Need some 603.970 service info
 

I've gotten some conflicting information regarding what the redline on the 350's engine should be. The W126 service CD set said it should be 4150, but the online W124 set says it should be 4650 in the W126 and 4750 in the W140.

Does anyone have late documentation that lists what this value should be?

Thanks,

-Jason

Anyone? :)

I think it's 4250 rpm full load as per owner's manual, no load 4650 rpm for the W126 as per factory CD.

The way a 350 is set up from the factory, though. You don't get very good acceleration once you're past the 4K rpm hp peak. Power plummets very quickly.

I would go by the service CD.

I did buy the service CD. From that service CD:

http://www.peachparts.com/shopforum/...1&d=1249705114

But, from the W124 service cd:

http://www.peachparts.com/shopforum/...1&d=1249705114

I then looked up that same document on the W126 service cd:

http://www.peachparts.com/shopforum/...1&d=1249705444

:confused: (I cut some stuff out of the first two images to make them fit better)

So it sounds like the governor should be 4,650, but the engine won't be able to make enough power to pull past 4,150 under full load due to the hp peak being at 4,000 and the power dropping off quickly thereafter.

ill watch the tach next time i drive

The 124 CD chart you have posted seems incorrect, I'm not even sure why it would list the 97x engines as they were 126 engines.

Anyway, the .96x (3L) engines are governed (mechanically) to 5150+/-150rpm. This governor starts to pull off full-fuel flow (throttling range of a mechanical governor) around 4600RPM which limits its horsepower at that point.

The .970 engine is the low-horsepower one of the bunch, the simple reason being that power (work) is a function of RPM and it is limited to a lower RPM; 4250+/-50RPM. When you cut the fuel at a lower RPM you limit the HP, but provided the torque-peak is below that point, you will not affect the torque-peak. The loss of power above ~4000rpm is a function of the IP's governor limiting max. fuel flow. This engine also has a larger displacement, a longer stroke, both increasing torque and on top of that an updated IP. I BELIEVE (from my experience in hot-rodding Cat 3208 IPs) that the .97x IP cam has a more aggressive profile providing a higher injection rate which besides reducing emissions helps to provide power at a lower RPM and thus the 2000RPM torque peak (vs 2400 for the .96x engines). The engine should be capable of more power with its greater displacement, larger turbo, updated injection, and upgraded IP but the numbers are 133hp for the .970 vs 148hp for the 3L .96x engine.

Having longer rods working at a greater angle seems to have some impact on the "rod bender" nickname for the 3.5s, but AFAIK nothing has really been discovered as the cause/cure of such problems.

The .971 engine in the 140s is the one to have/scavenge for parts. With all of the .970 parts, plus a better-flowing exhaust-to-turbo and no trap-ox, and they increased the RPM limit to IIRC 5000RPM and re-gained the lost horsepower plus some. How this was accomplished without detriment to the aforementioned longer rods I don't know, but it moves.

If one were to look for hidden power in the .96 engines, there is some in the governor. As I did with 3208s, you can increase the governed RPM, thus moving the start of fuel cut up to/above the max. RPM. This will raise the RPM of the HP peak, raise the HP, but you will have to govern max. RPM another way at that point (such as with your right foot). The mechanical governor is a huge waste of power. Remember that the power increase will not necessarily be linear, especially with a .96 IP as the injection rate and effective timing (due to port effect / the delay in injection from IP to nozzle due to injection line stretch) changing with RPM. Mechanical injected diesels especially tend to lose BSFE / efficiency with higher RPM.

Idealy I'd like to tune up my engine to W140 specs. Considering mine was made around 1998 I'd say the internals are going to be identical or better to anything in a W140. No .97x engines came with a trap ox AFAIK, my car doesn't have one though it still has that restrictive looking pipe in its place.

I don't know why the .97x info was in the W124 service set :confused:

-J