not scientific, for fun only

[RS4POWER]

( I should know the answer) But I do remember reading that there was a power loss with valves open, due to lack of back pressure, is this something that has been proven wrong?

i very much doubt it, this would kind of negate all free flowing after market exhausts.
how could this have even been measured in the first place?.

Slight thread drift but yes you right in that free flowing isn't always what you want however 'back pressure' is misunderstood.
The ecu and valve timing is setup based on OEM parts and certain assumptions are made. One of these is the exhaust characteristics and as such the timing, overlap and the parameters are set such as to maximise the scavenging effect of the exhaust. If you just change the exhaust then these assumptions are wrong and the benefit you get of a more free flowing exhaust is completely lost (and then some) by miss-matched settings.
This is why you do actually suffer a measurable (if slight) power loss if you just bolt on a miltek. However, remap things to suit the new exhaust and then you do generally get a net gain.

Well said.

[hlbeckley]

Ok what iPhone app did u use pls? Am keen to give it a go too!

[adsgreen]

Closing of the exhaust valves between 1000-3500 rpms in gears 1-2-3 in sport mode is to limit drone.

Unfortunately it's the EU noise regs causing that one. They stipulate a number of speeds and engine rpms <sigh>.

[ArthurPE]

Ok what iPhone app did u use pls? Am keen to give it a go too!

'dynolicious' http://www.bunsentech.com/products/dyno ... /index.php

there is a lot of info out there and runs vs actual drag strip runs are almost identical
and when they are 'off', reads higher (slower, not faster) than actual

http://www.streetfire.net/video/iphone- ... 175854.htm

[sonny]

( I should know the answer) But I do remember reading that there was a power loss with valves open, due to lack of back pressure, is this something that has been proven wrong?

Myth. I have tested the car with valves open and closed and it's identical. Lots of third gear runs from 2k-8k logged on vagcom etc.

There are enough restrictions in the stock exhaust that the valve isn't going to be so much of a game changer.

Closing of the exhaust valves between 1000-3500 rpms in gears 1-2-3 in sport mode is to limit drone.

Glad thats been nipped in the bud.

[ArthurPE]

sport mode exh flaps MIGHT cost a few lb ft of mid-range torque and gain a few HP at the top end, MIGHT, but not measurable and nor would it have any impact on performance
it's primarily for noise control/manipulation, anything else is a minor consequence and not intentional

[adsgreen]

Agreed - 5hp is less than most rolling roads published margin of error.

[ArthurPE]

a few more numbers
30-90 mph using gears
1st 6000 to 8000 rpm 30-40 mph
2nd 5000-8000 40-66 mph
3rd 5500-7500 66-90
basically 3 runs through the 5k-8k power band

R&T 7.6
R&T 7.3
C&D 7.4
sport auto 7.6 (extrapolated from kph)
R&T R8 7.4
Audi performance test spec ~7.5 (extrapolated kph)
average ~ 7.5

mine, average of 6 runs, consistent 0-30 and 0-90 times
9.21 - 2.23 ~ 7
run in 40-50F temps, high humid, 1100' ASL, half to full tank, valves cleaned 30k miles ago

for reference the mags
0-30 1.5, mine 2.2 or so, very bad launch, but once rolling meets or beats almost all tests

even if the measurement is off 0.5 sec (unlikely, the reviews state very accurate the or error is on the slow side not the fast) I'm still at 7.5 sec or around the average

the 1-2 change is so hard my owners manual launches from its cubby, lol

[sakimano]

I have had that happen at the dragstrip (owners manual). It's a bit hairy lol.

Get a couple of service receipts in there to thicken it up and it should be fine and stuck.

[adsgreen]

the 1-2 change is so hard my owners manual launches from its cubby, lol

Yes - I found the ipad fits in there perfectly... right up until something similar happens and it's not good!