Well I flew to NJ and retrieved my new car, an '88 745t manual with 183,000 miles. Drove 1100 miles from Jackson NJ to Memphis on Sunday. No problems, used 1/2 qt oil and noticed the turbo gauge was pretty active. Never went past the 12: o'clock position though. The car drove perfectly and I took it easy coming back. Not having driven one before and knowing it wouldn't be as strong as my 855t I didn't suspect anything.

Yesterday I changed the oil & filter, (M1 10W30 and Mann) and while under the car looked at the bottom of the turbo to find the actuator rod wasn't connected to the WG. So the WG was blowing open for the entire drive. I fitted the rod into place and of course there's noticeably more power and the gauge runs about the 3:00 position while accellerating at 3/4 throttle.

My question is about the actuator and rod. While all the pictures I've been able to find show a locknut and adjuster on the rod, from what I was able to tell mine is solid and there's a kink to allow for the offset between the actuator and WG lever. I'm picking up a pressure guage and measure boost as per the Haynes manual to see what's going on. Any input would be appreciated.

The car is great! Drives extremely well, tracks straight, stops straight, shifts perfectly, OD and all electrics work as they should, even the antenna.

I'll post more later.
Thanks,
--
Erwin in Memphis, '95 855t

"3:00 position while accelerating at 3/4 throttle"? I think that is about 15 psi, while stock is 12:30 to 1:00 position at about 8 psi. Perhaps someone adjusted that actuator rod and that is how it became disconnected. If you go much past 3:00 position, I think you risk engine damage. I suggest you be gentle with the throttle until you check with more knowledegeable bricksters than I like John or Philip.

Isn't there two different styles of boost gauges? one which is zero at the 12:00 position, and one which is more at 10:00?

Cliff Scott
89 740 16v

Will do. Thanks. FWIW, I've been driving it around very gently this week as I'm still becoming acclimated. I didn't secure the rod onto the WG and suspect it's fallen off again judging by the loss of power. I'll take care of that this weekend while I'm under the car.

Today I'm in my '95 855t and the difference between the cars is remarkable but I'm surprised to find the 15-year-old 745t to have a much quieter cabin. None of the 850's creaks and rattles.
--
Erwin in Memphis, '95 855t

I'm kinda confused by your comments. If the rod fell off your wastegate actuator you wouldn't have a loss of power; rather, your boost would continue rising at full throttle until you eventually threw a rod or otherwise detonated the vehicle.

The wastegate tops out the boost and keeps it as safe levels. It is basically just a safety valve or really basic way of controlling max boost. I would surmise the reason you are running such high boost levels is because you have no wastegate to cut it off and it just goes up and up. Very similar to the problem people encounter when the hose for teh WG actuator rots off on the front bottom of the turbo... it juist keeps going up.

What you want to make sure is that your emergency kill switch is safely attached to the system. In the event you redline the turbo and approach dangerous levels, it cuts off fuel to the engine. Not sure about you 88, but the one on my 85 745t is located directly above and slightly to the right of the gas pedal. You can find it by following the vacuum hoses in teh dash... a hose come from the bay and hits a T connector. One hose from teh T goes to teh dash gauge, and the other hose goes to the emergency cut-off switch.

good luck,
rt

"I'm kinda confused by your comments. If the rod fell off your wastegate actuator you wouldn't have a loss of power; rather, your boost would continue rising at full throttle until you eventually threw a rod or otherwise detonated the vehicle."

Nope. When the wastegate actuator comes off the wastegate, the wastegate goes full open and you get zero boost. Just ask my son. He came home one day, and told me his car needed a turbo. After I asked him what he thought that would cost, I jacked the car up, re-attached to arm and installed a cotter pin. That is the cheapest turbo overhaul I have ever done!

Okay. That seems logical enough. If the wastegate actuator rod is disconnected, you won't get any boost.

What would cause the wastegate to stay shut?

I've got two turbo'd Volvos, and a friend has one (88 760T). I've never spent a large amount of time behind the wheel of any other turbo'd cars.

The 84 (intercooled) has a clutch that slips a bit, but it's fantastically easy to peg the boost gauge. A few seconds after the boost gauge moves, I can feel the car start to speed up. If I'm not careful, it feels like I'm hitting some sort of fuel cutoff (obviously K-Jet has no rev limiter). In fact, it's hard to stay out of the yellow portion of the gauge (it's got one of those Volvo tri color gauges).

The 85 takes a while to build up boost, but it feels like it has more power (probably because it's got a good clutch) than the 84. Even if I try, I can't peg the boost gauge (and I believe it's the same 12psi tri color gauge as the 84). I can usually drive around in a fairly aggressive manner and barely get the gauge into the yellow.

The 88 felt pretty powerful, but I couldn't peg the gauge on the way down from Reno. The turbo <-> AMM hose was replaced, and the CBV hoses were affixed properly.. and now it's extremely easy to peg the boost gauge and get the engine to cut out (at under 40mph). Should it really be so easy to get one of these buggers to cut out like that?

Are any of these normal? :)

- alex

'85 244 Turbo
'84 245 Turbo

"Okay. That seems logical enough. If the wastegate actuator rod is disconnected, you won't get any boost."

"What would cause the wastegate to stay shut?"

The answer is simple. The exhaust can either go through the exhaust turbine or the wastegate. It incurs less pressure drop and seeks the path of least resistance, which is to push the wastegate open. The wastegate is not spring loaded except by the wastegate actuator. Without the wastegate actuator to hole it shut, it is going to open from exhaust pressure. It takes more energy to spin the turbocharger than to exit the wastegate which is not held shut.

