Throttle body spacer and cold air intake for high altitude usage

[Colorado S14]

What [MENTION=138742]Colorado S14[/MENTION] said is 100% true... at wide open throttle. A less restrictive air box (remove sound baffles, conical filter with more surface area, less dense filter media, etc.) will provide more air at WOT and therefore more power. You'll notice this when passing or racing. This would be useful with his "800whp cars and personal high performance car".

But my understanding is the OP specifically didn't want to run at WOT all the time. He wanted sufficient extra power to mash the pedal halfway and cruise along at 80. IMHO, at lower speeds opening up the air box won't make a noticeable difference in normal cruising power. But I could be wrong.

There are going to be improvements at all throttle positions but they wont be nearly as large. If you put on an intake that adds 10whp at WOT you may only be getting a 1-2hp gain at part throttle light acceleration. This may not be noticeable to the driver under those circumstances. I feel like the OP is looking for a golden goose to make the performance of the car night and day different and that does not exist in a cost effective solution for the 4Runner. You can add an intake, exhaust, etc. and you will make it better but we are talking 5% better than stock, not 50%. If you want gains like that from off the shelf, affordable modifications you need to be buying turbocharged cars. If you drove a VW Touraeg Diesel I could steer you towards 500 ft/lb wtq and 300whp for $500....

 

[1engineer]

There are going to be improvements at all throttle positions but they wont be nearly as large. If you put on an intake that adds 10whp at WOT you may only be getting a 1-2hp gain at part throttle light acceleration. This may not be noticeable to the driver under those circumstances. I feel like the OP is looking for a golden goose to make the performance of the car night and day different and that does not exist in a cost effective solution for the 4Runner. You can add an intake, exhaust, etc. and you will make it better but we are talking 5% better than stock, not 50%. If you want gains like that from off the shelf, affordable modifications you need to be buying turbocharged cars. If you drove a VW Touraeg Diesel I could steer you towards 500 ft/lb wtq and 300whp for $500....

I'm still waiting for all the "wrong" in this thread.
The OP is not going to run WOT.
We don't have 800 hp in the 4Runner nor can you crack the ECU.
We don't have a VW diesel.

I told him the realistic things he could do to improve his performance instead of waxing poetic about non applicable vehicles. Do you disagree? If so, state your case in this real world.

 

[nb rob]

There's nobody arguing with you. And I'm not sure what misinformation you're alluding to.

bottom line is that the money spent on the intake for the 4.0 1GRE-FE v6 engine is probably the difference in fuel for a very long time; therefore not worth the cost. The stock airbox is well designed. The stock air filter is a very good compromise between restriction and particulate collection.

Better fuel economy can be achieved by skipping the basket on the roof, light bars, fridges, 200lbs of stuff in the back, and careful tire selection.

OR - the 4r has exceptional trade in value.

 

[Colorado S14]

I'm still waiting for all the "wrong" in this thread.
The OP is not going to run WOT.
We don't have 800 hp in the 4Runner nor can you crack the ECU.
We don't have a VW diesel.

I told him the realistic things he could do to improve his performance instead of waxing poetic about non applicable vehicles. Do you disagree? If so, state your case in this real world.

I don't disagree with your suggestions and I was not talking about you when I said misinformation, nor did I just mean this thread exclusively. That is my mistake being too casual in my assertion, I'll delete it from my original post so as to not ruffle anymore feathers. I am referring to practically every thread on this board having to do with aftermarket intake systems where you get a bunch of folks yelling at people about how they are "snake oil", total BS, etc. That is what I was referring too, and it was mentioned early on by one poster. I have never seen a dyno on any vehicle, to my knowledge, that has not shown some gains from a well designed intake. There are dyno charts from the 4Runner and the FJ showing good gains from the AFE and TRD intakes.

I only mentioned 800hp cars and my background to attempt to add a bit of credibility to my post. I did not equate the 4Runner with those vehicles; although at the end of the day, to some extent, cars are cars and engines are engines. I only mentioned the Touraeg diesel to tell the OP that if he wanted bigger gains from aftermarket parts he needed a turbocharged engine. I am trying to figure out where I went wrong there....

