Better gas mileage with deckplate back on!

[BamaDrewski]

I may have stumbled across something. I have the "deck-plate mod" on my rig. I decided to screw the deck plate back on while I cleaned out my truck (to keep from losing it). I forgot to take it off and discovered I was getting really good gas mileage. By really good, I mean 2-3 MPG per gallon better mileage…... Anyone else experience this? (For now, I am leaving that deck plate on!!!)

I have recently done some major PM on my truck but I have run a few tanks of gas after that work was done. It was only after I put the deck-plate back on the air box that I saw a distinct improvement in mileage. Like some folks say, the Toyota engineers are pretty good and perhaps they designed our rigs to perform best without this particular modification.

 

[JayRolla]

I may have stumbled across something. I have the "deck-plate mod" on my rig. I decided to screw the deck plate back on while I cleaned out my truck (to keep from losing it). I forgot to take it off and discovered I was getting really good gas mileage. By really good, I mean 2-3 MPG per gallon better mileage…... Anyone else experience this? (For now, I am leaving that deck plate on!!!)

I have recently done some major PM on my truck but I have run a few tanks of gas after that work was done. It was only after I put the deck-plate back on the air box that I saw a distinct improvement in mileage. Like some folks say, the Toyota engineers are pretty good and perhaps they designed our rigs to perform best without this particular modification.

Nope, not sure how restricting air flow would help a truck get better mileage. I was able to get better mileage with my hot air intake.

Either way you would need to run a good 5 tanks of gas, on the same exact roads in the same exact environment and use your foot the exact same way. Not to mention need to fill up at the same gas station and pump to get good results.

 

[gamefreakgc]

I agree, it was most likely a fluke. Either that or your MAF is messed up and not reading the air flow correctly.

 

[Tyler James Inc]

I wouldn't be a bit surprised. From the actual flow tests and dyno results I've seen, the factory air box is best for stock engines. There's a lot of engineering that goes into it, and it may not be as simple as it seems.
Similar to more "free flowing" exhausts- often the dyno results show more loss than gain. The end HP might be higher, but if that power is at a higher RPM, you may have lost some power in the range you typically drive in and want that power in. So is it really a gain?
Many youngsters and old-schoolers alike will disagree with me, and that's okay [emoji6]
What MPG are you seeing?

 

[Nate_GB]

Sounds reasonable. More air means the computer is adding more fuel which could drop mpg but possibly increase power. I've read studies that show that a dirty air filter results in better gas mileage. 2-3 mpg sounds like a lot so it could be a combination or things going on though.

 

[BamaDrewski]

I wouldn't be a bit surprised. From the actual flow tests and dyno results I've seen, the factory air box is best for stock engines. There's a lot of engineering that goes into it, and it may not be as simple as it seems.
Similar to more "free flowing" exhausts- often the dyno results show more loss than gain. The end HP might be higher, but if that power is at a higher RPM, you may have lost some power in the range you typically drive in and want that power in. So is it really a gain?
Many youngsters and old-schoolers alike will disagree with me, and that's okay [emoji6]
What MPG are you seeing?

I track every fill-up with the date, the type of gas (Ethanol or non-ethanol) where I purchased the gas and the price. I have been running non-ethanol for the past 6-8 months.

My average "city driving" mileage was 15.72 MPG. That has moved to 17.43

I do not have a recent highway trip to give you that mileage but the last trip to Atlanta, about three hours, I was getting 21.56MPG.

I think there is something to using the factory air box without the deckplate mod. I understand the principle of allowing more air in, but the way I understand our air boxes, the air comes in from under the passenger wheel-well cover. I would assume this is cooler air than air pulling in from the engine compartment. I also wonder about "air pressure" and if that has anything to do with gas mileage. By "air pressure" I am thinking that perhaps the air from the original Toyota design is more focused and streamlined than from an open hole on the front of the airbox. Does that sound logical?

It may just be a fluke.....I will keep checking it and see what happens......could just be I got lucky.....either way, I will take better mileage any day of the week.....

 

[Tyler James Inc]

Nice! That's great for being city driving. Shoot, I would be happy with that for my mixed driving.
I do think that the pressure and velocity are huge factors when designing the air box.
Looking forward to seeing if you're results are consistent!

