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Engine Specific Info and Questions => TDI Engine -General Info => Topic started by: superman293 on July 14, 2006, 06:13:11 pm
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Is it possible to have a blow off valve on a turbo charged diesel
thanks
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Anything with enough $$$ is possible, but since the air is not throttled or controlled and when you sundenly let off the throttle just the fuel is reduced, the air flows in the same as always the turbo isn't restricted and doesn't surge (for all you people who like to nit pick, yes I am aware that there is a point with really high PR that a case could be made for one, but anyone who has built a diesel to that point would not be here asking that question). So in this case there is NO point.
If you just want the lame sound, burn it on to a CD and play it to yourself in the car :roll:
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http://www.bd-power.com/ram/product.php?pn=BD%20TurboGuard&tt=ram
With a manual transmission and decent fueling, you can 'huff' the turbo on every shift. I can do it with my '94 Ram/Cummins that has an automatic with ease.
Matt
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Diesels don't need a BOV. Anyone who knows how diesels work will be laughing their butts off at someone with a BOV on their diesel.
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I saw a few ads on Ebay.co.uk for TD/TDI/HDi dumpvalves kits which were basically a very expensive sliver box (housing a change over solinoid I believe) a micro switch, some wires a bit of tube a few fittings and a dumpvalve with T for around £300>. I decided to see if one could be done on the cheap using parts easily found in a scrap yard.
A mate of mine had a bailey motorsport piston dumpvalve with a t-piece lying around his shed off a petrol turbo project so that was the start of the project.
Firstly you need a source of vacume as a diesel doesent hve a throttle plate (well except on a ford transit diesel with EGR) simplest way is to use the vacume pump for the brake servo so using a check valve with two take off of an old 88 Golf 1.6 auto im braking I then had my vacume source.
Now I needed a way of turning this vacume on and off when the throttle comes to rest. I found an EGR switch that fits on the LDA off a Passat TDI, and I also used an EGR solinoid off the same Passat.
I fitted the LDA mounted EGR switch rigged it to a continuity meter and tested it by pressing and letting go of the accelerator and found it did the opposite of what I wanted, it closed the circuit when the throttle was pressed and opened it when the throttle was at rest.
So I started wiring and plumbing in the dump valve using a change over relay as a "not gate" by using the normally closed (57a) terminal of the relay
I once fitted I took it down the road to test it and found although when the the throttle returned to rest the dump valve would open as there was no boost in the pipe operating the dump valve it would be forced open by boost from the turbo resulting in a leak of boost.
To rectify this I added a second EGR solinoid valve off a VW TDI that was tapped in to the manafold to LDA pipe and connected this to the normally open (57) terminal of the relay the used a T connector to connect the "Vacume" solinoid and the "Boost" solinoid to the dump valve.
Once again I took it out on the road to test and found it worked, and cost me a few pounds in parts.
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this is pretty interesting, could you draw some sort of a circuit to help show what all your creation does, and how it works, it's hard to understand, heres a little td controller thing i came up with, it's really not that useful, but just to give you an idea of what i am asking for from you
(http://img.photobucket.com/albums/v306/Trev0rbr/tdcontroller.jpg)
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also, does it only work when you let competely off the pedal?
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correct me if i'm wrong but this is your setup here?
(http://img.photobucket.com/albums/v306/Trev0rbr/dieselbov.jpg)
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ok i see why my drawing wouldn't work, it's more or less your first setup, i don't understand what you changed though
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Plumbing diagram
(http://img.photobucket.com/albums/v112/A19VUU/DumpValvePlumbingDiag.jpg)
Wiring diagram
(http://img.photobucket.com/albums/v112/A19VUU/DumpValveWiringDiag.jpg)
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ok i get it now
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buy really the vacuum is not needed
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the thing i still don't get is what is the lda switch on? and what makes it the lda switch go on and off
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buy really the vacuum is not needed
So whats going to quickly snap open the dump valve?
The pressure of the boost on the piston?
Nope that would would only open a little bit, I didnt loose that much boost with the first version I made, you would end up with a quiet pffffftt noise rather than a PETUSSSSSSH.
the thing i still don't get is what is the lda switch on? and what makes it the lda switch go on and off
The "LDA" switch is the throttle switch thats mounted on the lda (thinking about it really I should call it a throttle switch or EGR switch) its fitted to EGR equiped cars.
(http://www.home.earthlink.net/~rps1976/Images/Diesel/Smog/Smog105410470.jpg)
pic "borrowed from one of VWRacer's posts
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you don't need vacuum because anytime there is more pressure on in the intake line than in the "signal" line the piston opens, i'm sure the vacuum helps to open it much mroe quickly , but i don't really see it being completely necessary
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I deactivate the dump valve with a dash mounted switch wired in series to the positive side of the vacuum solenoid as 99.9% of the time I don't want particularly want to hear a dump valve going off when I change gear or back of the throttle.
When the vacuum solenoid is turned off the dump valve doesn't open, this is on a 1991 1.6 IDI SB engine running 0.8-1bar boost using a Baileys single piston dump valve.
I think unless your running substantial levels of boost the dump valve wont open without vacuum being applied.
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the dump valve is a differential device, it opens if the force exerted by the air pressure from the turbo is more than the spring force on the other side.
plus, as the spring is on the same side as the piston that controls the opening of the DV, if that spring is weak enough it doesnt need vacuum, but it works like the BOV. it makes a good swoosh, but its pointless and that can damage the turbo by overspinning.
my opinion: dump valves are pointless in a diesel.
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my opinion: dump valves are pointless in a diesel.
I agree, when I had drilled my airbox and fitted a free flowing air filter, I took my mate out for a spin, he asked me if that sound was the turbo spooling up, then said you should fit a dump valve, there's one in my shed.
This was an exercise just to see if I could make up a system to actuate a dump valve from scrapyard parts, it has only been activated half a dozen times.
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the dump valve is a differential device, it opens if the force exerted by the air pressure from the turbo is more than the spring force on the other side.
plus, as the spring is on the same side as the piston that controls the opening of the DV, if that spring is weak enough it doesnt need vacuum, but it works like the BOV. it makes a good swoosh, but its pointless and that can damage the turbo by overspinning.
my opinion: dump valves are pointless in a diesel.
the dump valve is more safety on the motor, and i can definetly see it over spinning the turbo, but since with a bov you'd be letting off the throttle so it definetly won't over spin it
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the dump valve is a differential device, it opens if the force exerted by the air pressure from the turbo is more than the spring force on the other side.
plus, as the spring is on the same side as the piston that controls the opening of the DV, if that spring is weak enough it doesnt need vacuum, but it works like the BOV. it makes a good swoosh, but its pointless and that can damage the turbo by overspinning.
my opinion: dump valves are pointless in a diesel.
the dump valve is more safety on the motor, and i can definetly see it over spinning the turbo, but since with a bov you'd be letting off the throttle so it definetly won't over spin it
if that spring is weak enough it doesnt need vacuum, but it works like the BOV
and by BOV I mean that device that keep us from getting more than 0.7~8Bar from stock TDs. I too agree that mouted properly its a safety device for a gasoline engine.
by the way GTD. that was serious thinking! your solution is really simple!