Cat 3208 factory dyno comparison

[ChrisB]

I have engine serial number 02Z34882 in the family installed in an RV and recently looked at # 02Z14523 installed in a one ton pickup. The local CAT (Quinn Power) place sent me a .pdf file on each engine which includes the dyno test data recorded immediately after each engine was manufactured in Mossville, IL.

Unfortunately the dyno data is much more complete on the engine produced in 1987 (higher serial number) but I was able to compare the only data line produced for both at 2600 rpm.

02Z34882 is rated @ 300 hp at 2800 rpm but peaked on the dyno with 306 @ 2600 rpm. It in fact made exactly 300 hp @ 2800 rpm. It is turbocharged and aftercooled as installed in the RV. Special note mentions this engine configuration is only for fire engines and RVs, I guess because it's 'hot'. The only higher ratings I know of for this engine are in marine applications.

02Z14523 was manufactured in 1985 and is rated at 210 hp @ 2600 rpm. It is turbocharged but not aftercooled.

Engine #, RPM, HP, TQ, Manifold Pressure , INTAKE airflow

02Z34882, 2600, 306, 618 , 28.7" HG ,817 CFM

02Z14523, 2600, 209, 424 , 28.1" HG ,635 CFM


As you might imagine the first engine receives more fuel, but notice it is producing nearly identical boost, which if coverted to PSI would be roughly 14 or close to one atmosphere of pressure beyond standard atmospheric. However the second engine is drawing only 78% of the inlet air the first one is. The test data is listed as being corrected to standard atmospheric conditions. Manifold pressure as CAT listed it and as listed above would be more correctly listed as 'BOOST' since it's the only thing that makes sense given the other data.

The intake manifold temperature is listed as 104*F for the first engine but is not included in the data for the second. One would assume that without an aftercooler but at an almost identical boost level, the inlet air temp for the second engine is higher. Higher temp at identical pressure means lower density which if corrected to standard conditions would yield lower airflow as indicated.

Now I haven't done the math in order to estimate the inlet air temperature rise created by the boost alone nor do I know how efficient/capable the aftercooler is on the first engine and therefore how much it cooled the intake charge effictively increasing the volumetric efficiency over the non-aftercooled engine.

Assuming the significant difference for intake volume between two may not be fully attributable to the effects of the aftercooler, does anyone know of any differences in the cylinder heads, camshaft, manifold among 3208s? Smaller valves, lower lift/duration etc. may be responsible for lower volumetric efficiencies for a given manifold pressure.

Along with the data I received an extensive list of new and reman part numbers that coincide with both engines in many cases. There appears to be only one cam assembly for that era, but it appears as though there may be more than one cylinder head assembly. I am not seeing manifold references.

I expected to find lower boost numbers at identical engine speeds for the engine with less power and less fuel. The turbocharger part numbers are different and given the fact the second engine is not aftercooled, theoretically it could be producing more boost with a 'smaller' turbo because of the previously mentioned larger increase in charge air temperature due to boost, causing more air to 'back up' in the intake tract resulting in lower total airflow. Even with this fact I would still have expected less boost. My guess is one reason to keep boost relatively high and fuel low is to reduce EGTs by maintaining significant air flow, even if it is not needed for combustion, and increase durability in commercial applications more prone to long term abuse than fire engines and RVs.

Comments?

[rmr]

Do the dyno sheets show EGT's?
I have a 260 horse, turbo, no aftercooler in my boat, my old boat had a 210 horse non turbo.
I take it the boost reading is after the aftercooler in your case?
Maybe the aftercooler robs some of the boost?
But the denser charge and more fuel make more HP?
I think the cams are the same, except the newer engines have roller cams, don't know when they switched but my old boat engine was a 1979 model and a Cat mechanic told me it wouldn't have a roller cam. Also I think some of the turbo engines might have lower compression pistons with oil squirters, but I'm not certain on that.
Good questions, I can see where they would have went with your idea of higher boost for lower EGT for longer life.
Hopefully someone knows more than me

[Kaliburz]

The 300HP 3208 was also used in some Chevy/GMC trucks. If I recall, it was the Top Kick series and they were using the aftercooler. A former Cat mechanic told me that the 300HP 3208's usually didn't last very long, since the original design was a lower HP engine.... but Cat 'updated' the engine w/ a turbo and cooler. The turbo-ed versions had oil squirters under the pistons and I think an extra compression ring. Unfortunately, the 300HP versions when worked a lot (say 80,000 GVWR), the bottom end was said to go out- well, for on road applications. Anything

For the cam, valve size, piston (for compression), I don't know. I do know that the same mentioned Cat Mechanic built a running 3208 from 'salvaged' parts. And he said that he milled the deck a little and estimated from a NA 3208, he got 250HP.

[ChrisB]

I can't help but picture hp in the low 200 hp range and 400 something ft.lb from a turboed 636 cid engine, and think, that engine has to be yawning.

I wonder if there are differences between the pistons on a 300 hp road motor and a 400 hp marine version. That seems like decent output all things considered especially a probably higher average load per engine hour etc. in the water.

I'm not sure if this truck is still available but I may get to look at it tomorrow.....headed out to the desert tonight.

[Kaliburz]

The pics I've seen on the marine engine show MUCH better cooling. The exhaust manifolds and turbo are water cooled. Plus, water is used to cool the "engine coolant" vs air for on road.

Yes, the marine would be "working" all the time being in water. But it's a 'constant' type load. On road engines, it can very from mile to mile (hill to hill). Plus, shock load in the water would be non existent, unless the prop hit something.

[rmr]

A good friend of mine has a 375HP version in his boat. The aftercooler uses a seperate keel cooler, the antifreeze mix that circulates through the aftercooler does not mix with the engine coolant. The aftercooler system has a belt driven rubber impeller pump to circulate coolant (Jabsco).
It even has it's own expansion tank. I'm not saying all higher hp 3208 marine engines are plumbed this way, but his definetly is, I've helped him work on the engine a few times. I've seen the boat out of water and have seen both the keel coolers. That system has to give a much colder air charge than the truck system.