I went back and reread the original post and he does not have an intake already, so i will reiterate my sentiment from my original post. Get the intake it will help, but only a bit, don't expect a miracle. Forget the TB spacer. The problem is not the ECM; it is the altitude and air density in Colorado, the engine as a whole, and the vehicle it is in. You have 270hp trying to move 5000lbs of vehicle, passengers and gear at close to 2 miles of elevation. You wife's Forester XT is lighter and the turbocharger is able to make up some of the altitude difference via increased speed.

 

[1engineer]

I don't disagree with your suggestions and I was not talking about you when I said misinformation, nor did I just mean this thread exclusively. That is my mistake being too casual in my assertion, I'll delete it from my original post so as to not ruffle anymore feathers. I am referring to practically every thread on this board having to do with aftermarket intake systems where you get a bunch of folks yelling at people about how they are "snake oil", total BS, etc. That is what I was referring too, and it was mentioned early on by one poster. I have never seen a dyno on any vehicle, to my knowledge, that has not shown some gains from a well designed intake. There are dyno charts from the 4Runner and the FJ showing good gains from the AFE and TRD intakes.

I only mentioned 800hp cars and my background to attempt to add a bit of credibility to my post. I did not equate the 4Runner with those vehicles; although at the end of the day, to some extent, cars are cars and engines are engines. I only mentioned the Touraeg diesel to tell the OP that if he wanted bigger gains from aftermarket parts he needed a turbocharged engine. I am trying to figure out where I went wrong there....

I went back and reread the original post and he does not have an intake already, so i will reiterate my sentiment from my original post. Get the intake it will help, but only a bit, don't expect a miracle. Forget the TB spacer. The problem is not the ECM; it is the altitude and air density in Colorado, the engine as a whole, and the vehicle it is in. You have 270hp trying to move 5000lbs of vehicle, passengers and gear at close to 2 miles of elevation. You wife's Forester XT is lighter and the turbocharger is able to make up some of the altitude difference via increased speed.

Posted this http://www.toyota-4runner.org/5th-gen-t4rs/133786-cold-air-horsepower.html a few years ago.

 

[ArmedBear]

Your wifes Subaru weighs a shitload less than your 4Runner. Math.

My girlfriends Edge Sport with twin turbos and 315 HP will smoke my ass all day long going up Floyd Hill but ironically if we hit Tincup Pass and rocks and such the tables turn. ;-)

The 4Runner is a (fairly) large, heavy SUV. Just stay in the middle lane and enjoy the beautiful Colorado scenery.

I've had cars that will do 120 MPH all day long UP Floyd Hill but they weren't worth a shit when I wanted to hit the dirt road less traveled. ;-)

Funny enough, I test drove everything specifically up Floyd Hill (couple of Jeeps, an XTerra, and the 4runner.)

Good to have an apples to apples comparison. I am happy with the 4runner's performance.

 

[LandCruiser]

Tubos and blowers mitigate altitude effects more than anything else.

 

[m85476585]

It would definitely make a HUGE difference if re-gearing! Same change could be made by going with much smaller diameter tires (45 series vs. a 75 series tire).

When re-gearing, shorter gears will give you more torque at the expense of top-end speed.

So, basically, a shorter gear, like going from 3.73 gears to a 4.10 gear set (just as an example and not a specific ratio for a 5th gen) will allow more work from the engine to be applied to the same final turn of the wheels. Instead of 3.73 rotations of the engine to produce 1 turn of the axle, it can now use 4.10 rotations to turn the axle the same, single revolution. More torque, less top end.

So long as you're not trying to drive at 90+ mph all the time, this would help greatly with high altitudes and inclinations while driving over the passes.

Have you re-geared? If you have I won't argue with you since you probably have better experience. I haven't, but theoretically this is what I think will happen. I could be wrong if there are things I haven't considered or bad assumptions.

I don't think it will make much of a difference since you aren't towing and climbing hills in 5th gear. It will make a difference for cruising with less load because you are higher in the power band in 5th gear (higher RPM for the same speed), so you can stay in 5th gear longer. Edit: After working out the math for this post, my conclusions at the bottom are a bit different than this initial guess.

I found transmission gear ratios here: http://www.toyota-4runner.org/5th-gen-t4rs/179850-gear-ratios-5th-gen-5spd.html
Other assumptions:
5600 RPM Redline or transmission shift point
Speed is 65mph at 5600 RPM in 2nd gear
Neglect effects of the torque converter
There may be some rounding, minor rounding errors, and or typos below because I'm lazy.

