deposit performance impact

[PetrolDave]

My S3 hit 263PS on MRC dyno with 4k on the clock ... So unless they deliberately engineered that number, their dyno is pretty accurate

What it means is probably that their powertrain loss calculation for the S3 is accurate.

[ArthurPE]

trap speeds
look at trap speeds/weight/torque

the M3 vs RS4
torque difference is ~7.5%
wt difference ~ 12%
time difference ~ 1/1.12 x 1.07 ~ 0.96, speed inverse ~ 1/0.96 ~ 1.04
so the M3 time should be ~ 0.96 x RS4 time: assume 13 for the RS4 the M3 ~ 12.5, 0.5 sec, the margin is actually less, from what I've seen ~0.2 to 0.3 sec avg
you could say the RS4 has an awd advantage, but still, the difference is less than would be expected...
speed RS4 average 109 or so, making the M3 ~ 1.04 x 109 ~ 113.5, and this is pretty close to what they do, awd advantage for speed is small...

'Ring time:
same driver ~ 8:05 vs 8:09, 4 sec <1% (0.8%), over 13 miles at 95 mph
both on sport tires, both the same expert driver
and the M3 has a 4.3% torque/wt advantage, is better balanced (offsets the awd to some extent, has lower CoG, and the RS4 has ~ twice the drivetrain losses: 2 diffs, 4 axles, xfer gear set, F/R diff)
and yet, same effective speed...there is no way this could occur if the RS4 had only 90% of it's rated power/torque, 380 vs 420)
that would increase the torque/wt delta to 15% advantage M3!!

it defies all logic , science and engineering
not to mention law...the cars are independently certified by an EEC testing agency, NOT Audi

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How many approximations can you get in one post?
No calculation of aero? I'm disappointed.
What about tyre choice for the ring times?
Ambient weather?

I just don't get the obsession with these calculations conducted in this manner.
Esp when the result pretty much everytime is 'that's about what I'd expect'

[S4Player]

Haha I love it when you and Arthur have discussions it's sometimes the highlight of my day

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I'm here all week

[NIKKIrsSIXX]

trap speeds
look at trap speeds/weight/torque

the M3 vs RS4
torque difference is ~7.5%
wt difference ~ 12%
time difference ~ 1/1.12 x 1.07 ~ 0.96, speed inverse ~ 1/0.96 ~ 1.04
so the M3 time should be ~ 0.96 x RS4 time: assume 13 for the RS4 the M3 ~ 12.5, 0.5 sec, the margin is actually less, from what I've seen ~0.2 to 0.3 sec avg
you could say the RS4 has an awd advantage, but still, the difference is less than would be expected...
speed RS4 average 109 or so, making the M3 ~ 1.04 x 109 ~ 113.5, and this is pretty close to what they do, awd advantage for speed is small...

'Ring time:
same driver ~ 8:05 vs 8:09, 4 sec <1% (0.8%), over 13 miles at 95 mph
both on sport tires, both the same expert driver
and the M3 has a 4.3% torque/wt advantage, is better balanced (offsets the awd to some extent, has lower CoG, and the RS4 has ~ twice the drivetrain losses: 2 diffs, 4 axles, xfer gear set, F/R diff)
and yet, same effective speed...there is no way this could occur if the RS4 had only 90% of it's rated power/torque, 380 vs 420)
that would increase the torque/wt delta to 15% advantage M3!!

it defies all logic , science and engineering
not to mention law...the cars are independently certified by an EEC testing agency, NOT Audi

As expected, I am ~22%(22%) Less interested in this kind of debate since yesterday. I shall shortly spend >10 mins getting ready for bed assuming im wearing sports slippers/pyjamas that retain 90% of their peak cleanliness. I am wearing pheromone spray therefore I have ~ 20% chance of giving the missus one assuming I will be putting out rated Power.

[NIKKIrsSIXX]

My output was ~10cc lower than expected.

[ArthurPE]

My output was ~10cc lower than expected.

time between your last 2 posts...1 minute
doesn't sound like you gave the missus the attention she deserved

[Steve_C]

I'm loving these posts - life would be boring if we all had the same views!

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The ironic thing is that I think all our views are not that far apart. It's just slamming people with formulae and equations isn't the best way to make a point.
You can't say that because some cars have appeared to suffer a large drop in performance through deposits that all cars are affected.
Similary, just because another meets it's stats then all cars are fine.
Both statements just don't work logically.
I have issues with inappropriate data being quoted as scientific fact - these include both sides from dyno runs to ring times.
All this does is detract from an issue that I think we all agree would be ideal if it didn't happen in the first place. So how about focusing on that and agree to disagree on the severity of the impact to the car. There's likely to be a set of common scenarios that promote the buildup of deposits which is the underlying reason for some being worse than others and if that can be found then everybody will be happy.

