No more seafoam...no more scraping. You excited?

[bam_bam]

I am very very drunk though.

Arthur is as right as anyone can be on this matter, mostly 'cause he was the first to parrot the truth or logic behind carbon not being such a big deal. The rest of us refused to believe it could be true, me included. Since then I've read pretty much all of the FSI carbon stuff, my conclusion? Only in the super extreme cases does carbon build up degrade performance. On the way to the extreme, there's only a couple of tenths in it. Can you feel it? Probably/maybe/sometimes/never, but, for some, that's enough. I wouldn't worry about the the performance hit, if you read Arthur's many maths post on the subject, it's moot.
My main concern (as I will be getting a B7 soon enough), is the effect/affect on engine longevity. The tumble and fall of air/mix into the engine is disrupted with the carbon buildup in place thus causing hot spots. There's not a lot of data on this but the theory is sound, maybe Arthur can comment further. I worry that in such a highly strung engine, it'd not be long for this world but that said, the B7 RS it is getting on and with no samples of this issue arising, thus far, it could also be a red-herring, until JHM come up with a solution for this non-issue. Then we get this thread all over again. Can't wait.

Any thoughts or has this topic been done to death, too?

I need chickenman, water and bed.

[wellzieRS4]

I need chickenman, water and bed.

that is the best cure for going on a whitey in that order

[sakimano]

[
There's at least as many threads as opinions, ranging from the complete denial that build-up happens, through "yes there is build up but it's in places where there is low or zero flow so its effect on performance is minimal to zero", passing though "build-up happens but reaches a certain level and then doesn't get any worse, and if you clean it it comes back so quickly you've wasted your time & money", onto "build-up happens and can be cleaned but the benefit is small to minimal" and reaching "build-up is a disaster and robs me of 100+bhp".

Take your pick of which of those you believe - all I'll say is look at the data and not the opinions when making up your mind.

can you share some of the data you're referring to (assuming you have data that says there is no performance loss)? The data I've seen is that guys gain RPMs per second faster on logs post clean, dyno higher post clean, run faster dragstrip times/trap speeds post clean. I haven't seen anyone run the same when measuring properly (and by measuring I mean NOT doing a handheld stopwatch while driving, which is what the 3k to 8k test is.

I have only pre-carbon clean data for my own car, so I'm stuck reading other people's 'proof' one way or the other. However I haven't seen any data that says the car doesn't gain anything post clean. I'm not an engineer though, so I like to keep things simple i.e. measuring performance gains by looking at actual performance gains rather than textbooks.

[sakimano]

here's something to ponder
this car ran 13 flat 107-108 range: lighter, modded and cleaned...owner is familiar with the strip
Engine Mods: | JHM Tune | JHM Intake Spacers | Aux Radiator Delete | Secondary Air Pump Delete | Ram Air | Port & Polish IM, De-flapped, de-vaned | NGK Platinum Plugs | K&N Air Filter | Setrab Oil Cooler | Larger PS Cooler | 034 MAF Hose |
Drivetrain Mods: | JHM LW Flywheel | JHM Stage 3 Clutch | JHM LW Crank Pulley | 034 Tranny Mount Street Density | Apikol Rear Diff Mount | Stern Motor Mounts | JHM Short Shifter and Solid Throw |
Braking: | Alcon Front Brakes | Carbotech Bobcat Street Pads | SBS Pro Race Track Pads | Stoptech Rear Pads | Stoptech SS Lines |
Suspension: | Stasis MS 6/8/12 settings | 850/1300 Spring rates | Hotchkis F, R sway kit | Stern Rear Sway Links | Stern Adjustable Control Arms |
Exhaust Mods: | JHM 2.75" Cat Back Exhaust with Resonators | JHM 2.75" Downpipes with swappable test pipe and cat sections |
Weight Saving Measures: | Headlight Washer Removal | LW Battery Kit | Odyssey 925T Battery | DRC Reservoir and Line removal | Sunroof Delete | Bose Sub, Amp, Sirius delete | Current Estimated Weight: 3732lbs (-226lbs) |


uncleaned stock car w/30k miles runs 13.1/106-107 (on video with a weak launch)


my point is the RS4 package is pretty solid from the factory

Maybe I can help with a few facts.

1. that car never ran with that modlist. He made a few of those changes like some of the major weight reduction ones AFTER he ran at the strip with his JHM tune and exhaust.

2. The owner is mickf29, and his time was 13.0 @ 110.3 (not 107-108 range) ...despite a 2.17 second 60 foot time.

3. He is also not 'familiar with the strip'. I believe he has been 3 times getting only 2-3 passes each time...3 on this occasion, and the first time he went, his friend fried his clutch. In mick's own self deprecating words:

Well, it's unanimous. I suck at drag racing

http://forums.quattroworld.com/rs4b7/msgs/60832.phtml
That comment revolved around his having trouble launching the car on that particular night. He actually had the engine stall on him on one run.


