View Full Version : Dump Valve Question?
CupraTgirl
12-11-2002, 13:34
I really want to get a different Dump Valva for my Ibiza Cupra although i have been told that the ones that make the 'Whooshy' noise damage the turbo and the engine etc etc
So is it true or is there a good one you can get that makes that noise?
:confused:
LEO LION R
12-11-2002, 13:43
try this http://www.seatcupra.net/forums/showthread.php?s=&threadid=4870&highlight=dump+valves
and i found loads more in the search which will help.
:cheers:
Some light reading for you too. :p
FORGE DV REVIEW (http://www.seatcupra.net/reviews.php?descrip=Dump%20Valve%20Information%20Forge%20Review)
CupraTgirl
12-11-2002, 17:07
Do you know anyone who has one and have they had any problems as i have been warned off one that makes a woosh noise by about 4 people?
LEO LION R
12-11-2002, 17:13
Don't get one of those then, the engine's not designed for them to release to atmosphere.
You mans Scooby might have one, but that's a different engine and set up.
:cheers:
the atmospheric dump valve debate has been a long one.
some people have managed to get theirs working on standard cars, some havent. On tuned (chipped) cars its a no go. These trials have been done with the GFB valve.
i have been told by 2 people that there is a HKS one in the states that works on golfs, but its about £300.
http://www.g-force-motorsport.co.uk/HKS/hks_sequential_valve.htm
car is not running and atmospheric DV and is not designed for one, so IMO you should stick with a decent re-circ valve, especially if you plan on chipping the car in the future.
http://www.seatcupra.net/forums/showthread.php?threadid=7509&highlight=dump+valve
Hi CupraTgirl.
I fitted a Forge diverter valve to mine last weekend.
Must say that the car seems a lot happier with this than the standard Bosch unit. Booost seems more readily available whereas the original unit seemed to take an age to come on full boost. Definitely worth the £60 notes I paid for it at Alconbury.
Can't really coment on the whooshy type valves but every now and then I do get the odd whoosh when nailing it 'ard (quite normal, so I'm told). Besides, the difference in the way the car performs now, more than makes up for not having that whhtiishhhhh sound. The way I see it IMO, is that if it was meant to go whhtishhhhhhhh (luv speeling out sound effects, man) then they'd of made it do that as standard.
Don't forget that we've only got ickle turbo's on our cars and they need all the air they can get.
At the end of the day it's up to you. If you really want a whooosher then get one and try it. If it doesn't work out then I'm sure there's somebody out there who'd buy it off you.
If it was my decision though, I'd go the recirc route.
L@ters
Damo:D :D :D
Brokenlegs
13-11-2002, 14:17
Damo,
I see u are going through screens like me. Mine keep stress fracturing and I have got them replaced under warranty what is happening with yours?
As for the Dump valve issue well I am tied between a forge and a H/D bypass valve not sure what to do on this one but is a re-circ type.
Some tuning goodies for 1.8T's on this site
www.impossible-performance.cwc.net/seat_performance.htm
Mark.
Hi Brokenlegs (are they really?).
Yeah, windscreens are a really "Hot Topic" with me at the mo.
I broke the 1st windscreen while cleaning inside the car. I was leaning over the passenger side dusting the dash etc (as you do when it's new), and I clunked me head on the view mirror (damn hard) and took it clean off it's housing (twat!:rolleyes: ). Cracks appeared around the housing and splayed out almost to the bottom of the windscreen by the time it was replaced (3 months later!!!!!).
The 2nd windscreen died after a stone hit it on the motorway (far left hand side, right on the edge of the screen). The crack got bigger and bigger so had to get it replaced.
Now on my 3rd one which took a real hammering at the Alconbury track day and as a result I've got 2 10mm diameter chunks taken out of it, one on the drivers side towards the bottom and the other on the passenger side in the same place.
I could save this one by geting it treated but this one has a pants grey sunstrip across the top and I want the original green one back in, so will eventually get it replaced. Probably after Xmas when funds allow. Fortunately my insurance covers me for up to 3 windscreens per year at £50 a go, although I'd never thought I'd need to use it as much as I have.
What's the story or should I say stories with yours.
:cheers:
Damo:D :D :D
mark sheerin
13-11-2002, 16:57
I'm afraid you cant have the..KITCSHEEEEEEEE (wooshy)
dump valve
The Audi engine needs to recirculate the "waste" turbo pressure and it cant be vented externally.
