1999 4Runner 4x4 Streamlining

[kach22i]

Originally Posted by aardvarcus

My mental dyno tells me the drag coefficient of the vehicle hasn’t changed drastically, however I can tell the rear end feels much more planted in turns which I attribute to reduced rear lift.

I felt that way about the first huge air dam chin spoiler I built on my van back in 1983.

The added stability in cross winds made the effort well worth it, and it looked cool too.

[slowmover]

Originally Posted by kach22i

I felt that way about the first huge air dam chin spoiler I built on my van back in 1983.

The added stability in cross winds made the effort well worth it, and it looked cool too.

This goes to the heart of the thing. Handling adverse winds. I can run down the road with a 53’ van behind me (full skirt & tails) and it is more the position of the tandem trailer axles that alerts me to this adversity (tandems positioned to even out weight of load with the Drive Axles) as leverage increases with length past those axles position.

In other words, most of the time I don’t notice the effect of the tail (3.5’ deep). Not until wind loads increase. It’s only judging by the Current Fuel Economy readout that the advantage is obvious in every driving situation.

I think ABBA testing not a big deal. If fill up is possible at same station pump every time to first auto-shutoff it’s more than enough. That also rules out fuel blend changes per brand.

Reading engine hours is the last. Calculation of Average MPH per tank is handy. Accounts for operator changes. Keeping it at or above 26-mph is the key to long-term engine life and FE.

Same fuel, same basic routes, same average mph covers “transparency”.

Aero aids are cake icing. Operator inputs FAR outweigh it as this is a metro-mobile, not a highway runner. The margin added is in keeping MPG high versus weather penalties per tank.

.

.

[aardvarcus]

I don’t have extreme confidence in these numbers yet, but I have collected a few similar mostly highway tanks with and without the shell, same route, same pump sort of thing. Three of these tanks without the shell averaged 25.4 two tanks with the shell averaged 26.6, implying a 4.7% increase.

The reason I don’t have extreme confidence in the numbers is that I have noticed that both stop and go traffic and use of AC seem to drive fuel economy down, more so than I have experienced in other vehicles. I am not sure what to think of that fact yet. I am going to be doing plugs/wires/sensors on the engine soon. Also I plan to put heat rejecting tint on the windows and add some cab insulation to reduce the AC use.

I still feel the transition from the body to the shell is hurting me, I am planning on adding some thin aluminum strips formed to the contours to cover this gap, which would stop right at the front of the factory hatch. These would be attached to the shell mechanically. I tried to do something with fiberglass in this area when I initially created the shell but had issues…

I am still trying to form a good plan for the underbody coverage, one area of particular drama is between the front and rear tires. I am thinking running a flat bottom from the frame all the way out to the tires outside edge, turning up and forming a box shape, turning back in where the rockers pinch seam is, basically boxing in the area where the side steps usually go. This would give me a good surface to mount my tire spat flaps on.

[freebeard]

Beware the breakover angle.

[slowmover]

Originally Posted by aardvarcus

I don’t have extreme confidence in these numbers yet, but I have collected a few similar mostly highway tanks with and without the shell, same route, same pump sort of thing. Three of these tanks without the shell averaged 25.4 two tanks with the shell averaged 26.6, implying a 4.7% increase.

The reason I don’t have extreme confidence in the numbers is that I have noticed that both stop and go traffic and use of AC seem to drive fuel economy down, more so than I have experienced in other vehicles. I am not sure what to think of that fact yet. I am going to be doing plugs/wires/sensors on the engine soon. Also I plan to put heat rejecting tint on the windows and add some cab insulation to reduce the AC use.

I still feel the transition from the body to the shell is hurting me, I am planning on adding some thin aluminum strips formed to the contours to cover this gap, which would stop right at the front of the factory hatch. These would be attached to the shell mechanically. I tried to do something with fiberglass in this area when I initially created the shell but had issues…

I am still trying to form a good plan for the underbody coverage, one area of particular drama is between the front and rear tires. I am thinking running a flat bottom from the frame all the way out to the tires outside edge, turning up and forming a box shape, turning back in where the rockers pinch seam is, basically boxing in the area where the side steps usually go. This would give me a good surface to mount my tire spat flaps on.

Cylinder Pressure. Is everything.

.

[Tahoe_Hybrid]

Originally Posted by aardvarcus

Purchased a 1999 Toyota 4Runner, 3.4L V6, 5 Speed R151F Transmission, 4x4, 4:10s. It was selected because it has real 4WD, stick shift, 4 Doors, will fit two car seats and two adults, capable of towing and hauling, smaller than my Suburban, and has a comfortable ride. My wife has a similar one and I enjoy it (other than the missing clutch in hers). This vehicle will be for daily driving and moderate off-road use.

I am not going to mess with the powertrain on this one, mainly just some aero add-ons and a few off-road related items. I am putting this in the Aero subsection since that is the focus of this thread.

Currently planning the following:
Aero Mods:
Swap 265/70R16 Cooper AT3 to 245/75R16 Michelin LTX (in progress)
Remove roof rack, rear deflector, side steps, and fender flares.
Small boat tail attached to the rear hatch. (Fiberglass over foam)
Belly Pan/ Skid plates (1/4” Aluminum)
Tire Spats (Conveyor Belt)
Grill Ducting

Other Mods:
Change all fluids and stop oil cooler O-ring leak (in progress)
Upgraded Sway Bars
Front and Rear high clearance hitches, with winch on cradle.
255/85R16 tires on extra wheels to swap for dedicated trips.
Extra Insulation/sound deadening in interior.

