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-   -   2005 Dodge Magnum SXT - Auto>Manual Conversion- 10.3% decrease in fuel consumption (https://ecomodder.com/forum/showthread.php/2005-dodge-magnum-sxt-auto-manual-conversion-10-a-33302.html)

t vago 01-04-2016 05:32 PM

2005 Dodge Magnum SXT - Auto>Manual Conversion- 10.3% decrease in fuel consumption
 
This past March, my Dodge Magnum decided to shred apart its 4-speed automatic transmission. Shortly afterward, I decided to swap the 4-speed out for a 6-speed NSG370 transmission. I placed the Magnum back on the road with the new transmission this past October, and start gathering fuel consumption data for it in November.

2015 (with 6-speed NSG370)
DateOdometer (mi)Fuel (gal)FE (US)FE (L/100)
11/09/2015 19:56350.615.44322.710.4
11/20/2015 16:39353.614.45524.49.6
12/07/2015 08:04364.915.71923.210.1
12/17/2015 19:35380.115.47924.69.6
Total:1449.261.09623.79.9


2014 (with 4-speed 42RLE)
DateOdometer (mi)Fuel (gal)FE (US)FE (L/100)
11/10/2014 00:00342.215.12222.610.4
11/20/2014 18:48277.913.47020.611.4
12/05/2014 17:14284.014.15420.111.7
12/15/2014 18:26313.814.50121.610.9
Total:1217.957.24721.311.1


Note: I also changed the rear end from 3.636 to 2.87, in order to compensate for the top gear change from 0.69 (42RLE, 4th) to 0.84 (NSG370, 6th). However, the resultant decrease in engine speed from this swap (about 3.9%) cannot account for the 10.1% decrease in fuel consumption.

ksa8907 01-04-2016 07:21 PM

I read the title and thought you started using MORE fuel, glad i was wrong! contrats! I'm a bit jealous, i always wanted to drive a chrysler 3.5 with a manual trans.

what are the rpms at 60?

t vago 01-04-2016 11:31 PM

Quote:

Originally Posted by ksa8907 (Post 503789)
I read the title and thought you started using MORE fuel, glad i was wrong! contrats! I'm a bit jealous, i always wanted to drive a chrysler 3.5 with a manual trans.

Thanks! These 3.5L engines do seem to like being harnessed to a manual very much. Automatic transmission really sap a lot of power.

Quote:

Originally Posted by ksa8907 (Post 503789)
what are the rpms at 60?

About 1780 RPM. I also had to change out the rear diff. It was a 3.64 ratio, now it's a 2.87 ratio.

Here's a short vid, using Torque Pro and Track Recorder, shortly after I returned the Karen-mobile back to the road.

[youtube]yrAfN-1irGE[/youtube]

mcrews 01-04-2016 11:55 PM

....so h0w do you know it WASNT the rear gear change that improved the mileage.....and why not include that info in the first post......

t vago 01-05-2016 08:08 AM

Quote:

Originally Posted by mcrews (Post 503815)
....so h0w do you know it WASNT the rear gear change that improved the mileage....

Fair question.

Top gear on the dead 42RLE had a ratio of 0.69. Top gear on the replacement NSG370 has a ratio of 0.84. This represents about a 21.7% increase in propshaft rotation speed, for a given vehicle speed. If I were to have left the original 3.636 rear end in place, that should have resulted in a definite increase in fuel consumption.

The FDR was 3.636, while it is now 2.87. This represents about a 21.1% decrease in required pinion input speed, for a given vehicle speed.

These two changes almost cancel each other out, and the net decrease in engine speed (about 3.9%) does not account for the 10.1% decrease in fuel consumption.

Put it another way - Engine speed at 60 MPH was about 1850. Now, it's about 1780. There is no way that this change in engine speed (~3.9%), by itself, would have resulted in the measured decrease in fuel consumption.

Quote:

Originally Posted by mcrews (Post 503815)
.and why not include that info in the first post......

Because I forgot? I only regarded the rear end swap as a necessary adjustment to counter the larger top gear ratio of the installed NSG370, nothing more. I figured that the 3.9% drop in engine speed that I calculated back in April of last year, would have given me a very modest 2% decrease in fuel consumption. This is based on the rule of thumb that a percent change in fuel consumption will be about half the percent change in the rear end ratio. The 2% change would have been rather hard to measure as it is just above noise.

