So I've been thinking about this for some time and got bored and wrote up my thoughts. I'm now considering trying to get it published as an SAE paper. What do yo guys think?
On tuning the Mazdaspeed 2.3L DISI turbocharged MZR motor
Abstract: Reasons for leaning the air fuel ratio of the 2.3L DISI turbocharged MZR motor to levels at or above 12:1 are given. These include basic theory of direct injection, observation of fuel dilution in crankcase oil, collection of fuel and water in an installed catch can, observation of impellor deterioration in the exhaust side of the turbocharger, and one example of catastrophic failure with a vented but not evacuated crankcase.
Discussion: Gasoline direct injection (GDI) engines introduce fuel directly into the cylinder as a finely atomized spray that evaporates and mixes with air to form a premixed charge of air and vaporized fuel prior to ignition. Contemporary GDI engines require high fuel pressures to atomize the fuel spray. GDI engines operate with stratified charge at part load to reduce the pumping losses inherent in conventional indirect injected engines. A stratified-charge, spark-ignited engine has the potential for burning lean mixtures for improved fuel economy and reduced emissions. Preferably an overall lean mixture is formed in the combustion chamber, but is controlled to be stoichiometric or slightly fuel-rich in the vicinity of the spark plug at the time of ignition. The stoichiometric portion is thus easily ignited, and this in turn ignites the remaining lean mixture. While pumping losses can be reduced, the operating window currently achievable for stratified charge is limited to low engine speeds and relatively light engine loads.
The Mazdaspeed 2.3L direct injection spark ignition (DISI) turbocharged MZR four cylinder motor is supplied in three vehicles, the MazdaSpeed6, MS6; the MazdaSpeed3, MS3; and the CX-7. Other popular applications of turbocharged GDI engines are the BMW 335i, the 135i, and the Audi/VW 2.0 FSI. With ever increasing emissions requirements and fuel prices driving improved fuel efficiency as a market force, more and more manufacturers are turning to forced inducted direct injection technologies to meet the demands for power and fuel efficiency.
The MS3 and MS6 are very popular with car enthusiasts bent on increasing the power delivery by modifying various parts of the engine. Popular modifications are cold air intakes, higher flowing exhausts systems, downpipes, upgraded top mount intercoolers, front mount intercoolers, exhaust manifolds, upgraded cam driven fuel pumps, and higher volume turbochargers. Interceptor type engine managements systems are often employed with the goal of optimizing the power from the stock setup and any modifications. This is especially true for the MazdaSpeed vehicles as currently there are no systems capable of reprogramming the ECU. There are several systems available using varying degrees of complexity to intercept and modify mass airflow sensor (MAF) volatage, the cam position sensor, the manifold absolute pressure (MAP) sensor, the wastegate solenoid, etc. but the method for “tuning,” or modifying the air fuel ratio is essentially the same, i.e. modifying the signal from the MAF. What is unclear is what the properly tuned air fuel ratio should be. Figures 1 – 3 show dynamometer graphs of horsepower, torque, and important for comparison, air fuel ratios (AFR) for an unmodified or stock MS6 and a 335i. A quick perusal indicates that there is no real consensus of proper AFR among manufacturers. The MS6 is particularly rich at higher rpms while the BMW and Volkswagon vehicles are, comparing to typical port fuel injected turbocharged cars and the MS6, lean.
Figure 1. Dynomometer graph from a stock 2006 MazdaSpeed6 with a 2.3L DISI turbocharged MZR.
Figure 2. Dynomometer graph from a stock 2008 BMW 335i with a DISI Turbocharged V6.
Figure 3. Dynomometer graph for a Volkswagon Golf with a 2.0 L FSI turbocharged motor
For combustion to be chemically complete, the fuel-air mixture must be vaporized to a stoichiometric gas-phase mixture. A stoichiometric combustible mixture contains the exact quantities of oxygen and fuel required for complete combustion. The products of an ideal combustion process are water and carbon dioxide. For gasoline, this air-fuel ratio is approximately 14.7:1 by weight. A fuel-air mixture that is not completely vaporized, nor stoichiometric, can result in incomplete combustion and reduced thermal efficiency. If combustion is incomplete, some carbon is not fully oxidized, yielding carbon monoxide and unburnt hydrocarbons.
