Fiesta ST MPG Thread

[flbchbm]

I have taped off the wing slots on my car and I have hit a new freeway hi of 39 mpg with anS280! I am seeing 27 city and around 29 combined . This is crazy more info to come!

I don't think it's crazy at all. I posted about drag coefficient and how horrible the fiesta, focus and RS are. I don't remember exactly, but I think we were at 31 or was it 33? That is freaking horrible

 

[gtx3076]

I have taped off the wing slots on my car and I have hit a new freeway hi of 39 mpg with anS280! I am seeing 27 city and around 29 combined . This is crazy more info to come!

Wing slots?

I did expect better mpg on a laggier turbo. Should be easier to stay out of boost with normal driving.

 

[Dpro]

Wing slots?

I did expect better mpg on a laggier turbo. Should be easier to stay out of boost with normal driving.

My Turbo is not that laggy lol Before I did this I saw 25 combined with 22-24 city and about 29-32 hwy at best . You really need to check out a S280 in person before calling it laggy it’s not a Garrett. It spools up a tad slower than stock but not much.

Oh and I am not a 60 mph driver on the freeway thank you Socal freeway speeds are 80 mph average when it’s not rush hour. CHP usually does not pull you over unless your doing over 80.

 

[M-Sport fan]

Wing slots?

Those two rectangular cutouts, or yes 'slots' in the factory rear wing.

 

[ranger024x4]

I drive 125 miles round trip. 95% highway with cruise set at 78.

stock tune 30-31mpg is what I’ve seen this winter. First tank with dizzy stage 2 I saw 33.

 

[Black Fists Matter]

Best I’ve gotten is 33.8 avg miles per gallon. That’s city and hwy combined. I get on it occasionally I mean how can you not?

 

[AzNightmare]

Interesting. What benefit do those wing slots even do?
I can't imagine Ford would just design them there "for fun". They might not give better mpg, but do they serve any sort of performance function in exchange?

 

[Dpro]

Interesting. What benefit do those wing slots even do?
I can't imagine Ford would just design them there "for fun". They might not give better mpg, but do they serve any sort of performance function in exchange?

Actually the slots create a bit more drag. My buddy flow stripped them open and sealed off to see the effect. Oh and ya Ford actually designed the wing as purely cosmetic. they could have actually shaped it from the back of the slot openings aerodynamically and created an actual airfoil that would have given the car rear down force but then it would stick more and not be as playful. Ford took out camber in the rear twist beam for the same reason as the stock Fiesta twist beam had 1.5 degrees of static camber stock whereas Fists only have .5-.8. That was the make the car more playful. Adding moar camber in the rear actually does give you more stick but takes away some that playful slide. You really have to decide if you want more grip less slide or more playfulness though with the right tires and playing with tire pressures can bring some of the playfulness back even with more camber. Ya I have experimented with that stuff too.

Actually running a big wing at speed on a FWD car actually be very advantagous for rear stick and does more than running a splitter up front . Their are videos on youtube by an aereodynamic engineer explaining this stuff.

 

[AzNightmare]

Actually the slots create a bit more drag. My buddy flow stripped them open and sealed off to see the effect. Oh and ya Ford actually designed the wing as purely cosmetic. they could have actually shaped it from the back of the slot openings aerodynamically and created an actual airfoil that would have given the car rear down force but then it would stick more and not be as playful. Ford took out camber in the rear twist beam for the same reason as the stock Fiesta twist beam had 1.5 degrees of static camber stock whereas Fists only have .5-.8. That was the make the car more playful. Adding moar camber in the rear actually does give you more stick but takes away some that playful slide. You really have to decide if you want more grip less slide or more playfulness though with the right tires and playing with tire pressures can bring some of the playfulness back even with more camber. Ya I have experimented with that stuff too.

Actually running a big wing at speed on a FWD car actually be very advantagous for rear stick and does more than running a splitter up front . Their are videos on youtube by an aereodynamic engineer explaining this stuff.

What's a good psi for front and rear tires for better grip?

 

[rallytaff]

I'm also getting around 24mpg in LA.

 

[PhoenixM3]

In mixed city/rural driving I’m at 32mpg with an S280. We’ll see what the stock turbo does...

 

[Intuit]

Too much grip and/or suspension change may create rollover risk.
It's likely this influenced many of the suspension and geometry related design decisions.
https://www.fiestastforum.com/threads/fiesta-st-autocross-accident.25828/

I like they way it kind of "points" itself in long hard turn, and they way the suspension is able to quickly respond to steering input during rapid acceleration; the latter being a situation that gets many vehicles/drivers in trouble. Once it's understood why they did it, I think they did pretty well with balancing things out with what they had.

 

[New_Daily]

Drove my car on its longest trip in the 2 years I’ve owned it, aside from when I drove it home buying it.

Went from Ventura county to San Diego (took my buddy to pick up his new bronco). Little bit of traffic there, a bit more going home. Averaged a little over 31 mpg each way. Was actually a little disappointed with that as I thought full highway id see a bit better. And I purposefully drove pretty easy, keeping my foot out of it, always skip shifting, etc. When I drive it to work it’s not really highway, kinda a back road that’s 55 mph and can get unlucky with lights. And the long trip was basically the same 🤷‍♂️

 

[Intuit]

...... I thought full highway id see a bit better.....