Gear Ratios
1st 3.52
2nd 2.042
3rd 1.4
4th 1.0
5th 0.716
Reverse 3.224
Differential Ratio 3.727
Transfer Case (High/Low) 1.0/2.566 (4x4 SR5, Trail only)

Let's say with stock gearing 2nd redlines (or the transmission shifts at WOT even if it's not quite at redline) at 65mph. Now we can calculate the WOT shift point for each gear:

1: 37.8 mph
2: 65 mph (this is my assumption. It's not exact, but it's close)
3: 94.8 mph
4: 132.7 mph
5: 185.4 mph

The top speed is likely limited to around 115-120mph, so you can re-gear quite a bit and not run out of top speed. Top speed in 4WD Low is also quite high, probably around 60mph. I calculated 72mph, which sounds a bit too high. Maybe one of my prior assumptions is off a bit, but it doesn't matter to think about the effect of re-gearing.

Now let's calculate the engine speed as you accelerate through the gears at WOT:

1: 0 to 5600 RPM | 0 to 37.8 MPH
2: 3257 to 5600 RPM | 37.8 to 65 MPH
3: 3840 to 5600 RPM | 65 to 94.8 MPH

Let's say you re-gear from 3.73 to 4.10. That's actually only a slight change. The ratio between the two is 1.1, so 10% different. Now we can recalculate the numbers above:

1: 0 to 5600 RPM | 0 to 34 MPH
2: 3257 to 5600 RPM | 34 to 58.5 MPH
3: 3840 to 5600 RPM | 58.5 to 85.3 MPH

As you can see the shift points in RPM are exactly the same because the ratio between gears in the transmission is the same. The speed at which it shifts is different because the final drive ratio changed. Let's think about how this affects real world driving situations:

Gears multiply torque, so you have 10% more torque all the time. That's great for accelerating from a stop.

But the transmission has lots of gears, and if you are not starting from a stop and not at WOT it probably has a few it could choose from. I don't know how it works, but let's assume it shifts based on how fast you want to accelerate (it's telepathic, rumored to be in the 6th gen 4runner).

If you're cruising at 55mph stock you'd be at 1661 RPM in 5th. If floor it to pass someone it goes to 4738 RPM in 2nd and you quickly accelerate to 65.

If you are regeared cruising at 55mph you'd be at 1828 RPM in 5th, so you'd have a bit more power, but if you're trying to pass it would still need to downshift. It won't go to 2nd because it wouldn't be able to spend much time there before hitting redline, so it goes to 3rd and you're at 3573. You won't accelerate as fast now, because the engine speed is a lot lower. But the re-gearing increases torque, right? Yes, but it doesn't increase power.

Let's assume that power follows a linear slope proportional to RPM and torque is constant in the normal driving range. Close enough.

Torque is proportional to how fast you accelerate since it's basically a force, and the wheels convert rotational force (torque) to linear force (acceleration). Linear force is basically how hard you get pushed into your seat when you accelerate (though drag takes up more of it at higher speeds). The transmission and gearing multiply torque.

Let's ignore drag (aerodynamics, rotating friction, and anything that increases with speed).

Since we're assuming the torque of the engine is constant, that means the linear force is constant in each gear, and since mass is constant and we're ignoring drag then acceleration is constant. If we arbitrarily assume first gear pushes you into your seat with a force of 1 G (one times gravity. It's actually a lot less but it doesn't matter what it is) we can calculate the acceleration in each gear.

Note: At this point I don't know what my conclusion will be. I have an idea of what I think will happen, but I don't know if the calculations will support it or not.

(stock, WOT, across the entire RPM range)
1st: 1 G
2nd: 0.58 G
3rd: 0.4 G
4th: 0.28 G
5th: 0.2 G

If you're re-geared, multiply everything by 1.1:
1: 1.1 G (a significant improvement)
2: 0.64 G
3: 0.44 G
4: 0.31 G
5: 0.22 G

If you go with 18.75 gearing instead of 4.10 or 3.72 (because it makes the numbers convenient), multiply everything by 5
1st: 5 G
2nd: 2.9 G
3rd: 2 G
4th: 1.4 G
5th: 1 G
Top speed is 37mph

As you can see you accelerate faster in every gear. From a stop you should accelerate faster with lower gearing. (though acceleration doesn't seem that much faster in 4WD low for some reason?)