Conventional forced inducted port-fuel injected motors typically run rich mixtures with AFRs in the area of 10.0-11.0:1 under load and boost. This is done to prevent or minimize preignition leading to detonation in the cylinder due to the high pressures and temperatures associated with forced induction. Because of the inherent cooling effects of GDI it is theorized that higher compression ratios and leaner air fuel mixtures can be used under load conditions than those of conventional port-fuel systems. Examples of this are shown in figures 2 and 3. Both Volkswagen and BMW set their AFR under max load/boost to be 12.0:1 or higher.
The engineers at Mazda set the fuel system for the 2.3L DISI turbocharged MZR four cylinder vehicles to run excessively rich under load, indicated in figure 1. This is inefficient as optimum power is not made in gasoline combustion engines at AFRs below 13:1. Additionally, the excessively rich condition results in unburnt fuel leaking down the cylinder walls into the crankcase. This has been described by Sagawa et al., in SAE 2002-01-1647, "Study of Fuel Dilution in Direct Injection and Multipoint Injection Gasoline Engines.” Fuel dilution reduces the lubricity of oil and will result in excessive wear, heat, and, ultimately, seizure of moving parts resulting in catastrophic failure.
The following are website links to used oil analyses performed on MS3, MS6, and CX-7 vehicles. All indicate significant reduction in viscosity in comparatively short intervals.
Quaker State 5w-30
Mazdaspeed 3 - Castrol 5w 30 - first UOA - Bob Is The Oil Guy
Figure 4 is a picture of the contents of an oil catch can installed between the intake manifold and the crankcase. Under normal operation the crankcase is under vacuum and evacuating the crankcase. These catch cans were installed to eliminate the oil sludge forming inside the intake manifold, Figure 5. Owners report watery oily residue smelling of fuel when emptying their catch cans indicating fuel leakdown on the walls of the cylinders.
Figure 4. Pictures of the contents of oil catch cans installed between the intake manifold and the crankcase on two MS6s.
Figure 5. Image of the inside of the intake manifold of an MS6. The port where the oil sludge originates is connected to the crankcase PCV valve.
Excessively rich mixtures can result in unburnt fuel and reduced hydrocarbons exiting the exhaust resulting in an excessively sooty condition at the tailpipe. This particulate soot also contaminates the flow in the exhaust gas recirculation system (EGR). Figure 6 is inside the cylinder head of a Mazdaspeed6. The valves have been removed but the spark plug and injector port remain. This excessive buildup was observed in a vehicle operating under normal conditions for less than 25,000 miles and likely results from a combination of the oil sludge from fuel diluted oil and the particulate from the unburnt hydrocarbons in the EGR.
Figure 6. Cylinder head of a 2006 Mazdaspeed6.
The fuel rich exhaust will continue to combust and may actually detonate outside of the cylinder in the exhaust manifold or exhaust housing of the turbocharger. Figure 7 shows the impellor from an MS6 Borg Warner K04 turbo. Close inspection reveals areas of significant deterioration of the impellor blades in an erratic fashion. The damage is not repeated from blade to blade indicating discrete damage events affecting small areas. Also the type of damage on the blades suggests a wearing away or blowing away of material due to heat/detonation. This could only arise from unburnt fuel or partially combusted hydrocarbons passing out of the cylinder and into the turbine housing. Anecdotally, the MS6 and MS3 vehicles suffer from accelerated deterioration of turbocharger function indicated by burnt oil leaking from the turbocharger seals. This symptom may also be the result of excessive heat and/or detonation inside the turbocharger itself.
Figure 7. Exhaust turbine from a Borg-Warner K04 turbo from a 2006 MS6.
