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This many years on. as found the stock arrangement results in more un-metered air leaks and increased oil consumption. The cam-cover vents, hoses, elbows and O-rings all require attention. Again, do not let these components deteriorate and become unregulated leaks of air into your Intake System.
Left alone, the OEM corrugated hoses crack open, so replace them with this. See the spec written on the hose pictured above. Note use of this exact hose allows for a secure assembly which does not require any clamps whatsoever. The OEM black plastic quick-disconnect ends (pictured), some of which have integral elbows can be cracked, so check them too. The O-rings on thethese ends don't age well, unless they are the "orange" A4 versions or non-OEM silicone replacements (Mance recommends slightly over-sized strictly silicone O-rings 14mm ID, 3mm round cross-section available through McMaster-Carr).
The cam covers need to come off to clean-out the internal vent chambers. This periodic maintenance may reduce your oil consumption (particularly if done in conjunction with the below mod). The cam-cover gaskets may need replacement while you are there.
This Cam-Cover Vent mod will reduce your oil consumption:
20.) O2 Sensors; and the committee that puts them in charge...
The Intake System is not just about delivering air. Air is just the half of it. Most of our cars deliver too much fuel; most of the time. The intake system must also produce, hold and transmit vacuum, measure correctly all the air consumed, prevent leaks, capture crankcase and gas-tank gases, etc. Without doing all of that properly, the proportionate amount of fuel cannot be determined; nor delivered.
The engine sensors measure your conditions and send signal. Whether they are correct or not is up to you. Ensuring that these are fed good info, and are in good shape, that these "base conditions" are met is the only way your engine will ever perform to even it's design outputs, let alone any aspirations you may have; to move beyond that.
O2 Sensors:
Another pair of potential air leaks themselves, so remove, install and torque carefully. An air leak here in the Exhaust System makes it a defacto part of your Intake system. They only operate in a very narrow band, and feed-back oxygen content info used to fine-tune injector pulse-width. They don't know how that oxygen got there. If you have air-leaks here or elsewhere, they don't care.
These are the two items that the whole Motronic system wants to put conditionally "In Command" (with some assistance of various board members, depending) of fuel delivery, so getting these just right is quite important. However, if the rest of the Board can't get the mixture close enough to correct, or they don't agree on what to do, the O2's don't get to do their fine-tuning of the mixture job; and the result is; too much fuel.
Some of the most practical O2 sensor diagnostic info I've found:
The Motronic committee that is the "Board of Sensors" is always in session, deciding on outputs, fuel delivery being one.
Amongst the components (committee members) that sense the conditions necessary for the O2's to do their job, and allow the ECM to concede authority to them, here are two which often require attention:
The MAF needs to operate within spec. (deliver output signal both within the correct range, and fully across that range); and measure <i>all</i> the air being drawn into the engine. The original from the factory design base condition assumes that this is happening. However, if you have good compression, but engine vacuum is low (< what, 19" Hg.); your MAF is <i>not</i> sensing total air intake. Fuel delivery is compromised, power, mileage and drive-ability suffer.
The CTS needs to again, output within the electrical spec. range, to correctly indicate engine coolant temp. to the ECM; and needs a serviceable T-stat to have the engine even warm up. If your car <i>thinks</i> the engine is cool, you burn too much fuel. We are here some distance from the Intake System, my point being no amount of better than stock air-flow can ever correct for overdue maintenance and improper fuel delivery.
Given bad info, the fuel side of your Intake System can never deliver the right amount of fuel for a given occasion. The design defaults are all on the rich side to preserve the engine in the short term. But both power and economy suffer as a result. Often the system latitude is such that no fault codes will be registered or lit. Long term, as much of our day-to-day driving is done with the engine only lightly loaded and the throttle just barely cracked open, you should be getting excellent mileage and your system can and should deliver this result. Ensuring and returning to base conditions is a requisite step; often overlooked. Most of the time our engines are not starving for more air, they are drowning in fuel.
Last edited by Lago Blue; 10-01-2010 at 08:11 AM.
Reason: clarity
Part of your intake system's function is to provide for the ingestion of fuel. How much you historically and currently use, is key to maintaining your car.
Keeping a record of your exact fuel mileage is a window into knowing your engines state of tune, and is just good preventative maintenance. More than once I have detected a fuel leak simply from completing my consumption log. Yes, I'm talking fire prevention.
Because you don't get a CEL for not being in closed loop, you are going to have to keep track of what is going on. That your car has the ability to precisely meter fuel, you must know; when it is not.
If your odo/tripmeter does not function you can use point to point calculations to check consumption.
Your odo/tripmeter and trip computer (if installed) even if fully functional, don't know what good mileage is, but they can help you ensure you keep it.
You need a plan. I think one of the best ways to improve how your engine runs, is to fit improvement work into a comprehensive maintenance plan.
Before you head off to do any major component replacements or almost any part of the Intake Manifold Workshop, consider separating wants from needs.
Your engine probably exhibits more than one of the following:
a.) leaks oil; blows oil; and ingests far too much oil;
b.) leaks too much air in; both un-metered and vacuum leaks;
c.) develops too little Intake-Manifold vacuum at warm idle;
d.) provides too much fuel at idle;
e.) delivers poor fuel mileage even on the high-way;
f.) runs poorly at low load settings;
g.) suffers from basic drive-ability issues such as surging idle and stalling;
h.) has a constant or recurring CEL that requires frequent maintenance; &
i.) does not accelerate with authority at low speeds.