[neckarsulm]

I am happy.
My RS4 rips round to the rev limiter with a ferocity that still takes me by surprise especially for an n/a car (having lived with B5s in the past)
Do I really care that much about the exact PS? Can anyone measure the exact PS anyway?
Deposits occur on every car, as long as the vacuum system isn't defective and no faults are logged and the service parts are all reasonably fresh I bet most will be roughly inline with the Arthur's in-gear times which are a good benchmark and if yours is, be happy

[ArthurPE]

in YOUR opinion it's not the best way...to some it is the ONLY way
try to convince an engineer that something 'works' without calculations...or 'formulae and equations'

consider this, both members on this forum (approximate numbers)
avant 70k miles, never cleaned
sedan 40k miles, never cleaned

run side by side, same time, same road, in one gear and shifting
no difference, neck and neck, give and take

sedan develops a problem, takes some time to resolve, end game: heads removed, valves, pistons, chambers all cleaned, new plugs, head gaskets, etc., partial top end rebuild...worst deposits I've ever seen, beyond description...valves, pistons, chambers, plugs were fould extremely bad...
all work performed and verified by Audi
this occured shortly after the above tests...

after cleaning, the test was repeated
same results, no difference
please explain?

please explain how the car in the OP with 40k miles of deposits can be faster than when it had only 2k miles and minimal deposits?

the numbers I quote are 'scientific fact'
those ARE the 'Ring times...those are the wt/torque differences
a car with less power and more weight (for similar hipo cars/engines) can't be the same speed
I have given 2 anecdotal examples
take your pick

to validate your position 'we all agree' would asume 'we all agree', we don't, I do not think it costs measurable or quantifiable performance...

so therefore imo it doesn't matter if it happens, it will, it's a NATURAL and an UNAVOIDABLE consequence of the design...the only way to get rid of it it to toss DI, whose benefits FAR outweigh any negatives...

so THE question is, do normal deposits impact performance?

The ironic thing is that I think all our views are not that far apart. It's just slamming people with formulae and equations isn't the best way to make a point.

You can't say that because some cars have appeared to suffer a large drop in performance through deposits that all cars are affected.
Similary, just because another meets it's stats then all cars are fine.
Both statements just don't work logically.

I have issues with inappropriate data being quoted as scientific fact - these include both sides from dyno runs to ring times.

All this does is detract from an issue that I think we all agree would be ideal if it didn't happen in the first place. So how about focusing on that and agree to disagree on the severity of the impact to the car. There's likely to be a set of common scenarios that promote the buildup of deposits which is the underlying reason for some being worse than others and if that can be found then everybody will be happy.

[rs4mikek]

No formulas here, but my car produced 396ps before the clean, about 3 weeks later after cleaning and head porting 446ps. Massive difference which i do notice as well. Apparently mine was very clogged up according to MRC (which did everything)

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Thats the point - "try to convince an engineer". I'll take a wild stab but I'm guessing most people here are not engineers and throwing formulae and equations around doesn't help strengthen or help your case for the audience on this forum.
Just look at the posts here and in other topics - at best people skim over it or worst take the piss. Either way it just makes your posts amusing distrations rather then as helpful as they could be. The real shame is that under this mess of random data do lurk helpful opinions and decent insights... just a shame they are buried beyond any sense of usefulness.

As for the all agree - that was quite clearly pitched towards the opinion that we'd all rather avoid deposits if we could irrespeective if they cause significant performance impact whilst retaining the benefits of FSI. That was it... Am I going to spend thousands looking at this? nope. One thing is for sure though is that if somebody did find a reasonable "cure" they'd be set for life.

As for ring times - so what? there are so many variables at play that you can't draw any conclusions from it. For example, lets say you do a ring lap of 8 minutes. You tweak one setting and then do a lap of 7.59. is it better? Possibly but you can't say for certain as the margin of error over 13miles of flat out driving is simply to cummulative to be significant. I've driven the ring several times and it's the most god awful hateful bumpy unforgiving stretch of road I've ever seen (and I drive on the rural UK roads ). A place for accurate scientific study it aint.

All I said was a series of in gear tests are more helpful than 0-60, 0-100 or 1/4 mile times which no matter what is said are too reliant on the driver input. One fluffed gearchange and poof! There goes the 1.4 mile time.

Finally the two annecdotal piece are probably the most useful - all my posts on carbon/deposits have been sat on the fence as I confess I don't have enough facts to make a meaningful decision. However that would lean me towards the side of it not being as big a problem as made out.

[P_G]

Bigger question is though Arthur, what is 'normal'?

rs4mikek, not doubting your results and clean valves will no doubt produce better hp however that is missing the point somewhast because as mentioned in this thread the FSI patent has carbon as a by product and therefore the conditions MRC have created for you by cleaning it will never last. Even by introducing forced induction, NOS and various methods of water meth injection or oil catch cans, all cars modified this way still have carbon build up and to date there is no method of keeping it as clean as you could eat your dinner off it.

So the choice is live with it, collectively find the optimum way of driving and maintaining the engine so that CB is minimal is respect of not affecting power or spend £500+ every 6-12 months to have your car stripped and cleaned to have peak hp for a matter of days / weeks. If people have the money to do that then good luck to them. But with all of what I have said, carbon build up I would suggest does accumulate in optimum circumstances (i.e conditions that do not lend to excessive build up as some have seen) to a maximum level and then does not progress and that point is where perhaps rated power has been taken from, not clean and fresh out of the box.