My MPG gain is fenominal with a Pre F37 TCM

Joe Romas · **Posted:** Sun Oct 23, 2011 8:02 pm

yrkcrd wrote:

Hmm same as my TCM! Cool does that mean I have pre-F37?? :pepper:

Are you reading it off the tag on the outside or using some type of scanner interogating the tcm for the number :?:

If it's from the tag it only means what it had when it left the factory :JEEPIN:

yrkcrd · **Posted:** Sun Oct 23, 2011 8:21 pm

Joe Romas wrote:

yrkcrd wrote:

Hmm same as my TCM! Cool does that mean I have pre-F37?? :pepper:

Are you reading it off the tag on the outside or using some type of scanner interogating the tcm for the number :?:

If it's from the tag it only means what it had when it left the factory :JEEPIN:

Hmm good point. On the outside I'll scan it and see what it says. Thought they put a sticker on it though.

CATCRD · **Posted:** Sun Oct 23, 2011 9:06 pm

racertracer wrote:

Traveling speed varied - Mostly 63 to 75 MPH. I discovered that maintaining the RPM between 1700 to 1950 produced the best results.

75mph = 1950rpm.
63mph = 1700rpm

Racer

I'm curious how your CRD goes 75mph at 1950rpm while mine goes 67mph at that rpm. With your nearly stock tire size it should be about the same. Have you verified your speedo or odo with a GPS lately?

racertracer · **Posted:** Sun Oct 23, 2011 9:10 pm

CATCRD wrote:

I'm curious how your CRD goes 75mph at 1950rpm while mine goes 67mph at that rpm. With your nearly stock tire size it should be about the same. Have you verified your speedo or odo with a GPS lately?

I've checked it in the past and it was right on, I will for sure check my speedo again and let you know.

user113 · **Posted:** Sun Oct 23, 2011 10:18 pm

I wonder how much of these MPG differences are from the actual fuel used. Back in August I drove from Northern Virginia to Houlton, Maine. I filled up in Massachusetts on the way up. From there to Houlton the EVIC read 31.6 (pre GDE, pre F37). Two days later I drove to Bangor to pick my sister and her family up from the airport, and filled up there in Bangor. On the same road, same weather, same speed (cruise control), albeit with two other people in the car I was only able to get it to register 27.8 on the EVIC on the trip back to Houlton. I filled up again in Houlton where a tanker was restocking the gas station and asked the driver, he said that different states require different fuel and it does affect mileage. I spoke with another trucker who echoed the same thing, he said to fill up in Colorado going west because the fuel sold in Utah gets poor economy.

Bottom line, for true scientific results, we need to be using the same fuel for any comparisons.

Joe Romas · **Posted:** Mon Oct 24, 2011 8:07 am

racertracer wrote:

CATCRD wrote:

I'm curious how your CRD goes 75mph at 1950rpm while mine goes 67mph at that rpm. With your nearly stock tire size it should be about the same. Have you verified your speedo or odo with a GPS lately?

I've checked it in the past and it was right on, I will for sure check my speedo again and let you know.

My speedometer reads 69 at just below 2000 rpms and my GPS says that's an actuall 65 MPG and that is with both the stock size bad years and stock size BFG Long Trail tires.
So at 1950 rpm's it shows about 67 too :SOMBRERO:

I believe most members running stock size tires see the same speedometer error :JEEPIN:

As for the sweet spot look at this chart at GDE and you'll that from 1600 to 2000 is where the engine is the strongest with their full torque tune :BINGO:

http://www.greendieselengineering.com/f ... st/20.page

racertracer · **Posted:** Tue Oct 25, 2011 5:34 am

The GPS confirmed the mph is right on or a hair under.

user113 wrote:

I wonder how much of these MPG differences are from the actual fuel used.

I used B20.

CATCRD wrote:

I'm curious how your CRD goes 75mph at 1950rpm while mine goes 67mph at that rpm. With your nearly stock tire size it should be about the same.

