Rolling Road interested to know
 

Has anyone had their S8 D2 on a rolling road or mapped, did it make stock power figures? or less? :Confused:

Not my S8, but I did have my first D2 A8 4.2 remapped.

I was invited down to Superchips headquarters on a training day, due to my automotive development associations (long story), and got a free remap as a result.

Bearing in mind these were Superchip's best remappers, the first attempt actually lost about 10bhp. After several attempts they managed an increase of about 5bhp, which of course was barely noticeable on the road.

I had my D2 on the dyno at MRC, made factory 355 hp with 120k miles on the clock, I was very surprised was expecting a lot less. The often quoted 360hp is actually in ps, its 265kw in the manual.

Goran thats good results, i've heard MRC are the guys to use for mapping etc, did my stage 2 rs6 c5 before i bought it and went very well, do you think they could do much with an S8 D2? I suppose it would confirm if the car is healthy was it stock your car?

Moltuae, is your current S8 stock? ever tempted to see what its running?

It is stock. It would be tempting to know but, coming from my previous 4.2 A8s, which were dyno'd (but less powerful), the noticeable difference in the S8's power seems about right for the rated power.

I know a few garages with rolling roads. In fact I used to repair and maintain their rolling roads for them, but most of those aren't 4-wheel dynos. I do know one owner of a 4-wheel dyno but it's never been properly maintained or calibrated so I wouldn't trust its accuracy.

I am considering investing in a new 'sportier' exhaust system some time in the next year or two, so I might be tempted to pay for a 'before and after' roll, if I can find a local garage with a decent 4-wheel dyno.

I would definitely use MRC if I was to get mine mapped. I was planning to originally but I am not so sure any more. The power increase would be tiny I think, its not easy to get much out of a NA engine especially from a German one thats already been upgraded by the factory with a different cam, low friction ancilliaries, etc, to get the power increase compared to a A8.

Also having test driven RS4s, an RS6 and a Tesla made me realise if I want a huge power jump I can feel I have to get a different car. Currently I am very happy with the D2, I have accepted it for what it is.

The other, perhaps easier way to get a bit more noticable oomph is to lose weight, for example lightweight battery could save 20kg, custom exhaust could lose around 15kg, lightweight front discs around 7kg, rears around 3kg.
Lighter alloy wheels could lose up to 25kg if you count the spare too, depending how much you are prepared to spend.
Switching to manual seats for example Audi TT seats could lose another 20kg.
However I have partially given up on this too and I even bought a pair of TT seats, now gathering dust in the shed.
To make the D2 a much faster car would take something radical like swapping in an RS6 4.2 engine, manual trans, etc. Or going all out reducing weight and maxing the power of the stock engine. I am guessing either route would easily cost over £10k

Or Nitrous Oxide.........

I did think of Nitrous oxide and while it is fairly inexpensive to install the usage costs are too high.

So I looked at alternative. You could use compressor part of turbo hooked up to electric motor to give you on demand boost. Initial outlay will probably be higher but running costs very little. It is a while since I looked at it so things may have improved now. but I seem to remember that about £750 investment would give you 50% more power for 2 minutes with 30 minute re-charge time with which is compareable to 11lb NO2 bottle at about £50 for the same 2 minutes of boost.

Interesting idea, I like it +++
I assume the electric motor would run off a separate battery no the alternator, hence the re-charge time?

Only other question, would the engine be able to take it?

Lol, sorry, not the only question, would you still need to intercool the air?

Looks like Borg warner already have something.

https://www.borgwarner.com/docs/defa....pdf?sfvrsn=14

SQ7 Electric bi-turbo

http://fourtitude.com/emAlbum/albums...di-v6-1000.jpg

TT Clubsport Electric bi-turbo

http://fourtitude.com/wp-content/upl...15/05/tt-2.jpg

Both of these use a separate 48V electrical system for the turbo IIRC.

I saw a precursor to this about 15 years ago. It was the compressor side of a Powerdyne supercharger (ie turbo compressor) built on to a small but powerful 3-phase motor. It had an inverter the size of a car battery and power cables as thick as your thumb :D It was originally intended for truck engines I think.

Magnetti Marelli showed a potential OEM version of the heat recovery system used in F1 at the Autosport show a couple of years ago:

http://www.auto123.com/ArtImages/147...ers-inline.jpg

Excellent +++
Now we just have to wait for some used SQ7 turbos to start appearing on ebay.

Looks like SQ7 has a 48v battery? For all electric systems?
https://www.youtube.com/watch?v=sHZjo0e5aGg

So this is very interesting, if this can be made to work for under £1000 then I am seriously interested lol.

