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TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old February 25th, 2003, 14:16   #1
chefdiesel
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Join Date: Jan 2002
Location: Belgium
Default surging ???

Hello,

I have been playing around with turbochargers on diesels lately.
A 1.9TD with a turbocharger (non VNT) from a Volvo 2.5L 140 hp Diesel was plumbed together.
The turbocharger is a KKK unit that normally makes 10psi of boost. We installed a bleed off to increase the boost pressure. Where the steel tube is fixed on the turbine housing we installed a small orifice (+-1mm) in order not to blow off too much air. Then the tube has a T-piece installed, one leading to the wastegate and another tube (with an orifice of about +- 2.5mm) dumping into the air filter.

The thing is running 20psi of boost (fuel pump also modded) and is going really strong.

BUT, it makes a very weird sound when shifting or (to a lesser degree) when backing off the throttle.
This sound can best be compared to that of a big turbocharged diesel truck when shifting ("Pioew"). It is so loud that it can be heard about 100m from the car (everybody looks when I shift [img]images/icons/smile.gif[/img] )
The sound is higher pitched when the boost pressure was higher prior to shifting.

Could this be surging ?
Can it be that the turbo still is pushing to much air when I get off the trottle ?

CU

Stefan
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Old February 25th, 2003, 15:03   #2
LanduytG
 
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Join Date: Sep 2001
Location: Greenfield, IN
Default Re: surging ???

In a way that is a surge. What is happening is you let off the throttle fast and the compressor is making more air than the engine can take in. So what happens is the air stops and reverses and gives you a big wosh sound. My 95 GM 6.5TD does this and it has 160K on the clock. I bet you can hear it whistling as well when its making so good boost.

Greg
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Old February 26th, 2003, 10:31   #3
chefdiesel
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Join Date: Jan 2002
Location: Belgium
Default Re: surging ???

Hello,

No, I don't hear the turbo whistling at all, only when shifting (even when boost is as low as 5psi).

I wonder if in a normal (non bleeded turbo diesel setup) the waste gate is pushed open while shifting ?

CU

Stefan
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Old March 12th, 2003, 13:57   #4
IowaA4TDI
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Join Date: Mar 2003
Location: Omaha, NE
Fuel Economy: 1st tank: 52mpg
Default Re: surging ???

That almost sounds like that turbo has a BOV (blow off valve) - but that would mean it came from a gasser...!

The diesel shouldn't cause that much of a surge because there are no throttle plates closing to suddenly shut off the incoming air. I've heard of "barking" a turbo on TDR forums - but these are guys running 50+psi...
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Old March 13th, 2003, 01:15   #5
Captain_Chaos
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Join Date: Oct 2002
Location: aa
TDI(s): aa
Default surging ???

Quote:
Hello,

I have been playing around with turbochargers on diesels lately.
A 1.9TD with a turbocharger (non VNT) from a Volvo 2.5L 140 hp Diesel was plumbed together.
The turbocharger is a KKK unit that normally makes 10psi of boost. We installed a bleed off to increase the boost pressure. Where the steel tube is fixed on the turbine housing we installed a small orifice (+-1mm) in order not to blow off too much air. Then the tube has a T-piece installed, one leading to the wastegate and another tube (with an orifice of about +- 2.5mm) dumping into the air filter.

The thing is running 20psi of boost (fuel pump also modded) and is going really strong.

BUT, it makes a very weird sound when shifting or (to a lesser degree) when backing off the throttle.
This sound can best be compared to that of a big turbocharged diesel truck when shifting ("Pioew"). It is so loud that it can be heard about 100m from the car (everybody looks when I shift <img border="0" title="" alt="[Smile]" src="images/icons/smile.gif" /> )
The sound is higher pitched when the boost pressure was higher prior to shifting.

Could this be surging ?
Can it be that the turbo still is pushing to much air when I get off the trottle ?

CU

Stefan
Can't you get a sound file of what it sounds like? Sounds to me like you've got a 'howling' turbo like the old rally cars used to have (not sure if they still do, im not really a huge rally fan these days)...I'm unsure of what causes it though..probably something to do with excessively high boost, but 20psi isn't that high *confused*
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Old March 18th, 2003, 14:37   #6
TorqueMonster
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Join Date: Mar 2003
Location: Norway
Default surging ???

Had the same thing on my 1990 Golf GTD! This car had the "Banzai" approach; disabeled the wastegate, blocked the pop-off on the intake manifold(YES, they have one!), IC, and adjusted the pump until it smoked BAD when revving at standstill !!
Oh, the car had 250.000km when this was done, still lives 100.000 later with same mods
The point is, it would make EXACTLY that POW sound when shifting gears, I liked that sound! That is, until I found out why ......it was an exhaust leak not very visible before actually driving with boost
in my case it was 20cm downstream of the turbo outlet.
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