An upgrade to the stage2 C6 RS6

[A20LEE]

Mine made 609bhp std with no map on MRC’s rollers and Doug told me that the time C6 is still the daddy its the gearbox in the C7 that makes the difference. C6’s are usually 20mph faster than C7’s at Vmax.

I was recently chatting with Doug at MRC, he told me the difference in top speed C6 v C7 was charge cooler v intercooler? ie the faster the C6 goes the more power it makes relatively? He said that's why the C6 makes 200mph so much easier and the C7 can't?

That's what I thought he meant anyway

Regarding the C6 gearbox, 6th is so tall you need approaching 800ps to be able to accelerate approaching 200mph I believe. When I had mine stage 2'd one of the options by MRC was to have the rev limit increased to achieve true 200mph. Mine changes gear 5th to 6th somewhere around 195mph on the clock....the car is VERY quick to 190mph ish but once in 6th at those speeds acceleration is much slower. I have made over 200mph true speed.

Makes sense, i was looking at Vmaxx times and theres usually a C6 in the top ten hitting 195-205mph, the best C7 was 178mph. Think doug was talking about low end acceration when we chated about C7 feeling quicker low down. Obviously 100mph, theres no comparison.

[IanH755]

With the MRC stage 2 map raising the rev limit to 7k rpm you hit 206mph indicated (200mph GPS) when it changes to 6th, but the second you hit 6th all the acceleration dies on it's arse regardless of having 700hp or 900+hp because the gearing is so tall at that point.

[welwynnick]

That's an interesting post. Firstly it's quite a good answer to my nerdy question about how high the engine can rev.

Second, it's a bit more complicated. The stock engine has a nearly flat torque curve from 2000 to 6250 rpm, and the power curve is nearly a straight line over that range, then peaks and drops sharply. I'd expect a stock engine to fall on it's face changing up to 6th flat out, because you lose a lot of power on the up-change with a peaky power curve.

Stage 2 engines are quite different, with torque hitting 1000+Nm from 3000 to 5000 rpm, then tapering downwards to the red line as the turbos trade pressure ratio for mass flow. So the power curve has a plateau rather than a peak, typically reaching 700+bhp from 5000 to 7000rpm. It's a sign that MRC have successfully wrung the neck of the turbos, and they're flowing all they can flow. It's a great formula for acceleration, as the average power is high over the range of engine speeds actually used. See Ian's link.

http://www.ianhenshall.com/audi58.jpg

However, if a stage 2 car changes up at 7000 rpm at 200mph, it will find itself at 5700rpm in 6th, right on peak power for most stage 2 tunes. In other words, the engine will produce MORE power at 200mph in 6th than it does in 5th, so the acceleration should actually increase on upshift. I've heard lots of people describe the same thing, but something doesn't add up, and I don't know what it is. It's not rolling resistance, so all I can think of is the transmission loss is higher in 6th, or the boost is limited, which is all unlikely.

Nick

[don0301]

That's an interesting post. Firstly it's quite a good answer to my nerdy question about how high the engine can rev.

Secondly, it doesn't add up. The stock engine has a nearly flat torque curve from 2000 to 6250 rpm, and the power curve is nearly a straight line over that range, then peaks and drops sharply. I'd expect a stock engine to fall on it's face changing up to 6th flat out.

Stage 2 engines are quite different, with torque hitting 1000+Nm from 3000 to 5000 rpm, then tapering downwards to the red line. This means the power curve has a broad plateau rather than a sharp peak, typically reaching 700+bhp from 5000 to 7000rpm. It's a sign the MRC have successfully wrung the neck of the turbos, and they're flowing all they can flow. It's a great formula for acceleration, as the average power is high over the range of engine speeds actually used. See Ian's link.

http://www.ianhenshall.com/audi58.jpg

However, if a stage 2 car changes up to 6th at 200mph, while it's producing around 700bhp at 7000rpm, it will find itself at 5700rpm in 6th. This happens to be peak power revs for most stock turbo custom tunes. In other words, the engine will be generating MORE power at 200mph in 6th than it does in 5th. Therefore the acceleration should actually increase on upshift, rather than fall on it's face. So something, somewhere doesn't add up, and I don't know what it is. I've heard lots of people describe the same thing. All I can think of is that the transmission loss in 6th is much higher than 5th, but that seems an unlikely explanation.

Nick

You do talk sh1te....

It's because 6th is a much taller gear....

