1999 4Runner 4x4 Streamlining

[aardvarcus]

So panel gaps are far from the biggest aerodynamic problem with this 4Runner right now, but because I had to remove the front grill to access a leaky o-ring on the AC accumulator drier I decided to seize the opportunity and fill the panel gaps on the front end. I used a trim-lok edge trim with side weatherstrip profile between the bumper and the grill / filler panels and trim lock self-adhesive with the 3M adhesive around the headlight and the hood gaps. Used some thin pieces of door edge guard around the marker light to seal that up as well. Turned out pretty good I think.

[19bonestock88]

Looking good! I prob need to do the same on my car, does it help much?

[aardvarcus]

Haven't had a great chance to test the panel gaps, shortly after I filled them I tore all the suspension off the 4Runner to update it. Just completed that work and dropped it off for an alignment. 4Runner got new front wheel bearings, Bilstein 5100 struts, all bushings replaced, lower control arm, alignment keys, upper and lower ball joints, rebooted CV axles, upgraded sway bar, Etc. In the back it got new control arm bushings for the four link, Springs, , upgraded sway bar, Etc.

I think one of the culprits for strange MPG was one of the cylinders on the passenger side caliper locked up. I got it unstuck enough to get it in for the alignment, I've got new rotors calipers Etc on order to refresh the front brakes.

All of that work made the aerodynamics work take a backseat temporarily.

Broke out the 40 ton homemade press brake last night, started messing around with some aluminum for the underbody skid plates / belly pan.

I also started welding together some homemade Rock sliders for the side rails, they will go out to exactly the tire width and will hold the tire spats behind the front tire and in front of the rear tires.

[aardvarcus]

The alignment is completed, tying a bow on the suspension work. Got a few things built, mainly the main belly pan/skid for the underside of the engine up to the front crossmember. Made with ¼” aluminum, smooth side down. It needs some more bracing for true skid plate duties but is fine enough for now. This is the first of many pieces that need built to have a smooth belly on this vehicle.

This piece of belly pan doubles as a radiator duct on the bottom thanks to some strategically placed weather-stripping, just need some buy some black coroplast to finish ducting the upper grill to the radiator.

I built a hidden receiver hitch for the front, tucked back behind the stock crumple zone. It was not easy to build this piece around all the obstructions. It uses a removable extension to allow a receiver hitch on the front end sticking out of the center of the lower grill opening, for using a receiver mounted winch or other accessories while retaining a stock front bumper and stock crumple zone. I plan to build a cover to block the lower grill off (upper grille should be sufficient with ducting), but have it openable/removable for winch use.

[aardvarcus]

So I completely replaced the front brakes on the 4Runner, did the Tundra brake upgrade, so bigger calipers and pads, thicker rotors, same mounting dimensions. The best part is the Tundra calipers use the springs that push the pads away from the rotor, so the brakes should drag less. Should be much better than the partially locked up 20 year old dragging calipers that were on it.

Turned my attention to the interior, gutted the rear cargo area and removed the headboard. Added peel and stick insulation to all of the roof I had access to (sunroof is cramping access). Stuffed melamine foam (think magic eraser) into the open cavities that had a sufficiently sized access panel. Draped some thinsulate over the headboard and reinstalled. This is the beginning steps for an effort to insulate the cab to reduce AC usage.

Today after work I hope to get the cargo area sound deadened, insulated, and reinstalled. The car is noticeably louder with the thin plastic factory cargo side panels removed, so deadening that area should cut cab noise. [Edit: this wasn't entirely the case] Noted that the rubber mat and insulation in the cargo hold was melted/burned right above where the exhaust goes over the axle. Surprisingly there isn’t an exhaust heat shield there from the factory that I can tell, I will rectify that shortly.

[aardvarcus]

Turns out that I was wrong about the melted/burned rubber and foam being caused by the exhaust going over the axle, it appears the vehicle was operated without a tailpipe for some distance, and the muffler was dumping directly into the front floor pan. I got suspicious when I noted the closest passing of the muffler to floor had no heat damage above it and was over a foot from the burned spot. I already knew the tailpipe behind the muffler had been replaced, and when I looked at the heat damage it was exactly where the exhaust gasses would have hit the body if the tailpipe section was removed from the muffler section.

I only had enough time last night to get the peel and stick sound deadening installed in the cargo area, having to contour it to the corrugated floor and roll the surface down took far more time than expected. It still needs insulated, then the cargo area interior can go back in.

[aardvarcus]

I got the cargo area insulation and sound deadening project done and the interior back together. Made a decent difference in cab noise, which is nice.

I found an ideal aerodynamic positioning for a front mounted winch, it it called the cargo area. Using my hidden front hitch and an extension I can mount a cradle mounted winch on the front when needed, and take it back off to stow inside when not needed. It also works in the back receiver thanks to an extension cord.

MPG is definitely up after doing the work on the brakes. I have been driving without the kamm shell because I removed it to fix the leading edges that did not turn out well. I need to either find time for that or slap it back on for now.

[Tahoe_Hybrid]

Originally Posted by aardvarcus

I got the cargo area insulation and sound deadening project done and the interior back together. Made a decent difference in cab noise, which is nice.

I found an ideal aerodynamic positioning for a front mounted winch, it it called the cargo area. Using my hidden front hitch and an extension I can mount a cradle mounted winch on the front when needed, and take it back off to stow inside when not needed. It also works in the back receiver thanks to an extension cord.

MPG is definitely up after doing the work on the brakes. I have been driving without the kamm shell because I removed it to fix the leading edges that did not turn out well. I need to either find time for that or slap it back on for now.

I suggest also a wing for the rear end on the top my hybrid compared to the normal version has a slighty bigger wing on the rear of the SUV


also check the angle of it slightly more like 80 degrees instead of 90 degrees



I suggest an Air dam as well

Location is a must see the hybrid model vs non hybrid model..


the coefficient drag is 0.34 compared to 0.38(0.379)


the ride height is lower then the normal one I have not experienced any clearance issues I do pay attention to make sure i don't hit garbage on the road

[aardvarcus]

I have a relatively huge "wing" I built for the rear end this spring, that is the one I referenced as a kamm shell that I need to do more work to because the leading edge transitions are not smooth enough.

I did an air dam on my last two projects, but I am trying on this one to do a belly pan system and smooth the airflow through the underside versus directing the air around the sides. This approach is used on some production cars (e.g. tesla) however it puts me in a non ideal interim situation seeing as how I don't have the belly pans done yet.

This vehicle is built around compromise between on-road use and off-road use, so I am not looking to reduce ground clearance for off-road reasons. My front end is technically stock height, but mine has the "99 tall" springs (from factory) so it is the tallest "stock" 3rd gen 4runner. (Other year third gens often order the 99 tall springs as a "lift".)

[aardvarcus]

It has been a bit, but I did have a chance to work on the 4Runner this past week. I was able to build some additional belly pan/skid plates for the underside of the 4Runner out of 1/4" aluminum. I also built some "rock slider" steps out of steel 2" tube steel welded to the frame. The plan for these is to cover them top and bottom for a smooth surface, and then to mount my fore/aft wheel spats on the bottoms of them near the tires.

I also got a chance to use the 4Runner offroad this past weekend, swapping over to the 255/85R16 tires mounted on extra wheels. The trip went well, and I will swap back over to the street wheels and tires shortly but first I will put a weeks worth of driving on these offroad tires so that when I swap back I can compare the MPG between the two tire sets.

Anyway some pictures.