Figure 8 is a picture of the block of a Mazdaspeed 2.3L DISI turbocharged MZR four cylinder motor suffering catastrophic failure. The failure occurred under boosted acceleration after approximately 10 minutes of driving with ambient temperatures in the low 30s °F. This vehicle’s crankcase ventilation system had been modified in that the crankcase was no longer evacuated during operation but an ambient vented catch can was installed on the crankcase side. The intake manifold was, of course, plugged. The oil catch can was vented to the atmosphere constantly so that at no time was the crankcase seeing extreme pressure. The owner reported gradually increasing “knock retard” readings on his scantool during normal operation after installing the catch can in the described setup. The vented, non-evacuated catch can setup was used for approximately four weeks and 1500 miles. Upon failure the owner reported that no residue of any kind was found in the catch can.
Figure 8. Engine block of a 2.3L DISI turbocharged MZR four cylinder suffering catastrophic failure.
Upon disassembly of the motor, it was discovered that the rod and piston in cylinder number 2 suffered catastrophic failure. The rod was bent in two places and failed approximately 1 inch from the piston wrist pin. The piston shattered into fragments smaller than a 1 in2. The pistons and rods in cylinders 1, 3, and 4 showed no signs of adverse operating conditions. Additionally all bearing surfaces in the rods, including those of rod #2 showed minimal wear and not discrete damage markings.
The most plausible cause for this is catastrophic detonation in cylinder #2. It is possible that the oil was continually diluted with fuel from the ineffectual catch can setup to the point of lubricity breakdown and possible ignition resulting in detonation in the crankcase or oil vapor entering the cylinder and lowering the octane rating of the mixture. Another possible scenario is that some of the buildup observed in these motors was present and broke loose entering the cylinder and began to combust elevating the temperatures in that cylinder.
In a recent article by Luttermann and Mährle titled “BMW High Precision Fuel Injection in Conjunction with Twin-Turbo Technology: a Combination for Maximum Dynamic and High Fuel Efficiency,” SAE 2007-01-1560, it was revealed that the BMW fuel injection system “is able to vary the fuel pressure (up to 200 bar [2900 psi; approximately 1000 psi higher pressure than the fuel delivery system in the Mazda Turbo DISI MZR] and the number of injection pulses [up to three per cycle] in order to reduce the wall wetting. This is particularly important to avoid smoke emission and oil dilution.” Given this information one can postulate that Mazda overcame potential fuel heterogeneities and improper combustion of their lower pressure fuel delivery system by addition of more fuel. Consequently, this results in even more smoke (unburnt hydrocarbon particulate) and oil dilution due to fuel leak down in the cylinders.
Conclusion: Excessively rich fueling conditions result in fuel dilution of the crankcase oil as well as excessive carbon build up in the intake manifold and head. The rich fueling condition may be employed to mask problems resulting from incomplete fuel atomization at the 1700 psi fuel pressure utilized by Mazda. It seems Mazda’s approach was to add more fuel while BMW increased fuel pressure. It remains to be seen what the ability of the turbocharged 2.3L DISI MZR is in terms of leaner AFRs (12:1 and higher) under boost and load.
Acknowledgments: I wish to express my deep gratitude to Jordan Gartenhaus of Custom Performance Engineering and Ron Miller for some of the data supplied and many helpful discussions. Additionally, data and photographic evidence were supplied by PT Performance and Jonathon Martin.
Sticky worthy........very good will read it in greater detail tomorrow, but you basically brought out all of the pertinent Need to know information about this car for future buyers!!!!
Since I bought my car in January I've been asking why the AFR's are so rich and have yet to get any answers. At least your speculation of Mazda adding fuel when BMW added PSI addresses it a bit. Why do all the people with SB's and dyno tunes still run so rich though? This is exactly why I have been so reserved about getting a SB because I will be too tempted to lean it out especially at my altitude.
Very nice write-up Dada! There are several other UOA's in the UOA thread to support the fuel dilution in these motors. From what I've seen, following the manufacturer specs for OCI's, even the severe duty one, is a recipe for disaster. With the amount of fuel dilution happening, I think a 5W-30 or 10W-30 synthetic should be changed out around 3k, with a max of 4k under ideal conditions. In most cases even the best synthetics are being sheared down to the xW-20 range in as little as 3k miles...
