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I'm getting about 7mpg..

Old 05-01-16, 08:57 AM
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I'm getting about 7mpg..

So the car runs great with 20b. I have been tuning the car based on how it sounds and feels rather than chasing after afr for a while. I've also been going to the gas station almost everyday so I wanted to see what the mileage would be with conservative driving without going into boost hardly at all. I'm only getting about 7 - 9 mpg! The car has a mild street port.

It seems that when I tune for a specific AFR, whenever I ease into gas, there is a lean spot which causes hesitation. I can fix this with richening high vacuum / low RPM boxes, but the problem is, these boxes are also responsible for cruising. My afr during cruise is around 11 - 14 depending on RPM and load. My decel is now set at 5 vacuum. I know it can be better because when I drove after a professional tune, I was getting up to 20 MPG , but the city driving with mild load was really crappy. Is this about normal mpg for single turbo 20b with conservative driving? How would other ECU help with MPG if possible? Thanks in advance.

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Old 05-01-16, 10:03 AM
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If your AFRs during cruise are ever lower than 14.7, then you are too rich. AFRs should be in the 15s under cruise. Note that my definition of cruise is a steady load that stays around one MAP/RPM point. Those rich ratios would definitely account for your low mileage.

Without seeing your map correlated with a datalog, it is very hard to say why you are seeing lean spots. Unfortunately this is beyond the capability of the Microtech.

What I can say is that your cruise area should look like a valley within an increasing hill (the main map). The 4 or 8 bins in your cruise area should be significantly leaner than surrounding bins. So that when the engine settles to steady load, it runs lean. Then any throttle application moves the map up to the surrounding area that is richer.

The pump adds the fuel to account for the abrupt throttle transition. You may find better response if you set your pumps to reference TPS instead of MAP.

Would another ECU help? Yes, for a load of reasons. If you look even at a 12 year old Megasquirt MS1 you would wonder why you bothered with the Microtech. That's not a recommend to convert to a MegasSquirt MS1...but I wouldn't dissuade you from going to an MS3-Pro...which has capabilities light years ahead of anything Microtech has dreamed about.

But that's not to say you can't get acceptable results with the Microtech. It is capable of providing both power and fuel economy when tuned. I think the issues is that as a beginning tuner, there's a steep learning curve and without someone to look over the laptop and see issues, it is hard to know intuitively what to do.
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Old 05-01-16, 10:14 AM
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Thank you. Helpful as always. I will try tps pump and lean region for cruise as recommended. Honestly, I want to learn as much as i can from the microtech before transitioning. Besides, how i have this thing wired behind the dash, it would be a major operation to switch out the boxes. So far I'm learning tons just playing with the matrix. Once I feel its limits, I will likely move onto another platform. Thanks again.
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Old 05-01-16, 02:44 PM
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Just out of curiosity, how would tuning with other ECU be any different? This may be a basic question, but I have never work with other ECU on tuning it by myself. In my simple mind, tuning is just telling ECU how much fuel to inject at particular engine speed and manifold pressure. Not talking timing here because I rather leave those alone. Just curious to know how that process would be any different with other ECU. I don't mind going after each box and changing it manually...

Last edited by stickmantijuana; 05-01-16 at 05:01 PM.
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Old 05-07-16, 10:22 AM
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I'm not even sure where to begin as to how other ECUs are worlds away from the Microtech. But, here's what you can do.

Download TunerStudio MS (the tuning suite for the Megasquirt) and install it.
TunerStudio MS | tunerstudio.com

Then head over to here and download my 13B base map for the MS3 (bottom of page):
How To Megasquirt Your 2nd Gen RX-7: Programming The ECU (MS3X / MS3-Pro)

Unzip and open up the base map in TunerStudio, telling it to use a "Temporary project".

You can go through the settings offline from a Megasquirt and see some idea of what it's like to use. At the far right is the "3D Tuning Maps" button which allows you to access the maps in a graphical view.

Note that the registered version of TunerStudio has more features than the free. The most useful of which is AutoTune. YouTube "Megasquirt autotune" for an idea how awesome this is. Drive around while TunerStudio reads the AFRs form the wideband and adjusts the fuel table so they match a pre-defined AFR table you have set. For single person tuning, it's a gift from heaven.

MegaLogViewer is the log viewing application that can perform a VE analysis offline with a map and data log, accomplishing the same thing.
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