You can fit a different dump valve but it will still recirculate and not make the noise you desire
:)
P.S I hope my "dump valve" works on the seatcupra night out in leeds on 29th November;)
Brokenlegs
13-11-2002, 17:29
Damo,
Yeah winscreens. Well it was a few months ago when the first one went I got up one moring to find a 2ft crack straight across the drivers side mmmmmmmm, it was fine when i went to bed the night before. I rang seat as it was on a weekend and they said if it was a stress fracture they would replace it so auto winscreens came out and replaced the sceen.
They Guy who was fitting it said these screens are shite they are so thin they break far to easy from memory i think the make up of the screen is 2mm glass then 1mm laminate then 2mm glass he said on these new cars it saves weight but the screens break far to easy and he had replaced several of these screens. I thought considering there is not that many leon's out there this is a high number of screens to be replaced.
The second one went after a mad dash round wales and i hot a big bump then it cracked I dont know if there is just to much flex in the chassis and the screen is the first point of weekness. I have had this happen to me on my old rally car but never a road car. The suspension is standard so i thought there should not be a problem.
So lets see how screen 3 fairs the car is only 6 months old things might settle down with the chassis who knows...........
A screen costs from Auto Windscreens £176 as i had to pay for it then claim it back.
Mark.
Just fitted a forge 007.....works fine :D
Shock_Xe
13-11-2002, 23:38
I had the GFB 2in1 Hybrid Whooshy DV on my Beeza Cupra, Had it on the for 3mths with no problems at all and a lurrrrrvly sound. But my need for speed took over and had it chipped. It didnt like the GFB when chipped (power loss etc etc) so had to replace it with a forge re-circ valve. However if your car is standard, no problems!!! Give it a try well worth it imao .
ibizacupra
14-11-2002, 08:07
<Plug mode>
Forge DV006 and DV007P recirculating piston diverter valves are £74.95 plus £5 carriage from Badger5
<plug mode off>
regards
Bill
Dormouse
14-11-2002, 18:23
Or you can buy my secondhand one £40.
Personally I left the standard one on my R and that produces more than STD BHP and Torque anyway.
Dor.
I really am confused abou the power loss. if your doing a power run the foot is planted so the valve is closed. now if it is leaking then you would loose power but as my forge don't open under 1.6 bar of boost then you must have a doggy shipment. I can understand that teh atmospheric ones may make the car drive poor as the same thing can happen to mine car. the bailey DV 26 makes the car better to drive than the forge
ibizacupra
15-11-2002, 08:13
Originally posted by Dormouse
Or you can buy my secondhand one £40.
Personally I left the standard one on my R and that produces more than STD BHP and Torque anyway.
Dor.
DV has no effect on power or torque.
It can only allow faster action & boost spool up on gear changes.
any other effect is in your mind I think. :p
Bill
ibizacupra
15-11-2002, 08:14
Originally posted by vibrio
the bailey DV 26 makes the car better to drive than the forge
than the forge what.......?
which model?
Just interested. You're talking atmo valves now yea?
Bill
yeah comparing the two twin piston valves. the forge can make the car a bit rough when your changing gear of boost.
Dormouse
15-11-2002, 12:36
DV has no effect on power or torque.
Yes Yes, IIIIII Know that, but i'm simply trying to point out that some people DO think that becuase they don't understand what it does...
I.e Cor!...Sporty Dump Valve! = something To Do With The Turbo = Faster / More Power.
Like i say, i'm using the normal one and am prety happy with it.
dor.
I can't understand how chipped cars don't like atmospheric dump valves??? Could someone explain why?
ibizacupra
15-11-2002, 16:24
Originally posted by Dormouse
Yes Yes, IIIIII Know that, but i'm simply trying to point out that some people DO think that becuase they don't understand what it does...
I.e Cor!...Sporty Dump Valve! = something To Do With The Turbo = Faster / More Power.
Like i say, i'm using the normal one and am prety happy with it.
dor.
More Cheese? :p
:jog:
ibizacupra
15-11-2002, 16:25
Originally posted by LDoR
I can't understand how chipped cars don't like atmospheric dump valves??? Could someone explain why?
