Help on understanding remapping

[dazzer]

Hi Gents,

Would someone be kind enough to give me a brief explanation regarding issues associated with remapping. I have read some past posts on the subject and there are common acronyms popping up in them, namely TBB and DVT in relation to leaks, stressed turbos and bipipes. I think I get the general jist but would appreciate a dumbed down version to this area including worst case scenarios when things go wrong.

Many thanks in advance.
Dazzer

[KayGee]

Acronyms

TBB = Throttle Body Boot.
BPV = ByPass Valve. Recirculating valve.
BOV = Blow Off Valve. Vents to atmosphere.
F pipe = shaped like a f, if you ever replace one you'll work out an alternative.
MAF = Mass Air Flow Sensor
MBC = Manual Boost Controller
EBC = Electronic Boost Contoller
n75 = Electronic Pressure Valve
WG = WasteGate.
FMIC - Front Mounted Inter Cooler.
Bipipe = APR replacement for TBB.
Stressed Turbo = Running Turbo at a higher boost pressure than it was designed for or is optimal for the life of the turbo.
DVT = Don't know, best I can think off is drive train.

Overview of chipping/remaping. See http://www.rs246.com/index.php?name=PNp ... d03ae9464b

Audi designed the S4 to run small low pressure turbos (k03) which spool up fast but also spin at high RPMs. This gives a very flat power curve across a wide range of RPM's, however being small turbos they tail off at the top end of the RPM range.

Remaping means running the turbos at higher pressure levels and higher spindle speeds. This puts additional strain on the turbos and pipework as it has to generate and contain more pressure all ata higher temperature.

Running the turbos at higher pressure means more heat, heat is bad for the oil used to lubricate the turbos. If the turbos are running hot when the car is stopped, the oil gets cooked resulting in a build up of burnt oil eventually slowing oil flow and then the turbos need replacing. Audi redisgned turbo oil feed pipes on later models to combat this.

The S4 is designed with an afterun pump but the original hardly ever runs as the water temp has to be very high. Simple mod, change the switch for a lower temp switch. Very cheap, very easy, very worth it even on a std car.

Using larger intercoolers can reduce IAT (Intake Air Temperatures) helping to keep things cooler. RS4 or after market oil coolers can be used to keep oil temps down.

Common problems with S4 cars are torn TBBs and torn BPVs, although re: TBBs this appears to be more to do with the clamps used than the additional pressure. Early Bosch BPVs have quite thin rubber membrane which also tears. Later 710n model fixes most of these issues and are a lot cheaper than piston type (Bailey, HyperBoost, Forge) replacement options. Lastly early cars MAF sensors are an issue, they aren't very reliable. Later cars have a different make of MAF which seems to be more reliable.

APR Bipipe is a metal replacement for the TBB, alternative option is to use a Samco TBB when chipping. Cost of the APR Bipipe is quite high and again not fool proof. Samco TBBs seem reliable although also not perfect.

When larger turbos (k04/RS4 turbo is popular, starting to see quite a few hybrid options being offered) are used, probably best to look at uprating the clutch. RS4 clutch is an option, several after market clutches are available and lightweight fly wheels although these tend to be an aquired taste due to noise.

You stick another 100-350 BHp through the engine and drivetrain and something is likley to pop eventually. Don't complain about it, you tuned it, you fix it.

Any tuned car needs more maintenence, change the oil more often, change the belts more often, visit the petrol station more often. Common sense mostly. Most of this info applies to any tuned car, especially turbo charged cars.

S4 engine tuning runs from a std 250BHP(US model) to 600+ Bhp custom tuning options, depending on depth of your wallet.

[Golich]

Nice Write up

I'd recommend to anyone going the mapping route to have some kind of boost gauge fitted. Its always nice to know what pressure your car is running. in fact this is a good idea even if your car isn't chipped. I particularly like the gauges that store a max pressure incident.

[dazzer]

Cheers Kaygee,

That's a reply beyond my expectations, it is much appreciated. I am trying to anticipate the future costs I am likely to incur if I buy a modified vehicle.

As if that isn't enough I have some more questions for the wider audience:

Can the stock blowers be replaced with RS4 turbos without any additional work? How much for the swap?

What exactly happens when a vehicle goes into 'limp mode'.

Many thanks in advance
Dazzer

[dazzer]

Sorry geezers,

I have the answer for the KO4 swap. The answer was in the link Kaygee gave - just required me to get off my ar*e and look harder.

[Dippy]

Cheers Kaygee,

That's a reply beyond my expectations, it is much appreciated. I am trying to anticipate the future costs I am likely to incur if I buy a modified vehicle.

As if that isn't enough I have some more questions for the wider audience:

Can the stock blowers be replaced with RS4 turbos without any additional work? How much for the swap?

What exactly happens when a vehicle goes into 'limp mode'.

Many thanks in advance
Dazzer

It really depends on what you do and when. But also don't forget modding other than engine (consider suspension, brakes, shifter and exhaust too). My setup is about as much as you can do to improve the S4 short of changing the turbos. It cost about £7K.