Let's say you like transmissions, so you add a transmission in front of your transmission with 18.75 gearing to get back to normal top speed. The second transmission will have different gear ratios that a normal one, and I don't feel like figuring out the difference. I think all 5 gears are "overdrive" gears (that is a stupid term).

Now when the first transmission is in 5th the second one acts like normal. the top speed in each gear is:
1: 37.8 mph
2: 65 mph
3: 94.8 mph
4: 132.7 mph
5: 185.4 mph

and the acceleration at those speeds is limited to:
1st: 1 G
2nd: 0.58 G
3rd: 0.4 G
4th: 0.28 G
5th: 0.2 G

The first transmission can shift, too, so you basically have a 25 speed transmission with much lower gearing available than stock, and you can approximate many re-gear options.

The acceleration can be higher than the last set of numbers above since the first transmission can shift too, but only at a lower speed since the engine is at redline at those speeds but for a given speed there is a limit to how fast you can accelerate because the engine can't turn any faster while putting out the same torque. That is the definition of power.

Power is force times speed. The engine's power is limited, so at a given speed there is a limit to how much acceleration force you can get. At lower throttle positions you can have less acceleration at the same speed.

If you re-gear you can get a more acceleration in each gear at the cost of a lower top speed in each gear. You can accelerate from a stop faster in first gear, but after that the transmission has other gears to choose from.

The problem with analyzing this is what people want is weird. If you're towing a trailer up I-70, here are a few things you might want from the engine:
You want maximum acceleration to merge onto the highway and pass slow vehicles.
You want to be able to accelerate some if you change lanes and need to go a bit faster
You want to be able to accelerate without shifting gears because the transmission has some delay and the engine is noisy at high RPM.

If you re-gear 10% lower, here's how it affects each of those things:
Getting to highway speed form a stop is faster, but only up to 58.5mph. After that it's much slower. That is inconvenient because you probably want to go over 58.5 on the highway.

If you're driving 58.5 to 65 you have much less force to accelerate and pass since 2nd is no longer available.

If you're driving at 65-85.3 you have 10% more force to accelerate and pass someone in 3rd. You also have 10% more force to pass in any higher gear without downshifting, which is apparently desirable.

Cruising with light load at any speed the engine RPM is 10% higher, so it is a bit louder.

TLDR? Start here:
So re-gearing seems beneficial overall, but it could cause problems around 58.5-65mph if you don't have enough power to accelerate past that speed in 3rd. It will decrease fuel economy since the engine speed is usually higher, and it might make the engine a bit louder for the same reason.

If you want better acceleration without having to wait for the transmission to downshift and you don't like hearing the engine near redline, then re-gearing would probably help.

If you want to accelerate faster to highway speed, re-gearing won't help or will only help slightly. I think it would help if you had more gears in the speed range where you are trying to accelerate, but normal re-gear options only get you a fraction of an additional gear between 0 to highway speed. You need more power.

If you find that the gear ratios are too wide and your top speed is limited once the engine reaches redline and transmission is forced to shift to the next higher gear, re-gearing won't necessarily help. It depends on drag, the details of the power curve, and other things I neglected in the math above. You need closer gear ratios (more transmission speeds or lower 2nd, 3rd, 4th, and 5th without changing 1st) or more power. That is the problem my Civic had in the mountains.

So why did Toyota pick the factory gearing they did? Probably a few things:
- 2nd gear is placed above 60mph for the all important 0-60 time
- 5 speeds was a lot when they developed this transmission
- It gives reasonable efficiency and a quiet engine at typical highway speeds
- It seems standard compared to other vehicles I've driven. Maybe it was never designed for 85mph highways?

I hope this helps. It's probably hard to follow and it's a lot of math, but it makes sense to me at least.

 

[Colorado S14]

Tubos and blowers mitigate altitude effects more than anything else.

Turbos are king in Colorado. A supercharger adds more power but the speed of the blower is fixed to the engine speed.

A supercharger that spins 50,000 rpm at sea level is still spinning 50,000 rpm at 10,000 ft of elevation. Let's say that compressor speed delivers 10psi of additional pressure over atmospheric pressure of 14.7 psi. This gives us a total absolute pressure of 24.7psi, but at 10,000 ft. of elevation the atmospheric pressure is only 10.1 psi. So, now we add the supercharger and we have a total pressure of 20.1 psi.