Atmo valves by their design vent to atmosphere. They are after the MAF so metered, measured air is vented but the ECU thinks its going through the engine.... problems occur as a consequence.
Some atmo valves also seem to leak on idle also allowing the motor to stall.
regards
Bill
Arse, thats a pain. Wonder if we could move the MAF to a different position????
Dormouse
15-11-2002, 21:39
More Cheese?
Yes please and a bottle of beer too.
dor.
Scoobster
20-11-2002, 19:55
The GFB hybrid blow off valve DOES work on the Ibiza Cupra 20vT, and if it doesn't then I must have been dreaming for the passed few months.
I am running a GFB on my standard (non chipped) Cupra and have NO problems with running it. It takes a little bit of tweaking to get it set nicely so that you don't get any eratic idling (set too slack)or wastegate chatter (set too tight). Once set up it runs sweetly.
There is slightly more lag on the turbo than with the Forge DV007P (have one of those also), but there is less lag with the GFB than you get with the standard Bosch valve.
You get a healthy 'whooooosh' and if running an induction kit or performance panel filter i.e K&N (as I am) then it sounds pretty well, and noticable enough without being annoying (a la escort cossy).
So don't believe everything you hear. I agree that some cars have problems with them (chipped cars), and a full atmospheric valve is not suitable, but the GFB works fine.
Hope this info helps..
So basically the Forge 007 is better? in your opinion
Originally posted by Scoobster
The GFB hybrid blow off valve DOES work on the Ibiza Cupra 20vT, and if it doesn't then I must have been dreaming for the passed few months.
I am running a GFB on my standard (non chipped) Cupra and have NO problems with running it. It takes a little bit of tweaking to get it set nicely so that you don't get any eratic idling (set too slack)or wastegate chatter (set too tight). Once set up it runs sweetly.
There is slightly more lag on the turbo than with the Forge DV007P (have one of those also), but there is less lag with the GFB than you get with the standard Bosch valve.
You get a healthy 'whooooosh' and if running an induction kit or performance panel filter i.e K&N (as I am) then it sounds pretty well, and noticable enough without being annoying (a la escort cossy).
So don't believe everything you hear. I agree that some cars have problems with them (chipped cars), and a full atmospheric valve is not suitable, but the GFB works fine.
Hope this info helps..
Yeah much the same as what the big man here has just said plus I am running one on efectivly a Chipped Ibiza - that is a Ibiza Cupra R is basically a chipped Cupra and im having no probs.
My pal has a Remapped Octavia 20Vt and he's had no probs either.
Scoobster
21-11-2002, 10:36
The GFB works ok with my car, wihtout any problems and it works better than the standard Bosch valve is what I am saying..
The Forge DV007P runs less lag than both of the above mentioned valves, but you obviously don't get the 'whooooosh'.. so there is a slight trade off..
Running the GFB is ok, if you want that turbo noise.. if you want as little lag as possible, then give up on the idea of 'whoooosh' and go for the Forge DV007P..
Hope that makes sense.. ??
Jimmyboy
21-11-2002, 11:41
Originally posted by CupraTgirl
I really want to get a different Dump Valva for my Ibiza Cupra although i have been told that the ones that make the 'Whooshy' noise damage the turbo and the engine etc etc
So is it true or is there a good one you can get that makes that noise?
:confused:
Back to your original question about the whooshy noise there is an alternative. If you speak to Bill he sells Hurricane induction kits, whilst the noise is nowhere near as loud as a proper dump valve you do get a whoosh in between gears which is quite audible from the outside or if you have the windows open. When I fitted mine I drove around with the windows open night and day for the first couple of days and EVEN had the stereo turned down!
CupraTgirl
21-11-2002, 12:23
Ok then
Sounds good because really i want to get it chipped so i definately wont be able to have a proper one on there
Who is Bill?
Is this induction kit good quality (better than K and N or Green Cotton Filters?)
max_torque
21-11-2002, 12:34
While i agree that an open loop (ie vents to atmosphere) is a deffinate none starter on any car with a MAF sensor, i am amazed that anyone can detect any difference in lag between a std Bosch valve and any after market valve. I've been employed to develop turbo engines in a number of cars of the last 7 years, looking at maximising engine and vehicle performance with engine dyno, rolling road, computer simulation, test track etc. And all i can tell you is that they make a different sound. Once you have opened a hole post compressor so that the compressor pressure ratio falls close to zero i have not seen any difference in turbocharger shaft speed or boost build up for various valve / spring combinations. The size of the hole or how fast it opens has such small effects on a CPR that is so close to 0 when the dump valve is open.
