MPG after header upgrade.

[RobG719]

Hi,

I have an all stock 2010 miata with 18K miles that I purchased in 9/24. This winter I upgraded to RoadsterSport MAX Power 1.8 , RoadsterSport HELMHOLTZ and Super Q muffler.

I finally had some decent weather in MN and took it out for a 25 mi test drive. Sound is good, power is good, but I watched the gas gauge drop nearly 1/4 of a tank (approx 3 gal) during the test drive. I was not a lead foot as I know the ECU needs some time to adjust. The car MPG monitor showed ~28 mpg by the end.

I put the upstream O2 sensor in the header with a short extension and the downstream in the midpipe using the long extension. CEL is not lit.

I used Torque with a bluetooth OBDII adapter and noted some of these values after driving a while

Air temp: 39
Engine temp : 179

AFR
Idle ~ 14.6
Cruising 6th gear at 60mph ~ 14.4-14.8
6th at 60 mph WOT high 12s- low 13s. increased slowly with increased speed
6th at 60 mph throttle closed 20.4
6th at 60 mph clutch in (idling at speed) ~14.6

Normal driving around town ~14.4-14.8

I know AFR should is around 14.7. I don't know about when throttle closed. 20 seems high, but the rest of the drive seemed normal.

- Is the ECU learning at this point with increased air flow?
- How long does that take?
- Are these numbers pretty normal?
- Will the fuel consumption settle down?
- Is there something else I should be looking at?

Thanks
Rob

[Brian]

Reasonable O2 numbers, not grossly rich. The car should adjust fuel trims if the O2 sensors are working properly. Work with a Tuner and they can check fuel trims and get it dialed for max results. Tuner can also uncork the 2nd gear torque limit, makes the car noticeably faster. Mike at Xero Limit, or Bryan at Fab9 for the tunes.

If you drive the car precisely as before, gas mileage is usually a bit better since there is less resistance to pumping out the exhaust gasses. But human nature tends to not be able to resist pushing the gas pedal harder than before, to hear the exhaust fun just added. I have been in the car as passenger with the computer plugged into the car so I can see throttle position and the customer driving it will be telling me that they are using same amount of gas pedal as before, but the computer looking at throttle position sensor says in reality they are giving the 'go pedal' a good bit extra.

[RobG719]

Thanks Brian. I was concerned about the gas gauge drop, but the O2 sensors did not confirm a problem. As long as it drives ok and O2 data looks good I will just monitor.

A tune is on my list of upgrades. Do you have a preference between ecutek or versatuner?

[Brian]

My own NC are all tuned by Mike at Xero Limit with Ecutek. He can do it remotely.

IF you might add cams do that first, then tune.

Reach Mike at his site below.

https://xero-limit.com/

Brian

[RobG719]

I worked with Mike at Xero-Limit on a tune. After a couple of iterations, all seems good.

I was not expecting much of a difference going from stock tune to ecutek tune, but I was pleasantly surprised. The car is much more responsive and pulls really well above 4K RPM.

[Brian]

Awesome!

Indeed Mike does great work, glad you are enjoying it.