Let's run some math, a naturally aspirated engine went from 14.7 psi. to 10.1 psi., and 10.1/14.7=0.687, so, our naturally aspirated 4Runner engine is only producing 68.7% of the power it would at sea level.

The supercharged engine went from 24.7 psi. to 20.1 psi., 20.1/24.7=0.813, so the supercharged engine is producing 81.3% of its sea level pressure.

But what about turbos? Because a turbocharger is not driven at a fixed RPM but rather by exhaust gasses it has some advantages over the supercharger. With a turbo system when the boost pressure hits the desired psi a wastegate opens and diverts exhaust gasses around the turbine wheel to prevent the turbo from spinning faster and over-boosting. Lets say in our example that the target boost pressure is 10 psi. over sea level atmospheric or 24.7 psi. When the wastegate, or the solenoid controlling it, sees that 24.7 psi. it will open and slow the turbo to maintain that boost pressure. Lets say that is 100,000 rpm of turbo shaft speed at sea level. Well at altitude the wastegate is still looking for that 24.7 psi. of total pressure. Only now the turbo may have to spin to 130,000 rpm to deliver that pressure.

Now, the constraint here is that past a certain point you are asking too much of the turbo when spinning faster and faster and it loses efficiency. When you are at this point you just cannot spin it fast enough to get the boost you want and things start getting hot. You could go to a bigger turbo but then you add in more turbo lag, so there is always a trade off.

Moral of the story is buy the turbo option if you live at altitude, case in point, I have a buddy with a F150 Raptor 6.2L V8 and another buddy with a F150 Ecoboost 3.5L V6. They are both pretty equal around town in Denver, but on the mountain passes the Ecoboost is king.

 

[Jhalko]

Better fuel economy can be achieved by skipping the basket on the roof, light bars, fridges, 200lbs of stuff in the back, and careful tire selection.

There is no fun in this though... Just like reading yet another CAI argument thread.

:deadhorse:

 

[flyinhawaiian01]

Have you re-geared? If you have I won't argue with you since you probably have better experience. I haven't, but theoretically this is what I think will happen. I could be wrong if there are things I haven't considered or bad assumptions.

In the 5th gen? No. In my '87 truck? twice.

Went from 4.10 to 4.56, then to 4.88. With a 4 cylinder engine, every little bit helps.

You're not understanding the theory here. you are NOT gaining horsepower by re-gearing, you are gaining TORQUE. You are not changing gear ratios in the transmission, but you are changing the final ratio at the wheels.

It takes 4.10 turns of the engine to turn the wheel once. If you change that to 4.88 turns, at a specific rpm, the only thing that will change is the speed at which you move, but you WILL gain more torque. Its the same theory as a 4 hi vs. 4 low from take off. You are trading revolutions for higher torque.

At x,000 rpm, let's just say 3,000rpm, in 4th gear, the difference between the two gear ratios will be several miles per hour, but you would gain more power in the form of TORQUE.

 

[MasonCO]

I'd just like to add that compared to our first BOF 4x4 (1988 2.6L Trooper), our new 4Runner does just fine going up hills.

I spend most of my weekend time driving up 285, and on the way back home, I have no problem with Crow Hill, even without downshifting to 3rd and mashing the pedal to the floor. We'll see how it does when I get bigger tires on it...

Oh, if you want to really experience the thrills of elevation change, try running a stock carb'ed suzuki samurai at 12,000 feet. Thank god for Low Range and momentum.

 

[1engineer]

In the 5th gen? No. In my '87 truck? twice.

Went from 4.10 to 4.56, then to 4.88. With a 4 cylinder engine, every little bit helps.

You're not understanding the theory here. you are NOT gaining horsepower by re-gearing, you are gaining TORQUE. You are not changing gear ratios in the transmission, but you are changing the final ratio at the wheels.

It takes 4.10 turns of the engine to turn the wheel once. If you change that to 4.88 turns, at a specific rpm, the only thing that will change is the speed at which you move, but you WILL gain more torque. Its the same theory as a 4 hi vs. 4 low from take off. You are trading revolutions for higher torque.

At x,000 rpm, let's just say 3,000rpm, in 4th gear, the difference between the two gear ratios will be several miles per hour, but you would gain more power in the form of TORQUE.

word.^

 

[m85476585]

In the 5th gen? No. In my '87 truck? twice.