You do bring up an interesting idea - What if I had left the original 3.636 rear end in place? Engine speed would have been about 2250 RPM at 60 MPH, which would have resulted in a net increase in engine speed of... 21.7% from when the 4-speed was still installed. I would have expected a 10.9% increase in fuel consumption just from swapping in the NSG370, if I were to have treated the engine speed increase as a result of swapping in a (nonexistent) 4.43 rear end.

Daox 01-05-2016 09:44 AM

Nice mod. I bet its a lot more fun to drive now too.

t vago 01-05-2016 12:54 PM

Quote:

Originally Posted by Daox (Post 503828)
Nice mod. I bet its a lot more fun to drive now too.

Oh, yah! I like to think that the Karen-mobile now has performance that approaches the available 5.7L V8, while having fuel economy that approaches the available 2.7L V6.

Shortly after I placed the Karen-mobile back on the road, I accidentally gave too much gas when starting in 1st from a dead stop. I left a nice, pretty black tire stripe for about 20 feet on dry pavement. Obviously, not good for either tire life or fuel economy. I shudder to think what would have happened, had I left that 3.636 diff in.

cRiPpLe_rOoStEr 01-05-2016 09:36 PM

The lower weight of a manual transmission and the absence of the torque converter slip should be taken into account for the final results, but what about the gear spread of the 4-speed automatic and this 6-speed manual? Is it the same transmission used in the Wrangler and the Sprinter, right?

ksa8907 01-05-2016 11:01 PM

The 42le and 42rle were really just a modern take on much older transmission design. The increase is probably a result of no converter slip when accelerating, no pumping fliud, etc. Plus now you're essentially doing mini pulse and glides whule shifting.

t vago 01-06-2016 01:01 AM

Quote:

Originally Posted by cRiPpLe_rOoStEr (Post 503899)
The lower weight of a manual transmission and the absence of the torque converter slip should be taken into account for the final results, but what about the gear spread of the 4-speed automatic and this 6-speed manual? Is it the same transmission used in the Wrangler and the Sprinter, right?

The Jeep Wrangler used this transmission on the 3.8L V6 engine (which was what made this swap possible - the 3.5L and the 3.8L V6 bellhousing bolt patterns are nearly identical). The Chrysler Crossfire also used this transmission, but with a radically different bellhousing bolt pattern.

42RLE gears
1st2.80
2nd1.55
3rd1.00
4th0.69


NSG370 gears
1st4.46
2nd2.61
3rd1.72
4th1.25
5th1.00
6th0.84


The gearing appears to be more closely spaced together on the 6-speed. That would help with fuel economy during acceleration, particularly with city driving.

I think that the two largest power drains were torque converter slippage and pumping losses through the transmission oil pump.

Not sure if transmission weight itself would have played much of a part. I lost maybe 50 lbs or so from the swap.

Quote:

Originally Posted by ksa8907 (Post 503917)
Plus now you're essentially doing mini pulse and glides whule shifting.

Heh, that's true, too.

mcrews 01-06-2016 10:47 AM

Quote:

Originally Posted by t vago (Post 503824)
Fair question.

Top gear on the dead 42RLE had a ratio of 0.69. Top gear on the replacement NSG370 has a ratio of 0.84. This represents about a 21.7% increase in propshaft rotation speed, for a given vehicle speed. If I were to have left the original 3.636 rear end in place, that should have resulted in a definite increase in fuel consumption.

The FDR was 3.636, while it is now 2.87. This represents about a 21.1% decrease in required pinion input speed, for a given vehicle speed.

These two changes almost cancel each other out, and the net decrease in engine speed (about 3.9%) does not account for the 10.1% decrease in fuel consumption.

Put it another way - Engine speed at 60 MPH was about 1850. Now, it's about 1780. There is no way that this change in engine speed (~3.9%), by itself, would have resulted in the measured decrease in fuel consumption.