Previously I had thought that at some point I would want to fit bigger turbos. But to do it properly really required uprating the air intake and fuel systems as well, and that gets rather expensive. So currently my expectations for when my turbos start to die is that I might consider putting a new or reconditioned RS4 engine instead.

Limp mode is where the ECU limits the boost to about 0.4 bar maximum. Basically you push the accelerator pedal and it starts accelerating but the big 'boost' never happens and you think you've got a 3 litre NA engine instead.

[dazzer]

Thanks Dippy,

The one on classifieds looks like a reasonable example but has been modded. I am guessing that having done 65K that it would make sense to have a reserve fund for some new blowers in the near future for a motor like that.

Dazzer

[KayGee]

There are several 100K+ cars still running factory turbos. Failures seems to be less common here, possibly due to the oil used. It seems you're keen on modding the car anyway so why not buy a car with the basics or the work your planning already done. Its generally a much cheaper way of doing things.

[Dippy]

Dazzer,

KayGee is right, but of course you never know how well the car has been looked after. Aside from the technical issues (which oil and when etc.), there are the driver/owner issues (such as driving the car away from cold and using full boost!). So indeed no matter how much you look at things like FSH, buying a used car with 'medium' mileage is a bit of a lottery.

When I was looking for an S4 5 years ago I couldn't afford a new one so I looked for used. I wanted a nearly new one with low mileage and in good condition. No chance. So I decided to import a new one instead (still more than I wanted to pay, but I managed it).

Now that I've modded the car, although I do not regret buying the car new, in hindsight I think I should have bought a high mileage car in the best condition I could find, and just had the engine overhauled and tuned.

Although I hope to still keep my S4 for a few years yet, if the worst happens I may take that same strategy myself, but with an RS4...

[ChrisG]

The S4 is designed with an afterun pump but the original hardly ever runs as the water temp has to be very high. Simple mod, change the switch for a lower temp switch. Very cheap, very easy, very worth it even on a std car.

Any further info on this ?? Are there part numbers and temperature ratings?

[S2tuner]

the easiest way is to do what we do on 5 cylinder engines, simply short the sensor out so you have automatic afterrun for 10 minutes after every time you turn the engine off. Actually, my car's afterrun pump runs for a couple of secs every time I turn the engine off, no matter how warm it is... or maybe it's not the afterrun pump???? I'll look some more into that...

Mihnea

[Nige_RS4]

The S4 is designed with an afterun pump but the original hardly ever runs as the water temp has to be very high. Simple mod, change the switch for a lower temp switch. Very cheap, very easy, very worth it even on a std car.

Any further info on this ?? Are there part numbers and temperature ratings?

Do a search on RS246 for "after-run pump" - it's a VW/Audi part #.

[dazzer]

Dippy,

I am probably as frustrated as you were when looking for a low mileage late model - I am spending all my money on wanted ads with not joy.

I am going to look at the Silver S4 on the classifieds. I didn't particularly want a modified example but as you point out it's a bit of a lottery and that goes for unmodified example also - you pay your money and take your chance.

Being a tight northerner I hate the thought of making a big mistake so if you have any tips for inspecting the car then I am all ears.

[KayGee]

Try these.

http://www.audisport-iberica.com/ftp_as ... yguide.pdf
http://www.s4turbo.com
http://www.hpicheck.com (get your own done, it isn't dear considering the money your spending)

A few phone calls cost next to nothing, you may well find enough to put you off paying for HPIchecks, RAC inspections etc. However IMO before spending the money they are pretty much essential when paying £10K-20K for a second hand car.

If you don't know a big end from a track rod end, get someone who does. Check the service guide and phone the garage(s).

If it's miles away a £20 hpicheck on the reg number is money well spent. Before purchase do a full HPI check against VIN number (I saw one car that had a reg change, £20 check came up blank unlike the full check, cat D recorded and had a substantial hair cut). Audi cars generally wear miles very well, like BMWs this makes them prime targets for barbers.

RAC or Audi specialist inspection before purchase is a wise investment, worst case it'll probably pay for itself it negotiation points, a dealer will usually choose to do the work before selling the car.

Check the service guide, is it due for a major service, if so negotiate. The seller probably knows this already. Ask them how much it cost to service it last. Phone the garage and check. If possible phone the last owner to check mileage and status.

Dealer inspections IMO opinion tend to miss expensive items that need replacing and find lots of inexpensive ones. Anyone who doesn't agree to an inspection, walk away.

Be realistic, if you're going to tune it, do you need a full Audi service history with warranty? Look at the cost of mods, if they are what you intend to do then a pre-tuned car is usually more financially attractive. Phone the tuner, get the receipts to prove the work was done there. If you're going to do 30K year in it why buy a low mileage example?

Be patient, took me six months to find mine. Still very happy with my choice, just need a another 100 BHp or so.