Cat,

I don't know why either, but a long highway, keeping the foot off the pedal and not making too many stops produced these results. In the past and before the cylinder head swap, I did not pay attention to the RPM and MPH gauges as I did for this trip, so I can't make a comparison.

The tripletreds are highway tires, and they make for a smooth ride. The tred on the tires is very low, which may be good for MPG gain (less resistance) but bad for the snow, I will be replacing them before the snow comes and the MPG may change then.

I may do another run soon on the way to Maine and reconfirm the results.

I believe that If this test was done on a flat highway with less hills and turns, the MPG results might have been even better.

Here In New England we have a ton of hills and turns that will reduce the MPG average.

flash7210 · **Posted:** Tue Oct 25, 2011 12:34 pm

CATCRD wrote:

racertracer wrote:

Traveling speed varied - Mostly 63 to 75 MPH. I discovered that maintaining the RPM between 1700 to 1950 produced the best results.

75mph = 1950rpm.
63mph = 1700rpm

Racer

I'm curious how your CRD goes 75mph at 1950rpm while mine goes 67mph at that rpm. With your nearly stock tire size it should be about the same. Have you verified your speedo or odo with a GPS lately?

I have taller tires with no lift.
At 1800 rpm I'm doing about 64 mph, according to my gps.
At 1900 rpm I'm doing about 69 mph.
At 2000 rpm I'm doing about 73 mph.

Racer, changing the TCM did not change your gear ratios.
Maybe your CRD has a unique set of gears that our do not?

racertracer · **Posted:** Tue Oct 25, 2011 1:33 pm

flash7210 wrote:

CATCRD wrote:

racertracer wrote:

Traveling speed varied - Mostly 63 to 75 MPH. I discovered that maintaining the RPM between 1700 to 1950 produced the best results.

75mph = 1950rpm.
63mph = 1700rpm

Racer

I'm curious how your CRD goes 75mph at 1950rpm while mine goes 67mph at that rpm. With your nearly stock tire size it should be about the same. Have you verified your speedo or odo with a GPS lately?

I have taller tires with no lift.
At 1800 rpm I'm doing about 64 mph, according to my gps.
At 1900 rpm I'm doing about 69 mph.
At 2000 rpm I'm doing about 73 mph.

Racer, changing the TCM did not change your gear ratios.
Maybe your CRD has a unique set of gears that our do not?

I believe I have the same transmission as everyone else does. I will recheck and report back on the next trip I take. The throttle was sensitive and very responsive more so then ever before. Just a touch at the pedal and the CRD flew while it was in momentum at those speeds. I have been reading other posts about members experienceing similar MPG when swapping out their TCM to the pre F37 TCM. All to incredulous non pre F37 TCM owners.

Maybe your tires are too big for the transmission, or your transmission is not performing at peak performance. When was the last time you changed transmision fluid, are you using convetional oil, did you clean your map sensor, are your brakes locking up, is your engine running at peak performance..... your motor may need an Italian tune up. Maybe all you need is an oil change with some good slippery oil, who knows.

racertracer · **Posted:** Tue Oct 25, 2011 2:42 pm

Chrysler HQ just called and they want the Jeep Back for testing, I think I hit a nerve.

papaindigo · **Posted:** Tue Oct 25, 2011 2:51 pm

Too many apples, oranges and tangerines in this discussion. All the 2005 and 2006 CRDs have the same transmission and as far as I know the same rear end ratio. Frankly I have no clue how accurate the tachometer is but I can say that the speedometer and odometer accuracy varies between individual CRDs (if I correctly recall an earlier discussion the factory acceptable accuracy deviation from actual is 5%; so either instrument can be over or under actual by 5%) and I can positively state the speedometer and odometer accuracy variation on the same vehicle is not correlated (e.g. one can read high while the other reads low). No rocks to throw at Jeep or Chrysler as this is an industry wide issue and has been for decades if not longer. Bottom line is unless you have run a good GPS check (ideally 50-100 interstate miles for the distance check) and have filled the tank consistently to the same level (ideally at the same station/pump and up to visible fuel in the filler neck) any mpg calculations, especially on a single tank, are suspect. Don't even get me started on the EVIC although mine is pretty close with the recent EcoTune update.