Sticky worthy........very good will read it in greater detail tomorrow, but you basically brought out all of the pertinent Need to know information about this car for future buyers!!!![/b]
Excessively rich mixtures can result in unburnt fuel and reduced hydrocarbons exiting the exhaust resulting in an excessively sooty condition at the tailpipe.[/b]
Reduced? Is that a typo or am I missing something.
Thanks for the write up. Good info and makes you think. I will be doing my oil analysis with GC 0w30 as soon as I get my kit, and installing a OCC if I can figure out how to do it soon.
Reduced? Is that a typo or am I missing something.
Thanks for the write up. Good info and makes you think. I will be doing my oil analysis with GC 0w30 as soon as I get my kit, and installing a OCC if I can figure out how to do it soon.[/b]
I meant chemically reduced as in graphitic or unsaturated hydrocarbons - lots of double bonds and carbon black. Oxidized would be CO2 or CO. Sorry. I am a chemist after all. LOL.
sooo.... am I right in saying the gist of this whole article is that the mazda DISI needs a combination of better injectors + better fuel pressure in order to lean out the mixture? Does this mean the current injectors don't atomize well enough or are they just too weak to provide enough fuel in the required time frame? I am not a chemE or a mechE (but I am an EE), but this article is definitely provides some interesting information, even if I don't quite understand all of it.
Everything is debatable at this point as to why the fueling is so rich. Because it is, I think a catch can is an absolute must, Pennzoil Platinum is the oil of choice, and blocking off the EGR like Whoosh should seriously be considered. When I pulled my intake mani off to put the new pretty red one on, it was covered in thick black soot. My old mani was spotless (b/c I cleaned the hell out of it) when i reinstalled with the catch can and I was definitely surprised to see more gook in there and it all came from the EGR.
Edited for correctness. Oil is always a debatable topic and there is data to support most choices. My choice after seeing available data is avoid xw-30 (GC is not really a xw-30) because none have the right properties to hold up in the engines. Nederlander has done much research on the subject of oil and viscosities in the engine. I've got 6000 miles on AMsoil Euro 5w-40 to sample to add to the data as well. This engine needs an oil with a pack much like diesel oil because of the properties. From what I have seen, if the oil has the "energy conserving" rating it will not last in the engine.
Very good write up. Lot's of good info in there. However, I think it should be clarified that there is a way to flash an ms6 ecu very effectively through the Piasini retailers. They can do alot of things now than they were advertising before. Anything with timing, anything with injectors, anything with the throttle, anything with the rev limit, ect... all user specified if desired. They showed a dyno of an mps6 making very impressive gains all the way to 8000rpm on oz mazdas board. Just my $0.02.
Did you explore how EPA regulations, particularly emissions, may have contributed to Mazda's decision to use a richer condition.
There's a hypothesis in the naturally aspirated Mazda6 community that postulates that the reason the car runs rich is to meet stringent EPA Tier II regulations. I wonder if it carried over to the Mazdaspeed6.
EPA Tier II regs state that a car must meet be able to meet specific emissions targets within a certain number of miles in its life.
It's somewhere between 100K and 120K miles - I don't remember the exact figure.
The point is, everything in the car has to operate in such a way to meet those emissions targets for that number of prescribed miles - including the engine and catalytic converter. Theoretically, running rich accomplishes two things:
A richer running engine has a cooler combustion chamber as compared to a leaner running engine. As a result, running rich extends engine longevity and therefore helps an engine meet the 120K mile life span. Obviously, your analysis points out that Mazda's execution is actually working against to meet this requirement! :blink:
An engine that runs rich produces exhaust gases that are cooler as supposed to an leaner burning engine. Cooler exhaust gases mean that catalytic converters are not degraded as quickly as supposed to when much warmer exhaust gases run through them. As a result, running rich extends catalytic converter life which means the car can catalyze exhaust gases to meet the emissions targets within the prescribed mileage lifespan as dictated by the EPA.
A richer AFR means a cooler combustion temperature which is what you'd want to meet NOx emission targets. You get higher production of NOx from a high temperature environment.