But hey - it's your money!:D
CupraTgirl
21-11-2002, 12:52
So in other words you dont think it would be ok if i got a 'whooshy' dump valve and got it chipped?
max_torque
21-11-2002, 13:21
Well you could fit a loud "wooshy" open circuit valve, but the car would run like sh*t and stall, which rapidly becomes a pain in the arse round town! (very, very, hard to look cool bunny hopping down the local high street)
If you want a nice noise, get the air box changed for something like an induction kit that has not got an external cold air pic up (ie filter under bonnet not in a box) Although this will loose you power it will make the dump valve sound louder.
Or perhaps just infect a close friend with the flue virus and get them to sneeze every time you change gear!
I think i would just spend the cash on a nice sounding exhaust back box or system, might just make a bit more power perhaps and sounds nice when you blast past someone. (unless you do lots of motorway miles when loud exhausts are fun for about 5 mins)(sat for 2 hrs in a car going "BAAAAAAAAA" when you are doing 80 mph (70 officer!) is not my definition of fun)
Dormouse
21-11-2002, 13:25
Agree with max_torque on the difference between the forge and the std dump valve.
I am still amazed that soem of you guys can get decent use out of a vent to atmos type valve. I'd really like to see some of that in action...still sceptical, but open to being proved wrong!
Back to your original question about the whooshy noise there is an alternative
Or a drain pipe and attach it to your airbox...hehe
Who is Bill?
He runs a badger sanctury / prison just outside stroud :)
Dor
Cuprasport2000
21-11-2002, 13:27
Originally posted by CupraTgirl
[B]Who is Bill?/B]
OMG!! Who is Bill ???????
Bill is the all seeing, all knowledgable mecca of information concerning all things mechanical. The fantastical tower of information and wisdom that is... Bill.
Also known as just plain Bill from Badger5! He is a regular web rat like us who patrols these forums in search of motorists with unaswered queries.
He can be reached at www.badger5.co.uk although he probably knew you were going to post this thread before even you did.....
:devil:
Dormouse
21-11-2002, 13:33
That's still no excuse for badgernapping.
Dor.
Cuprasport2000
21-11-2002, 13:41
Originally posted by CupraTgirl Is this induction kit good quality (better than K and N or Green Cotton Filters?)
My eyes, my eyes.... I am bleeding from my eyes...
I cannot beleive what I read!! Anything that the great being that be called 'Bill', sells is nothing short of perfect. If bill sells the Hurricane kit then take it as read that this is the best merchandise that money can buy. In fact it was rumoured a while ago in the upper echelons of society that the queen mum had one of this fitted to her Rolls...
'tis true...
max_torque
21-11-2002, 14:03
Talking of royalty
I spent 3 years doing performance development for the Bentley Arnarge T (450 bhp (actually 469) and 875nm (actually 886)).
The connection?
The Queens' new Bentley has "my" engine in it (although she opted for lower 400bhp spec tune)!
(if your reading this Queen Liz, i've got a calibration that gives your car an extra 100bhp!)(that should stick the corgies to the rear window!)
:p
Jimmyboy
21-11-2002, 14:37
Originally posted by CupraTgirl
Ok then
Sounds good because really i want to get it chipped so i definately wont be able to have a proper one on there
Who is Bill?
Is this induction kit good quality (better than K and N or Green Cotton Filters?)
Bill is on here as ibizacupra.
Originally posted by max_torque
Well you could fit a loud "wooshy" open circuit valve, but the car would run like sh*t and stall, which rapidly becomes a pain in the arse round town! (very, very, hard to look cool bunny hopping down the local high street)
If you want a nice noise, get the air box changed for something like an induction kit that has not got an external cold air pic up (ie filter under bonnet not in a box) Although this will loose you power it will make the dump valve sound louder.
Or perhaps just infect a close friend with the flue virus and get them to sneeze every time you change gear!
