97 4runner to 99+ 4runner airbox/MAF conversion

[toytech76]

I just converted my 97 runners airbox/MAF to the newer 99-02 style. In case anyone deosnt know, the 96-98 MAF steups are more restrictive and very expesive to replace. (about $600 from the dealer)

http://i4.photobucket.com/albums/y147/phelix1976/IMG_2485.jpg


You alos need to repin the MAF connector to work with the newer MAF. I was able to with the help of MTL4runner. The stock wire colors while looking at the back of the connector left to right are, Black/white stripe, brown/black stripe, yellow/green stripe, red/white stripe, white/blue stripe.

http://i4.photobucket.com/albums/y147/phelix1976/IMG_2478.jpg

The modified pin setup is now, brown/black, yellow/red, red/white, black/white, white/blue.

http://i4.photobucket.com/albums/y147/phelix1976/IMG_2484.jpg

While I had the airbox out, I also remove the airtube insde the fenderwell and removed the 90 deg off the plate the airbox hooks into.

http://i4.photobucket.com/albums/y147/phelix1976/IMG_2480.jpg

http://i4.photobucket.com/albums/y147/phelix1976/IMG_2481.jpg

http://i4.photobucket.com/albums/y147/phelix1976/IMG_2482.jpg

http://i4.photobucket.com/albums/y147/phelix1976/IMG_2483.jpg


Removing the 90 and the airtube is reported to give you better airflow, better throttle response and slightly better MPG's. It also is reported to give you more rear wheel HP than a K&N cold air setup for supercharged motors. Go to gadgetonline.com for more in depth details about that. Its actually one of the steps involved when installing the TRD 7th injector. I also upgraded my headlights to the 99-02 styla and will be installing my HID coversion in a couple weeks when my kit arrives. I will be doing a writeup on that when its done. Hope this helps anyone attempting this conversion!

[MTL_4runner]

Sweet, nice pics too. :thumbup:
I'm sure this will be popular when people see how easy it is.

Link from the MAF pinout thread:
http://www.ultimateyota.com/index.php?option=com_smf&Itemid=26&topic=3901.0;topicseen

[YotaFun]

I will try this when I have the cash to get the 99+ setup.
Now question, do you have to get a 99+ airbox or is the 96-98 easily modified?

[toytech76]

you need the 99+ airbox plus the newer sensor. I got a used airbox for $50 from a tacoma at a wrecking yard. The runner boxes and tacoma boxes are the same. You will also need a new MAF sensor if it doesnt come with it. They are about $130 new from the dealer. Total you shouldnt spend more than about $200. Not bad considering the price of a new MAF for the 96-98 setup

[MTL_4runner]

You should get the MAF and the airbox at the junkyard together and expect to spend around $40-100 for both depending on where you live. If you need a new 99-02 MAF I have seen them go on ebay for around $30 too.

[arjan]

I can't believe it's that simple.
Interesting how Toyota stuck to the same sensors, but messed with the wiring order.

[toytech76]

They are 2 different sensors. Thays why you want to upgrade to the newer one

[arjan]

Yes but the sensor characteristics of the actual electronic sensor must be the same, else it wouldn't work.

[MTL_4runner]

Yes but the sensor characteristics of the actual electronic sensor must be the same, else it wouldn't work.


The principle is the same on almost any vehicle that uses a hot wire MAF sensor instead of a MAP sensor or an AFM. You could probably figure out how to wire any vehicle's MAF sensor (whether it be a Chevy or a Range Rover or a Toyota, etc) in there provided the voltage outputs were more or less the same as the donor vehicle.

[arjan]

But doesn't the hotwire system really measure airspeed (airflow over the sensor)?
That would mean if the maf housing is less restrictive (ie larger diameter) the airspeed would be lower
The efi computer would register less air, and that would royally bugger up your air/fuel ratio I would think.

Unless the computer 'learns' the characteristics from the results at the oxygen sensor, then it wouldn't matter. I don't know into that much detail how the fuel curves are setup.

[MTL_4runner]

But doesn't the hotwire system really measure airspeed (airflow over the sensor)?
That would mean if the maf housing is less restrictive (ie larger diameter) the airspeed would be lower
The efi computer would register less air, and that would royally bugger up your air/fuel ratio I would think.

Unless the computer 'learns' the characteristics from the results at the oxygen sensor, then it wouldn't matter. I don't know into that much detail how the fuel curves are setup.


Exactly, it does "learn" from the O2 or A/F sensor so it doesn't matter. The MAF simply registers a voltage for a given air speed through a fixed opening (ie the MAF cross-sectional area). The voltage may be different at the same speed even if you change MAFs with an identical part therefore this "learning" part is critical to the ECU functioning properly. So using a larger MAF won't ruin your fuel ratio, it will only remove the airflow bottleneck and the ECU will eventually learn what voltage corresponds to what volume of air.

[toytech76]

Very true to all of that. I believe it measures more volume than speed of the air. They all have the same components, hotwire, air temp sensor, 5v reference. Amazing how it all learns and adapts

[MTL_4runner]

I believe it measures more volume than speed of the air.

You are indirectly right. In reality, the wire measures the airspeed and the flow or volume of air per amount of time (usually given units of cubic feet of air per second or ft^3/s) is calculated by multiplying the airspeed measured by the sensor (the voltage converts back to an airspeed which is then adjusted to take into account the effects of temperature) times the cross-sectional area of the MAF itself. Now not every stock MAF will flow exactly the same and it will definately change if you swap in a larger MAF so really the engine doesn't care much about absolute values, it is just interested in relative values from the MAF sensor......thus why the "learning" is so important for it to work properly.

Here's a good page on how MAFs work:
http://www.sensorland.com/HowPage060.html

[toytech76]

thats a good page!

[arjan]

You're right Jamie, it looks like any maf which is designed for a similar sized engine would likely work. As long as the voltages are within an acceptable range so they don't throw any codes.

You probably need a minimum amount of airspeed so a MAF for a 5L wouldn't create enough airspeed at idle for a 1.6L engine.
I bit extreme, I know, but it is as an example.

[MTL_4runner]

You probably need a minimum amount of airspeed so a MAF for a 5L wouldn't create enough airspeed at idle for a 1.6L engine.
I bit extreme, I know, but it is as an example.


I think you're right but without experimenting it's hard to say what would be the range of MAF sizes and voltages that would fall into the acceptable range or what would throw a code. I know the FSM is pretty specific on MAF codes and max/min voltages so that would likely be a critical part in the selection. If you started on forced induction I'd bet you could start looking at MAFs made for larger displacement engines.

[simpletallman]

Well, I just tried this conversion. Didn't work. Truck would barely run. Positive I had it wired as listed. My only thought is maybe the MAF sensor I got is bad. Gonna see if I can try it out on someone else's 3.4, but past that, I am stumped.

[blarchitect]

Where did the original “97 4runner to 99+ 4runner airbox/MAF conversion” thread go?? Appears to have been deleted.
I want to do this mod.

[Seanz0rz]

Looks like the pictures have died over the years.