Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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This was being discussed a while ago, and a few people were saying its fine to fit an atmospheric DV on a vag engine, I and others were saying its not, heres the reason
A modern engine management system, ie the Bosch Me unit fitted to 1.8T's has "adaptive" learning on the fuel, ignition and airflow side.
Because Me is a Torque based structure it's calculation of engine torque verses driver demand is critical to the driveability of the car and it's performance / durability.
When you fit a "leak" in the intake system (open circuit valve) the original calibration of the MAF sensor to manifold and cylinder filling modeling will not corespond. However due to the 20% allowance in the long term adaptive values the ECU will relearn you engine and "leak"
At idle the inlet model calculated airflow will exceed the MAF meters measured output, and depending on the state of your particular components - ie MAF ageing / contamination, throttle plate leakage, Fuel tank purge vapour concentration this may, or may not push the adaptive to it's 20% limit. If it hits the limit the ME unit will run in FMEM mode (Failure mode and effects management) causing reduced system efficiency. The Me unit will use the switching signal from the lambda sensor to return fuelling to lambda 1, storing the correction as a map agaisnt airflow. and add this correction to the fueling calc when operating at non closed loop conditions, ie WOT, fuel injector reenstatment (after overrun shut off, traction control intervention etc.) Now depending on how you drive and how sensative you are this may or may not be felt by the driver during certain manovevers. The throttle plate position will also learn the new airflow to maintain control of idle speed, but you may notice poor engine load rejection, ie turn on the aircon and the engine speed varries etc. or engine speed flares on starts or when operating PAS when parking.
However in all cases this will result in "incorrect" fueling. Now by "incorrect" i mean, not as the manufacturer intended. A post MAF leak will cause rich operation initially, but the adaptives will pull fuel out and become negative. This tends to cause a rich to lean spike on tip outs and other throttle transient. Now it is extremely diffucult for an untrained observer to spot these effects as they occur mainly on throttle transients, when the average drive may not notice. Therefore you could say "why do i care?". Well, any AFR excursion from the intended fuelling set by the manufacturer will result in non-standard engine operation. because of the adaptives this is unlikely to cause immediate engine problems, but over the course of time will change things like catalyst ageing, exhaust and turbo charger valve durability etc. Manufactures spend millions accruing miles on development fleets so hopefully the customers don't get landed with big bills as time goes on, and with most modern cars life'd at 150k miles (min design life) this is a big task.
It is unlikely that this will result in any performance loss, as at WOT the system is open loop, but you may see the result of an open circuit valve oas over fueling on gear changes etc. (a tell tail puff of black smoke is what you can see, a 1200 degC Catalyst is what you can't see, as excess fuel when injection reenstates and excess air from overrun shut off period combine in cat)
Now as you can see this is a seriously complicated subject and i haven't even mentioned the dreaded EOBD or OBDII words yet. Typically Bosch Me units have approximately 9000 calibratable parameters (constants, maps etc) and an engine calibration program will take a team of 8 calibration engineers 18 months to do the basic mapping and OBD validation. These days it's no problem to do the basic fuel and spark mapping, maybe 4 weeks on a midlimit engine on a dyno, but the diagnostics and emmisions devs takes years.
Moral or the story, before you start playing with something you don't understand, find someone who does!(And not just thinks they do!)
(for anyone thinking, "hey what makes me such an "expert" on this subject?" then i'd better mention the last 10 years i've spent as a senior calibration engineer at Cosworth and Prodrive!)
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StuartVRS
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Registered: 9th Feb 03
Location: Bromley Common, Greater London
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Interesting info, but as i said, i go by my experiences and that of people i know, worked for me and has worked for others.
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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yeah it just points out about the long term effects that you might not be seeing yet
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Adam-D
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Registered: 11th May 02
Location: Cheshire
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summary?
is it good or bad to fit a atmospheric d'v on a vag engine
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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according to that, bad
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dave17
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Registered: 3rd Sep 02
Location: Greater London
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summary would be super
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CorsAsh
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Registered: 19th Apr 02
Location: Munich
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Summary - Don't fit one.
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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Ok summary of what hes saying
The VAG ecu's have a learning ability which takes into account several factors and adjusts the fueling/airflow to suit.
Introduce an open air DV, this has the effect of acting as a leak on the system.
In the worst case short term scenario the car will go into limp home mode, and generally be undrivable. (but this may not happen)
In the long term this leak will cause the car to overfuel, and the learning ability of the ecu will counteract and pull too much fuel out so the car underfuels.
