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Engine / Transmission Swap

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AlanMcR
Posts: 7729

Re: Engine / Transmission Swap

Post#211 » Sun Dec 27, 2015 6:00 pm

Well, the factory OM606 setup, with the 722.6 overdrive transmission and the overdrive transfer case, averages 20mpg if driven reasonably. Maybe 22mpg if driven gently in good weather. 2600rpm at 65mph.
...Alan

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Chris
Posts: 4549

Re: Engine / Transmission Swap

Post#212 » Sun Dec 27, 2015 6:33 pm

The OM606 swapped F250 likely has 3.55:1 axle ratio, coupled with 33" tires, and overdrive 722.6 auto, the engine is barely above idle when cruising on English B roads.

In a 460 G with basically 5:1 axle ratio, even with overdrive transmission you'd have to run 47" tall tires to equal the ford's super economic cruise RPM.

The super low gearing found in nearly all 460s makes for some pretty terrible economy numbers.

The Gs squared off edges and heavy weight amplify this affect.

In college I studied transportation design at The Art Center in Pasadena, my aerodynamics teacher demonstrated how a vehicle sized 'brick' with sharp 90' edges in a wind tunnel behaves (not very aero), then he put the same brick in the tunnel but with 4 inch radius (think uhaul trailer) on all the edges, this yielded 40% decrease in drag at the same speed.
IG: #traildustrestoration

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inkblotz
Posts: 8203

Re: Engine / Transmission Swap

Post#213 » Mon Dec 28, 2015 2:33 am

Chris wrote:The OM606 swapped F250 likely has 3.55:1 axle ratio, coupled with 33" tires, and overdrive 722.6 auto, the engine is barely above idle when cruising on English B roads.

In a 460 G with basically 5:1 axle ratio, even with overdrive transmission you'd have to run 47" tall tires to equal the ford's super economic cruise RPM.

The super low gearing found in nearly all 460s makes for some pretty terrible economy numbers.

The Gs squared off edges and heavy weight amplify this affect.

In college I studied transportation design at The Art Center in Pasadena, my aerodynamics teacher demonstrated how a vehicle sized 'brick' with sharp 90' edges in a wind tunnel behaves (not very aero), then he put the same brick in the tunnel but with 4 inch radius (think uhaul trailer) on all the edges, this yielded 40% decrease in drag at the same speed.


So Chris,
If you added a front spoiler to the equation to get the air moving around instead of under the vehicle would you not get the same 40% reduced drag results?

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Chris
Posts: 4549

Re: Engine / Transmission Swap

Post#214 » Mon Dec 28, 2015 4:51 am

A chin spoiler would help aero, it has been said that the underside of a vehicle affects aero more than the top. It's anybody's guess exactly what % affect it would have on Coeficient of drag.

Look at the area around the windshield on Jacky Ickx's rally G for the radiused edge I'm referring to:https://clubgwagen.com
IG: #traildustrestoration

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Re: Engine / Transmission Swap

Post#215 » Mon Dec 28, 2015 9:54 am

vadimivanovich wrote:FWIW the W210 uses the overdrive 5-speed 722.6


Hm... this is the first I've heard of that. Looks like you and I will be the US guinea pigs, Vadim!

Well... you more than me at this point. :(
Filmmaker, Musician, Car Nitwit
Hollywood, CA USA

1980 Mercedes 300GD SWB - OM606/5-speed "Puchy"
2003 Mercedes C32 AMG "Dolores"- FLOODED AND TOTALED
2015 Kia Soul - BOOOOOOOO

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Re: Engine / Transmission Swap

Post#216 » Mon Dec 28, 2015 9:59 am

G Nome wrote:Drew,

Our G ways in at about 5000 pounds. SWB 463. Square box vs pretty slinky W210 or w124. Meaty tires vs street tires Etc. 20 MPG would be nice.

Kent


I thought my SWB weighed more than that... 5600 lbs or so. And you're right... driving it at speed is like shoving a brick through jello.

I had 30.5" tires on the old W460 with the OM617, and with the entire interior stripped, I was getting 22-23 mpg. I plan on getting some 33" tires after the rebuild... and was hoping to at least get the same mpgs after the swap.
Filmmaker, Musician, Car Nitwit
Hollywood, CA USA

1980 Mercedes 300GD SWB - OM606/5-speed "Puchy"
2003 Mercedes C32 AMG "Dolores"- FLOODED AND TOTALED
2015 Kia Soul - BOOOOOOOO

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Re: Engine / Transmission Swap

Post#217 » Mon Dec 28, 2015 10:02 am

AlanMcR wrote:Well, the factory OM606 setup, with the 722.6 overdrive transmission and the overdrive transfer case, averages 20mpg if driven reasonably. Maybe 22mpg if driven gently in good weather. 2600rpm at 65mph.


