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Discussion Starter · #1 ·
Lovely as my SW is, there are still things I would like to improve. One thing that frequently bugs me is the turbo lag on changing gear whilst accelerating hard.

Would a dump valve be as effective at combatting this on a relatively low-revving JTD as it is on a turbo-charged petrol engine?
 
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I'm told they serve no purpose whatsoever on a diesel...uless you want that lovely whoosh sound of course :D

wrinx
 

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wrinx said:
I'm told they serve no purpose whatsoever on a diesel...uless you want that lovely whoosh sound of course :D

wrinx
that whoosh sound on a deisel :eek: behave yourself man...

if you want your alfa to sound like a subaru or a renault 5 gtt, then get one of these....am i right in saying a dump valve only releases the pressure during gear changes to keep the turbo spinning...
i also have heard you cannot get them for a diesel car..
 
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You are correct....they release the pressure....and they can be sourced, friend of mine has one on his Pug...specially made.

wrinx
 

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No Dosh - When Alfa Nige came to remap my car late last year he had a BMC CDA (Carbon Dynamic Airbox) on his 2.4 JTD Splurtclaggon.
He reckoned he was getting around 215 bhp with loads of extra torque. Would the CDA work as well with your PSI (?) chip?
 

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No Dosh said:
Lovely as my SW is, there are still things I would like to improve. One thing that frequently bugs me is the turbo lag on changing gear whilst accelerating hard.
1st to 2nd isn't so great on mine, but after that the power delivery is pretty seamless I reckon. I wonder if your fettling has moved the power bands?
:confused:
 

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Discussion Starter · #7 ·
The "problem" only really comes into play when working the car very hard through the gears. Although power delivery is there from around 2000rpm, when changing up having taken the car to around 4,000rpm it usually drops to around 2500, smack bang in the middle of the power. What tends to happen though is that there is a noticable lag before the power comes on. It's definitely the turbo stalling rather than a remap thing, so more power from a CDA airbox or different remap won't effect it.

It's only a half-second thing, but it still sometimes allows the prey a moment of relief before I start reeling them in again :D
 

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Does a dump-valve always result in the boy-racer noise? Can't you get one that dumps into the exhaust system or something?
 

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bazza said:
Does a dump-valve always result in the boy-racer noise? Can't you get one that dumps into the exhaust system or something?
Not sure. I suspect all the after market ones sound like Ivor the Engine.
:rolleyes:
Bazza - out of interest, what dials do you have in the Cooooooopeee? Us sensible car types ;) were pondering over the dials in the 159 and it looks like it has an oil temp gauge in the centre console.
:cool:
 

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bazza said:
Does a dump-valve always result in the boy-racer noise? Can't you get one that dumps into the exhaust system or something?
i think you can get silent ones so you dont have to have that steam engine sound as you change gear :rolleyes:
 

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I was offered such valve for 300Euros but Other then the sound it servces no purpose on the diesel :cool:

p.s:there must be something wromng with your car...you should feel the turbo lag only below 2000rpm but at more then 2500rpm you car should be flying...
 

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Discussion Starter · #14 ·
kgb said:
I was offered such valve for 300Euros but Other then the sound it servces no purpose on the diesel :cool:

p.s:there must be something wromng with your car...you should feel the turbo lag only below 2000rpm but at more then 2500rpm you car should be flying...
When accelerating through 2500 there's no problem. It's only when an upchange takes me from around 4000rpm to 2500rpm that I get the hesitancy. Having driven "laggy" cars in the past it's the same feeling.
 

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No Dosh said:
When accelerating through 2500 there's no problem. It's only when an upchange takes me from around 4000rpm to 2500rpm that I get the hesitancy. Having driven "laggy" cars in the past it's the same feeling.
please do not fit a dump valve. there should not be any turbo lag at
2500 rpm,do not know if you have another type of problem,but mine
is remapped it pulls from 2000 rpm, past 4500 rpm with no lag.
how many miles have you done, mine has done 100 k and had a new
turbo fitted at 80k before i bought it.not saying the turbo's on its
way out,but the dump valves a no no,just incase it makes the problem
worse.
 

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First thing I noticed when I got my JTD was the lag changing gears and I thought about a dump valve, over time though it seems I have learned to drive around the problem and I haven't really noticed it since. I don't see why a dump valve wouldn't be just as effective on a JTD as a it is on a petrol far as I can tell the boost path is the same as a petrol ( I haven't looked hard so feel free to correct me) , the boost levels are no doubt just as high so can a diesel not suffer from the same issues as a petrol in that the boost pressure comes back on itself and stalls the turbo which creates lag? How is the turbo controlled on a JTD, it has no vacuum controlled wastegate, does it? is there the same sort of vacuum occuring in the inlet manifold as there is on a petrol? (I know bugger all about diesel, just that its cheap to run :lol: ) Just thinking of what you would need to plumb a DV into.
 

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I guess there are ways to install a dump valve on JTD as well however It serves only the purpose of the sound. The dump valve is supposed to "dump" the exessive turbo pressure at the moment when you close the throttle e.g. while changing gear. Now when it comes to diesels I've understood that you don't have a butterfly valve and hence there is no such problem with a sudden increase in turbo pressure as air will flow through the inlet manifold all the time. It could be that the bost pressure regulating mechanism (e.g. the wings in the VNT turbo) are are jerky and in the need of cleaning or something else (leak?) causing this lag.
 

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As far as I know there is a dump valve on the JTD...just try accelariting and then release the gas...and listen...you may open your window for better sound...VAG TDI engines have very nice sound on letting the pressure out but they use KKK turbo's which are worse then the Garret used in Alfa,MB,BMW
 

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Isn't the lag just caused by the difficulty in getting the turbo to spin up...a twin turbo set up with help ;)
 

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Discussion Starter · #20 ·
kgb said:
As far as I know there is a dump valve on the JTD...just try accelariting and then release the gas...and listen...you may open your window for better sound...VAG TDI engines have very nice sound on letting the pressure out but they use KKK turbo's which are worse then the Garret used in Alfa,MB,BMW
I understood that noise was the wastegate. Which is another idea I have..... :D
 
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