If you are like me, you have probably never driven a 1984 turbo diesel G-Wagon. They are kind of like Unicorns, we like the idea of them, but they were just never made. Why you ask? First of all, there were no G-Wagons sold in the US in the 80's and secondly the turbo diesel G-Wagon was not even built until the 90's.
The thing was, the power from the OM617 5 Cylinder Turbo in my car seemed pathetic. Why would anyone want to have this? The term SLUG comes to mind. I was getting 0-60 in something like 30 seconds and forget about a mountain climb at anything near the speed limit. So I started digging for more power. Turns out the first thing I tried, adjusting the ALDA, was just the thing I needed. It was easy and did not take long, required no special tools or instruments and WORKED!
The OM617 Turbo has an ALDA that controls the amount of fuel sent to the engine. The ALDA is a simple mechanical device that that measures altitude of the vehicle and the pressure from the turbo intake manifold pressure to adjust the fuel made available to the engine. I could tell mine had not been adjusted since the engine was assembled at the factory because the cap was still covering the adjustment screw.
My first step was to make sure the pressure from the intake manifold was reaching the ALDA. I started by removing the nut at the rear of the intake manifold with the banjo connecting to the plastic hose and make sure the airway was clear. It had some build up in the nut and the banjo so I cleaned it with a solvent and replaced it.
The next step for the pressure from the manifold was a cutoff valve. There is a switch on the top of the intake manifold that measures pressure inside the manifold. Too much pressure and the switch connects to ground and causes a bypass valve to release the pressure before it gets to the ALDA so the turbo will not overload. In my case the wires going to the bypass and manifold switch were disconnected.
Just to make sure, I removed the bypass switch connected the hoses tested it on my bench. It worked perfectly. After checking all the remaining hoses I removed the cap from the top of the ALDA.
The top of the cap is plastic so I used a sharp razor blade to cut through the plastic on top and a pair of diagonal cutters to cut the metal along the side ring. This reveled a hex lock nut and the adjustment screw. I kept working at the cap until I could get to the locking nut. By removing the locking nut from the ALDA, I was able to remove the remaining part of the metal ring and plastic.
Once the cover was removed, I replaced the large washer that was under the nut with the locking nut but did not tighten it all the way. With the nut loose, the screw in the middle was easy to turn. Do not force the screw, it will break! I turned the screw counterclockwise about 1/8 of a turn to increase the fuel flow and took the car for a drive. I tightened to hex hut to hold the screw in place. WOW what a difference. Much better acceleration below 2000 rpm and a HUGE improvement once the turbo kicked in.
I repeated the steps above and adjusted it one more time and got another increase in acceleration and responsiveness. I was careful not to adjust so far that black smoke came out of the exhaust indicating too much diesel to was being provided for the the engine to burn.
The next step was to get the overload bypass working again. I simply installed the bypass switch and reconnected it to the manifold overload switch. Unlike what some other said, I experienced NO LOSS OF POWER by replacing the properly working pressure release switch. Most importantly the engine is now protected from turbo over boost. Even with the overbuilt nature of the OM617A, too much turbo could damage the engine.
There is a lot of talk on the internet about whether or not to adjust the ALDA. Some even say you should completely remove the ALDA. Others turn the screw all the way out till it stops. I think my results speak for themselves. The car was a slug prior to the adjustment and now it is downright zippy with 0-60 now less than 22 seconds that is almost a 30% increase in acceleration. My feeling is a 30 year old mechanical device could use some adjustment.
One more note: I also performed a Diesel Purge that provided more of a performance boost. CLICK HERE for detail instructions.
If anyone wants to drive a 1984 300GD Turbo, just take a short drive to Park City and I'll let you take it for a spin. Because unlike the mythical unicorn, they really exist. Warning: after driving the turbo, you will hunting for an OM617 Turbo to put in your W460!
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| ALDA with Cap In Place |
The thing was, the power from the OM617 5 Cylinder Turbo in my car seemed pathetic. Why would anyone want to have this? The term SLUG comes to mind. I was getting 0-60 in something like 30 seconds and forget about a mountain climb at anything near the speed limit. So I started digging for more power. Turns out the first thing I tried, adjusting the ALDA, was just the thing I needed. It was easy and did not take long, required no special tools or instruments and WORKED!
The OM617 Turbo has an ALDA that controls the amount of fuel sent to the engine. The ALDA is a simple mechanical device that that measures altitude of the vehicle and the pressure from the turbo intake manifold pressure to adjust the fuel made available to the engine. I could tell mine had not been adjusted since the engine was assembled at the factory because the cap was still covering the adjustment screw.
My first step was to make sure the pressure from the intake manifold was reaching the ALDA. I started by removing the nut at the rear of the intake manifold with the banjo connecting to the plastic hose and make sure the airway was clear. It had some build up in the nut and the banjo so I cleaned it with a solvent and replaced it.
The next step for the pressure from the manifold was a cutoff valve. There is a switch on the top of the intake manifold that measures pressure inside the manifold. Too much pressure and the switch connects to ground and causes a bypass valve to release the pressure before it gets to the ALDA so the turbo will not overload. In my case the wires going to the bypass and manifold switch were disconnected.
Just to make sure, I removed the bypass switch connected the hoses tested it on my bench. It worked perfectly. After checking all the remaining hoses I removed the cap from the top of the ALDA.
 |
| ALDA Cap Partially Removed |
Once the cover was removed, I replaced the large washer that was under the nut with the locking nut but did not tighten it all the way. With the nut loose, the screw in the middle was easy to turn. Do not force the screw, it will break! I turned the screw counterclockwise about 1/8 of a turn to increase the fuel flow and took the car for a drive. I tightened to hex hut to hold the screw in place. WOW what a difference. Much better acceleration below 2000 rpm and a HUGE improvement once the turbo kicked in.
The next step was to get the overload bypass working again. I simply installed the bypass switch and reconnected it to the manifold overload switch. Unlike what some other said, I experienced NO LOSS OF POWER by replacing the properly working pressure release switch. Most importantly the engine is now protected from turbo over boost. Even with the overbuilt nature of the OM617A, too much turbo could damage the engine.
There is a lot of talk on the internet about whether or not to adjust the ALDA. Some even say you should completely remove the ALDA. Others turn the screw all the way out till it stops. I think my results speak for themselves. The car was a slug prior to the adjustment and now it is downright zippy with 0-60 now less than 22 seconds that is almost a 30% increase in acceleration. My feeling is a 30 year old mechanical device could use some adjustment.
One more note: I also performed a Diesel Purge that provided more of a performance boost. CLICK HERE for detail instructions.
If anyone wants to drive a 1984 300GD Turbo, just take a short drive to Park City and I'll let you take it for a spin. Because unlike the mythical unicorn, they really exist. Warning: after driving the turbo, you will hunting for an OM617 Turbo to put in your W460!
Now that I read how pathetic your OM617 us, perhaps I should have passed on buying the 300GD? I know for sure it doesn't have a Turbo. Perhaps I should consider retrofit one. I will have to find the Kit.
ReplyDeleteThe OM 617 is fine and will serve you well around town. It is the same engine in the 300 series MB cars from that time. My current car is a OM617 non turbo and works fine locally on the roads and is a MONSTER off road. Putting a turbo on a OM617 is not a great idea because the OM617 can't withstand the extra stress from the turbo boost. Consider finding a good OM617a with a turbo and dropping it into your G. It is a very easy engine swap.
DeleteWell that's plain silly. The OM617 came with turbo too.
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