Another stake in the heart carbon naysayers

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As for the theory on the intake spacers...interesting but I wouldn't put much stock in it. Easy thing to point to I guess. Must folks will say they will give you a mild torque bump if anything.

Yes you'll get midrange torque increase from the intake length however it's effecively moving the entire torque curve down by about 500 rpm. Les torque at high rpms though so less ultimate power with the same peak torque at lower revs.

Anything to back that up on the RS4?

We've seen plenty guys dyno with them and they don't have any drastic shifts that I've seen. In fact this is the first I've heard of such a dramatic shift.

In any event, His MPH was improved last night, ever so marginally. His best MPH last week was 107.6 MPH and last night he hit 108.2 a couple of times. In fact top end was the least of his problems last night...his times would have been a hair better if he wasn't launching the car with 1.88-1.90 60 foot times. I reckon he had a 12.99 @ 108 in him last night. Would have been fun to drive his car, but again I don't think it would help our test...it would simply identify who shifts better.

I did drive another friend's car last night. His best 13.30 @ 106.9. My one pass in his car was 12.83 @ 109.75

Theres nothing specific about the rs4 - it still obeys engineering and physics Intake length is (pretty much) directly proportional to peak torque location. Shorter trumpets give high rpm torque, longer trumpets lower rpm.
http://www.emeraldm3d.com/articles/emr- ... th-intake/
http://auto.howstuffworks.com/question517.htm

Specifically to the rs4 - why do you think the engineers built an intake manifold where the intake tracts for each cylinder are of such a length that they need to be complex curves. Would have been far easier to manufacture if the tracts were shorter so that they didn't need the complex curve (plotting pressure wave dynamics and airflow through a bend is not fun) before the valves.

I have spent long hours over manifold trumpet lengths on track cars and this isn't some made up theoretical nonsense.
if people claim that adjusting the manifold intake tract length has no effect the they are really really wrong.
The real question is that is the effect smaller or bigger than any power loss through heat soak. If so then worth doing if not then well.

[sakimano]

Nobody claimed anything...but you. I asked you for an example of testing showing that this rather hard and fast 500 rpm torque shift number applies to our car. Fast is you are implying it is a negative to sort your argument. I haven't seen anything that would indicate anything either way. In fact everyone I have heard on the subject has said it is so nominal it is not worth discussing.

Anyway if you have any actual testing of this or any of your many other theories about the rs4, I would enjoy seeing the results.

Would be interesting to see what you yourself said about it in the old jhm intake spacers thread. Let's see...

agree with sonny - same as CAI really. won't give you more but let you keep what you've got for longer.

So there we have it. you appeared to brush them off as a minimal effect before even though you were an intake length expert then ( that was only a few months ago) but now they are negative enough that you need to point to them to refute the dragstrip results of this thread. Cute.

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Since you spend sooo much time looking at stuff I'm surprised you can't read basic English.
I think I clearly said 'rough rule of thumb' which you have somehow interpreted as 'hard and fast rule'.

I'm not claiming anything - this is a fact. messing with intake length will change the characteristics of the torque curve.

The comment was purely based on temperature effects ofte manifold.

Hah - I'm no intake expert and not claiming to be. It's a very difficult subject.

Also the main point of the argument is lost as its taken up with your JHM zealot protectiveness ('all hail JHM'). The main point is that your test car changed more than the factor being examined and you are claiming that this suggests carbon does not cause problems. it's no different to saying after a drag run 'JHM intake spacers are <beep> as the times are slower... Oh but I did also change the airbox too'. Completely pointless statement.

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*click. Ahh better.

[sonny]

Hail JHM


Sorry could not resist....



Interesting about the IM spacers, makes sense. Im tempted to take mine off.

iirc it raises the IM by 10mm.

[P_G]

JHM

[sakimano]

you guys are nuts if you think an observation about his intake manifold being much cooler than mine makes someone a JHM zealout

If you want to debate the power profile effects of the intake manifold spacers, that's great. I just think to make driveby comment a like adsgreen did that the carbon cleaning 'gains' may have been offset by negative effects of intake spacers (which is <beep> laughable) is a bit irresponsible, and when he backs it up with nothing regarding our car, it shows he's just looking for an argument. His old post on the subject pretty clearly shows he thinks the effect is nominal, and certainly not detrimental. If he is indeed a well educated expert on the subject, I find it funny that in all of the other discussions he never mentioned any of this...only now. I also find it funny that he's an expert in one post, then he's not an expert in another once he realises he has been shown talking out of both sides of his mouth.

I have spent long hours over manifold trumpet lengths on track cars and this isn't some made up theoretical nonsense.

Hah - I'm no intake expert and not claiming to be. It's a very difficult subject.

^^^when you figure out what you're talking about, please let us know.

Since you think this makes the results of the comparison useless, do tell how negative an effect power wise the addition of intake spacers would be on an RS4. You being the expert and all (when you want to be). Because the car was basically unchanged results wise from 10 days ago to Wednesday. So if he did indeed make power gains from carbon (is this your new theory? SHould I dig up posts where you say you don't think it's much of an effect?) your intake spacers theory would rely on either

a) carbon cleaning gives such nominal gains that a mod with negative, but nominal effects like intake spacers can offset them
b) carbon cleaning gives significant gains, and intake spacers are SO negative that they erase those significant gains.

You do realise that either statement is a contradiction of your past posts on the forum...and that the least contradicting one...a)...means carbon cleaning gives negligible gains (in this instance.) so you're kind of stuck agreeing with me.

So...which is it going to be?

