Haven't really seen anyone put together a best practices list for maintaining a tuned Gen II and thought the community could benefit from one. Preventative maintenance is the key to maximizing your Mini’s new found performance and helps ensure you can enjoy it for years to come.

Oil changes:
Forget what BMW says about oil change intervals. It’s utter drivel and spouted by those that make money selling parts. If you operate a Stage 1 or 2 tuned Gen II make sure your oil change intervals are at least every 5,000 miles. Why? Carbon accumulation in the oil. Carbon is what turns your oil from that nice amber color to black. Carbon is also an abrasive that accelerates wear and accumulates in the most inconvenient spots. Wear is the underlying cause for timing chain stretch, which is why cryo treating the chain extends its life. During cryo treatment some of the remaining austenite is converted to martensite. This occurs at a higher rate near the surface and increases wear resistance. (On a side note if you choose to cryo treat a replacement chain do not treat the chain tensioner. The tensioner contains a spring which is already in a loaded condition. Altering the hardness in a compressed state will result in less spring pressure when oil pressure is low at idle.) If you’re running meth injection, I recommend shortening that interval to every 4,000 miles. As cylinder pressure increases so does blowby. Meaning more combustion byproducts including unburnt fuel and methanol are introduce to the crankcase and your oil.

Engine flush:
Every third oil change perform a flush. (I add five ounces of Seafoam and drive for about ½ an hour before draining the oil) As mentioned above carbon accumulates in the most inconvenient spots such a turbo bearings and oil squirters. When a turbo bearing fails it tends to be obvious and can be solved relatively easily, albeit not cheaply. Plugging an oil squirter however, will have drastic consequences. Cylinders 1 and 4 are surrounded on three sides (if a cylinder can be said to have sides) with coolant, while cylinders 2 and 3 are only surrounded on two sides. This means cylinders 2 and 3 have less intrinsic cooling capacity than 1 and 4. The oil squirters primary function is to cool the bottom of the pistons. When the oil flow through a squirter on a #2 or #3 piston declines the piston temperature rises and detonation is right around the corner. I also recommend pouring the balance of the Seafoam in the gas tank and filling up with your flavor of octane at the same time. Our vehicles use a single primary O2 sensor as opposed to a per cylinder setup. Which means its possible for a low flowing injector to result in one cylinder running leaner than intended which can also lead to detonation. Feel free to replace Seafoam with an oil flush and injector cleaner of your choice.

Air Filters:
I recommend staying away from oiled air filters. While some enthusiasts have gone years without problems. If the air mass sensor gets contaminated with oil it is often necessary to replace it. It can be cleaned but that tends to be hit or miss due to the intricate air passages in the MAF before it gets to the hot film element. In addition, it has been proven that while oiled air filters may flow more initially, they flow less air than non-oiled filters once they both become dirty. Finally, many tests have shown that even when an oiled filter is new, the quality of the air passing through it is lower than with non-oiled filters. Meaning more dirt is getting into your engine. AFE and several other companies make excellent non-oiled high performance air filters.

Spark Plugs:
Ensure they are gapped at 0.024” and torqued properly when replacing them. If you don’t have a torque wrench, I strongly recommend investing in one. There are many maintenance applications where proper torque can be critical. Spark plugs are one of them. As far as brands go, I recommend steering clear of anything but NGK. Beru and others while often enough for stock applications, have proven to be less than adequate many times once tuned. Replace the plugs every 20K miles.

Coolant:
Draining and flushing the coolant every two years may seem excessive at first glance. However, glycol degrades and the pH of coolant changes over time. Coolant contains buffers to absorb pH changes but once utilized the coolant can become alkaline and quickly cause problems. I only recommend BMW branded coolant. Summit Ice Water coolant, while very effective at lowering temps, should be reserved for race only applications as it has no anti-freezing additives.