This is in the LWB W463, correct? You're permanently 4WD and weigh significantly more than my SWB W460. I have to assume there's some parasitic loss along both our powertrains, but somewhat more in yours versus my RWD. But very good info to know, Alan.

I'll have to let you know what I end up choosing for my IP setup in my G... I'm hoping for around 150 hp but better mpg... it may or may not work, but there will be a lot of trial and error this time next year when I can afford to drop the engine in.
Filmmaker, Musician, Car Nitwit
Hollywood, CA USA

1980 Mercedes 300GD SWB - OM606/5-speed "Puchy"
2003 Mercedes C32 AMG "Dolores"- FLOODED AND TOTALED
2015 Kia Soul - BOOOOOOOO

Suppatime
Posts: 1215
Contact:

Re: Engine / Transmission Swap

Post#218 » Mon Dec 28, 2015 10:05 am

Chris wrote:The OM606 swapped F250 likely has 3.55:1 axle ratio, coupled with 33" tires, and overdrive 722.6 auto, the engine is barely above idle when cruising on English B roads.

In a 460 G with basically 5:1 axle ratio, even with overdrive transmission you'd have to run 47" tall tires to equal the ford's super economic cruise RPM.

The super low gearing found in nearly all 460s makes for some pretty terrible economy numbers.

The Gs squared off edges and heavy weight amplify this affect.

In college I studied transportation design at The Art Center in Pasadena, my aerodynamics teacher demonstrated how a vehicle sized 'brick' with sharp 90' edges in a wind tunnel behaves (not very aero), then he put the same brick in the tunnel but with 4 inch radius (think uhaul trailer) on all the edges, this yielded 40% decrease in drag at the same speed.


I'm looking for happy mediums, and it's all experimentation. I know it's a brick and there's nothing I can do about that (come on, we all love the look!) aside from tiny improvements like fender flares and the G55 A-pillar deflectors (more of a noise improvement, really). I'm hoping some 33" tires and a detuned OM606 coupled with my 25 gallon fuel tank will get me about 500 miles before the need to refuel.

Another thought I had, to add to your drag conversation, was to add thin metal plating to the underbody as they do in race cars and off-road racers. Sure, it'd add some weight, but would help with the underbody drag.

Chris, are you still in SoCal?
Filmmaker, Musician, Car Nitwit
Hollywood, CA USA

1980 Mercedes 300GD SWB - OM606/5-speed "Puchy"
2003 Mercedes C32 AMG "Dolores"- FLOODED AND TOTALED
2015 Kia Soul - BOOOOOOOO

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Chris
Posts: 4549

Re: Engine / Transmission Swap

Post#219 » Mon Dec 28, 2015 11:07 am

Nor-Cal now, freeway gridlock and bad food make Chrissie a dull boy.

I think bone stock G500 weighs 5600lbs, being fully optioned it should be one of the heaviest G on the road, though somehow Jeremy got his old G500 adventurewagen up to 8000lbs (!).

My 280GE LWB cabriolet weighs exactly 4700lbs with Warn 8274 winch, 6 point roll cage, heavy duty bumpers, rock sliders and 37" tires.
IG: #traildustrestoration

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AlanMcR
Posts: 7729

Re: Engine / Transmission Swap

Post#220 » Mon Dec 28, 2015 7:16 pm

I think the G300 comes in at 5700lbs, w/o fuel/tools/spares. Add 5 people, gear, extra fuel, dog, etc. and it adds up to 7000lbs very quickly.
A deployable chin spoiler or belly pan might help, but thermals would need to be considered.

The OM606 would be a bit more efficient with a properly geared stick shift. The 722.6 auto has some annoying traits that damage fuel economy. Basically it tries to guess what you might do next. Most notably: when you are cruising along below the torque peak (60mph&2400rpm) and you gently accelerate (or hit a gentle rise), it makes the assumption that you might want some real power and releases the lockup. Now you are going 60mph&2600rpm, with the extra power being wasted in the torque converter. This continues for quite a while before it decides to lock up and save some fuel. The practical result of this is that driving in the 50-60 mph range is not as efficient as 65mph, where it almost never unlocks.
...Alan

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