Ok before I start getting flames to hell. I don't have a diesel and I don't intend on putting a dump valve on one but I need a bit of help on an internet argument that I'm about to lose. The argument is about putting dump valves on diesels and can be found Here on a facebook gorup Although I think its a closed group. Also I'm well aware that I'm a child trying to prove a point to someone on the internet but hes an "engineer" for garrett and is adamant that a dump valve will make a tdi feel way better and has done so on all of his previous diesels.

 

Basically I know how diesels work, but as It turns out I also don't. So a couple of questions.

 

1) My understanding is, all the throttle and power is controlled by fuel so there is no need for a throttle butterfly like on a petrol turbo as any positive pressure will just work its way through the cylinders and out the exhaust. However when I go and look at something such as  This which does seem to have a butterfly. Whats up with that?

 

2)Why do diesels make the pigeon noise when you put a straight through exhaust on them? True "compressor stall" comes back through the air filter (as it has to go back through all the Intake pipework and spin the turbine blades the other way causing the choppy air/fluttery sound) and sounds much better than the diesel pigeon noise I hear on the straight piped tdi's near me. Is this because my original theory is correct and the excess air is coming out the exhaust and getting cut up by the turbo blades on the exhaust side but not actually causing the turbine to spin in reverse (because the exhaust gasses don't get sucked back through the cylinders?)

 

3)On my brief google search I have hear talk of variable vanes on tdi turbos or some magic like that. Does this apply to diesels and dump valves?

 

Thanks in advance for Reading Here are some quotes from the argument. The guy I'm arguing with will be called "chump" in these quotes and also theres a third guy who set him off

 

 

 

3rd Guy - "Dumpvalve is pointless on a Diesel engine! They don't have butterfly's that close"

 

Chump - "But they still create boost , and therefore back pressure which stalls compressor on over run and changing gear. Every diesel I've ever fitted a dump valve to it's improved driveability. Although on a vnt turbo it would be pretty pointless as the turbos vanes shut to free wheel turbo"

 

3rd Guy - "You only get compressor stalls on petrols when running high boost and when you change gear because the butterfly closes and boost builds up between there and the compressor... Hence the dumpvalve to empty boost to avoid wear to the turbo"

 

Chump - "Ok Jamie and eddy, as a engineer working for garrett for 10 years I kno fk all! You carry on looking at each other's cocks!"

 

Chump - "Put a boost gauge on a diesel and tell me compressor stall doesn't happen! Come back when your out of nappies"

 

Chump - "Omg, so back pressure and compressor stall is better for a turbo than free wheeling ready to come on boost when it's needed hahahhahahahahahhbbBbBbBbbBbBbbull****" <- Totally random!?

 

4th GUY - "Can I fit 1 on my 110 non pd 1.9 gttdi golf"

 

Chump - "If it's got a boost pipe that will take a t-piece it can be done And I put £100 on that ur car will drive better"

 

ME - "Ok CHUMP Clearly works for Garrett and knows full well that the majority of domestic diesels have no throttle plate as its all controlled by fuel. When you cut the fuel all that manifold pressure just keeps on going through the cylinders and out the other side and it does it pretty fast. To stick a standard VTA dump valve on a diesel would be counter productive. But I shouldn't argue with the "engineer" that works for garett...the company that is well known for making dump valves and fuel injection components. Plus the few people who do waste their time fitting a dump valve to a diesel still have a **** sounding diesel with some blinged up piece of metal that sounds like a deodorant can to go with it. If you want a nice sounding dump valve (i think they all sound a bit naff tbh) then get a petrol car."

 

Chump - "Vag Diesel engines, pd, ppd and even the newer common rail all have butterflies, 2000 and newer bmw diesels have swirl flaps that open and shut part of manifold. Vovlo Diesel engines have butterflies, Peugeot group do as well. The diesel 24hr hdi endurance car had dump valve, to stop compressor stall lol. If you have heard any wagon with a straight thru exhaust or even a diesel runnin high boost , you can hear the compressor stall, some people call it pigeoning. It's funny, I had a mg Zr Td many moons ago with a derv doctor dump valve, increased driveability and turbos were lasting longer, a lot longer. Dump valve sound pretty good to. When you 18"

 

 

 

Help?

