deposit performance impact

[ArthurPE]

it's order of magnitude...

I would not consider 1 sec out of 8 minutes a 'change'

I would not consider 2 cars with a 15% power/wt delta with the same driver running numerous laps to get the optimum lap, running the ~same time (<1%) possible...same for drag et/trap speed

as far as 396 to 446 due to cleaning & porting, almost 13% gain, no way..
if we assume stock 420 and deposits ~ 396 or a 24 HP/5.7% loss and the extra 26 HP/ 6.2% gain from porting, I'm 'skeptical' to say the least...

if we assume the engine was over-rated and only made ~400 HP from the factory then the loss is 4 HP or 1%, which I can 'buy'...
if we assume 380 from the factory, like many say, then deposits ADDED power..lol
but in that case the porting would add 46 HP/12% due to the porting...nope

if Audi could get 25+ HP/46 HP (by simply partially porting a manifold they would have extrude-honed all of them (their cost, a few bucks over many cars, on a car that is a flagship loss leader to begin with) they would have done it...they did everything they could to eek out power...and the extrude-hone would yeild more power..

they don't have monkeys designing these cars...they probably had 5 guys on the manifold alone!

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.

[ArthurPE]

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

if the runs described above are any indication, the avant has 'normal' deposits (based on the 80k miles, as bad as it gets as long as no other system failures)...and from the pictures, the sedan abnormal...
but from the results it seems like it doesn't make any difference either way, cleaned vs uncleaned...
so I would say 'normal' is an extremely wide range, and abnormal seems to have none or very little impact...'normal' even less...

[S4Player]

I kind of understand but if a car dyno's 398 then 446 or whatever on the same dyne after cleaning is that not evidence to show the porting/cleaning must do something?

[pad125]

Pardon my ignorance fella’s as I’ve not had chance to read all the posts but am I right in thinking that the purpose of the thread is to demonstrate that carbon build-up doesn’t have any or little effect on performance??

If this is so and I don’t disbelieve Arthur’s figures for a minute but I don’t think this is where the CB issue should be focused.

If CB is going to become a point of discussion again (and god forbid!!) then I think we must all appreciate that these cars leave the factory at the top end of the emissions scale and because of that the carbon build-up is more likely to cause the engine to fail the emissions test at MOT time than deliver any noticeable reduction in power…..believe me I know!

Don’t get tangled up in horsepower this, horsepower that! A failed MOT because of emissions will hurt your wallet far more.

[P_G]

I kind of understand but if a car dyno's 398 then 446 or whatever on the same dyne after cleaning is that not evidence to show the porting/cleaning must do something?

No doubt Danny but like said earlier, it is creating a false working environment as FSI engines will never have internals as clean as cleaning does at any time in their lives unless never used / within the first few hundred miles after cleaning / cleaned again.

I would say however this is Audi, not McLaren or Bugatti; so as much as Arthur's ideal of how Audi design parts for the engine there is the reality of life cycle costing involved in building any mass produced car and I would suggest certain elements could be designed better and have been after-market. The brakes are my gripe; IM porting does show gains but to have the IM manufactured in its OEM form is perhaps cheaper than the ported versions that have been done retro.

Like pad125 has said though, it is a hugely subjective issue and not all about absolute power.

[Steve_C]

Has anyone stuck a nearly new/low mileage RS4 on the rolling road to see what bhp is makes out the box?

[P_G]

Which dyno though Steve C? As and example I have used 5 different dyno's in my 3.5 years of ownership and ranged between 358 and 396 bhp.

[Steve_C]

Point taken, P_G. But if the same dyno was also used to measure older cars as well we would at least have some comparisons to deduce the reduction in power over time (albeit we may be comparing 420 with 370 or 390 with 350 etc).

[SR71]

In this discussion distinction must be made between the effects of "cleaning" and "porting".

If having either done, it is pointless not doing the other, so getting a grip on the relative effects of the two things is difficult.

I reckon cleaning is about ~2% but porting can have a bigger effect. Doug can comment.

A Gen 1 3.6 997 came out of the factory with 320hp?

The Gen 1 3.6 997 GT3(RS) runs 415hp?

I'm sure the exhausts differ but out of curiousity, and I think there is a small change in displacement, do the intake manifolds?

95hp out of somewhere and Porsche are no slouch at designing good cars...

[neckarsulm]

Damian (VARSITY on here) who worked next door to MRC had his B7 taken back by Audi because it was down on power.
I don't want to speculate on how old it was or the mileage or who dynod it (MRC didn' have a dyno then) but it was a good few years ago so must have been nearly new.

[adsgreen]

95 bhp is more from a much higher rev limit but this in itself would benefit from porting as the gas flow requirements would be different.
I dont think audi would pull all the stops out to extract every last bhp. needs to be balanced with commercial aspect such as manufacturing costs and reliability/warranty implications.

[P_G]

Point taken, P_G. But if the same dyno was also used to measure older cars as well we would at least have some comparisons to deduce the reduction in power over time (albeit we may be comparing 420 with 370 or 390 with 350 etc).

That's been done at Paramount and that is where I got my 358 bhp reading from. Stock cars ranged from 338bhp to 390bhp IIRC and granted the ones at the lower end were found to have issues and subsequently fixed however mine was one of the ones at the lower end of the scale yet still does consistent runs both 3k-8k rpm, using Racelogic boxes, pitted up against other Avants and saloons and can produce a 396 bhp figure as recent as a few weeks ago.

Now I'm either incredibly lucky witha degree of mechanical sympathy for my car or the demonstrable effect of CB as a single route cause of power inhibition is exacerbated and more likely a number of other factors which manifest themselves in forms including excess CB; e.g running rich, misformed valve seals; oil contamination to name but a few are the real issue.

[neckarsulm]

more likely a number of other factors which manifest themselves in forms including excess CB; e.g running rich,

I'd say if you do a high proportion of cold starts AND low overall mileage this has to have some effect as I have never smelt a modern car that runs that rich when cold.
It's fact that the factory supplied a new set of plugs with each car for the dealers to fit at PDI as they were being fouled when moving the cars around from the factory to the dealers and if the plugs are getting fouled surely that's related to CB?
If that is the case then maybe the software version has some effect on why some cars are worse than other as they are definitely tweaking something fueling related with the two later versions 0080 and 0090