FifthWheelPuller

There are various boost control mechanism which control the turbo's boost pressure by opening the by-pass port. I have the static type where there is no manual control over it. In other words, it is a sealed canister with a given spring and cannot be adjusted.

Is it better to have another style or not?

Mine engine is the '93 6.5l turbo diesel with automatic trans on the C3500 big trailer hauler.

Gumby22

It shouldn’t be a “static” control if everything is factory. The wastegate actuator does have a spring inside it to keep the wastegate closed, but it’s controlled by the ECM using vacuum via a solenoid.

If there’s no vacuum line on the actuator, it’s either missing/fallen off or the actuator has been removed/replaced by a PO.

The wastegate is opened/closed to maintain ideal boost pressure at all engine speeds/loads. Incorrect boost pressure can not only result in poor performance but could also cause catastrophic engine damage.

If it’s not broke, don’t fix it.

Or…. break it for the sake of fixing it, just make sure to use components that meet OEM specifications when you do.

FifthWheelPuller

I am pretty positive that the old couple who had the truck new before me never did any change to the turbo system. The whole thing looks stock to me. It has no vacuum lines to the canister. Therefore it is a static unit with only an internal spring. 1993

Gumby22

So I’m still trying to confirm this, but it appears GM changed to a static actuator for 1993 models only, but as to exactly why, I don’t know yet.

It’s not really of consequence to my original answer, however - keep it stock.

FifthWheelPuller

If they are basically the same engine in all those years, then why the difference in the first place? Were they just trying something else to see what happens?

We have seen clear evidence from many experts and users that tweaking things in small ways here and there can accumulate to increased performance, and to longevity as well. I would be inclined to look into some improvements over stock. The thing is currently a fuel hog.

Gumby22

Again, I haven’t been able to confirm it yet. Haven’t had the time. If you can use a search engine, you can find just as much information about it as I have up to this point.

I’m not an expert on the 1993 models; however I am quite familiar with trucks of this era and most of them used similar controls. Vacuum-actuated waste gates were used across all makes which is why I thought it should have one.

Not the point I was making. My opinion is to leave it stock for the simple reason that modification/tweaking/etc tends to have unintended consequences.

It’s your choice and if you want to pursue it, good luck.

That’s because it’s a diesel being used to pull a 5th wheel. Even modern diesel engines are barely getting 10 MPG while towing.

FifthWheelPuller

No, I think you are correct. I would only make changes if others have proven them. And even then, I tend to think like you in regards to not straying far from stock.

My first comment portion was only rhetorical. It is always hard to understand the automotive industry.

BTW, I don't think I'm getting more than 7mpg without the trailer. But the original owners said 7 with the trailer. Obviously, tuning is not uncalled for at this stage, along with some further diagnostics.

Do you mind telling us where you found reference to 1993 having a static unit? I'd like to read that.

Thanks mucho.

Gumby22

So far I’ve seen it mentioned on 3 diesel-specific forums as I’ve been doing general research; but it’s only been mentioned, not explained.

One thing I’ve found is that 1992-1993 was when the 6.5 was introduced. It’s the first turbocharged diesel GM used (the 6.2 was naturally aspirated).

IME it’s not uncommon for a first generation product to have slightly different controls which are then modified or deleted in subsequent generations as they work to resolve problems, so that’s my best guess in this case at this point.

Here’s the Wikipedia page for GM diesel’s - it doesn’t explain the actuator but it’s the most info I’ve been able to find so far - https://en.m.wikipedia.org/wiki/Detr...esel_V8_engine

FifthWheelPuller

As always, thanks, Gumby.