 

EDIT: I apologise for my comment about diesels sounding naff. Please ignore it for the purpose of this argument.

Edited 17 April, 201412 yr by Disiesel

I can't really comment as I don't know but if you like arguments you should join splitter scuffers

Not arguing back at this point would p1ss him off more tbh

I don't know enough about the subject matter to comment, but I was under the impression that they are indeed counter-productive for the Mk1 vRS Fabia...  I'm sure someone on here with the proper technical knowledge will be along at some point to confirm/deny. I know they are frowned upon on here, even if I am a chav and actually like the noise secretly!!

 

However, the last line in Mr Chump's quotation is a little baffling.... '....and turbos were lasting longer, a lot longer.'  The question is, how quickly does he apparently go through turbos!?! Every 5k miles by the sounds of his comment!

I like how he himself says VNT turbos don't benefit at all, then says all VAG diesels will benefit...

The reason they are pointless on VAG TDI engines is that they have a variable vein turbo. So when the car no longer needs boost the veins inside the turbo move and the boost drops... Hence you don't need a dump valve as there's nothing to 'dump'.

Phil

That "throttle body" linked to is actually the anti shudder valve. It cuts off the air supply to the engine to shut it down cleanly.

 

As you said, there is no throttle plate to control the amount of air going into the engine, whatever air is in the system (boosted or not) will just go into the cylinder and out the exhaust, making a dump valve useless.

Ok, thanks for the input guys. I just didnt want to find out I was indeed wrong but my basic diesel knowledge is good enough in this case.

 

Anyone able to answer number 2 for me? Its not part of the argument i'm just curious as to why it happens.

The only diesel that sounds good with a dump v/v, Scania V8......

http://www.youtube.com/watch?v=rQSZwij9Gog

see here

 

http://tdiclub.com/TDIFAQ/TDiFAQ-6.html#e11

Don't want to get all boring but all manufactures spend millions developing engines/turbo systems so I'd leave it alone.

And dumping excess pressure is surely the wastegates job??

And dumping excess pressure is surely the wastegates job??

 

It is, but diesels don't build up excess pressure as they continuously suck through as much air as you can throw at them.

Hang on a sec, there could be an element of true to the argument of fitting a dump valve for increased efficiency even though a dump valve is not needed, if you suddenly come off throttle and go into overrun there is no need for any pressurised air at all so it's more beneficial for the compressor turbine to run in a vacuum because it will stay spinning faster for longer which aids spool up after the throttle is reapplied. The Garrett engineer is correct when he says you do get compressor stall on diesels when you come off the power, it's far ess prominent on vnt stuff though.

Oh god, dump valves as driveability aids. :(

 

There may be something to it but every true British person and motorist should stand again it by god!!!

Don't want to get all boring but all manufactures spend millions developing engines/turbo systems so I'd leave it alone.

And dumping excess pressure is surely the wastegates job??

 

wastegate is there to bleed off exhaust gas to regulate boost pressure. VNT turbos don't have a wastegate

I can say this with 100% certainty... engineers dont like to proved wrong, and are argumentative until WD40 pours out their ears. Dump valves are the most pointless "addition" to a diesel engine. Its already been sais why, so I won't repeat it. There is no pressure to release, not enough to dispense. Come on the pete's sake... we are talking about a diesel engine, not a highly stressed petrol turbo engine here. Having a dump valve, is like blowing up a straw into a massive hot air balloon. Not much effect...

 

I think the best mod for diesels, like the "CHUMP" are these....

 

http://www.soundracer.se/?p=98

 

Then maybe, he can pretend its a V8 and fiddle with his crotch at the 'lights....