Adding Intercooler to D24 NA?

[DieselScout]

Are there any benefits to adding an air intercooler between the air filter and intake manifold on a D24 NA? (power, fuel economy, cooler running engine, etc...)

[ngoma]

NA? Can't think of any. Doesn't the stock airbox pull in (cooler than underhood) air from the front of the car? Unless the flapper is stuck?

Water injection has been used to combat preignition and may provide some additional benefits you listed.

Does you car have an overheating problem?

[DieselScout]

Yes, the D24 NA pulls air as you describe.

My wagon has overheated several times in the past, but hasn't done so since I lowered my thermostat to 80c, added a radiator with more fins/tubes, replaced my hoses, flushed the cooling system, checked injectors, compression, etc..., but it has spiked once recently when accelerating onto the highway (about 210F for about a minute) and it tends to fluctuate a little more (180-195F) than my sedan, which seems pretty steady at 180-185F.

The car is difficult to cold start, producing a lot of smoke on start-up and seems to be running a little rich at the moment with about a 50-100F EGT difference between the two exhaust manifolds, which I am attributing to the injection pump, which is leaking diesel fuel on the engine-side (hope to have rebuilt soon)

[ngoma]

You have EGT probes on each exh. manifold section?

[DieselScout]

Yep, one probe monitoring cylinders 1-3 and the other probe monitoring cylinders 4-6.

[ngoma]

The Bosch VE series IP, being a rotary design is probably not the source of the differing EGT readings. The rotary IPs have only one piston and the charge gets distributed to the various lines via a rotating sleeve directing to one at a time. Should provide equal charges to each line. Need to look further downstream to explain the differences.

[v8volvo]

Agreed. I would look at valve clearances first (not since it's necessarily the most likely explanation, but it is by far the easiest to check and it's routine maintenance anyway so may as well regardless unless you know it has been done very recently), then second injector condition and cylinder compression since those two make sense to check at the same time, overlapping work to R&R the injectors.

On the other hand, if it runs pretty well otherwise, it might not be worth really worrying about this. Other explanations could also exist that would have no negative significance, like design differences between the 1-3 and 4-6 exhaust manifolds that let one of them shed heat to the air faster, differences in EGT probe placement, etc.

As for cooling the intake charge, can't see it helping in any real way if as you say it's already drawing cool air thanks to the airbox design. The big reason for the intercooler helping on a turbocharged engine is because the turbo itself adds a very large amount of heat to the charge air, both due to contact with hot machinery and also (mostly) due to basic physics of pressurization (see Ideal Gas Law (https://en.wikipedia.org/wiki/Ideal_gas_law)). By cooling that heated air back down between the turbo and the engine using an intercooler, it makes it denser (more oxygen, more power potential) and also helps control engine temps, giving dual benefits in that situation of a forced induction design. But since nothing is adding heat to the charge on a NA engine, you don't have to worry about any of that, as long as the engine has access to reasonably cool ambient air in plentiful supply.