Coyote & CAI, gears, and tuning, and how those affect MPGs

This might get moved.
I thought I'd post my experience with fuel economy after 4+ years of the swap.
This info is based on a factory stock, junkyard 5.0 coyote.
Gear change alone has a very noticeable impact on MPG's, and the tune.

So here are my MPG averages with each gear ratio under daily driving:
3.55s 21.88 MPG
3.73s 20.5 MPG
3.89s 19.x MPG
The only change to the tune with the gear change was the gear ratio in the tune, so there are no other variables changed. What else I find interesting with the copperhead pcm, tuning for MPG I was unable to find any gains OR losses.

So the only thing that is left to test is the gears affect on laptimes.
So far, 3.73s were yielding better laptimes at WGI and Summit point main circuits. The next test is in 2 weeks at NJMP Thunderbolt, where I have logs with 3.73s from 2 years ago.

JLT 2 vs stock airbox. As posted before, unable to see any performance difference.

Driving impressions, SOP and sound. Just the gear change, changes the sound of the exhaust. I like the way the exhaust sounds with the 3.55s best, 3.89s worst. I need to dig further into why this is, suspect it has to do with load calculations - further testing/logging needed on this.

Glasstop, what do you think?

Juice, I'll try to keep it short......but I reserve the right to go off the rails.......you did ask.....


1. As far as what you've posted concerning the MPG's noted w\ the various gear changes, this IMHO is right in line w\ the strengths of the Ford Copperhead PCM using Tri-VCT along w\ spark timing along w\ FI along w\ DBW to closely calc load% using the mechanical TQ advantages from the trans gearing\diff gearing\tire dia to essentially remove engine load% being a major contributor to MPG.... thus only the VE changes from running engine RPM's due to the rear gear ratios at any given vehicle speed, ie, more engine RPM's, more air mass\more fuel used, less engine RPM's, less air mass\less fuel used....this you can't get around as it is strictly a function of the gearing itself. This is about as efficient as 1 can get w\ a gas-powered ICE & why the Ford Coyote V8 is the std nowadays for efficiency, reliability & sheer performance capability....all wrapped up in 1 package.

2. As far as CAI's go, this IMHO is 1 of the biggest snake oil sales of all time...especially since the 3V days. The base dynamics of a larger MAF section vs a smaller 1 is simply not an issue until the airflow velocities reach sheer (frictional drag on the inner walls cause the airflow to compress inward from air mass "rolling across inner wall" causing an effective inner wall ID "reduction" thus restriction) which most engines will NEVER reach on their own...the engineers designed this in so this has never been an issue of "restriction" per se due to air's compressibility dynamics thru the MAF & tube size....only in the amount of useable air filter surface area & porosity ahead of the MAF to maintain the necessary MAF resolution (clean, smooth airflow thru the MAF sensor). All tuning is doing is making up for the meat the Ford engineers left on the table from the detuning they did in other areas of the tune files to meet the emissions targets\goals they set. When tuning the MAF transfer function tables alone to recalibrate a larger MAF section to line up w\ an established calibrated MAF curve you're essentially just lining up to the curve of a calibrated stock MAF transfer function table so the air mass calcs are the SAME between the 2 thus no HP\TQ difference until you get into much, much higher airspeeds where the MAF\air tube sizing can make a difference....competitive racing comes to mind. The only other item left then is the actual air mass flowing IAT difference which determines final air mass density which will influence the amount of fuel used thus will determine actual HP\TQ....here is where the Ford engineers made the difference since the 2010 MY onwards w\ the redesign of the stock airbox's "snorkel" to receive all airflow ahead of the car's radiator core support...thus colder, ambient air exclusively during all operating conditions from idle to WOT....we know how much HP\TQ difference this will make by itself....very little. So IMHO unless 1 is going w\ FI....forget changing out the stock Ford CAI from MY 2010 onward for performance reasons....unless you're only going for looks. If anything slap a K&N filter in the OEM CAI & call it a day. But you can't blame folks for milking it since it drove up sales....even Ford got in on it themselves.

I have to say that I find it funny that so many in general talk down using a larger TB but absolutely talk up using a larger CAI when the dynamics are the same around both. At least when comparing to the same TB open angle, the larger TB has the definate advantage in airflow thruput thus engine load% output at every open TB angle position...but most don't realize that the advent of DBW has negated this advantage since the larger TB is controlled by the PCM using the MAF readout along w\ it's load% calcs & not directly tied to your right foot....so they SEEM to not provide any advantage...but it is there (easily noticed in throttle tip-in performance) as opposed to a larger CAI alone which is not possible........but I digress. Too much science I suppose..........