I think i would just spend the cash on a nice sounding exhaust back box or system, might just make a bit more power perhaps and sounds nice when you blast past someone. (unless you do lots of motorway miles when loud exhausts are fun for about 5 mins)(sat for 2 hrs in a car going "BAAAAAAAAA" when you are doing 80 mph (70 officer!) is not my definition of fun)
Fair play mate you obviously know a lot more about this stuff than me , Christ im a Sales Manager in a Gym not a Fn Machanic but the truth is I havent experenced any of these side effects with the GFB DV. Infact I have recently went back to the standard Bosch one because it was in for a service and It doesnt feel any different.
As I say mate im not saying your talking p_sh beacause you work in the industry and you will know that in theary if shouldnt work but I can assure you it works fine man.
ibizacupra
21-11-2002, 16:38
Originally posted by max_torque
While i agree that an open loop (ie vents to atmosphere) is a deffinate none starter on any car with a MAF sensor, i am amazed that anyone can detect any difference in lag between a std Bosch valve and any after market valve. I've been employed to develop turbo engines in a number of cars of the last 7 years, looking at maximising engine and vehicle performance with engine dyno, rolling road, computer simulation, test track etc. And all i can tell you is that they make a different sound. Once you have opened a hole post compressor so that the compressor pressure ratio falls close to zero i have not seen any difference in turbocharger shaft speed or boost build up for various valve / spring combinations. The size of the hole or how fast it opens has such small effects on a CPR that is so close to 0 when the dump valve is open.
But hey - it's your money!:D
I think the Bosch diaphragm unit suffers from the stiction of the rubber to the housing and this is made worse by its location above the exhaust manifold/turbo and all the heat around there. Its a lazy DV... The lag I guess (not talking a lot here btw, feels slightly more) is possibly some compressor stall/surge type thing by the slight delay between throttle closing and DV opening.
Or this might be compete tosh... :p My theory tho.
I tried my stock DV and did notice a difference in a backward more laggy kind of way.
regards
Bill
ibizacupra
21-11-2002, 16:41
Originally posted by Cuprasport2000
My eyes, my eyes.... I am bleeding from my eyes...
I cannot beleive what I read!! Anything that the great being that be called 'Bill', sells is nothing short of perfect. If bill sells the Hurricane kit then take it as read that this is the best merchandise that money can buy. In fact it was rumoured a while ago in the upper echelons of society that the queen mum had one of this fitted to her Rolls...
'tis true...
LOL :laff:
Blimey!
What have i been missing this afternoon....
(the cheques in the post ;) )
regards
Bill
ibizacupra
21-11-2002, 16:43
Originally posted by max_torque
Talking of royalty
I spent 3 years doing performance development for the Bentley Arnarge T (450 bhp (actually 469) and 875nm (actually 886)).
The connection?
The Queens' new Bentley has "my" engine in it (although she opted for lower 400bhp spec tune)!
(if your reading this Queen Liz, i've got a calibration that gives your car an extra 100bhp!)(that should stick the corgies to the rear window!)
:p
Not so much a Garfield "splat" as a Corgie "splat"
now thats an image which makes me smile :laff:
886nm !!!! Jeeeeez. :eek:
Bill
Cuprasport2000
21-11-2002, 16:44
bored... and bored.
:(
(...oh, and bored)
ibizacupra
21-11-2002, 16:49
http://www.badger5.demon.co.uk/bin/hurricane-1.jpg
Hurricane is a cold air fed induction kit. Cannister (polished one in piccy) has a large cold air feed pipe, which routes to colder air, from either the lower front spolier area, or upper inner wheel arch area like the stock airbox does.
Internal to the cannister is a pleated cotton gauze cone type filter.
Only one left in stock btw.
regards
Bill
Jimmyboy
21-11-2002, 16:54
Bill, just while we're on the subject of Hurricanes, how long do they last before you have to do anything with them? I guess there's no element to replace during a service etc?
ibizacupra
21-11-2002, 17:25
Originally posted by Jimmyboy
Bill, just while we're on the subject of Hurricanes, how long do they last before you have to do anything with them? I guess there's no element to replace during a service etc?
Its between 5000-10000 miles...
I think Tuning Concepts had something in the instructions relating to it.
Its a cotton gauze filter inside, so a degrease, rince and airdry, and a "light" reoiling will clean it up Ok.