Went from 4.10 to 4.56, then to 4.88. With a 4 cylinder engine, every little bit helps.

You're not understanding the theory here. you are NOT gaining horsepower by re-gearing, you are gaining TORQUE. You are not changing gear ratios in the transmission, but you are changing the final ratio at the wheels.

It takes 4.10 turns of the engine to turn the wheel once. If you change that to 4.88 turns, at a specific rpm, the only thing that will change is the speed at which you move, but you WILL gain more torque. Its the same theory as a 4 hi vs. 4 low from take off. You are trading revolutions for higher torque.

At x,000 rpm, let's just say 3,000rpm, in 4th gear, the difference between the two gear ratios will be several miles per hour, but you would gain more power in the form of TORQUE.

Let me start by saying I think I agree with you. My previous long post was mostly to convince myself of the effects of re-gearing by working out some math.

If your '87 truck was automatic it was probably 4 speed. If it was manual then probably 5 speed, but I'm not sure. The fewer gears you have the more re-gearing is likely to help, I think.

I understand that you're changing the final drive ratio, but the effect is the same as changing all the gears in the transmission by a little. It doesn't make sense to think about final drive ratio without thinking about the transmission too. Downshifting the transmission by 1 gear is similar to re-gearing a lot. If you re-gear then the transmission upshifts to a higher gear then it somewhat cancels out the effect of re-gearing. Re-gearing helps because it is in smaller steps than the shift from one gear to another.

Re-gearing gains torque at some speeds, but horsepower basically sets an upper limit on torque at a given speed no matter what the gear ratios are. That is what I learned while writing my previous very long post.

Since these transmissions only have a small number of gears, re-gearing gains torque at the low end of each gear, but it also forces redline shifts to occur at lower speeds, so you lose torque at the high end where the transmission of a re-geared truck must be in a higher gear than a stock truck (from 58.5-65mph in my previous post).

If you had an ideal CVT then re-gearing would not matter at all, since the transmission could always be in the best gear ratio no matter what the final drive is. It would sit at the peak power output of the engine near redline slowly changing the gear ratio as you accelerate. That's exactly what CVT cars do, and it sucks all the fun out of driving.

In general I agree with you that re-gearing helps at least a little. The truck should have to downshift less, which will make it more pleasant to drive. But I don't think it will make acceleration necessarily much faster since you are not gaining horsepower, so re-gearing is not necessarily the solution to OP's towing problem.

 

[tnine]

Thanks for all the input guys. That's a lot to take in! Being a software guy, I love empirical measurements and test driven results. I appreciate all the thoroughness in everyone's posts.

In regards to re-gearing, I probably won't be doing that any time soon as I still have 4 years and 80k miles on my extended warranty.


For lightening the load, I do a LOT of camping. As a result, I use my GOBI roof rack all the time. I've built some 38" sliding drawers too to hold my gear. Unfortunately, those are made from plywood instead of aluminum since I don't know how to weld. They're heavy and definitely add weight once I have my tool kit, chains, and high lift accessories.


I was thinking of removing the 3rd row seats since I never use them, and they take up about 8" of vertical cargo space. Does anyone know what they weigh? I'm questioning if it's worth the effort to save on weight and get the extra cargo space.


Lastly, I have 285/70/17 K02 tires on my rig at the moment. Since their installation I've had a noticeable decrease in power at altitude at speeds of > 50 mph. They look cool with the Bilstein 3" lift, but they really only provide me with an extra 3/4" lift of the transfer case since the tires are 1 1/2" larger in diameter than 265/70/17.

Frankly, I'm not sure the looks are worth the massive performance hit I've experienced at highway speeds. Given that I deflate my tires to 17 PSI when I off road as well, I'm not sure the wider tread of the 285 is really buying me all that much.


It seems as if my best bet it is to remove my 3rd row seats to decrease weight, and then go back to factory tire sizes when I buy my next set of tires.

Thoughts?

 

[Colorado S14]

What's the 3rd row weigh in these things, I dont think you will notice much pulling 75lbs of static weight out of a 5,000lb truck.

The tires do make a difference though, both in rolling resistance and weight, your 285 KO2s weigh 58lbs a piece, the C load rated 265s weigh 46lbs. So you are moving around 48lbs of extra rotational mass which is the worst mass there is on a car. A Cooper AT3 in 285 is only 49lbs, the 265 Coopers are only 41 lbs. Going from a 285 KO2 to a 265 AT3 saves you a massive 68 lbs of rotational weight.