 

[BamaDrewski]

I track every fill-up with the date, the type of gas (Ethanol or non-ethanol) where I purchased the gas and the price. I have been running non-ethanol for the past 6-8 months.

My average "city driving" mileage was 15.72 MPG. That has moved to 17.43

I do not have a recent highway trip to give you that mileage but the last trip to Atlanta, about three hours, I was getting 21.56MPG.

I think there is something to using the factory air box without the deckplate mod. I understand the principle of allowing more air in, but the way I understand our air boxes, the air comes in from under the passenger wheel-well cover. I would assume this is cooler air than air pulling in from the engine compartment. I also wonder about "air pressure" and if that has anything to do with gas mileage. By "air pressure" I am thinking that perhaps the air from the original Toyota design is more focused and streamlined than from an open hole on the front of the airbox. Does that sound logical?

It may just be a fluke.....I will keep checking it and see what happens......could just be I got lucky.....either way, I will take better mileage any day of the week.....

UPDATE: Checked the mileage today. It's at 17.46mpg for city driving and deckplate is still on.

 

[nissanh]

I want your air box.

I got all stock (except wheelspacers) with 209K miles . I get 17 MPG on highway and 13ish MPG in the city :-(

 

[Ruiner]

I want your air box.

I got all stock (except wheelspacers) with 209K miles . I get 17 MPG on highway and 13ish MPG in the city :-(

thats about what i get with fj wheels and bfg tires. I get worse on the highway though because the toll roads here are 80mph and the low gearing on these makes that speed rev pretty high.

 

[BamaDrewski]

UPDATE: Checked the mileage today. It's at 17.46mpg for city driving and deckplate is still on.

UPDATE: Another fill up and getting 17.40mpg

I also noticed something else with the deckplate back on. I run the torque app and intake air temp is now around 9-11 degrees above the outside temperature.
When I had the deckplate off, it was running 18-25 degrees over outside temperature. Not sure if this makes a difference or if I am just getting extremely lucky with the gas I am buying (Same station everytime)

 

[ThorInc]

I may have stumbled across something. I have the "deck-plate mod" on my rig. I decided to screw the deck plate back on while I cleaned out my truck (to keep from losing it). I forgot to take it off and discovered I was getting really good gas mileage. By really good, I mean 2-3 MPG per gallon better mileage…... Anyone else experience this? (For now, I am leaving that deck plate on!!!)

I have recently done some major PM on my truck but I have run a few tanks of gas after that work was done. It was only after I put the deck-plate back on the air box that I saw a distinct improvement in mileage. Like some folks say, the Toyota engineers are pretty good and perhaps they designed our rigs to perform best without this particular modification.

I noticed the same thing, stock engine.

I wouldn't be a bit surprised. From the actual flow tests and dyno results I've seen, the factory air box is best for stock engines. There's a lot of engineering that goes into it, and it may not be as simple as it seems.
Similar to more "free flowing" exhausts- often the dyno results show more loss than gain. The end HP might be higher, but if that power is at a higher RPM, you may have lost some power in the range you typically drive in and want that power in. So is it really a gain?
Many youngsters and old-schoolers alike will disagree with me, and that's okay [emoji6]
What MPG are you seeing?

Totally agree.

 

[Ron Burgandy]

not everything you read on here is a positive mod. I also don't think external tranny coolers are beneficial, unless running in conjunction with the factory one.

 

[tvpierce]

I wouldn't be a bit surprised. From the actual flow tests and dyno results I've seen, the factory air box is best for stock engines. There's a lot of engineering that goes into it, and it may not be as simple as it seems.
Similar to more "free flowing" exhausts- often the dyno results show more loss than gain. The end HP might be higher, but if that power is at a higher RPM, you may have lost some power in the range you typically drive in and want that power in. So is it really a gain?
Many youngsters and old-schoolers alike will disagree with me, and that's okay [emoji6]
What MPG are you seeing?

Well said.

Manufacturers often tune the same engine differently for different applications.

In the old days, AMC/Jeep would put the same 258 inline 6 in their cars and trucks. The cars would be fitted with a 2 barrel carb, the truck with a single barrel. (there would be other changes too: cam, valve timing, etc.) But the reduced intake flow of the single barrel carb delivered more low-end torque, albeit at the expense of top-end HP.