Because I forgot? I only regarded the rear end swap as a necessary adjustment to counter the larger top gear ratio of the installed NSG370, nothing more. I figured that the 3.9% drop in engine speed that I calculated back in April of last year, would have given me a very modest 2% decrease in fuel consumption. This is based on the rule of thumb that a percent change in fuel consumption will be about half the percent change in the rear end ratio. The 2% change would have been rather hard to measure as it is just above noise.

You do bring up an interesting idea - What if I had left the original 3.636 rear end in place? Engine speed would have been about 2250 RPM at 60 MPH, which would have resulted in a net increase in engine speed of... 21.7% from when the 4-speed was still installed. I would have expected a 10.9% increase in fuel consumption just from swapping in the NSG370, if I were to have treated the engine speed increase as a result of swapping in a (nonexistent) 4.43 rear end.

I like a man who can run the numbers!!:thumbup:

ksa8907 01-06-2016 06:02 PM

If i remember correctly, the intrepid (42le) with 3.66 gears was 2000 rpm @ 60 and with 3.89 and 215's instead of 225's i was running about 2200@60. I still brushed 30mpg average with the 3.89's.

ksa8907 01-06-2016 06:05 PM

Quote:

Originally Posted by t vago (Post 503922)
The Jeep Wrangler used this transmission on the 3.8L V6 engine (which was what made this swap possible - the 3.5L and the 3.8L V6 bellhousing bolt patterns are nearly identical). The Chrysler Crossfire also used this transmission, but with a radically different bellhousing bolt pattern.


The first gen intrepid came stock with a 3.3, same as 3.8

cRiPpLe_rOoStEr 01-07-2016 07:46 AM

Quote:

Originally Posted by t vago (Post 503922)
Not sure if transmission weight itself would have played much of a part. I lost maybe 50 lbs or so from the swap.

Sure it's not the most important reason for that mileage improvement, but is not to be neglected at all.

RustyLugNut 01-07-2016 03:31 PM

Drag racers certainly would think it significant.
 
Quote:

Originally Posted by cRiPpLe_rOoStEr (Post 504045)
Sure it's not the most important reason for that mileage improvement, but is not to be neglected at all.

I can't remember what the rule of thumb was for performance gained from weight reduction.

I should quit driving around with my wife. She's 100 pounds.

Fat Charlie 01-08-2016 07:46 AM

A navigator/commo/spotter that only costs 100 pounds is golden.

t vago 01-15-2016 11:05 AM

Well, made a few discoveries since last posting -

I had flashed the Magnum with a DiabloSport canned performance 93 octane tune a few years ago, and left it in there for up until a few days ago. I found out that this canned tune had caused my cold idle speed to be about 3000 (three thousand) RPM, and warm idle to consume about .55 gallons per hour.

I reverted the Magnum's tune back to stock, then played around with the stock tune with the limited tweaking capability built into the Predator. Basically, I advanced ignition timing by 8 degrees from 0-4000 RPM, and experimented with lowering the idle engine speeds (idle in P/N w/ no AC, idle in R/D/3/L w/ no AC, idle in P/N w/ AC on, idle in R/D/3/L w/ AC on).

Turns out that advancing stock ignition timing does wonders with fuel economy, above and beyond with what the performance 93 canned tune did. I got 28 MPG on a mostly-highway 29 mile drive last night, then got 25 MPG on a 6.5 mile city drive about an hour later.

Also learned that messing with the stock idle speeds is counterproductive, even with lowering the speeds by 50 RPM. When warm, the Magnum would attempt to idle at the lowered idle speed, then somehow the engine computer would experience some sort of underflow condition and cause idle speed to jump up to about 2000 RPM. I returned the idle speeds back to stock settings, and that solved the idle speed problem. I am also consuming about 0.35 gallons per hour in idle, now.

Also, the performance 93 tune messed with DFCO. The Magnum is now more willing to enter DFCO when I let off the gas.

Fat Charlie 01-15-2016 12:10 PM

Nice work!

oldtamiyaphile 01-15-2016 07:45 PM

I feel like it's been left out than an Auto on it's last legs may have had issues that caused poor economy. I had a 1.3 Suzuki with dead trans that struggled to get 25mpg.

