Valves- carboning up

[P_G]

It may make it with a different combination of mods, remember the RS5 has twin throttle bodies and I don't know what is involved with changing from single to twin if at all possible with our engines and I believe the grille design on the RS5 allows proptionately more air flow through each of its intakes then you would get from the RS4. Then there is the mapping and increasing the redline.

It may be dual air intake, remap, filters and exhaust would give you the same RS5 bhp and more torques? I imagine the real cost though is in relocating the coolant and hydraulic reservoirs and the labour involved.

[ArthurPE]

Unless you know anything otherwise Sims then I was led to believe by Audi people at Geneva that it is the same 4.2 FSi V8 unit with revisions as per the press specs, i.e twin air intake rather than single and dual 70mm throttle bodies rather than a single 90mm one on our cars as per the pics I posted up oin the RS5.

The dual air intake is the basis of the mod some German tuners are doing on RS4's; essentially they are taking the designed air intake system off the RS5 and putting it direct on to the RS4 after rehousing the hydraulic fluid and coolant resevoirs into the false battery space in the engine bay.

that is my understanding, identical engine...different intake(s) and obviously ECU programming...the power comes from rev'ing it higher, 8k vs 8.4k iirc (P = T x w: Torque = same as RS4, as expected, Cr and V remain the same, so the ONLY way to increase the power is to raise the revs, w = engine speed) the revised airbox supplies the additional air required by the higher rpm...

the dual airbox mod (and SW) sounds like an interesting mod...which tuner(s) are doing it?

[P_G]

I don't know to be honest, mate of mine whilst in Germany on 'business' for a famous car marque with four rings saw a tuner's development RS4 with this on. Don't know if it is mainstream or not but he has no reason to make these things up.

[ArthurPE]

I don't know to be honest, mate of mine whilst in Germany on 'business' for a famous car marque with four rings saw a tuner's development RS4 with this on. Don't know if it is mainstream or not but he has no reason to make these things up.

that sounds like a good mod, difficult to implement, and probably expensive, but real HP, not 'imaginary' ones

if someone told me on a given engine they were getting ~7% more HP (T ~ the same) by getting more air to the engine so they could rev it ~7% higher, I would have no problem believing that...

if they said +7% HP same rev limit (no other changes), I would be hard pressed to accept that...

[northernpar]

Very interesting, IIRC it has been stated Audi always had a problem getting the airflow through this engine so be interesting to see what variable geometry the RS5 has compared to the RS4 and what the controls are.

I also recall reading something about the con rods being a perceived weak point in the RS4 engine which was the reason given for the throttle limiting in 1st to 3rd gears (I think I recall that it was someone from Oz that psoted this info). Can't remember where I read this but apparently the issue is around the stresses on the con rod when throttle is removed at high revs. Not sure how much of this is fact or fiction but there has to be some reason for the limiting. Would be interesting to find out though.

[P_G]

I don't know to be honest, mate of mine whilst in Germany on 'business' for a famous car marque with four rings saw a tuner's development RS4 with this on. Don't know if it is mainstream or not but he has no reason to make these things up.

that sounds like a good mod, difficult to implement, and probably expensive, but real HP, not 'imaginary' ones

if someone told me on a given engine they were getting ~7% more HP (T ~ the same) by getting more air to the engine so they could rev it ~7% higher, I would have no problem believing that...

if they said +7% HP same rev limit (no other changes), I would be hard pressed to accept that...

Agreed hence why adding the air intake off the RS5 to our RS4's would not give 450 hp. Some mappers are raising the rev limiters on the RS4's now although I'm not sure how happy I would be about that on my car.

[ArthurPE]

Very interesting, IIRC it has been stated Audi always had a problem getting the airflow through this engine so be interesting to see what variable geometry the RS5 has compared to the RS4 and what the controls are.

I also recall reading something about the con rods being a perceived weak point in the RS4 engine which was the reason given for the throttle limiting in 1st to 3rd gears (I think I recall that it was someone from Oz that psoted this info). Can't remember where I read this but apparently the issue is around the stresses on the con rod when throttle is removed at high revs. Not sure how much of this is fact or fiction but there has to be some reason for the limiting. Would be interesting to find out though.

I think they limit the torque in lower gears for driveline preservation and traction management
in low gears you are doing high torque multiplication

internally in the engine, I would think no difference on the stresses regardless of what gear you are in...

then again, releasing the throttle under high load (compression braking) would seem to impart more force or reflect more load back into the engine, the lower the gear...hmmmmm

[ArthurPE]

I don't know to be honest, mate of mine whilst in Germany on 'business' for a famous car marque with four rings saw a tuner's development RS4 with this on. Don't know if it is mainstream or not but he has no reason to make these things up.

that sounds like a good mod, difficult to implement, and probably expensive, but real HP, not 'imaginary' ones

if someone told me on a given engine they were getting ~7% more HP (T ~ the same) by getting more air to the engine so they could rev it ~7% higher, I would have no problem believing that...

if they said +7% HP same rev limit (no other changes), I would be hard pressed to accept that...

Agreed hence why adding the air intake off the RS5 to our RS4's would not give 450 hp. Some mappers are raising the rev limiters on the RS4's now although I'm not sure how happy I would be about that on my car.

I agree, 8000 seems sufficient
the torque drops off so rapidly >7000, doesn't make much sense to rev higher, unless top speed is the only concern...

[Sims]

Unless you know anything otherwise Sims then I was led to believe by Audi people at Geneva that it is the same 4.2 FSi V8 unit with revisions as per the press specs, i.e twin air intake rather than single and dual 70mm throttle bodies rather than a single 90mm one on our cars as per the pics I posted up oin the RS5.