More air intake, colder air intake and more engine cooling decreases mileage. (a result of emissions programming) Also needs a taller sixth gear for better highway mileage. The automatic transmissions can put the RPMs very low at highway cruise.

 

[New_Daily]

More air intake, colder air intake and more engine cooling decreases mileage. (a result of emissions programming) Also needs a taller sixth gear for better highway mileage. The automatic transmissions can put the RPMs very low at highway cruise.

Well, my entire intake tract is stock, including the air filter. So I'd think the only time I'm pulling in greater than stock air volumes is at higher than stock boost levels achieved through the Dizzy tune?

The intercooler, I guess due to cooler more dense air means a bit more fuel, but I really thought the main difference with a stock location aftermarket IC was more its resistance to heat soak and therefore lower sustained charge temps, especially with a lot of heavy boost use. But just highway cruise, the post IC charge temps would be fairly close to the stock IC, at least close enough it wouldn't really make difference in MPG?

Just my thoughts and why I would still think at least at highway cruise the MPG should be the same.

As a quick PS, I dont have any exterior body mods, the car is lower but I thought if anything lowering a car would slightly improve MPG, at least not make it worse. And the Rota wheels being 6 lbs or so lighter per wheel would help MPG.

 

[Intuit]

ST even when completely stock isn't an MPG vehicle. Personally, have never succeeded in keeping my foot out of it. 😆 I'd probably have to unlearn the computer before even trying to roll it as an MPG vehicle.

 

[New_Daily]

ST even when completely stock isn't an MPG vehicle. Personally, have never succeeded in keeping my foot out of it. 😆 I'd probably have to unlearn the computer before even trying to roll it as an MPG vehicle.

Yes I understand, especially when compared to a base Fiesta.

I was simply comparing my experience in driving a kind of mixed city / highway drive VS a full highway trip of 150 miles each direction. Since I don't drive my FiST very often and this was the longest drive I've taken it on, I figured I would see an improvement in MPG vs my normal driving use but it was nearly the same.

 

[jmrtsus]

Yes I understand, especially when compared to a base Fiesta.

I was simply comparing my experience in driving a kind of mixed city / highway drive VS a full highway trip of 150 miles each direction. Since I don't drive my FiST very often and this was the longest drive I've taken it on, I figured I would see an improvement in MPG vs my normal driving use but it was nearly the same.

You should remove the tune and see what your mileage is if you can. Also do some gas testing. With my MP-215 Fifi with favored gas gets 38-39 mpg with less favored gas 36. I am pissed when economy driving if I get less than 36. So it can be done. I suspect your tune is the issue. Last summer a 4.5K mile road trip returned 36.2 avg mpg with many miles in the TX, NM and AZ desert mid summer. I would think stock you should see the same or better.

 

[Intuit]

Run'n Regular or Premium? Which octane?

 

[jmrtsus]

Run'n Regular or Premium? Which octane?

93, best mileage (39 mpg) is a non-alky 93 but damn near impossible to find but 2 stations within a couple of miles of my home sell it. On the road I look for a BP or Amoco. The MP-215 tune was tasked with meeting emissions to stay legal and not affecting other items like drivability or economy. I did not test stock mileage as the MP-215 went in as soon as I got the car. It is damn hard to NOT run our cars hard. I bought the FiST as a DD and road car and I think my age has a lot to do with the restraint needed for good mileage. I had a kid in fart can equipped smoke blowing junk Honda recently want to race me at a light, I don't need to beat the fool, I'm happy knowing I can and not doing it. What he really wanted to know was how fast was my FiST.
We are shooting for 34mpg this year on vacation as this will be predominantly 2 lane scenic highways in the eastern mountains. There is a time to waste gas and a time not to do so. I do run Fifi hard on the right roads and conditions like the Tail Of The Dragon in our area. A 2 hour run through ND at 95-100 mph (and still getting passed!) returned 32.5 mpg year before last vacation. Shocked me!

BTW, 87 octane runs like crap on my MP-215, serious HP losses and a one second delay in the weaker throttle response. Push the pedal and wait......... both Ford and Mountune say if you want the hp you bought use 93 octane. Test your cars specific handling of different brands of gas. This is how I discovered Shell and the MP-215 does not agree with each other that was later confirmed by Mountune that they had issues with Shell developing the tune. Lots of debate because other tunes and stock are fine with Shell. Reasonable conclusion is the MP-215 tune does not like the Shell additives, yet our Coyote Mustang and sons built Trans Am loves it, LOL! Keep in mind that all 93 octane fuels are not the same and with multiple types of mods and driving styles comparing gas mileage with other FiST drivers is a joke. Unless you have my car, my gas, my driving style and my roads you have no valid comparisons to my mileage. Can a FiST return great mileage? Yes, if you do your part. You just need to find the right combination. As to the non legal tunes I'm sure they are all about HP not efficiency so I think if you can easily switch tunes to stock you should get better mileage. If not you will need to find out why. FiST on!