3. As for the sound, this is again IMHO tied more to the engine's VE from running RPM's based on the effective rear gear ratios & less on actual engine load% (think actual flowing exhaust gas density & velocity thus exhaust frequency output thru the exhaust components installed) in general...thus why the distinct tonal changes you've experienced from the rear gear ratio changeouts more than any tonal changes you could tie to the engine's load% alone (they're present but less so) due to the same engine control setup characteristics as outlined above in #1.

My 2 cents. Hope this helps.

Well, yes it makes sense.
The change in sound is most notable WOT, the sound of is noticably different for the better. Less crackle, more roar. lol
I will update my results from NJMP in 2 weeks. Not sure what to expect, but I have a baseline time to compare.

Now why I didn't type anything about any lap time differences is that there are just too many variables involved to pinpoint to any 1 or set of variables....but in general the gear ratio\tire combo that allows the most efficient use of all the engine's available power area under the curve from off idle to WOT should provide the fastest lap times....all other variables being equal.

But in order to find this, 1 has to be established to then establish the other.....other wise we always end up being the dog that constantly chases his tail.....

We either have to establish the engine's HP\TQ curve 1st then find the best rear gear ratio\tire combo to fit it, or we have to establish the running rear gear ratio\tire combo 1st, then tweak\tune the engine's HP\TQ curve to fit to achieve the goal(s) we want..... There's only so much we can figure out thru math....the rest is thru experience....how it feels (the engine TQ application to the mechanical gearing).

If I were to use your data as given, it would appear that you're gonna end up bracketing the 3.73 gears as the best all around choice.....but that will depend upon the results from your next run at the track that you got your best times while running the 3.73's to judge from.

Good stuff here.................

FYI........Since I changed out the IM, fixed the other stuff & got retuned, the extra low speed TQ output increase I've gained during CL, part throttle operation has me admittedly starting to doubt myself on installing the 3.90's I have....not from the numbers I ran but from the unknown factor....how they'll feel as this extra low speed engine TQ output has made this 3.73 gear\26" tire dia combo I'm running feel much, much better to me than I thought they would right now. This is the part of an engine's power curve performance you can't see\predict on any dyno graph....but is the most important part that you'll feel\experience during most all street driving\light canyon carving & too short a gear ratio can mess this feeling up thus my hesitance on the gear change....but the rest is definately happening cause that's gonna improve the performance--especially in\out of turns--regardless of either gear ratio installed so I gotta make up my mind soon...........

Well I changed from BP93 gas at $4 a gal with no alcohol to Sheetz88 E-15 at $3 a gal. For years the dash said 18.5 mpg overall with the BP gas. Now it's 19.5 overall. The Track Apps Cluster says no difference in performance. Roadkill changed a ratty Fox Body 5.0 from 3:08 to 3:73 only and it went from an average of 14.2 quarter mile to 12.7 quarter mile. They did the change of complete rear end from brake to brake right at the strip.

With the gears, on track, I have determined that:
I cannot use 5th, which is an overdrive. Using 5th lost time at WGI.
So going taller, and making 4th taller makes logical sense.
I'm hoping 2nd will be usable with 3.55s. Even in the tightest section of Shenandoah circuit at Summit, second still seemed too short. You watch, I'm going to end up putting in the 3.31s I got a few years ago. That never got installed into the fox. (Has 3.27s lol)

Juice said:

With the gears, on track, I have determined that:
I cannot use 5th, which is an overdrive. Using 5th lost time at WGI.
So going taller, and making 4th taller makes logical sense.
I'm hoping 2nd will be usable with 3.55s. Even in the tightest section of Shenandoah circuit at Summit, second still seemed too short. You watch, I'm going to end up putting in the 3.31s I got a few years ago. That never got installed into the fox. (Has 3.27s lol)

Click to expand...

Do you mean this place?

Yes, Summit point West Virginia.

Juice said:

So here are my MPG averages with each gear ratio under daily driving:
3.55s 21.88 MPG
3.73s 20.5 MPG
3.89s 19.x MPG

Click to expand...

Haha, I think the highest mileage I have seen (3 tank average) is just under 13 mpg.