mbc after remap because the stock boost control system makes nasty spikes with upped boost. Mainly with 1.8T engines, dunno about diesel though..

only ones operated by electricity for about