A manual swap+ EOC would have sent that into the 60's.

t vago 01-16-2016 12:25 AM

Quote:

Originally Posted by oldtamiyaphile (Post 504867)
I feel like it's been left out than an Auto on it's last legs may have had issues that caused poor economy. I had a 1.3 Suzuki with dead trans that struggled to get 25mpg.

It's certainly within the realm of possibility. I did not consider it as a factor, however, because
  • Out of 58 model year 2005 Dodge Magnums being tracked on Fuelly for gas mileage, mine made the top 5, with an average of 22.7 MPG, at the time the transmission died;
  • The torque converter locked up normally and showed no signs of slippage;
  • The transmission clutches all had normal measurements at the time the transmission failed (OD=125,UD=37,L/R=43,2/4=46);
  • The transmission fluid was not burnt when I drained the transmission upon initial diagnosis; and
  • The rear carrier assembly of the transmission had literally shredded itself into two separate pieces, once I took apart the old transmission to find out what had failed.

Here's the part that failed. It's part of the rear carrier assembly, the part that transmits engine power through 2nd, 4th, and reverse. Part of this rear carrier assembly is still inside the transmission. In the background, you can see the rear annulus, front carrier assembly, and a couple of large snap rings.

http://www.tom-viki.com/spgm/gal/Car...1509120004.jpg

Here's a picture of a complete and unbroken rear carrier assembly. The part I'm holding in my hand is the bottom of the complete assembly.

http://www.tom-viki.com/spgm/gal/Car...1509140000.jpg

ALS 02-03-2016 05:06 PM

1 Attachment(s)
I did the same swap in my old Volvo turbo wagon for better mileage.The automatic a non locker, had a .69 OD and 3.90 rear gears. The manual had a .80 OD and I also swapped in 3.31 rear gears.

Highway mileage the best I could get with the automatic was around 340 miles per tank, 15.8 gallons. After the swap including lowering the vehicle I jumped the mileage to 425-440 miles per tank.

Almost always the best bang for the buck mod for better mileage is swapping out the automatic for a manual and higher rear gears.

ksa8907 02-03-2016 11:06 PM

Quote:

Originally Posted by oldtamiyaphile (Post 504867)
I feel like it's been left out than an Auto on it's last legs may have had issues that caused poor economy. I had a 1.3 Suzuki with dead trans that struggled to get 25mpg.

A manual swap+ EOC would have sent that into the 60's.


I would vote no on that theory. The 42rle same as the 42le and 41te, were also known as chryslers "ultradrive" transmissions. They would automatically adjust themselves to operate as close to factory spec as possible no matter how worn the transmission got. Which is one reason why chrysler transmissions had the bad reputation for suddenly dieing with no warning, they were designed that way.

t vago 02-04-2016 06:25 AM

Quote:

Originally Posted by ksa8907 (Post 506399)
I would vote no on that theory. The 42rle same as the 42le and 41te, were also known as chryslers "ultradrive" transmissions. They would automatically adjust themselves to operate as close to factory spec as possible no matter how worn the transmission got. Which is one reason why chrysler transmissions had the bad reputation for suddenly dieing with no warning, they were designed that way.

Yah, that, too. ;)

Xist 02-04-2016 11:21 AM

Chryslers were designed to die without warning?! That explains so much! :)

What rear end came stock with the manual transmission. It looks like we have yet another automatic geared for fuel efficiency, while the manual was designed for acceleration.

What kind of mileage would the automatic have had with the new rear end? :)

t vago 02-04-2016 12:03 PM

Quote:

Originally Posted by Xist (Post 506441)
Chryslers were designed to die without warning?! That explains so much! :)

I am a lifelong Chrysler fan, and I approve of this message! :D

Quote:

Originally Posted by Xist (Post 506441)
What rear end came stock with the manual transmission. It looks like we have yet another automatic geared for fuel efficiency, while the manual was designed for acceleration.

Well, the Dodge Magnum was never offered with a manual transmission.

However, the later model Challenger, which is based off an update to the platform that the Magnum was built on, was offered with a 6-speed Tremec manual. It could have either a 3.73 rear end, or a 3.92 rear end.

