solenoid vacuum line - charge air pressure control system - 85 240 GLT

They used that system for just a couple years to give a boost increase in the high RPM range. The hose from the solenoid valve should just poke into the hole in the intake pipe with a tight friction fit. You'll probably wanna clean the compressor wheel of the turbo with some carb cleaner or something after having that hole open, yes that will make the engine run poorly too, I'm surprised it ran at all with such a large vacuum leak after the airflow meter.

Personally I just bypassed that system, after several years it doesn't seem to have hurt anything and it improves low end torque.

The rpm relay and solenoid came standard on 85YM cars. It was previously sold as an accessory called the "turbo +" boost kit. The idea is to restrict pressure going to the wastegate actuator in order to hold more boost on the motor for a longer period before allowing the wastegate to dump pressure on the system thus yielding an increse in hp at whatever rpm the rpm relay is programmed for. Once the specified rpm has been reached the solenoid opens and allows full manifold presure to the wastegate to keep the overboost relay from shutting off the fuel pump.

You'll proably want to go to:

muck around. There are several modifications that allow the tube to be open and the hose disconnected that simply let the boost overpressure relay control overboost. There are also tweaks to the boost overpressure relay that allow a higher maximum boost pressure. You can also tweak the length of the actuating rod for the waste gate actuator to raise the maximum boost pressure. Read, learn, be very precise in your changes and use accurate instrumentation. The dynamic pressure of a detonating flame front is very impressive. If the hose has been removed from the intake pipe then someone has adjusted the fuel distributor screw way rich to compensate for the vacuum leak. If you return the hose to its correct place you will have to lean the mixture way back to allow the motor to idle correctly.

If you go to:

read about the turbo plus kit it seems to say that it couldn't be retrofit on -86YM cars. However if memory serves, and lately it doesn't seem to have as much accurate info as it once had twenty years ago, there was a boost kit available in '85. Someone I knew had installed the rpm relay and solenoid on a factory employee car that grounded the #11 pin on the fuel control unit to drive the mixture full rich whenever the boost control solenoid was energized. Bob

IIRC the Turbo + kit was for the LH-Jet 700 series cars. The one on the

240, or at least the setup that was on my 240 Turbo is a solenoid which remains closed until the engine reaches around 4000 RPM at which point it opens, dumping some of the air pressure from the wastegate hose into the intake which causes the boost to increase. When it was hooked up, the boost would sit in the middle of the yellow, and then spike up almost to the red at high RPMs. After I bypassed it, it would go up to the base of the red right away. The same circuit cuts out the A/C compressor and IIRC turns on the aux fan in front of the radiator.

That's so cool! I've been wanting to know this for years. How does one go about cleaning the compressor wheel? Just disconnect the hoses and spray? Or should the turbo be pulled?

The car's been running poorly for a very long time. Last 2-3 years have cost a bunch just trying to pass inspections. Now I know why. Kind of bummed as we really thought highly of the mechanic we'd been seeing. Guess I'll hook it back up, clean the turbo, adjust the fuel distributor and see how the car runs. Have always wanted more low-end, so will consider bypassing the solenoid.

Mike

Man, I'm so stoked! I was just hoping to find out what the hose was supposed to plug into. Now I know why my car runs so poorly and the exhaust always smells so rich. Thanks for the info and links. Skimmed some of the brickboard turbo mods and will print them out and study them for a while. Lots of detail to consider, but since I'm still in restoration mode, performance improvements will have to wait until a little ways out in the future. Read the article on swedishbricks and found this admonition pretty sobering:

"For increased specific power output, the wastegate can be adjusted so that the high/low boost settings are higher. The caveats of this are plentiful, I have known MANY turbo Volvo's with altered boost levels that while awe-inspiringly fast, tend to eat u-joints, transmissions, motor mounts, etc."

Between that and your sentence about, "The dynamic pressure of a detonating flame front is very impressive" (that's a great quote!), figure I'll just take your advice and start slow and take my time. Heck, the car's been running so poorly for so long that just getting back and running well should be gratifying - for a little while.

Mike