In addition, assuming flat terrain, speed at a given RPM is going to vary depending on the gear you are driving in and the diameter of your tires. I've driven a 2005 pre and post F-37 tranny flash and, post dump truck encounter, another 2005 that had the F-37 service WITHOUT the F-37 tranny flash but subsequently got the GDE EcoTune and later the GDE TCM tune. In all the variations of those vehicles in top gear with the TC locked (never mind what speed it locked at) 61-62mph (GPS verified) = 1,800rpm with the OEM stock tires. If you have tires with a larger diameter your rpms will be lower for mph relative to mine.

On the vehicle without the F-37 tranny flash on dead flat Florida roads driving a steady 61-62 no hyper mile games I could occasionally touch 30mpg but consistent hwy mpg was more like 27-28; EVIC reported much better mpg than actual and on stoudogs 2006 wildly much better than actual. Remember we drive an aerodynamic brick so I suspect wind speed relative to travel direction would have a significant impact on mpg. In addition, unless you are driving well into the top gear lockup range on a post F-37 tranny flash I would expect in hilly terrain that the tranny would drop out of lockup fairly easily would would hurt mpg. At the same time if you are driving from say Flagstaff to Tempe AZ which is overall down hill I'd expect better mpg than going the other way.

I do know the EcoTune produced a significant bump in mpg and I have 10k miles of data to prove it. I also know that factors other than the above can have a noticable impact on mpg. Kayak on roof rack of gasser right side up vs upside down vs right side up with solid cover over seat hole; the latter 2 were worth 4mpg. Gasser truck with bed length such that air over cab "falls" into the bed before the tailgate; bed cover or tailgate down is worth 2mpg but different truck and different air flow no change. CRD on same road clear weather no wind 33mpg; same road rainy weather head wind and tstat going 28mpg.

Pardon my rambling. My point, such as it is, is that there are a host of factors that impact mpg even for a single vehicle never mind trying to compare between vehicles unless those vehicles are driven at the same speed on the same course at the same time.

yrkcrd · **Posted:** Sun Oct 30, 2011 9:51 pm

yrkcrd wrote:

Joe Romas wrote:

yrkcrd wrote:

Hmm same as my TCM! Cool does that mean I have pre-F37?? :pepper:

Are you reading it off the tag on the outside or using some type of scanner interogating the tcm for the number :?:

If it's from the tag it only means what it had when it left the factory :JEEPIN:

Hmm good point. On the outside I'll scan it and see what it says. Thought they put a sticker on it though.

OK scanned the TCM today with vagcom aka vcds and it reports part number 56044737AF

So just to confirm this is a pre F37 TCM correct?

Thanks :mrgreen:

racertracer · **Posted:** Sun Oct 30, 2011 10:02 pm

yrkcrd wrote:

So just to confirm this is a pre F37 TCM correct?

Thanks :mrgreen:

That wont tell you if it has been flashed.

Here is a way to tell.

Take the CRD out for a long drive on an open highway and pay close attention to the transmission shifting, the last shift should be at 57 - 58 MPH anything above that and your TCM has been flashed with the F37.

yrkcrd · **Posted:** Sun Oct 30, 2011 10:22 pm

racertracer wrote:

yrkcrd wrote:

So just to confirm this is a pre F37 TCM correct?

Thanks :mrgreen:

That wont tell you if it has been flashed.

Here is a way to tell.

Take the CRD out for a long drive on an open highway and pay close attention to the transmission shifting, the last shift should be at 57 - 58 MPH anything above that and your TCM has been flashed with the F37.

I scanned it with a scan tool so this is the part number that Jeep would see if they hooked up to it.

The PCM comes up as 56044562CF which is the latest NA flash for the 2005 IIRC

But yes real world would make it easy :frankie:

My MPG gain is fenominal with a Pre F37 TCM

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