deposit performance impact

[ArthurPE]

no rabble rousing, no baiting, no flaming, intended or desired, please
just want to share something I found interesting....

I found a new vs 40,000 mile performance test (C&D 2/11) for an Audi A4 2T quattro...2009 direct injection, same car, standard service schedule, no cleaning...

.test....new.....40k miles
0-60.....6.4.........6.4
0-100...17.2.......16.8
0-120...27.5.......27.2
1/4......15/94.....14.9/94

at 40k miles the car is marginally faster, I would call it even
it appears the car lost no performance (power)
I would assume direct injection would have deposits, similar in magnitude to the RS4, since it is the same basic control strategy...

I have similar tests for other DI vehicles (Porsche, VW, etc.) that show similar results...

comments, but please, let's keep it civil...

[neckarsulm]

in the words of Bulldog Briscoe "that's total BS"

Only joking but it's an interesting point.

One would expect a car that's well run-in to be faster than a tight new car so if the 40k car is no faster then I'd be disappointed

[P_G]

Had a go at some 3k-8k rpm tests yesterday on my normal road with following conditions;

2006 RS4 Avant; BMC air Filter; non res valved exhaust, OEM map
External temp 5 degrees C
Full tank V-Power 99
78450 mileage
Oil change 4 weeks ago with Castrol Edge 5W-30

Times were

8.5
8.7
8.4
8.6

Pretty much what they were 20,000 miles ago when I last tried doing this and concurrent with my last dyno power run.

[HYFR]

i did 1 run yesterday, in a Cab ... it that heavier ? I got 8.3 ... fresh oil, 19k on the clock ?

need to do some more

[ArthurPE]

in the words of Bulldog Briscoe "that's total BS"

Only joking but it's an interesting point.

One would expect a car that's well run-in to be faster than a tight new car so if the 40k car is no faster then I'd be disappointed

well, the new car had a ~2000 on it when tested, so broken in
and the 40k was faster, 0.4 sec to 100

with modern manufacturing tolerances break-in isn't the issue or benefit it was in the past...

this car did not lose 15%+ of its HP

[neckarsulm]

this car did not lose 15%+ of its HP

how do you know it was making it's quoted HP when new or is that irrelevant?
Are you just commenting on performance losses vs mileage covered?
If so then it's a good point and PG's data is on your side.

[ArthurPE]

this car did not lose 15%+ of its HP

how do you know it was making it's quoted HP when new or is that irrelevant?
Are you just commenting on performance losses vs mileage covered?
If so then it's a good point and PG's data is on your side.

doesn't matter, it doesn't appear to have lost any due to deposits, and we have to assume it has deposits, same control strategy, direct injection
who knows if it was making rated power, but that is irrelevent, the test is relative...same car
wouldn't matter if 0-100 were 20 sec, as long as it were 20 sec at 40k miles

I would expect power to be ~ the same at 40k...unless as stated by some it lost 15% due to deposits, that does not seem to be the case
this car did not lose any power (perhaps gained a bit)

I don't think mileage alone decreases HP, as long as the engine is driven and service properly until you get well above 100k miles for a modern engine, and very little then

[ArthurPE]

as far as P_G's time, they would seem to indicate his car is running as good as new

his avant is heavier than the tests I have...5-6 tests avg all cars <5k miles, most 2-3k
I assume he knows how to use the timer and is being 'honest'
his avg ~8.5 in 3rd gear w/almost 80k miles!
the avg for the tests and Audi's spec? ~8.4-8.5
using ALL gears for the same speed range (36-96 mph) avg 8.0...

[neckarsulm]

do you think that a 40k car that had done lots of short journeys would perform differently?
It's generally accepted that short journey cars will have greater deposits do you agree with this?
If so are you saying that the amount of deposit does not have an impact on performance?

[ArthurPE]

do you think that a 40k car that had done lots of short journeys would perform differently?
It's generally accepted that short journey cars will have greater deposits do you agree with this?
If so are you saying that the amount of deposit does not have an impact on performance?

I am divided on the deposit rate short vs long trips
I can see both sides, but personally think it doesn't make much difference

the arguement could be made short trips, oil thicker=less seepage, cooler=less vapor, lower speeds/engine speeds/loads, so less deposits

if the deposits are fuel (and may be in large part) then yes, because the engine runs richer when cold...

my opinion is well known (infamous, lol)
what do you think from this limited test data?

[andre3k]

Sorry, where has the value 15% been derived from?

[HYFR]

ok, so .... deposits dont cause a loss of power.

that means RS 4's came out of the factory underpowered ?

[neckarsulm]

what do you think from this limited test data?

My scientific understanding of this is inferior to yours but I have followed the threads and understand the points being made.
I also have a respect for the engineers at Audi and find it difficult to believe that FSI in itself (i.e. without other mitigating factors) can have such a flaw so you could say I am in the Arthur camp
I do think the deposits are fuel and that there is a correlation between town bound cars and greater deposits - it's been accepted for decades that a car that has done lots of short journeys needs a period of hard driving (aka italian tune-up) to perform as its best again so I don't think it's contentious to suggest a loss of performance could occur but that this would not be specific to an FSI engine

I suppose this leaves a question as to what causes an engine to lose performance when its been town bound? do you acceot this phenomenon can occur Arthur?

[ArthurPE]

Sorry, where has the value 15% been derived from?

people have attributed 40-60 HP (wheel) losses to deposits...
whp ~300 HP, 13 to 20%, used 15%

I personally think it's max 2%, if that...

this test would seem to indicate none

[ArthurPE]

ok, so .... deposits dont cause a loss of power.

that means RS 4's came out of the factory underpowered ?

actually every HP/trap speed calc I can find shows the RS4 UNDER-rated
this may be skewed by awd, but none come up with <420 HP

when compared to cars with similar wt/torque(not HP)/rpm band it is similar...and I've compared it to many

drag/frontal area and top speed videos would seem to confirm >400 HP