Fuel:
This one should be obvious, but I still get surprised by having to explain it to new clients. Stick with Tier One gasoline providers (Shell, Mobil, Chevron, Exxon, etc.). While cheap gas at the “fill in the blank” may be priced attractively, you are taking a gamble running it in a tuned engine. Tier One gasolines typically have higher quality control standards and include additional additives to help keep injectors clean and reduce carbon accumulation. That doesn’t mean you’ll never get a bad tank of gas from a Tier One provider. It is possible for the underground tanks to be misfilled or leak allowing water in. If this ever happens drive sedately until you can burn it off.

Oil Catch Cans:
If you don’t have one, buy one. Doesn’t matter if you’re tuned or not. If you are only able to plumb one side of the PCV system make sure it is plumbed into the PCV line that runs from the valve cover to the intake tube just before the turbo. The greatest amount of blowby occurs in boost as the cylinder pressures are higher. In addition, the PCV port on the back of the valve cover is designed to close from the raised manifold pressure while in boost. Since the crankcase still needs to be vented the excess gasses come out the other side of the valve cover and are plumbed back into the intake just before the turbo. Installing an OCC will have almost zero effect on carbon accumulation. That’s not our goal. Our goal is to prevent detonation. If oil mist gets into the intake charge it can lower the effective octane of that charge from 93 to 89 or lower. Oil contamination of the intake charge is one of the primary reasons even stock untuned Gen II’s running 93 octane can generate Super Knock codes and break ring lands. Will an OCC totally prevent the entry of oil mist? No, but it’s the best solution currently available. Try to purchase an OCC that is baffled. This slows the air and helps the oil precipitate out of it. Also look for a unit that uses 5/8” or ¾” hoses. If the hoses are too small, they not flow enough and allow crankcase pressure to rise.

On a side note: If you’re thinking of venting to atmosphere…don’t do it. A source of negative pressure is necessary to keep the crankcase from becoming pressurized. If the crankcase becomes pressurized the compression rings can float off the ring lands. When this happens, the rings do not seal as effectively which makes blowby even worse. In extreme cases the crankcase can become pressurized to the point that the engine develops oil leaks, oil flow back to the pan can be interrupted, and oil can even be blown out the dipstick.

Boost Gauge:
This really should have been standard equipment from the factory in my opinion. Whether your run a dedicated gauge or use an OBD solution, everyone considering or currently running a tune should have one. Otherwise you don’t know if the engine is over boosting or under boosting. Many will at some point replace or upgrade their turbo’s. Knowing whether the new unit is performing properly would be at the top of my list of things I’d want to know.

BMW Code Reader:
Something else every owner of a Mini should have in their arsenal. Being able to read and clear codes is of tremendous value. It will help you to diagnose problems, often saving you a trip to the mechanic. In many cases, it can help you identify and correct minor problems before they become major ones.

I've rambled on a bit, and probably left some odds and ends out, so feel free to add to this for the benefit of our fellow NAM members.

Happy Motoring

 

This is so ridiculously important. You absolutely need to be able to monitor this and be aware of the limitations of OBD based sensors.

 

What will the map sensor on an N18 JCW read up to?

 

The S sensors are designed for 250 kPa and the JCW is 300 kPa. They will however read about 10 kPa over that, so the ecu can calculate load based on boost up to about 1.6 bar and 2.1 bar.

The issue with commercially available OBD boost gauges is the standard PID query/reporting function returns an 8 bit value. This limits the maximum reported manifold pressure to 255 kPa (1.55 bar of boost) regardless of the sensor installed. So in my case while the boost gauge is showing 25 psi, an off the shelf OBD device will only show a little over 22 psi.

To read what the ecu is actually seeing via OBD requires special logging software that can report/record the actual pressure reported by the MAP sensors.

From an end user perspective its just much nicer having a gauge giving you this information all the time without having to fiddle with an adapter, software, etc.