 

[m85476585]

Increasing the diameter by 1.5 inches is about a 1.048 change in gearing, or about 5%. Between that and extra weight you'll probably notice it a bit.

I would take the 3rd row out first since that's free. In a 4500lb truck 75lbs is about 1.67% of the weight, so not really noticeable but it would help a little if you really never use it. You should also make sure you're using the correct pressure for your tires, which is probably around 38-40psi if they are LT tires not the typical 32psi for P rated tires. There are threads on here about how to determine the correct pressure. Also note that trailer tires should generally be inflated to the pressure on the sidewall regardless of load (very large trailers might be different). They are constructed differently than car or truck tires.

 

[catrains]

you posting is mostly I agree with . I do not agree with your comment of toyota programed air/fuel ratios . this is set to 14.7 to 1 .... which the PCM is programed for a target perfect ratio . it will never always be this exact amount but should be within 5% . now if the PCM cannot achieve this ratio by adjusting the injector on time monitoring the O2 sensor feed back you will get a lean or rich code CEL... normally a 25% fuel trim will CEL...

now race cars and vehicle owners with tuners do change this fuel ratio to compensate for performance engine changes .

my point was as you go higher in elevation at a hywy speed the ram air system will increase air pressure into the air box therefore creating a higher pressure like at a lower altitude...

I'm not suggesting installing cold air intake on a vehicle with a OEM cold air intake.

I fabricated my ram air system with scrape metal around the property just to see if it worked .it worked when towing my boat up the mountains 3K feet ..

 

[1engineer]

Thanks for all the input guys. That's a lot to take in! Being a software guy, I love empirical measurements and test driven results. I appreciate all the thoroughness in everyone's posts.

In regards to re-gearing, I probably won't be doing that any time soon as I still have 4 years and 80k miles on my extended warranty.


For lightening the load, I do a LOT of camping. As a result, I use my GOBI roof rack all the time. I've built some 38" sliding drawers too to hold my gear. Unfortunately, those are made from plywood instead of aluminum since I don't know how to weld. They're heavy and definitely add weight once I have my tool kit, chains, and high lift accessories.


I was thinking of removing the 3rd row seats since I never use them, and they take up about 8" of vertical cargo space. Does anyone know what they weigh? I'm questioning if it's worth the effort to save on weight and get the extra cargo space.


Lastly, I have 285/70/17 K02 tires on my rig at the moment. Since their installation I've had a noticeable decrease in power at altitude at speeds of > 50 mph. They look cool with the Bilstein 3" lift, but they really only provide me with an extra 3/4" lift of the transfer case since the tires are 1 1/2" larger in diameter than 265/70/17.

Frankly, I'm not sure the looks are worth the massive performance hit I've experienced at highway speeds. Given that I deflate my tires to 17 PSI when I off road as well, I'm not sure the wider tread of the 285 is really buying me all that much.


It seems as if my best bet it is to remove my 3rd row seats to decrease weight, and then go back to factory tire sizes when I buy my next set of tires.

Thoughts?

You have done everything exactly wrong if you are complaining about power.
Pull the seat
Take out the drawers
Remove all the crap you are carting around every day in those drawers thinking you might need it. You won't. Pack a bag and leave in the garage for when you go off road.
Get rid of those tires and get some stock size C rated. You'll be fine.

You can't have it all.

What's the 3rd row weigh in these things, I dont think you will notice much pulling 75lbs of static weight out of a 5,000lb truck.

The tires do make a difference though, both in rolling resistance and weight, your 285 KO2s weigh 58lbs a piece, the C load rated 265s weigh 46lbs. So you are moving around 48lbs of extra rotational mass which is the worst mass there is on a car. A Cooper AT3 in 285 is only 49lbs, the 265 Coopers are only 41 lbs. Going from a 285 KO2 to a 265 AT3 saves you a massive 68 lbs of rotational weight.

Yes 75 lbs does make a difference and I think it is about 125 lbs for the seats.

 

[HOJeepster]

Or another way to look at this OPs question is this - when does traffic ever move faster than 50 mph anyway going up to the mountains on I70 to necessitate more power anyway?

Buehler?