So how would the coding work? Can it all be kept separate form the engine ECU? I assume the DC permanent magnet motor has its own dedicated chip and software, would it need a sensor attached to the throttle pedal or something to know when to switch on? I am guessing if its similar to an rc plane electro-ducted-fan then it can simply go to full throttle when its on no need to modulate motor speed.
Would it need to be manually switched off completely when its emptied the capacitors to allow them to recharge?

If in our applications it runs off a dedicated capacitor bank, we could have some cool charging state LEDs to display when its fully charged to go again?

Would it go after the air filter but before the MAF, and would it need to be in a butterfly valve controlled by pass tube so that its not blocking the airflow when its not in use?

And is the D2 ECU software adaptive enough for that much extra airflow or would it need a custom map?

Run a reserve of compressed air in a tank for charge purposes using the existing 12v system.
Then either drive a turbo with compressed air, or pump the air directly into the manifold (driving a turbo is probably more efficient use of the air reserves). Audi are already doing something like this to cancel out turbo lag in some models.

Then: Extra air = extra fuel.
You'd need a dedicated injector, like a throttle body injector or something and a standalone ecu to drive it. The stock ECU and injectors won't have the adjustment range to cope with intermittent pressure spikes.
All a bit complicated.

Wet shot of NOS is much simpler!

Also, where would you use this intermittent power surge?
Drag strip? Traffic light grand prix? It wouldn't be of much use up through the windies on a mountain climb.

Agreed about where you would use a compressed air shot on the streets, and NOS for that matter.
Hence why electric turbo seems more convenient and a milder boost that could be available often as it keeps charging as you drive.

Not sure why compressed air should be different from a NOS shot, surely in the cylinder the result is the same, increase O2 density requiring more fuel to burn to produce more powerful bang. If stock injectors can cope with a certain level of NOS they can cope with air compressed to similar O2 density as the NOS surely?

Apply some beermatematics to the compressed air idea:

The V8 consumes 2.1 litres per revolution. Lets work on 0.5 bar of boost, making that 3.15 litres per revolution. A 0-60 dash in an S8 with 500hp would be sub-5 seconds. We'll use 5 seconds for simplicity, and lets assume an average of 4000 rpm (1000-7000 range)

4000rpm for 5 seconds would consume 1050 litres of air. A standard scuba tank holds 2300 litres, so would be good for two 0-60 runs, or 10 seconds. The second run might not be quite so good as the pressure in the tank reduces significantly, but the gearbox would have blown up after the first run anyway so that probably doesn't matter :ROFL:

Delivering 7psi boost on 11:1 compression with indirect injection is asking for trouble anyway.
My idea with an air tank is to use a relatively small one and drive an air drill/die grinder type arrangement with it to spin a turbine.
10-15 thousand rpm with high torque should get some decent boost.
You'd need high pressure in the tank though (100_150psi) which I'm not convinced a 12 volt compressor could deliver, which means a mechanically driven compressor, which results in mechanical losses at which point you may as well supercharge it...
(How's that for a circular argument!)

As for delivering extra air, that's only half the story.
Air in and of itself will not give you power.
What it gives you is the ability to burn more fuel.
Providing as little as 10% more air to an engine will go beyond the ability of the injectors (and ECU map) to provide sufficient fuel to burn at the ideal stoichiometric ratio of 14.7:1 (minimum air:fuel ratio at which complete combustion occurs and therefore provides maximum efficiency).

So without adding more fuel you're wasting your time.

You end up with a lean burn which beyond being a waste of all this air you've gone to the trouble of generating, actually burns hot, thereby reducing engine efficiency too.

Similarly with NOS. NOS in and of itself does not provide power. It provides a very rich and dense oxygen mixture with a lower stoichiometric ratio than that of regular air - the same volume of NOS can burn about 30% more fuel than that of air and achieve complete combustion. It's stable and won't explode like pure oxygen might.
But it still needs fuel.
Most NOS comes as a 'Wet Shot', which contains fuel at the correct ratio to burn. That's why they call it "power in a bottle".

One idea I have been playing with is some sort of water injection. They use it in turbocharging to create a cooler denser charge in the cylinder, but beyond that steam has a higher expansion ratio than air and won't affect air fuel ratios. So adding a small volume of water (we're talking droplets here!) might improve the energy of expanding gases during combustion as it flashes to steam and might slightly improve engine efficiency as it absorbs some of the heat energy.
Though like most things, if there was something in it someone would already be doing it!

Hi mate, long time no speak!! Just wondering, was this figure for the current manual car you have or the one you sold me?

Car is still running great btw. Engine still feels very strong, gearbox shifting perfectly. Only issues right now - a front driver’s side cv joint or bush somewhere is knocking a touch and the blower fan brushes have literally worn out causing the thing to just stop dead (blame the solar sunroof and hot summer lol). Aside from that, bulletproof.

Hi! Hope you are well. Glad to hear its still running good.
That dyno was for my current manual S8.