Dual Intake

[tjts1]

In extreme cold weather it helps warm up the engine faster. Most of these cars also use a hot wire air mass meter between the airbox and the throttle body. The sensor works by measuring the amount of electricity required to maintain a preset temperature on a heated wire in the air stream. It also uses a built in thermometer to reference the air temp. The air flap mechanism in the volvo airbox works to maintain a minimum 70f intake temp in order to make the AMM readings more accurate. The problem with the volvo device is that its controlled by a wax filled thermostat device that pushes against a spring. When the thermostat fails (usually after 5-10 years), the air flap goes into hot air only setting. In this situation the intake temp shoots up to 180-200f, slowly destroys the AMM and increases NOx emissions by a factor of 10 and drops fuel economy below 20mpg. Most volvo mechanics know to replace this $5 item but more often than not, these cars end up in the junkyard due to failed emissions test.

[RH77]

Originally Posted by tjts1

In extreme cold weather it helps warm up the engine faster. Most of these cars also use a hot wire air mass meter between the airbox and the throttle body. The sensor works by measuring the amount of electricity required to maintain a preset temperature on a heated wire in the air stream. It also uses a built in thermometer to reference the air temp. The air flap mechanism in the volvo airbox works to maintain a minimum 70f intake temp in order to make the AMM readings more accurate. The problem with the volvo device is that its controlled by a wax filled thermostat device that pushes against a spring. When the thermostat fails (usually after 5-10 years), the air flap goes into hot air only setting. In this situation the intake temp shoots up to 180-200f, slowly destroys the AMM and increases NOx emissions by a factor of 10 and drops fuel economy below 20mpg. Most volvo mechanics know to replace this $5 item but more often than not, these cars end up in the junkyard due to failed emissions test.

Great info.

That's a shame for a decent car: $5 or the junk heap. I'm sure the hot air created a fair share of detonation as well

The 'Teg has a wax plunger for the Fast Idle Thermo Valve. It's over 10 years old now -- good to know they tend to wear out, and what to look for.

One addition question -- do you know why the FE would drop so much? Does it "freak-out" into open-loop or cool the charge by running rich?

RH77

[tjts1]

Originally Posted by RH77

One addition question -- do you know why the FE would drop so much? Does it "freak-out" into open-loop or cool the charge by running rich?

RH77

A few reasons. One, if you look at the picture in the previous post the hot air side intake (on the right) is about 1/4 the size of the cold air side. The engine was breathing through a straw. Secondly the AMM reads maximum air temp so the ECU does everything in its power to protect the engine from detonation. It retards timing and enriches the fuel mixture. The engine management was smart enough to hide the symptoms from the driver so the car still ran fine. It just had poor fuel economy and reduced peak power. Most owners think this is normal because 'obviously' all volvos are heavy, thirsty and slow. A good 240 5 speed only weighs 2900lb and can touch 30mpg on the highway.
While volvo produced the same body style for 18 years (240) and same red block engine for 24 years, the engine management was always on the cutting edge. Volvo was the first manufacturer to use an O2 sensor and catalytic converter in 1974 and knock sensor in the early 80s. The same red block engine in the US went from CIS mechanical injection in the 70s to Bosch LH 1, 2, 2.2, 2.4, 3.1 and finally motronic.

http://www.swedespeed.com/news/publi...ticle_800.html

Today volvo is just another ford brand. Its best days are behind it.

[Arminius]

Originally Posted by Chris D.

I'm still learning my SG, you can measure HP with em?

Probably not. I was hoping you were the teacher. I'm certainly the student.

[Chris D.]

Originally Posted by Arminius

Probably not. I was hoping you were the teacher. I'm certainly the student.

I guess I am the teacher now

heres what you imput on the X Guage feature..

Gross Brake Horsepower. (gasoline engines)

TXD = 00

RXF = 4000800000000

RXD = 0000

MTH = 000A0017000

Name = HPR

--------------------------------------------

Gross Brake Horsepower (Diesel engines)

TXD = 00

RXF = 4000800000000

RXD = 0000

MTH = 000A0024000

[Arminius]

I've been schooled.

[Chris D.]

I just went out and tried it myself..

according to this I have 246hp comming
out of my pretty much stock 145hp 2.4 dohc 16V..
weak..

[trebuchet03]

Originally Posted by tjts1

In extreme cold weather it helps warm up the engine faster. Most of these cars also use a hot wire air mass meter between the airbox and the throttle body. The sensor works by measuring the amount of electricity required to maintain a preset temperature on a heated wire in the air stream. It also uses a built in thermometer to reference the air temp. The air flap mechanism in the volvo airbox works to maintain a minimum 70f intake temp in order to make the AMM readings more accurate. The problem with the volvo device is that its controlled by a wax filled thermostat device that pushes against a spring. When the thermostat fails (usually after 5-10 years), the air flap goes into hot air only setting. In this situation the intake temp shoots up to 180-200f, slowly destroys the AMM and increases NOx emissions by a factor of 10 and drops fuel economy below 20mpg. Most volvo mechanics know to replace this $5 item but more often than not, these cars end up in the junkyard due to failed emissions test.

So it wasn't the hot air directly and instead the hot air destroyed the sensor? I mean, my car uses that same type of sensor - but there's nothing to keep the sensor at a certain temperature (and I haven't had any problems with adding heat etc.). Did volvo use a part spec'd for a small temperature range (thus resulting in bad readings when out of range)?


All that said - having a dual intake would be an awesome way to do some testing... you could do ABA on the fly if you're got it rigged for on the fly switching

[tjts1]

Exposing the AMM to extreme head over a long period of time eventually damages the wire in the sensor. The sensor is still acurate up to about 100c but at this temperature the ECU is setup to retard timing and run rich in order to prevent detonation. It will not stay in closed loop.

[apgrok1]

Ok we know all of the things that can go wrong, but we still don't know why it is there. I know that GM Quad 4's had cold start emmision problems, I am assuming this could also apply to the volvo's. The hot air intake would help emmisions in that case.