Raynmen, thank you very much for that information. It's a likely possibility. I think it will be very interesting to get a look at the next DI motor from Mazda/Ford and look at the fuel pressures and injector pulses. As far as we can tell, the DISI MZRs only get one pulse per cycle.
John at PTPerformance first revealed that buildup issue in the head. What's interesting about that is that the EGR is only in operation in closed loop, light cruise while our engines are running stoich at 14.7:1. Yet I still saw tremendous soot coating my intake mani. I don't know what the hell to make of that.
Edited for correctness. Oil is always a debatable topic and there is data to support most choices. My choice after seeing available data is avoid xw-30 (GC is not really a xw-30) because none have the right properties to hold up in the engines. Nederlander has done much research on the subject of oil and viscosities in the engine. I've got 6000 miles on AMsoil Euro 5w-40 to sample to add to the data as well. This engine needs an oil with a pack much like diesel oil because of the properties. From what I have seen, if the oil has the "energy conserving" rating it will not last in the engine.[/b]
I'm not sure if going to a xW-40 is necessarily the answer as there are downsides to running a thicker than called for oil...especially in colder temperatures. If you are trying your best to run out to a 6k+ OCI, then maybe that works for you. I disagree personally, and it makes more sense from what my testing has shown in the UOA thread to get a high quality xW-30 synthetic and change it more often.
In the end, your xW-40 may hold up better to the chemical shearing, but after all those miles it's still going to have a TON of fuel in it...
Did you explore how EPA regulations, particularly emissions, may have contributed to Mazda's decision to use a richer condition.
There's a hypothesis in the naturally aspirated Mazda6 community that postulates that the reason the car runs rich is to meet stringent EPA Tier II regulations. I wonder if it carried over to the Mazdaspeed6.
EPA Tier II regs state that a car must meet be able to meet specific emissions targets within a certain number of miles in its life.
It's somewhere between 100K and 120K miles - I don't remember the exact figure.
The point is, everything in the car has to operate in such a way to meet those emissions targets for that number of prescribed miles - including the engine and catalytic converter. Theoretically, running rich accomplishes two things:
1. A richer running engine has a cooler combustion chamber as compared to a leaner running engine. As a result, running rich extends engine longevity and therefore helps an engine meet the 120K mile life span. Obviously, your analysis points out that Mazda's execution is actually working against to meet this requirement! blink.gif
2. An engine that runs rich produces exhaust gases that are cooler as supposed to an leaner burning engine. Cooler exhaust gases mean that catalytic converters are not degraded as quickly as supposed to when much warmer exhaust gases run through them. As a result, running rich extends catalytic converter life which means the car can catalyze exhaust gases to meet the emissions targets within the prescribed mileage lifespan as dictated by the EPA.
3. A richer AFR means a cooler combustion temperature which is what you'd want to meet NOx emission targets. You get higher production of NOx from a high temperature environment.
Very good write up. Lot's of good info in there. However, I think it should be clarified that there is a way to flash an ms6 ecu very effectively through the Piasini retailers. They can do alot of things now than they were advertising before. Anything with timing, anything with injectors, anything with the throttle, anything with the rev limit, ect... all user specified if desired. They showed a dyno of an mps6 making very impressive gains all the way to 8000rpm on oz mazdas board. Just my $0.02.[/b]
Just letting you know that flash tuning is available, contrary to your post. Not really sure, but I imagine there's some kind of laws about publishing and/or copywriting false or misleading information. Whether you feel comfortable with it or not, it is available, and it's all at request, no longer ots unless that's what you want. Just saying.
As title says is it possible to take the girdle that holds the crankshaft with the gearbox still attached? I know the crank can't be taken out, but I would at least like to check half of the bearings, those than sit in the girdle.
Thank you in advance.
Edit: I want to add that I took all 10...
Notes on fluids & associated part information for the MS6
Please do post corrections or suggestions-
I'll integrate to this post as appropriate
This was mostly copied & pasted from dozens of posts,
or taken from the '06 MS6 owners manual
-notes gathered mostly just to make my life easier...