Ok, so if the actuator arm fails, or drops off, the wastegate will open under any pressure.

What happens if the vaccuum hose pops off the wastegate actuator? The same thing (ie. no boost), or else will the wastegate be held permanently shut, creating unlimited boost and possible damage?

If the hose comes off the wastegate actuator nothing limits the boost. Eventually the overboost switch under the dashboard will cut the fuel pumps out.

Thanks for the reply,

I'm learning as I go here just to make that clear. I understand what a turbo is and how it works but my practical experience with them to this point is limited to occassionally wringing the neck of my 855t.

As they say on the local news, "here's what we know...", I believe you're right about the hole in the actuator hose scenario. The actuator holds the gate closed and the result is excessive boost. Again, excercising my limited knowledge on the topic, manual boost controllers give you the "hole" in hose but a REGULATED hole.

When under the car I found the wastegate doesn't have any supplemental spring assist and is free to flap back and forth when the rod is disconnected. The actuator's diaphram places the rod in tension, clamping the gate closed. At the prescribed pressure, the actuator pushes the WG open.

Yesterday I found several pics of disassembled turbos on the web and I've learned what my WG actually looks like. Pretty simple but not what I expected. (Things rarely are, but that's for another forum.)

So I'm guessing here, with the rod disconnected, the WG was free to be pulled open by vacumn or neg exhaust pulses or some other exhaust event black magic and leak. I can tell you that during my 1100 mile drive back to Memphis, the boost guage behaved like it was tied to the gas pedal with a string. Step on the gas and the needle shot to 12:00 but never beyond. Very linear. Never went into the red (orange?). Once I connected the rod, I had no trouble pushing the needle into the red area. Disconnected, when revving the engine in neutral (to about 2k) the needle rose and fell with rpm. With the rod connected, the guage will rise then drop slightly while rpm remains constant.

Until I get under the car again and connect a pressure guage to find out just what is happening I can't offer any more information, fact or speculation.

I appreciate all the responses. I've been over on the 850 board for a year and learned quite a bit about those cars also. I hope along the way I've helped a few folk too.

BTW, how in the heck do I get my profile to stick? I keep adding my 740 to my sig but it won't update.

Regards,

--
Erwin in Memphis, '95 855t

hmmm very confusin...but a couple of points...

a turbo will behave like the guage iis tied ti the pedal...it is in effect...the fact that its getting to anywhere suggests the waste gate is closed...otherwise it would stay firmly pegged down...

you will NOT get any boost regestering whilst reving in neutral...simply the engine swallows more air than you are producing you will only get boost showing whilst the engine is under LOAD...I know you are producing boost...but dont forget you dont have BOOST guage (i know its called that but it isnt ACTUALLY measuring boost its measuring manafold presure!)

As i understand it (which may be wrong!) the waste gate is activated by prsure along that rod...

The picture below shows the wastegate actuator rod on the wastegate arm. Originally the shaft on the wastegate arm had an external snap ring to retain the rod end from the wastegate actuator, and the hole was for a lead seal and wire to prevent tampering. Now cotter pin through the shaft hole does the job nicely.

john is that a garrett 9looks suspiciously like mine which is....

Until I break down and buy a digital camera (still processing and scanning) all I can do is describe it. Instead of the threaded adjuster and locknut, my rod is solid with two shallow bends in it to offset. Out of the actuator, straight, 30degree bend, straight, opposite 30degree bend, straight, then the flattened section with the hole for the WG actuator. I'll get back under the car this weekend and get a better look at things.

Thanks,
--
Erwin in Memphis, '95 855t

You previously stated that you thought the turbo on your car was a Garrett, so I posted a Garrett picture. The turbo must be a Mitsubishi TD05. Whether Mitsubishi or Garrett, the rod connects the same to the pin on the wastegate actuator arm. A cotter pin will serve this duty just as well on a Mitsubishi as a Garrett. Who cares if there is an offset in the rod? It still has to attach to the wastegate arm.

Yes, obviously it does need to be connected and I have done so. I was commenting on the difference in rods and that I haven't come across a pic of one similar to mine. If it is a Mitsubishi and doesn't have the threaded adjuster, how is pressure regulated or set? There's also a small hose from the top of the intake manifold to a device on the upper front of the turbo I'm not sure about. Guess it's time to surf for turbo info.

Regards,
--
Erwin in Memphis, '95 855t

That is the Compressor Bypass Valve, CBV. The CBV allows air to re-circulate within the turbo under conditions of high vacuum. This is to prevent compressor stall. If the CBV fails you will notice a "stutter" to the engine when taking your foot of the gas other than real slow.

I think you will find threads inside the rod where you can't see them.

After the long drive home with no boost, it must be a real thrill to drive this car with the turbocharger working. The Mitsubishi turbos used on the B230Ft are small and spool up very nicely. The later 1990 and on TD04s really spool up fast.

Did you see my post on turboshargers? Below is one picture from it.

That looks very much like what I have. I was under the car just long enough to change oil and filter, re-attach the rod before I had to stop for the day. I'll get under it this weekend and get a better look. I'll also try to get a few pics. My Canon SLR seems to be dying so it might be time to buy a digital camera.

Thanks for the pic.
--
Erwin in Memphis, '95 855t

Mine ( a Mitsu) is secured by a small metal cotter-pin-like clip through a hole in the wastegate fitting.