Thanks

[Prosecutor]

Greetings and thanks to all who have provided information on this forum.
I am a relatively new owner of a 1987 300SDL. The information contained in this forum is amazing. Thanks to all for providing the information necessary to operate and maintain a 603 diesel engine. Based on the information in this forum, I have changed injectors, delivery valve seals and flushed the coolant system. New shocks are forthcoming when the weather warms. I just finished replacing the drivers seat springs and it was a pita, but not real difficult. If you do this, take pictures and have sturdy platform to work on, otherwise, the seat will fall and parts will go everywhere. Then it will take forever to figure out where they go again. Don't ask me how I know. Seat is much better now.

[Brian Carlton]

Welcome to the forum.

You seem like a very capable fellow who can build on the experience of others.

The SDL can always benefit from input and experiences of our members. There are just not that many of them operating as compared to the older W126 or the W123 vehicles.

[Prosecutor]

Thanks, I also removed the alda based upon your thread and the car does run much better. Based on my experience, the alda is not necessary.

[Brian Carlton]

Originally Posted by Prosecutor

Thanks, I also removed the alda based upon your thread and the car does run much better. Based on my experience, the alda is not necessary.

I agree, however, I remain a bit concerned about the potential for an overboost condition because there is, effectively, no overboost protection.

[Prosecutor]

Boost and overboost are concepts that I haven't yet got a firm grasp on. I drive conservatively and it does not seem to be a problem. Boost is something I need to get a grasp on as my backup vehicle is a 1999 Saab 9-3 turbo.

[Brian Carlton]

The turbo provides pressure to the manifold that is above atmospheric pressure. This occurs when the rpm's get sufficiently high to spin the turbo at sufficient speed.

We refer to the concept of pressure in the intake manifold as "boost". The turbo is capable of putting out much more boost than the engine can safely handle. Levels above 14 psi can be considered dangerous to the engine.

The turbo is equipped with a "wastegate" that dumps excess exhaust pressure to limit the boost level to the setting on the wastegate.

If the wastegate fails, or the hose that operates the wastegate fails, the turbo will "overboost" the engine.

Our engines have a safety device to prevent this occurrence. It's the overboost protection valve and it restricts boost pressure to the ALDA if the manifold pressure were to climb above 15 psi. Without a boost signal, the ALDA will restrict fuel to the engine and the exhaust pressure will immediately drop and protect the engine.

Without an ALDA present, the engine is fully fueled depending strictly on your right foot. Only you and the wastegate control the pressure in the manifold. If the wastegate fails and you're not aware of it, you buy the cylinder head if the pressure gets too high.

A boost gauge is therefore recommended for such operation without an ALDA.........provided that you're watching it........of course.

[Prosecutor]

Thanks, any suggestions for hooking up a boost gauge. Again thanks for the short couse on boost. The saab has a boost indicator. The SDl does not. A blown head is not something I am ready to do at this point, at least until the weather warms a bit

[JimmyL]

Originally Posted by Brian Carlton

The turbo provides pressure to the manifold that is above atmospheric pressure. This occurs when the rpm's get sufficiently high to spin the turbo at sufficient speed.

We refer to the concept of pressure in the intake manifold as "boost". The turbo is capable of putting out much more boost than the engine can safely handle. Levels above 14 psi can be considered dangerous to the engine.

The turbo is equipped with a "wastegate" that dumps excess exhaust pressure to limit the boost level to the setting on the wastegate.

If the wastegate fails, or the hose that operates the wastegate fails, the turbo will "overboost" the engine.

Our engines have a safety device to prevent this occurrence. It's the overboost protection valve and it restricts boost pressure to the ALDA if the manifold pressure were to climb above 15 psi. Without a boost signal, the ALDA will restrict fuel to the engine and the exhaust pressure will immediately drop and protect the engine.

Without an ALDA present, the engine is fully fueled depending strictly on your right foot. Only you and the wastegate control the pressure in the manifold. If the wastegate fails and you're not aware of it, you buy the cylinder head if the pressure gets too high.

A boost gauge is therefore recommended for such operation without an ALDA.........provided that you're watching it........of course.

A very good explanation, and it greatly enhanced my understanding of "what goes on"......

[Brian Carlton]

Originally Posted by Prosecutor

Thanks, any suggestions for hooking up a boost gauge. Again thanks for the short couse on boost. The saab has a boost indicator. The SDl does not. A blown head is not something I am ready to do at this point, at least until the weather warms a bit

Hooking it up is easy. If you've removed the ALDA, you've already plugged the open boost line. This was the line that previously was connected to the ALDA. Just connect this line to the boost gauge.

Now, mounting it in the vehicle cabin will present the challenge. Some folks have done a fabulous job of putting it right where the ashtray would normally be.........so that it looks like a factory installation. But, this requires some careful workmanship and planning.

[winmutt]

I just read about someone putting a gasser gauge in with the "fuel economy" gauge acting as a boost gauge.

[Prosecutor]

Thanks gentlemen, I'll do some searching for a suitable boost gauge.