KPerez

Everybody agrees that the OEM tune has been a nightmare since delivery in January of 08; very,very low A/F ratios means the X is running extremely rich dumping in excessive amounts of fuel so much so that many have complained about backfiring, hesitation under acceleration (https://www.evolutionm.net/forums/ev...omfort-me.html ), and potential dilution of the engine oil with fuel through the rings (https://www.evolutionm.net/forums/ev...l-problem.html). This is nothing new for the EVO’s for others have stated that VIII and IX also ran very rich.

When I asked in April of 08 what the causes were for this condition, I was told (Touring Bubble, https://www.evolutionm.net/forums/ev...e-consist.html ) it was Mitsu’s compensation to protect the engine from detonation under all conditions of temperature and altitude. However, I am now wondering whether this is the totality of the cause for the rich OEM tune. Specifically, Mr. EVO IX (https://www.evolutionm.net/forums/ev...e-consist.html ) stated that an OEM tuned 07 STI’s engine blew because of the extremely lean A/F programmed into the ECU. Could it be that Mitsu, upon hearing this information, decided that they would make sure this never happened to their EVO and made an excessively rich tune for the X?

Another possible explanation may rest with the fuel differences between the US and Japan. Our octane range is 91-93; Japan has 95 octane (100 RON) and it is this fuel that is used to develop the fuel maps for all the higher performance production cars. Is it possible that Mitsu had difficulty accurately tuning the ECU for the lower octane fuels in the US? The numerous factory reflashes, which do lean out the car some, certainly supports this suggestion.

Finally, was Mitsu just providing a rich OEM fuel environment which when tuned by aftermarket sources would yield a higher HP output (we have seen 70whp or more with just a tune) thereby creating the GTR mystique where the advertised HP of the car (~265 HP) was well below the potential (500-800 HP) of the engine?

This rambling is just my attempt to understand how Mitsu could have allowed production of a vehicle that is so badly out of tune. As a result, many of us have been “forced” to pay for an aftermarket tune, not necessarily to increase performance but to get the car to run right. I do not mind spending $$ for aftermarket parts to increase performance. But to spend additional funds to correct a factory installed problem seems to be above and beyond the call of duty for the consumer. Perhaps there are other car manufacturers which produce vehicle specific deficiencies like the X or the STI alluded to above. Does the BMW 135i have this type of problem? If not, then why not? Are these issues confined to rally based turbo charged cars? I just do not know.
Your thoughts ….. ?

Later, Ken

TTP Engineering

iTrader: (465)

With our understanding of the ECU and new air metering system used on the 4b11t only compared to their 4g63t karman vortex metered engines is that the new system is using a hotwire maf sensor weighted heavily in manifold pressure readings.

Its ALMOST halfway to a full speed density setup as one could opt for on a standalone ECU.

With this said, we are certain that the diverse geographic regions and octane fuel variances throughout the USA had to be blanketed with USDM ECU fueling and ignition timing numbers which would be safe for the streets of Malibu, CA on 91oct to the Rocky Mountain tops of Colorado at 91oct to Daytona beach on 93oct to the winter in Ohio on 94oct to the valleys of Anchorage, AK on 90 octane in subzero temperatures.

Covering all of those location in both octane, intake air temps and altitude on a heavily weight manifold pressure sensing vehicle would have Mitsu err on the side of caution with additional fueling to keep it ridiculously safe is our opinion.

KPerez

Ok, so if it is just environmental conditions then wouldn't you say Mitsu's attempt to have a "good" tune everywhere failed; yes , they didn't blow any engines but they run like crap and may even jeporidize the engine, not from detonation, but fuel dilution.
Now I assume there are BMW's for example in Alaska, Florida and cruisin through Death Valley. Do 135i have as rich fuel maps as well? I do not think so but I am guessing here.

Later, Ken

TTP Engineering

iTrader: (465)

Someone with more BMW experience as to what algorithm is used to determine load in the 135i may need to share details about the twin turbo BMW engine.

PlayinWithFire

iTrader: (3)

I was talking to a tuner who told me with the older evos that the USDM ones were detuned because of stricter emission requirements and that just by flashing the JDM maps you could make a considerable amount of power.

I too am very skeptical about the AFRs being extremely low and it seems as though they have crossed the point of being safely low to deal with environmental differences and are causing some issues (as stated above).

I do wish we got more power from the factory, but I also embrace the fact that there is so much room to pull some extra power out of the engine. It is an interesting topic to discuss, but unless we get one of the EVO X engineers on the forums, I don't think we can really find the true answers to why they chose to run the cars so rich.

EDIT: BTW your post was really well thought out and I really appreciate the effort you put into with sources cited and all.