As for the RS4 being pretty solid from the factory, it sure is. However audi left a TON on the table, considering that another customer with mick's same JHM parts (intake spacers, exhaust, tune, clutch/fywheel, crank pulley) but NO weight reduction mods (actually his wheels/tires are a good bit heavier than stock) ran 12.2 @ 112.4...on a day when a stock RS4 (mine) ran 13.1 @ 106.0 at the same track.

http://www.youtube.com/watch?v=vuXShGfjT0c

[adsgreen]

Can we change the record please? Ok - we get it. JHM add a hundre horsepower using magic.
Fine
Let's move on.

[ArthurPE]

can you share some of the data you're referring to (assuming you have data that says there is no performance loss)? The data I've seen is that guys gain RPMs per second faster on logs post clean, dyno higher post clean, run faster dragstrip times/trap speeds post clean. I haven't seen anyone run the same when measuring properly (and by measuring I mean NOT doing a handheld stopwatch while driving, which is what the 3k to 8k test is.

I have only pre-carbon clean data for my own car, so I'm stuck reading other people's 'proof' one way or the other. However I haven't seen any data that says the car doesn't gain anything post clean. I'm not an engineer though, so I like to keep things simple i.e. measuring performance gains by looking at actual performance gains rather than textbooks.

I know people who don't have it don't trust 'book smarts', but honestly Audi's are designed by Phd's not shade tree mechanics

the data is cleaned cars run no faster than uncleaned...that is also fact
in fact in one case on here side by side both cars pre-clean, dead even
after one was cleaned by Audi, heads removed, new plugs, etc....same road, side by side, no difference...the uncleaned car is heavier to boot...and had 70k miles iirc

I have 3k to 8k data for >150 runs (actually a lot more) for >60 cars, 15% cleaned...no difference

back on topic...the 'solution' proposed is stupid...dumping fuel into the manifold is illegal...it violates every fed/state reg
and it won't help....the deposits, as far as I can tell are 'soot' from combustion...that is why fuel quality (the better the fuel the less residue) and running the car hot is important...get the combustion process up to efficiency as fast as possible becuas in open loop warm up the mixture is rich, ie, more soot

[ArthurPE]

my point is the RS4 package is pretty solid from the factory
Maybe I can help with a few facts.

1. that car never ran with that modlist. He made a few of those changes like some of the major weight reduction ones AFTER he ran at the strip with his JHM tune and exhaust.

2. The owner is mickf29, and his time was 13.0 @ 110.3 (not 107-108 range) ...despite a 2.17 second 60 foot time.

3. He is also not 'familiar with the strip'. I believe he has been 3 times getting only 2-3 passes each time...3 on this occasion, and the first time he went, his friend fried his clutch. In mick's own self deprecating words:

you wouldn't recognize a 'fact' or the 'truth' if it bit you in the ass

not true...the only mod perhaps not done was the clutch...perhaps
it's the trap SPEED that matters and skill has little to do with that

the fact is a highly modded car appears to no faster than stock: C&D (?) ran 12.8/111 in a stock car

what is a 'ton' in terms HP or lb-ft...for us who aren't schooled on the science like you...
you lose all credability with statements like that...are you saying 20% >80 HP (or 60 lb-ft) can be gained reliable with no effect on drivability, longevity and effciency?
with NO change to Cr or displacement?

you are deluding yourself (or shilling for others) if you think a 'ton' of power/torque can be had in this engine without changing the displacement, compression ratio, major rpm increase (power only, no torque, provided you can fuel/spark/air it) or vol eff thru forced induction...
show me in an engines torque equation WHERE and WHAT is changed for this 'tonnage'...these are called 'facts'

people aren't morons, stop the condescending BS and treating them as such

[ArthurPE]

Can we change the record please? Ok - we get it. JHM add a hundre horsepower using magic.
Fine
Let's move on.

elixer of the gods...and violator of federal law

[bam_bam]

can you share some of the data you're referring to (assuming you have data that says there is no performance loss)? The data I've seen is that guys gain RPMs per second faster on logs post clean, dyno higher post clean, run faster dragstrip times/trap speeds post clean. I haven't seen anyone run the same when measuring properly (and by measuring I mean NOT doing a handheld stopwatch while driving, which is what the 3k to 8k test is.