Today, motorcycle manufacturers do it too. It's common to put the same 1200cc inline 4 in a sport bike and a touring bike. Again, through the use of various tuning techniques -- including smaller throttle bodies on the touring version -- the output of the engine is changed.
The sport version might have a 14,000 rpm redline and makes 160hp. While the touring version redlines at 12,000 rpm and makes 140hp, but more torque, and that torque comes on at a lower rpm.

Long way of saying that less restrictive is not necessarily more efficient.

 

[phattyduck]

UPDATE: Another fill up and getting 17.40mpg

I also noticed something else with the deckplate back on. I run the torque app and intake air temp is now around 9-11 degrees above the outside temperature.
When I had the deckplate off, it was running 18-25 degrees over outside temperature. Not sure if this makes a difference or if I am just getting extremely lucky with the gas I am buying (Same station everytime)

IATs will definitely be lower with the stock air intake location - it is outside of the engine bay. I have a feeling you could re-lower the intake temps with some clever ducting to the headlight opening, but that negates the 'simple' nature of the deckplate mod.

I didn't do it for power, I did it for the sound. Its a mood thing for me, though it is always closed for long trips!

-Charlie

 

[BamaDrewski]

IATs will definitely be lower with the stock air intake location - it is outside of the engine bay. I have a feeling you could re-lower the intake temps with some clever ducting to the headlight opening, but that negates the 'simple' nature of the deckplate mod.

I didn't do it for power, I did it for the sound. Its a mood thing for me, though it is always closed for long trips!

-Charlie

UPDATE: Another fill-up and it was 18.28MPG! (I couldn't believe it and no change in driving....all city driving....same gas station)

I'M LOVING THIS!

 

[2016 4Runner SR5]

not everything you read on here is a positive mod. I also don't think external tranny coolers are beneficial, unless running in conjunction with the factory one.

Factory tranny "coolers" that are built into the radiator are actually heaters. They heat the transmission fluid using the hot antifreeze. Thanks but no thanks. There have also been many cases of radiator failure which lead to antifreeze being introduced into the transmission which of course lead to complete transmission failure. Bypass the factory "cooler" and run an external cooler only. If you want to get fancy, use an external cooler with it's own electric fan.

 

[Hepar]

I bet with a supercharger, it's the other way around. I know Gadget has done dyno tests as far as the hp goes.

Air Induction

 

[phattyduck]

Factory tranny "coolers" that are built into the radiator are actually heaters. They heat the transmission fluid using the hot antifreeze. Thanks but no thanks. There have also been many cases of radiator failure which lead to antifreeze being introduced into the transmission which of course lead to complete transmission failure. Bypass the factory "cooler" and run an external cooler only. If you want to get fancy, use an external cooler with it's own electric fan.

The factory trans cooler is at the BOTTOM of the radiator - where the coolant is cool. It keeps the fluid around 100*F above ambient (generally cooler than the engine coolant temp) except under extreme conditions. It doesn't heat up the transmission fluid faster when the engine is cold - there isn't even any coolant flowing through the radiator when the engine is cold.

The engine oil cooler/heater on the other hand regulates the oil temp to heat up faster on cold starts (good!) and cools it down once the engine is warm (good!). It does that by using coolant that is not directly from the cold side of the radiator.

-Charlie

 

[2016 4Runner SR5]

The factory trans cooler is at the BOTTOM of the radiator - where the coolant is cool. It keeps the fluid around 100*F above ambient (generally cooler than the engine coolant temp) except under extreme conditions. It doesn't heat up the transmission fluid faster when the engine is cold - there isn't even any coolant flowing through the radiator when the engine is cold.

The engine oil cooler/heater on the other hand regulates the oil temp to heat up faster on cold starts (good!) and cools it down once the engine is warm (good!). It does that by using coolant that is not directly from the cold side of the radiator.

-Charlie

Tranny cooler tank is mounted on the SIDE of the radiator. Inlet is at the bottom, outlet at the top. The tank is part of the radiator, the antifreeze and transmission fluid are against the same inner wall of the radiator. If your antifreeze is at 200* your transmission fluid will be at the same temp. Do what you want with your own vehicle however an external cooler bypassing the OEM cooler is absolutely the most ideal situation.