The dual air intake is the basis of the mod some German tuners are doing on RS4's; essentially they are taking the designed air intake system off the RS5 and putting it direct on to the RS4 after rehousing the hydraulic fluid and coolant resevoirs into the false battery space in the engine bay.

This is a worthwhile read.

http://www.automobilemag.com/reviews/dr ... index.html

References to engine highlighted below for convenience:

While most future RS models will be powered by twin-turbocharged engines, both the upcoming, Europe-market RS4 Avant and the RS5 coupe get a high-revving, normally aspirated, direct-injection, 4.2-liter V-8. It makes 450 hp, 30 hp more than the old RS4's V-8 of the same displacement. Stephan Reil, R&D chief in charge of all Audi RS and R models, explains: The high-revving V-8 is better suited for this particular vehicle concept than a twin-turbo V-6. When you consider the extra plumbing, the more complex exhaust system, and the additional cooling requirement, the weight penalty of the V-8 shrinks to less than 40 pounds. The engine for the RS5 was practically developed from scratch. It develops more power and torque than the outgoing unit, yet it uses twenty percent less fuel. Although the redline was pushed up to 8500 rpm, maximum torque, an identical 317 lb-ft is now available between a less hectic 4000 and 6000 rpm. Engineering highlights include a two-mode intake manifold with tumble blades, variable intake and exhaust timing, and a multimode exhaust system. To trim parasitic losses, Audi reduced piston friction, lightened the DOHC valvetrain, and fitted a variable-output oil pump. A regenerative braking system increases alternator output during deceleration and reduces its output during normal driving.

[HYFR]

good find Sims

[ArthurPE]

it's the same:
RS4 dual mode tumble flaps
it develops more torque, then the same torque?
RS4 puts it peak torque out between....4k and 7k, less peaky than the RS5
the RS4 has a variable output oil pump
that is the same lingo in the RS4 press release...
To trim parasitic losses, Audi reduced piston friction, lightened the DOHC valvetrain, and fitted a variable-output oil pump.
multi-mode exhasut = flaps, same as RS4
RS4 has variable intake/exhaust timing...

the engine is the same, it would make no sense to change it for such a limited production car...but gotta give credit to the PR dept.

look at the bore/stroke, identical...
8500/8000 x 414 ~ 440 HP, rating is 444 (SAE)
sure went to a lot of effort for an engine that makes the same torque, and only a bit more HP due to 'wringing' it out, lol

btw: that article was released today, ~ 2 hours ago...

This is a worthwhile read.

http://www.automobilemag.com/reviews/dr ... index.html

References to engine highlighted below for convenience:

While most future RS models will be powered by twin-turbocharged engines, both the upcoming, Europe-market RS4 Avant and the RS5 coupe get a high-revving, normally aspirated, direct-injection, 4.2-liter V-8. It makes 450 hp, 30 hp more than the old RS4's V-8 of the same displacement. Stephan Reil, R&D chief in charge of all Audi RS and R models, explains: The high-revving V-8 is better suited for this particular vehicle concept than a twin-turbo V-6. When you consider the extra plumbing, the more complex exhaust system, and the additional cooling requirement, the weight penalty of the V-8 shrinks to less than 40 pounds. The engine for the RS5 was practically developed from scratch. It develops more power and torque than the outgoing unit, yet it uses twenty percent less fuel. Although the redline was pushed up to 8500 rpm, maximum torque, an identical 317 lb-ft is now available between a less hectic 4000 and 6000 rpm. Engineering highlights include a two-mode intake manifold with tumble blades, variable intake and exhaust timing, and a multimode exhaust system. To trim parasitic losses, Audi reduced piston friction, lightened the DOHC valvetrain, and fitted a variable-output oil pump. A regenerative braking system increases alternator output during deceleration and reduces its output during normal driving.

[ArthurPE]

http://www.caranddriver.com/news/car/10 ... s_and_info
At the Geneva auto show, we’ll meet the upcoming Audi RS5, the wildest evolution of the A5 coupe, and as direct a competitor to the BMW M3 coupe that exists. Here, Audi's 4.2-liter V-8 makes 450 hp at 8250 rpm, and maximum torque is 317 lb-ft, available between 4000 and 6000 rpm. The hand-built engine is direct-injected and closely related to the 420-hp V-8 which powers the R8 supercar.

http://www.caranddriver.com/news/car/10 ... .-car_news
Interestingly, Audi is sticking to its extremely high-revving engine, an evolution of the former RS4 and current R8 unit,

http://cars.uk.msn.com/news/photos.aspx ... =152278007
The powerful coupé has the same 4.2-litre engine as used in the Audi R8 supercar, with a 24bhp boost to bring the total power output of the RS5 up to 444bhp.

[ArthurPE]

RS5 dyno curve

RS4 > 400 Nm 2500 to 7000 ~ 4500 rpm band
RS5 > 400 Nm 3500 to 8000 ~ 4500 rpm band, just shifted up

HP at 7800 RS4 = RS5 ~ 420 PS, RS5 might be a bit higher (10 HP), better breathing due to the air boxes
HP @ 7000, identical, 400 PS
6000 RS4 360, RS5 345
5000 RS4 290, RS5 280

power difference 8300/7800 x 414 ~ 440 HP, almost exactly the rating
a couple more HP due to less pumping losses, better breathing...
no magic here

[Gumball0r]

Could somebody please help me clarify, is checking for carboned valves and thereafter possibly cleaning, an engine out job?

[ArthurPE]

Could somebody please help me clarify, is checking for carboned valves and thereafter possibly cleaning, an engine out job?

heck no, remove manifold, clean away
removal & reinstall might be 2-3 hours total...less if practiced
cleaning takes a while, maybe 8 hours+

but it will be back in <2000 miles...