[P_G]

It is feasible for someone to spend hours on a subject and still not be an expert (no offence intended ads)?

saki, the truth is your friend had a decoke and spacers put on at the same time so you can't come on here preaching one or other variable is responsible for the increase in power and then use that to support your original statement because unfirtunately you can't quantify either. If he had just had a decoke then fine, if he then had spacers put on after taking runs just on the decoke and did more runs even better; but the results you have just produced are invalid at proving either point.

As for the JHM bit, it looks like you have missed the sarcasm, leave it be.

[chunky79]

*

Very wise words though.

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Not claiming to be an expert and no offence taken. Quite happy to be corrected by a true expert (and has happened often). What I do know from experience is changing the intake length has an effect. How much well thats the expert bit I don't know.

For all we know it could mean carbon is a major problem but it's hidden by the performance boost of the spacers. Works both ways..
(am liking foe mode btw)

[rs4lee]

id like to add my own experience that i have had with my RS4

i bought my b7 with a 133000 miles on the clock ,and i am fortunate to work in a garage that has a 4wd dyno.So naturally i wanted to get it straight on the dyno to hear that sweet v8 roar and to make sure everything was as it should be .... well to my suprise it only managed 350hp(and i ran it 5 times) ,well i scratched my head for a while ,double checked that i had the dyno in the right mode etc (which it was).At this point i was not a happy bunny so i hit the net in search of some answers, as a scan with VCDS had come up with no faults , so i find a few topics on carbon build up and decide to remove the inlet manifold ...WOW!! she was gunked up good and proper !! so a good clean out of all the inlet valves, ports and manifold and it was staright back on the dyno ....first run 397hp now thats more like it i thought ! so all was well and i started to enjoy RS4 ownership ..or so i thought ....

Untill one night i was out on a spirited drive when all of a sudden i felt a noticable drop in power and the loss of the kick at 5k ....this time i managed to get a fault code from VCDS "implausable signal from intake runner control flap" i drove the car and did some logs ,it seemed that ignition advance was being retarded drastically on one bank ...so again the inlet manifold came off.This time i found a huge amount of free play in the runner that oprates the flap ,at this point i decided to de-flap the inlet manifold ,so i bought another manifold and de-flapped it ...a couple of days later i fitted the de-flapped manifold and the power was back as it was before ...great i thought thats that, no more issues with those flaps removed surley

Low and behold on thursday on my way home from work i went to open her up ,but instead of the usual get up and go it was as flat as a pancake and even held back at 5k !!!
so friday night i scanned it with VCDS ...no codes !! i thought balls to it and strapped it to the dyno ...268hp !! wtf i thought ,even my boss who has had a couple of RS4's was shocked.So it couldnt be carbon build up ...it couldnt be the flaps cause they had been removed , my head was scrammbled trying to think what the fault was this time that was sapping so much power from the car.Well we managed to trace the fault to a split vacum pipe that operates the diagphrams for the runners ?? i can only assume that the sensors on the end of the inlet manifold were monitoring the runners still in the manifold and not seeing them actuated to the desired position the ecu was pulling ignition timing ?? i dont fully know the workings of the rs4 ecu stratagies so this is purley an assumption ....needles to say without moving the car off the dyno i repaired the vac pipe and ran the car again 390hp !!

So it would seem that carbon build up if bad enough does cause a fair chunk of horsepower to be lost ,but there are also other failures due to inlet manifolds and its operating systems that can cause the same if not more dramatic power losses.

[sakimano]

^^^ interesting info to add. Would have been great to see you do some performance testing with such a bad case. A friend had a similar mileage rs4...never cleaned. I mentioned it above, that he cleaned it and sorted it and it is ridiculously fast now.

How is your car now?

PG...have a look at what I said above in the OP...this entire thread is my opinion. If you disagree with it or aidsgren does that is just fine and dandy. I am just sharing information that I have garnered about our car, in real world testing.

[sonny]

Rs4lee, thats very interesting, it just goes to show how sensitive this engine is, the vacuum leak os the new "boost leak".

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The problem is I suspect (but cannot be sure) is that the ECU only checks the flap position when a change is required.
So when the car hits 3k rpm it's likely to have sufficient vacuum stored to actuate the manifold flaps. ECU checks the sensor output see it asking for 100% position and sensors reporting say 98.5% (so within tolerance) and all ok.
However under full throttle and considering the actuators need vacuum to keep open any vacuum leak would mean that the system was now losing vacuum faster than it could generate it. So slowly but surely the manifold flaps would start to close choking off the air supply to the cylinders. Thus circa 280ps (it's a common figure) with no fault code. As the revs drop under 3k rpm, the ECU asks for 0% flap position and looks at the sensors and yep, back to 0% so all fine. Now the vacuum leak is not leaking and lower rpm means lower throttle body position so the system can recharge the vacuum and the process repeats.
I don't know if this is how it works however it matches the symptoms - if the ECU did check the flap position more regularly then it would throw a code instantly.

Problem would be worse in non sport mode as the system uses vacuum to hold the valves closed.

What I don't understand is why Audi didn't engineer the system to err on the side of caution - IE, reverse the flap position system so that it needed vacuum to close. The problems of running manifold flaps open at low rpm are consdierably smaller than closed flaps at high rpm.

[P_G]

ads, the manifold flap runners are continuously meausred for % opening / angle and my original faults were because it could not read between 0% and 10% i.e they were getting stuck. When Audi Roadside stuck their diagnostic tool on it and pushed the white plastic arms outside the manifold with a screwdriver you could see the % movement all the way through the rane and supposedly so can the ECU's.

Saki, I wasn't disputing your opinion but you have been quick to dismiss other data because there was more than one variable involved and likewise the same has to be applied to your friends data because it wasn't just a decoke, it was decoke and IM spacers. It's like Ben Johnson saying before I could run the 100m in this time but after chaing my training program I could run this time. Oops did I forget to mention the boxful of steriods I also took, I'm sure that didn't affect my performance?