MPG and tune+headers

[wimbrow]

hi guys. please excuse my ignorance as i am not a mechanic but i've a few questions for the forum. i have a 2016 GT MT. I've had her for 6 months and wanted some upgrades. i got the track handling pack which has made a big difference in ride quality. i also got a full streetfighter exhaust , CAI and tune from CTB in auckland. there was a significant increase in power and torque on the dyno. the lower gear shifts are smoother. what i am wondering about is why is there now a large amount of engine braking, which is nice ,and why is the MPG reduced when on the highway in 6th doing 65mph from 31 mpg to 23 mpg ? I thought the engine should run more efficiently now. of course when you get on the power i expect much reduced MPG but coasting? please explain. thanks, tom

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[Terminator2]

hi guys. please excuse my ignorance as i am not a mechanic but i've a few questions for the forum. i have a 2016 GT MT. I've had her for 6 months and wanted some upgrades. i got the track handling pack which has made a big difference in ride quality. i also got a full streetfighter exhaust , CAI and tune from CTB in auckland. there was a significant increase in power and torque on the dyno. the lower gear shifts are smoother. what i am wondering about is why is there now a large amount of engine braking, which is nice ,and why is the MPG reduced when on the highway in 6th doing 65mph from 31 mpg to 23 mpg ? I thought the engine should run more efficiently now. of course when you get on the power i expect much reduced MPG but coasting? please explain. thanks, tom

Maybe your pedal vs actual throttle tables are more aggressive in the tune which could explain a drop in cruising MPG.

 

[Taneras]

Any chance its an E85 tune? Running E85 will reduce your MPG.

 

[wimbrow]

Any chance its an E85 tune? Running E85 will reduce your MPG.

hi taneras. no, it was tuned on 95 octane. thanks, tom

 

[GSLSE20B]

your 6th gear low load cruise mpg should have increased . you are probably in cat protection mode dumping fuel . what is your afr showing during cruise ?

 

[wimbrow]

your 6th gear low load cruise mpg should have increased . you are probably in cat protection mode dumping fuel . what is your afr showing during cruise ?

hi. sorry , what is afr?
air fuel ratio? is that one of the gauges?
thanks, tom

 

[GSLSE20B]

hi. sorry , what is afr?
air fuel ratio? is that one of the gauges?
thanks, tom

Yes , the afr on your gauge cluster . What is it reading during low load cruise . I have a manual 3.73 car on e85 that gets better than 23mpg on the highway.

 

[wimbrow]

Yes , the afr on your gauge cluster . What is it reading during low load cruise . I have a manual 3.73 car on e85 that gets better than 23mpg on the highway.

i'll have to check that out for you. i have a MT 3.55 using 98 octane and was getting 26-28 mpg prior to the tune and headers, now 19 mpg.

thanks, tom

 

[Terminator2]

Yes , the afr on your gauge cluster . What is it reading during low load cruise . I have a manual 3.73 car on e85 that gets better than 23mpg on the highway.

This. I get about 23-24 on E-85 on the hwy. It was closer to 28-29 before the E-85 but I've got 3.31s.

 

[armykyle1 [HACKED ACCOUNT]

I got 24-25 stock, with 3.73s. Running 80ish

With cai, headers and tune. I'm 23-24.

Both running premium.

 

[wimbrow]

I got 24-25 stock, with 3.73s. Running 80ish

With cai, headers and tune. I'm 23-24.

Both running premium.

oh OK, so im about the same. were you in 6th gear doing 80? thanks, tom

 

[wimbrow]

Yes , the afr on your gauge cluster . What is it reading during low load cruise . I have a manual 3.73 car on e85 that gets better than 23mpg on the highway.

Hi GSL , i checked it yesterday on the HWY in 6th doing about 65mph under 2000 rpm and the afr was kinda jumping between 37-42. also the mileage improved a bit for some reason, maybe just had to break in. thanks, tom

 

[armykyle1 [HACKED ACCOUNT]

oh OK, so im about the same. were you in 6th gear doing 80? thanks, tom

Yea, if I'm 55+ I go into 6th for cruising. I'd like to have 3.55s honestly

 

[Kahboom]

3.73 with everything in Sig on 91 I get 26-29 on highways, e85 its 22-25mpg on highways 75+ mph

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