I have only pre-carbon clean data for my own car, so I'm stuck reading other people's 'proof' one way or the other. However I haven't seen any data that says the car doesn't gain anything post clean. I'm not an engineer though, so I like to keep things simple i.e. measuring performance gains by looking at actual performance gains rather than textbooks.

I know people who don't have it don't trust 'book smarts', but honestly Audi's are designed by Phd's not shade tree mechanics

the data is cleaned cars run no faster than uncleaned...that is also fact
in fact in one case on here side by side both cars pre-clean, dead even
after one was cleaned by Audi, heads removed, new plugs, etc....same road, side by side, no difference...the uncleaned car is heavier to boot...and had 70k miles iirc

I have 3k to 8k data for >150 runs (actually a lot more) for >60 cars, 15% cleaned...no difference

back on topic...the 'solution' proposed is stupid...dumping fuel into the manifold is illegal...it violates every fed/state reg
and it won't help....the deposits, as far as I can tell are 'soot' from combustion...that is why fuel quality (the better the fuel the less residue) and running the car hot is important...get the combustion process up to efficiency as fast as possible becuas in open loop warm up the mixture is rich, ie, more soot

...and on the topic of air/mix 'tumble and fall' being disrupted by carbon build up, thus creating potential hotspots and/or further complications? I'm not trying to start something here, I'm just interested if this is an issue or if there is known data, experiences or reports.

[ArthurPE]

...and on the topic of air/mix 'tumble and fall' being disrupted by carbon build up, thus creating potential hotspots and/or further complications? I'm not trying to start something here, I'm just interested if this is an issue or if there is known data, experiences or reports.

the air velocity is so low and the pressure drop so small (vel = k sqrt(dp) ) that it is moot

as far as hot spots if pieces were breaking off and causing detotnation (or even pre-ignition) many engines would have fragged, since all engines have deposits

if someone is hyping the 'scourge of deposits' beware, they are trying to sell you something...usually a load of dung

[Shoppinit]

Is the carbon deposit naturally self limiting then? Because presumably if a layer continues to build up then sooner or later it will restrict the air.

[ArthurPE]

Is the carbon deposit naturally self limiting then? Because presumably if a layer continues to build up then sooner or later it will restrict the air.

it appears to be...I've seen pics of cars at 10k, 20, 50k, etc. and it seems to be ~ the same (except for the case where some other system has failed)

air is compressible, if flow is constricted it speeds up, but volume changes little, you do get a bit more pressure drop which means higher pumping losses, but in modern engines very little impact...an engine is a pump (vacuum), the cylinder draws air in and atm pressure is the driving force...it changes little (at a given elevation)

if a car with 50k of normal deposits lost 1 to 2% torque I'd be surprised...a 10 deg air temp variation has more impact...so does fuel grade, etc.
either way not meaureable on the road or dyno

the fact that this issue detracts anything what so ever from the RS4 ownership experience that we are so lucky to enjoy is what tweaks me (for others, not me, I know it is a red herring)
and it is all raised for the profit driven motives of others...trust me, I'm a capitalist, I like $$$ as much as the next guy, but I don't want it by fear mongering or conning people out of it...

drive the car, enjoy the car, if you get a check light take it to the shop, get it fixed...then repeat...other wise drive the car, enjoy the car...

I would NEVER install a system that dumps fuel into the manifold, the negatives outweight the positives
If for peace of mind one is compelled to clean the valves every 50k miles (or even 25k) so what, the e46 M3 needs an expensive valve adjustment every 25k or so
it's part of the price we pay for the experience

[Shoppinit]

I suspect the carbon buildup issue would have been easier to swallow if the RS4 was making its rated power more frequently. It's understandable that people go looking for the lost horses, I guess, and to the layman that would seem like an obvious culprit.

[bam_bam]

...and that's a wrap, can we go home now people?

[ArthurPE]

I suspect the carbon buildup issue would have been easier to swallow if the RS4 was making its rated power more frequently. It's understandable that people go looking for the lost horses, I guess, and to the layman that would seem like an obvious culprit.

I don't subscribe to the under-rating arguement either
when I look at actual performance numbers for various cars of similar HP and wt the RS4 is FASTER than it should be
case in point, it is seperated by only a few seconds in 8 minutes/13.2 miles from an M3 which is >300 lbs lighter, both on sport tires
it's faster than an e60 M5 around the 'Ring and very clsoe to a 997S driven by one of the best drivers...

look at 1/4 times/speeds for American muscle cars of similar power/wt, etc., this despite the fact that the RS4 has twice the drivetrain losses
muscle car 1 tranny, 1 diff, 2 axles
RS4 1 tranny, 2 diffs, xfer case, 4 axles

I have a meeting now, I get to drive mine, and guess what? I'm glad to do so