[don0301]

With the MRC stage 2 map raising the rev limit to 7k rpm you hit 206mph indicated (200mph GPS) when it changes to 6th, but the second you hit 6th all the acceleration dies on it's arse regardless of having 700hp or 900+hp because the gearing is so tall at that point.

The map doesn't raise the rev limit generically if I recall, I was asked if I wanted it.

At those speeds, tyre tread depth, even what pressure will likely affect measured speed (speedo). As I said, mine changed at about 195 indicated when I did it. I had 213 indicated (203 gps) and still slowly increasing but had to shut off, that was with 770ps and 1100Nm.

[welwynnick]

You do talk sh1te....

It's because 6th is a much taller gear....

I was hoping you'd say that.

When you disagree with someone, it's hard to accept they might be right, but I had actually begun to doubt myself.

But in one single post you have removed all of those doubts.

Thanks,

Nick

[rtd]

I went from a C6 to a C7. Did 60k in the C7 in two years with no major issues- as a ownership experience it was a fantastic car the perfect all round car. But I never stopped hankering after a C6, it has its flaws no doubt but it’s an epic car with a legendary engine. Recently had a sepang blue car drive past me and guess what I’m back looking for one in the classifieds. There is just something about them which I can’t explain - those who have owned one will know what I mean......


Sent from my iPhone using Tapatalk

[don0301]

I went from a C6 to a C7. Did 60k in the C7 in two years with no major issues- as a ownership experience it was a fantastic car the perfect all round car. But I never stopped hankering after a C6, it has its flaws no doubt but it’s an epic car with a legendary engine. Recently had a sepang blue car drive past me and guess what I’m back looking for one in the classifieds. There is just something about them which I can’t explain - those who have owned one will know what I mean......


Sent from my iPhone using Tapatalk

Had mine over 5 years now, starting to look to replace as financially i can, but still love it. I'd love to keep it but practically not sure that's viable. Good luck with your search, must be getting harder now to find good ones.

[welwynnick]

Mine made 609bhp std with no map on MRC’s rollers and Doug told me that the time C6 is still the daddy its the gearbox in the C7 that makes the difference. C6’s are usually 20mph faster than C7’s at Vmax.

I was recently chatting with Doug at MRC, he told me the difference in top speed C6 v C7 was charge cooler v intercooler? ie the faster the C6 goes the more power it makes relatively? He said that's why the C6 makes 200mph so much easier and the C7 can't?
That's what I thought he meant anyway

Audi seem to be keeping it quiet, but they've decided to go back to a pair of side mount air-air intercoolers on the C8 RS6.

Nick

[c3nturi0n]

That's an interesting post. Firstly it's quite a good answer to my nerdy question about how high the engine can rev.

Second, it's a bit more complicated. The stock engine has a nearly flat torque curve from 2000 to 6250 rpm, and the power curve is nearly a straight line over that range, then peaks and drops sharply. I'd expect a stock engine to fall on it's face changing up to 6th flat out, because you lose a lot of power on the up-change with a peaky power curve.

Stage 2 engines are quite different, with torque hitting 1000+Nm from 3000 to 5000 rpm, then tapering downwards to the red line. This means the power curve has a broad plateau rather than a sharp peak, typically reaching 700+bhp from 5000 to 7000rpm. It's a sign the MRC have successfully wrung the neck of the turbos, and they're flowing all they can flow. It's a great formula for acceleration, as the average power is high over the range of engine speeds actually used. See Ian's link.

http://www.ianhenshall.com/audi58.jpg

However, if a stage 2 car changes up at 7000 rpm at 200mph, it will find itself at 5700rpm in 6th, right on peak power for most stage 2 tunes. In other words, the engine will produce MORE power at 200mph in 6th than it does in 5th, so the acceleration should actually increase on upshift. I've heard lots of people describe the same thing, but something doesn't add up, and I don't know what it is. It's not rolling resistance, so all I can think of is the transmission loss is higher in 6th, or the boost is limited, which is all unlikely.

Nick

when you did those observations on Stage ii car, assume it was tested in "S" (gearbox wise)?

[welwynnick]

when you did those observations on Stage ii car, assume it was tested in "S" (gearbox wise)?

I'm an impostor mate, I haven't even bought my RS6 yet (though I've already bought VCDS and a 4 post lift to look after it). The observations are other people's - several owners said acceleration dies when you change up to sixth. My comments are just based on gear ratios and dyno charts. Yours is up for sale isn't it?

Nick