RS4 with milltek, without remap feels slow?

[PetrolDave]

Taken from the RS4/Q7 engine study guide:

Cylinder Heads

The cylinder heads are similar in design to the Audi V6 four-valve FSI cylinder heads.
Specifications

-Aluminum cylinder head
-FSI intake ports with horizontal divisions to produce a tumble effect
-Four-valve technology with centralized layout of the spark plugs
-Inlet valve: chrome-plated solid stem valve
-Exhaust valve: chrome-plated sodium-filled hollow stem valve
-Valve lift 11 mm
-Lightweight, low-friction valve gear, valve actuation via roller cam followers with hydraulic backlash compensation, single valve spring
-Two assembled camshafts per cylinder head, driven by hydraulic swivel motors
-Intake valve opening angle 200 crank angle degrees
-Exhaust valve opening angle 210 crank angle degrees
-Adjustment range of the camshafts is 42 crank angle degrees
-The adjusters are locked by locking pins when the camshaft is at a standstill; intake in advance position, exhaust in <beep> position
-Return spring in exhaust camshaft
-Implementation of “internal exhaust gas recirculationâ€

[ArthurPE]

I think f1 is a bit if curveball as there's lots of factors at play.
Heat is a real big problem (hence why all the problems with blown diffusers) and secondly the aero can help with exhaust flow as you say above.

Taking another extreme example, drag and tractor pulling engines vent straight through ridiculously short exhausts and the only objective is ultimate objective.

Be interesting to find out the amount of valve overlap on the rs4- I'm guessing it's an interference engine so makes scope for overlap small.

stretch or not, that is why back pressure is required, more so on a street car...you can't have unburnt fuel cycled out the exhaust during overlap resulting in flames from the spontaneous combustion when it hits the atm's O2 like on a dragster or tractor pull...

bad for overall efficiency also
makes less power unless you are overfilling like a supercharger...

it becomes less critical as rpm increases, ie, opening time is less...and the force for filling remains the same, the atm pressure, so less is lost...

hence the loss of low end torque more than high end

[adsgreen]

But the RS4 is FSI so there's no chance of fuel being added with the exhaust valve open. Agree though on conventional injection this would be bad.

By coincidence I spoke to my engine builder over the weekend (beers were involved so a bit hazy). My examples of tractor pulling and aero were rubbish as they are generally forced induction and any back pressure is bad.

[ArthurPE]

But the RS4 is FSI so there's no chance of fuel being added with the exhaust valve open. Agree though on conventional injection this would be bad.

By coincidence I spoke to my engine builder over the weekend (beers were involved so a bit hazy). My examples of tractor pulling and aero were rubbish as they are generally forced induction and any back pressure is bad.

sure there is...
both valves are open at the same time when fuel is injected during the intake, ie, homegenous mode, not during the compression stroke before TDC...

it's not truely DI, ie, injected right before TDC on the compression stroke
(maybe during cold start?) but in normal operation fuel is injected during the intake stroke and as such, there is exh valve overlap...

I agree, back pressure has little effect with a sc, no real need for it...
but with a turbo some calculated amount is desired to 'load' the turbine