Until these issues are eradicated, you will be less satisfied with the result of anything else you attempt of a more sexy nature. After the above are addressed, you will be pleasantly surprised what normal actually feels like.
I recommend that you clean the engine compartment by hand, as there is less possibility to contaminate the electrics with fluids, since you are not spraying anything under pressure. Your engine management system is relying on those connections to correctly transmit data. The boots over these connectors are for weather protection, and are not steam or pressure-washer proof.
<b><u>Stage II: Return to Base Conditions.</u></b>
You'll need to research and prep for the job(s) you want to carry-out, but basically you are trying to restore to as new conditions, or slightly better in a couple of cases.
Your list might begin with something like this:
a.) start a log-book of your work;
b.) pull, record and erase DTCs, even if you have no CEL;
c.) clean the MAF Sensor;
d.) clean the ICS/ICV by removing the bottom cover if linear style;
e.) replace all the small O.D. vacuum hoses;
f.) do the EGR Freq. Valve Vent Mod;
g.) replace the Noise-damper to Throttle-body seal;
h.) do the Telephone-cord Mod;
i.) make some new CCV hoses;
j.) do leak-down tests on all branches of your engine vacuum system;
k.) replace all 12 injector o-rings;
l.) measure and record at warm idle:
- the peak engine coolant temp.;
- the I/M vacuum;
- the Injector pulse width;
- the O2 sensor voltage outputs and cross-counts;
- the MAF sensor output voltage;
These will give you an idea what normal looks like. Normal may not be great yet, but it can be made better.
One of the best places to start is the junk-yard.
a.) Pick up a set of injectors and send them away while you continue to drive on your current ones.
b.) ditto Valley-pan;
c.) ditto Cam-covers;
d.) ditto Intake-manifold, complete with ICS if you didn't get this when you got injectors;
Q. (from EDIGREG) "By modifying the Velocity Stack, you've "ruined" the angles/tapers that Mance...determined to be ideal. Why spend money on his VS just to modify it? " A. Understood. However, there are few alternatives. Because his stack, Mk I or II, offered the best starting point for what I wanted to do. I would have prefered a 2nd-hand Mk II, however, at the time, it was the only one on the market. You could look at it this way: at least I haven't "ruined" a Mk II. This was much easier than starting from a raw piece of tubing. That would have been beyond what I could probably do.
Q. (from EDIGREG) "I'm not sure what you mean by mk1-2. AFAIK there is only one version of the VS...At least the picture you showed is the S3 VS, and that's the only version I know of. The new version, "XVS", hasn't been released yet... " A. ...Check this out...
Q. (from EDIGREG) "Ah, that was before my time here...But I don't see why that would make a difference...in your desire to modify it. But, to each their own. " A. I believe this may be a later version...
vs1.jpg
...Compare the above with the below shot of one like what mine was as received... vs_1_stock_v-stack.jpg
One of the things I like best about forums like this, is that I get to consider & build on (or choose not to, or to take a different route to) that which others have done & written about without necessarily having to repeat exactly what they have done.
The alternative to modding one is that I'd be working by myself, & having to experiment even more, learn how to re-invent Mance's entire process, just working a whole lot harder to get to the same spot. Later on I hope to show some examples of this, for instance, how I picked & chose items off Mance's I/M Workshop Menu like I was ordering dinner, & asking the waitress for substitutions & some mistakes I made along the way.
"I took the road less traveled & that has made all the difference."
More "why":
...This method may also accomplish the following:
a.) By eliminating the transition(s) from V-stack I.D. to MAF Housing I.D., it is hoped that more laminar flow will be delivered to the sensor; &
b.) By moving the V-stack closer to the sensor (without physically cutting it shorter), it is hoped that the Velocity-stack's positive effect will be enhanced.
You may also gather from reading below that what Mance may have been aiming for with his selection of aluminum tubing diameter for his eventual A4 V-stack was "matching I.D.s". It never did fit as well in the larger exit ID of the "90" air-box lid.
What I am aiming for, is hopefully at least as good a fit & function as when one of Mance's originals is used in an "A4", but in a "90" instead, right through it's filter-box lid & with the modified velocity stack's O.D. fitted directly into the MAF housing's front-end relief-cut I.D., providing as seamless as possible, a step-less air passage all the way through from the V-stack bell-mouth inlet to the MAF housing outlet.
I should also concede that the lack of issues I've experienced with this mod may be in part due to the apparent fact that, with my stock medium mouth MAF, it is rather less sensitive to screen removal to begin with. This may also help explain my previous success with V-stacks made from paper coffee cups & plastic wood-fill containers! Your experience may differ.
Why its' specific shape -may- not be so critical...
You don't always see every velocity stack following the same identical set of proportions. Even amongst VAG, they are not identical.<ul><li><a href="https://forums.audiworld.com/12v/msgs/377.phtml">https://forums.audiworld.com/12v/msgs/377.phtml</a</li></ul>
This is an excellent thread full of quality info. Probably "old news" to many, but I just picked up my first B5 (and first 12v) so this is all great info to read up on. Thanks for cleaning it up!
08-16-2010, 10:02 AM
19.) Cam Cover Vents & Hoses...