Light reoiling mind... :eek:
don't want to kill a MAF
I can get the oil and cleaner fluid if req'd.
regards
Bill
Jimmyboy
21-11-2002, 17:32
I was hoping you were gonna say that it didnt need cleaning until every 100000 miles!
Dormouse
21-11-2002, 18:10
Anything that the great being that be called 'Bill'
Flippin heck Bill, you must be the only person on the site to have groupies.
Whatever next?....
Dor.
cmsmpau1
21-11-2002, 19:20
Hi Cupra Girl
Found this UK dumpvalve that may take you liking. Ive been looking for a wossh valve for ages but have always been told to stear away, but i found this.
I havent bought or fitted one but take a look anyway
http://www.impossible-performance.cwc.net/mk4_latest.htm
P.S If anyone has any reviews on this product could you please make a post or email me at
cmsmpau1@livjm.ac.uk
markpaul300@hotmail.com
ibizacupra
21-11-2002, 20:06
Originally posted by Jimmyboy
I was hoping you were gonna say that it didnt need cleaning until every 100000 miles!
Wot like K&N say... :laff: cos thats a bit misleading....
Same construction as a K&N so maybe I should make up some nonsense like the 100,000 mile thing.
Easy to check, undo the large jubilee clip on the cannister, slide it off 'ave' a butchers @ it (probably perfectly fine), slide the can back into the groove, retighten the jubliee clip and carry on for another (x) miles.
Mines still visually as it was when I first put it on. Now has over 8000 miles on it. :)
regards
Bill
Icecavern
21-11-2002, 22:26
Originally posted by max_torque
While i agree that an open loop (ie vents to atmosphere) is a deffinate none starter on any car with a MAF sensor, i am amazed that anyone can detect any difference in lag between a std Bosch valve and any after market valve. I've been employed to develop turbo engines in a number of cars of the last 7 years, looking at maximising engine and vehicle performance with engine dyno, rolling road, computer simulation, test track etc. And all i can tell you is that they make a different sound. Once you have opened a hole post compressor so that the compressor pressure ratio falls close to zero i have not seen any difference in turbocharger shaft speed or boost build up for various valve / spring combinations. The size of the hole or how fast it opens has such small effects on a CPR that is so close to 0 when the dump valve is open.
But hey - it's your money!:D
Quite a few Ibizas are running a GFB with varying success, same with Leons. I have a fully atmospheric forge 004BOV on my Loen at the moment without and noticable problems. No noticable loss in power, no stalling, no rough idling, just a satisfying "whooosh" every time I let off the throttle...
I certainly didn't seem to be down on power against any of the Leons or Ibizas at Alconbury..
I'm waiting to plug a VAG-COM back into it soon to check for errors but the only one I am likely to have is the one saying check DV... And that is only because the ECU detects the air leak, or might do, I don't know if the error is there yet.
All this running rich is rubbish too IMO. I'm an embedded software engineer by trade and if the ECU doesn't detect the engine running rich and compensate then VAG should get some new software engineers...
Anyway that's my 2p worth...
Pete
ibizacupra
22-11-2002, 08:07
I would say from peoples posts generally about atmo DV's, is that some people get em to work and some don't. No rhime or reason.
Lucky Dip anyone :p
Bill
Pete
How did u set up the 004? I had one of Pete @ Forge on trial and tried all the spacer and spring comninations and my car just died on overrun.
?
:cheers:
max_torque
22-11-2002, 10:05
"No rhime or reason"
But:
(and concentrate, here comes the science bit!)
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!)
(sorry , another monster post!)
Wow , Is there still a 4wd F1 car lying about ??
I must congratulate you If you had any part to play in the engine in the Vanquish , you know the one - 2 duratechs velcro'd together - That is the most beutifull sounding car in the world , I mean words can barely describe the sound - Its just one of those things that make the hair on the back of yer neck stand up.
Another question when im thinking about it - The BDA was developed by Cosworth - but the BDT was developed by Brian Hart , the engine in the Nobel Mwhat ever , was it developed by cosworth or was it a outside body that done the conversion to Forced induction like what happened with the BDT.
I once asked a pal who's in the know about Mapping and he descibed it as a "Black Art" lol. But the likes of Ahmed Bayoo or what ever his name is can charge £600 per hour to Set a Ecu to get the most out of a highly tuned car.
So you have a belter of a job mate......Jammy B_stard :p