 

I completely agree, especially about the boost gauge! I have a dedicated gauge reading from the manifold. It can tell you so much about what your car is doing, combined with other OBD PID monitoring if wanted. But just seeing the boost/vacuum and feeling/hearing my car can tell me if a problem is developing long before I get a CEL or any kind of warning. In my opinion, if you spend time to get to know or “become one with it” you can feel or hear something off, even if it’s a minor thing....maybe that’s just me, but watching boost is a important indicator of the health of it in general.
It may not be apparent what’s wrong, but that something is going on, as an early warning is always a bonus

 

On the subject of cleaning engine internals, any advise whether spraying seafoam or CRC through the intake is beneficial for cleaning the turbo and the IC (not for the intake valves I know what a polarizing subject that is!)

 

Some good info here, subscribed...

 

I advise against spraying it pre-turbo. Seafoam is roughly 80% petroleum based and 20% Isopropanol. That means it will not rapidly vaporize like methanol. As such is has the potential to pool in the intercooler. Having a couple of ounces of that pulled into the intake charge at WOT would fall under the heading of "Not a good thing". I have sprayed the aerosol version thru the MAP sensor port to the left of the valve cover while the engine is at about 4,000 rpm. This will do nothing for caked on carbon around the valve stems, but it can help remove carbon from the top of the piston and combustion chamber. I've verified this with a boroscope but putting it in the fuel tank accomplishes the same thing just more gradually.

 

This was very helpful thank you!

 

This is great info! Thanks for putting this together. Hope MODS can mount this up to a sticky in this modified section, too. It really need to be the first thing any interested modifying guys should see.




Besides what's mentioned, shouldn't we add valve cleaning for the N14 engines and an interval to do so? I truly believe the factory recommended interval is way too long. Those valves can get greasy even on first oil change of 5k miles. And if you don't clean those off, you can get slight cake by 10k miles. On 15-20k miles, it may as well call for a complete walnut blast again. I have two N14's, one modded, one stays stock, and I've kept the stock one untouched, just observing carbon build up every time I do the oil change. And it's quite obvious how 10k miles is enough to get a think layer of black cake around the stem of the valves. On my modded N14, I observe much greasier valves on EVERY oil change interval, but I walnut blast them every oil change, keeping them clean. Nowadays I've worked on enough N14's to rebuild after burnt valves, and 100% of those folks had their valves really caked up. And I can easily reach in with a long screwdriver and poke at the cake, it'll just fall off. I can only imagine that this can happen during driving and when the carbon cake does fall out and get into the combustion chamber, if it could attach to exhaust valves and create localized burn, then I suspect greatly that's how those exhaust valves fail. This hypothesis has been very consistent with the valves I repaired so far.




Of course an oil catch can would be an existential preventive action and prolong the need for walnut blasting, as mentioned by OP in his original post. Yet, i'd still strongly recommend for folks to invest in a walnut blasting set, and perform valve cleaning as much as needed.

 

Doh! (Palm to forehead) I knew I was forgetting something. Thanks Yupetc. If you're following the recommendations above concerning an OCC and Seafoam/intake cleaner I recommend walnut blasting every 30k miles for an N14 and 40k miles on an N18. At that point the buildup will be enough that you will notice a difference after blasting. Waiting too long to clean the valves can turn a four hour job into a six hours job. The carbon becomes so caked on and hardened it can be necessary to spray solvent in the ports, let it soak and chip away at the carbon so that the media blaster is able to remove the rest of it. If you're mechanically inclined and have a compressor capable of driving a spot blaster then I definitely recommend getting your own blaster as it will save quite a bit over time. If your not mechanically inclined pay someone else to do it. You really don't want a couple of ounces of ground walnuts to be sitting inside the cylinder when you go to start it.

