My understanding is that this is only for non-turbo 850s. Tech can correct me if I'm wrong.
When I first learned of this small modification... lets just say I figured you get what you pay for - right?
I finally decided to try a few things, even though I didn't believe it was going to work.
The first thing I did was to disconnect the pipe that provides heat to the airbox, and cover the hole where the heat came in. Sometimes it ran better, and sometimes it felt the same. Then a few weeks later I took the airbox off the car, and looked at what was going on. I saw how the thing worked, and I realized why it ran better sometimes, but not others. This is when I decided to make a more permanent change.
When you remove the airbox, the part that has the inlet for the heat comes off, and can easily be taken apart. Then taking out the parts that can be removed, leaves some molded plastic pieces that I removed with a hacksaw blade. Once that was done, I used a pad on a cordless drill, for removing paint and rust, to smooth out the places where I had cut the plastic. I covered the small holes with a piece of scotch tape from the inside, then epoxied the outside, and when the epoxy dried, I removed the tape leaving a nice smooth job. I covered the hole, where the heat entered the airbox after I reinstalled the airbox. I would be tempted to get some pipe to fit the hole, and extend it to the front of the car, where it could draw in more cold air if I weren't going to modify the whole thing later.
Yes, there is a difference / gain in power - no question. And the difference is in the low to midrange RPM - where the engine is used the most. I'm not claiming 100hp gain or anything like that, and I can't tell that the gains are in the 4000 to 6000 rpm range. I don't have any idea how much Hp or torque increased by making this change, but I can say that it is certainly noticeable.
An improvement in power, and it is doesn't cost anything - what could be better than that?
One more thing, if there was a change in fuel mileage, it wasn't enough that I can tell a difference.
Here is a picture of the pieces after being modified.

 

Two questions...Any pictures of your engine bay? That might answer my second question;

And the "pipe that provides heat to the airbox", can u explain? I dont understand why there is/was a pipe bringing in hot air to the airbox? Is/was this bringing in engine bay air?


And thanks for the post

 

S60R the hot air is brought into the Air box to help the engine warm up faster.

 

Thanks Tech, I guess theres a flap/valve of some sort that closes when its warm? Just curious...

 

Yes there is a vaccum controlled valve that opens a Valve to allow the hot air in.

 

That is correct. There is a spring loaded flap that opens to allow warm air into the airbox. At the back of the engine, there is a heatshield with a flexible metal hose going from the heat shield on the exhaust pipe, to the bottom back side of the airbox. Simply removing the flexible hose doesn't help, because the flap closes, and the engine tries to draw in air from a hole that should be closed off now. I'm guessing that the engine has to pull enough vacuum to force the flap open, if you don't remove it.
I don't have a picture handy, but can take one if this isn't clear.
Cranky

 

That was pretty clear...thanks

 

Bumping up this old thread, a worthwhile mod. This was on a '99 N/A V70.

What I did was open up the airbox, slide out the sub-assembly containing the valve body and flap, basically force the valve into the 'cold air' position, epoxy welded the flap so that it permanently blocks off the warm air, then closed it all back up and put it back in the car.

I think my valve was broken and permanently stuck in the 'warm air' position.

This made a very noticeable difference in my top end power ( > 3k rpm) and I also have gained maybe 5 mpg. Well worth the 20 minutes I spent on it. It really does pull much harder. If your car has a heater flap in the airbox,

I've also apologized to the engine for feeding it warm air all this time!

 

Hi guys, well i don't know if this will work/help, but i just disconnected the flex tubing from the heatshield and pushed if further down in the engine bay to fetch more colder air..

Secondly, i'm having a problem with the intake tube that is at the front of the car just above the rad. that goes into the airbox, where it goes into the air box, it tends to fall off of the airbox, i was thinking of putting some plumbing ABS and sticking the intake to the airbox..will this work? thanks
fabs