Dream wishlist:
E-locker axle swap.
Dyna 5th gear swap in transmission during future rebuild.

I am open to suggestions, please give me your ideas on what all I should do/not do to this vehicle. I will post some more details below of my planned aero mods.

front clip from 2002 toyota prius

[aerohead]

Originally Posted by aardvarcus

I don’t have extreme confidence in these numbers yet, but I have collected a few similar mostly highway tanks with and without the shell, same route, same pump sort of thing. Three of these tanks without the shell averaged 25.4 two tanks with the shell averaged 26.6, implying a 4.7% increase.

The reason I don’t have extreme confidence in the numbers is that I have noticed that both stop and go traffic and use of AC seem to drive fuel economy down, more so than I have experienced in other vehicles. I am not sure what to think of that fact yet. I am going to be doing plugs/wires/sensors on the engine soon. Also I plan to put heat rejecting tint on the windows and add some cab insulation to reduce the AC use.

I still feel the transition from the body to the shell is hurting me, I am planning on adding some thin aluminum strips formed to the contours to cover this gap, which would stop right at the front of the factory hatch. These would be attached to the shell mechanically. I tried to do something with fiberglass in this area when I initially created the shell but had issues…

I am still trying to form a good plan for the underbody coverage, one area of particular drama is between the front and rear tires. I am thinking running a flat bottom from the frame all the way out to the tires outside edge, turning up and forming a box shape, turning back in where the rockers pinch seam is, basically boxing in the area where the side steps usually go. This would give me a good surface to mount my tire spat flaps on.

The old-school,SAE testing protocol was to drive at a constant highway speed,with and without,on the same route,same day,as soon as possible.This reduces variables down to one,about as much as we could hope for.In mixed driving,you'll get a composite number,but it will impossible to arrive at a delta-Cd.
At a steady highway speed,a 10% drag reduction is going to net you close to a 5% improvement in MPG.A two-to-one,shoot from the hip metric.
You ought to see around 10% better mpg.

[aardvarcus]

Freebeard,
I have measured the underbody and plotted out the points to be aware of. The 4runner has a low center belly with crossmembers dropping substantially below the frame rails, so boxing in the outer area between the tires at the frame height will still be significantly higher than the center. This is quite a bit different than other vehicles I am used to (e.g. suburban) in which the frame rails are the lowest point.

Slowmover,
I hope there is no issue with the engine beyond just sensors…

Tahoe Hybrid,
Interesting, it looks as if the widths match, I would have guessed narrower. I just replaced the front bumper though and I don’t want to mess with the crumple zone, but a novel concept nonetheless.

Aerohead,
Agreed on the suggested methodology being better, however I don’t have extra time for too awful much testing, so I just compare my tanks week to week and try to compare similar tanks/conditions to get estimates. Once I get multiple projects completed I may consider ABA for a suite of things, but I can’t do that for every change I make.
I am just surprised how much lower the “bad” tanks are from the “good” ones, it is more than I had experienced in the past.
I am not getting 10% better MPG with the kamm extension. I assume I need to fix the transition from bodywork to extension.

Everyone,
Current progress on the 4Runner has been replacing both oxygen sensors (actually air to fuel ratio sensors) on the exhaust and the throttle position sensor. Also removed the rear driveshaft and replaced the rear u-joint which was going out and vibrating at higher speeds. Carefully greased the double cardan joint to extend its life, ensuring new grease made it into each cup. Rear u-joint was a pain because the rear yoke was sloped, made it a bear to press the spider out. Eventually had to weld up custom fixtures to hold it, then it was easy.

I have done some figuring on the underbody. My current plan is to lift the vehicle a small amount (about 1”) during some upcoming suspension work, which will put the lowest parts of the underbelly about the height of the rear axle tube. From there I can run a 6 degree diffuser from behind the axle tube to the rear hitch. I picked up some materials (steel tube) for my between the tires filler panel, still doing final design on that.

[freebeard]

Put an aerodynamic bicyclist helmet upside down on the pumpkin.

[Tahoe_Hybrid]

Originally Posted by aardvarcus

I don’t have extreme confidence in these numbers yet, but I have collected a few similar mostly highway tanks with and without the shell, same route, same pump sort of thing. Three of these tanks without the shell averaged 25.4 two tanks with the shell averaged 26.6, implying a 4.7% increase.

The reason I don’t have extreme confidence in the numbers is that I have noticed that both stop and go traffic and use of AC seem to drive fuel economy down, more so than I have experienced in other vehicles. I am not sure what to think of that fact yet. I am going to be doing plugs/wires/sensors on the engine soon. Also I plan to put heat rejecting tint on the windows and add some cab insulation to reduce the AC use.

I still feel the transition from the body to the shell is hurting me, I am planning on adding some thin aluminum strips formed to the contours to cover this gap, which would stop right at the front of the factory hatch. These would be attached to the shell mechanically. I tried to do something with fiberglass in this area when I initially created the shell but had issues…

I am still trying to form a good plan for the underbody coverage, one area of particular drama is between the front and rear tires. I am thinking running a flat bottom from the frame all the way out to the tires outside edge, turning up and forming a box shape, turning back in where the rockers pinch seam is, basically boxing in the area where the side steps usually go. This would give me a good surface to mount my tire spat flaps on.

Don't use shell Fuel it's garbage mobil or chevron do the job better