The biggest cause of carbon accumulation is exhaust gas re-circulation or EGR for short. There is a period of time when the intake valves are opening and the exhaust valves have not yet closed. During this period of overlap, vacuum in the intake manifold will pull the exhaust gasses past the intake valve and into the intake tract. The N18 suffers less valve coking because 1) The intake manifold has less vacuum since the intake butterfly is fully open and the valvetronic system is using intake valve lift as the throttle and. 2) The N18 includes an exhaust vanos so it is possible to reduce valve overlap some in cruise conditions without a marked effect on emissions or gas mileage. When you're in boost the manifold pressure is higher than the cylinder pressure during overlap so there is an advantage to driving it like you stole it. Another contributor to coking is valve stem seal leakage. All valve stem seals leak a little. After shut down a small amount of oil will travel down the valve stem. Since we have no fuel passing over the valve there's really no way to solve this without secondary injectors. Meth helps a little but since your not supposed to beat on it till its warm its of less help than we would like.

When tuning the Gen II for race applications we limit the RPM to 7,200 specifically because of carbon accumulation. It was found that at higher RPMs the valve shock was high enough to cause carbon accumulation to chunk off. Once that happens there's only one place for it to go. Nick first ran into this on the Challenge series cars which are pretty well maintained. So if your RPM limiter is set to 7,000 RPM or higher I'd cut the walnut blasting intervals above in half.

 

Very thorough details and well explained.

I have the walnut blaster kit at home and I have the fittings to do BMW, MINI, and Audi vehicles. That's why many local folks come to me for such service at half the price they'd pay out there, and from many observances, these direct injection engines really suffer from the carbon build up greatly. OCC can really stretch the interval, but it's good to undo the intake manifold at least every 10k miles and visually inspect those valves. They may catch anyone off-guard and surprise ya. Between my MCS and my wife's MCS, both being N14, I simply go for valve cleaning as much as I can. I've gotten really good at it, whole thing can be done within just 45 minutes.

Oh, and to prevent walnut shells accidentally go into the engine chamber, I plug another vacuum cleaner's air outlet into the spark plug hole while walnut blasting. It'll help blow things out to the vacuum line if the valves aren't in closed position.

 

Just wondering why you state not to cryo treat the tensioner as Detroit Tuned and others do this in their kits.

Also is there a Tuning list as to what is good to do and what is a waste of money? Reason being my 2006 N14 has most things done that are a simple bolt on, namely

JCW Turbo
JCW Manifold
Milltek TBE
Sports Cat
AEM
FMIC

was going to get a remap to tie that all together, but was then thinking about TTE300 turbo instead. Headwork and cams would be nice but not many seem to bother. Forged rods and pistons and possible closed deck via carton sleeves are also an option but I guess these are more for long term reliability than anything else.

 

That's a good question and one I probably didn't address as thoroughly as I should have. I don't recommend cryo treating the chain tensioner for two reasons. The first reason is that in my opinion cryo treating a spring in a COMPRESSED state is not a good idea and I'll explain my reasoning. Cryo treating is a great process for improving wear resistance and fatigue life. This occurs because of two processes that occur. The first process is the conversion of some of the retained austenite into martensite as noted above. This increases wear resistance and appears to occur at a higher rate as you near the surface of the part. The second process is the precipitation of submicroscopic carbides within the martensite matrix. This reinforces the martensite matrix and results in greater material strength and toughness which improves fatigue life. Unfortunately, when you alter the molecular structure of the material in a compressed state you create some relief of the tensile residual stress within the part which creates a set as it were. Beyond this set or in the case of a spring cryo treated in an uncompressed state the tensile strength is higher than an untreated spring. Various studies show that depending on wire diameter the spring material may gain an additional 500 to 2,000 psi in tensile strength.

This leads to the second reason I don't recommend the process for the tensioner. I myself have personally seen a transient chain rattle in a brand new treated chain assembly on a freshly overhauled motor that was not the result of low oil pressure as verified with a separate oil pressure gauge. Subsequent replacement of the cryo treated tensioner with an untreated unit from the factory eliminated the rattle. Cryo treatment of valve springs is a tried and proven method of improving the fatigue resistance of valve springs. However, they are always cryo treated in an uncompressed state.

 

Bump on this thread because good information is good, and I want to subscribe