This is so small that anyone else who is not very experienced will not notice and over tiem ageing of the engine and things like cat will come about a lot quicker
[Edited on 28-02-2006 by Corsa_Sam]
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StuartVRS
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Registered: 9th Feb 03
Location: Bromley Common, Greater London
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My main argument with people about these is the fact people say they dont work at all. I dont know about the long term effects, but i did over 50k miles in the audi, most of that with atmospherics on and didnt have any DV related problems.
Dave - Summary is simple, Atmospherics are not the best for long term engine reliability.
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vibrio
Banned
Registered: 28th Feb 01
Location: POAH
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the main fact is that VTA valves reduce performance
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Gavin
Premium Member
Registered: 3rd Apr 02
Location: West Midlands
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i'd stick to the re-cir DV
pew pew pew pewwwww
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jammo20
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Registered: 17th Nov 03
Location: in your mum
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im having this problem at the mo i have a 2000 golf turbo with jabba sport
remap 220bhp and its fast as fook but it has a bailey dv atmosperic (sp) fitted,
and i have been told thease valves only work on agu coded engine but as
stuart said his worked fine so does mine but the more i read about this
subject i have found out the only work ok on cable throttle engines but my car
is a arz code (the very first of fly by wire which ive been told that it is a
glorified agu lump with fly by neway wot im trying to say is my car has 220bhp
with rolling road print out with the bailey fitted but if been told if i go back to recirc dv it will be a differnt car btw i bought it like it
[Edited on 28-02-2006 by jammo20]
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jammo20
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Registered: 17th Nov 03
Location: in your mum
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sorry bout shit post i done it in quick reply so could see it come out gash lol
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vibrio
Banned
Registered: 28th Feb 01
Location: POAH
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the engine code is irrelavent. your creating more lag using a VTA
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whitter45
Member
Registered: 15th Nov 02
Location: Norton
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stick with recirc and fit DV in reverse as standard orientation is done to make it quieter
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beattie17
Member
Registered: 13th Dec 02
Location: perth Drives: 02 ibiza 20v turbo
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Ive had an Atmospheric on my ibiza and done about 10k n no problems! changed bk to recirc 1 cause car feels quicker! And drives smoother
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Cybermonkey
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Registered: 22nd Sep 02
Location: Sydney, Australia
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all FPV,Ford Falcon XR6/XR6 Turbo and XR8 models adapt themselves over time according to how they are driven. the turbo engines can also sense if the driver needs extra power, and increases boost momentarily where its needed.
The ECU also ups the boost in very hot conditions so you dont loose power 
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3CorsaMeal
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Registered: 11th Apr 02
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didn't read it, but is it about the temp of the air being recirc'd being warmer than if an atmospheric is used?
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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quote:
Originally posted by Cybermonkey
all FPV,Ford Falcon XR6/XR6 Turbo and XR8 models adapt themselves over time according to how they are driven. the turbo engines can also sense if the driver needs extra power, and increases boost momentarily where its needed.
The ECU also ups the boost in very hot conditions so you dont loose power
this isnt talking about power loss, wether you get a power loss is debatable, it is saying that a VTA can cause excessive wear on certain engine components due to inconsitent fueling and compensation of this by the ECU
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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3cm i think your getting confused with EGRvalves 
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James_DT
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Registered: 9th Apr 04
Location: Cambridgeshire
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quote:
Originally posted by beattie17
Ive had an Atmospheric on my ibiza and done about 10k n no problems! changed bk to recirc 1 cause car feels quicker! And drives smoother
So, no problems but you feel the car drives better on a recirc?
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3CorsaMeal
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Registered: 11th Apr 02
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quote:
Originally posted by Corsa_Sam
3cm i think your getting confused with EGRvalves
no, the air thats recirculated with a recirc value is hotter than the air used if your dumping to atmosphere
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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the air around my ass is hot when im dumping into the toilet
[Edited on 02-03-2006 by Corsa_Sam]
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Cybermonkey
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Registered: 22nd Sep 02
Location: Sydney, Australia
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quote:
Originally posted by Corsa_Sam
quote:
Originally posted by Cybermonkey
all FPV,Ford Falcon XR6/XR6 Turbo and XR8 models adapt themselves over time according to how they are driven. the turbo engines can also sense if the driver needs extra power, and increases boost momentarily where its needed.
The ECU also ups the boost in very hot conditions so you dont loose power
this isnt talking about power loss, wether you get a power loss is debatable, it is saying that a VTA can cause excessive wear on certain engine components due to inconsitent fueling and compensation of this by the ECU
yeah i wandered a bit in that post, but i mentioned about the ECU learning and adapting to driver style
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whitter45
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Registered: 15th Nov 02
Location: Norton
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DV fitted in reverse
Don't use any other apart from a recirc
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