Quote:

Originally Posted by Xist (Post 506441)
What kind of mileage would the automatic have had with the new rear end? :)

That's a 21.1% reduction in gearing from 3.636 to 2.87, so I would estimate a 10.5% reduction in fuel usage. I would also estimate that my Magnum would have gone from an average of 21.3 MPG (last winter 4-fillup average) to an average of 23.8 MPG. Performance would have suffered, though.

Xist 02-04-2016 12:49 PM

What performance? You would have been at 1,460 RPM on the freeway! :)

t vago 02-04-2016 01:09 PM

Quote:

Originally Posted by Xist (Post 506456)
What performance? You would have been at 1,460 RPM on the freeway! :)

Yes, but it would also become a LensCrafters car. You know...

"0 to 60... in about an hour!"

RoadRaceJosh 02-06-2016 04:44 PM

The old overall high gear ratio was 2.51:1 (3.636*.69). The new overall high gear ratio 2.87*.84 is 2.41. So the engine spins 96% as fast as it used to assuming no slippage. That's darn close.

What I'm curious to see is how you took a 4x4 trans and put a tail housing on it.

t vago 02-06-2016 06:59 PM

Quote:

Originally Posted by RoadRaceJosh (Post 506690)
The old overall high gear ratio was 2.51:1 (3.636*.69). The new overall high gear ratio 2.87*.84 is 2.41. So the engine spins 96% as fast as it used to assuming no slippage. That's darn close.

What I'm curious to see is how you took a 4x4 trans and put a tail housing on it.

Yah, that was the fun part - In the end, I basically made a franken-tranny.

In May 2015, I was scratching my head at making the rear of the Jeep transmission work in the Magnum. After several days of brainstorming, I came up with the remarkably bright idea of swapping transmission parts with a Chrysler Crossfire manual transmission (which was supposedly also an NSG370). Of course, I wasn't completely sure. Using Chrysler parts manuals for both the Jeep and the Crossfire, I performed a parts comparison between the Jeep transmission I had and the Crossfire transmission, and found out that they share 95% of the same parts.

So, I bought a Crossfire manual transmission, and inspected both transmissions. It turned out that I needed a sleeve bearing. Apart from that, I could mix and match the Jeep and Crossfire transmissions. Also made installing a shifter much easier.

Here are some pictures:

Comparison of front case internals for JK NSG370 and ZH NSG370
http://www.tom-viki.com/spgm/gal/Car...1505230000.jpg

Comparison of rear case internals for JK NSG370 and ZH NSG370
http://www.tom-viki.com/spgm/gal/Car...1505230001.jpg

3.8L V6 case, with a new shift shaft sleeve bearing installed
http://www.tom-viki.com/spgm/gal/Car...1506060000.jpg

Original shift shaft sleeve bearing, pulled with blind hole bearing puller
http://www.tom-viki.com/spgm/gal/Car...1506060001.jpg

Should someone want to power their JK Wrangler with a Mercedes engine, they can use the below transmission. Obviously, not going to happen - will probably keep this transmission for spare parts.

JK/ZH Franken-tranny
http://www.tom-viki.com/spgm/gal/Car...1506070004.jpg

The item that will make it possible for a V6 Magnum to have a manual transmission...

LX Franken-tranny
http://www.tom-viki.com/spgm/gal/Car...1506070005.jpg


Modified transmission mount, showing two drilled and tapped holes
http://www.tom-viki.com/spgm/gal/Car...1507260000.jpg

Transmission mount, installed
http://www.tom-viki.com/spgm/gal/Car...1507260001.jpg

RH, looking forward
http://www.tom-viki.com/spgm/gal/Car...1507260006.jpg

LH, looking forward, with clutch slave cylinder
http://www.tom-viki.com/spgm/gal/Car...1507260007.jpg

Close-up of clutch slave cylinder and clutch hose
http://www.tom-viki.com/spgm/gal/Car...1507260008.jpg

Rear view, showing transmission crossmember in "NAG1" configuration
http://www.tom-viki.com/spgm/gal/Car...1507260009.jpg

RoadRaceJosh 02-06-2016 07:55 PM

That's impressive! I used to want to put a RWD transmission behind a 3.5 V6, but buying 2 transmissions to build 1 is more of an undertaking than I desire.

EcoManny 02-08-2016 11:56 PM

impressive :thumbup:


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