Modifications to D24 NA for Mountain Driving?

[DieselScout]

I just completed an 8,000 mile road trip across 22 US States and 1 Canadian Province. The rebuilt NA engine on the car performed wonderfully with no faults. The only item that broke was a hood hinge at the Grand Canyon, which I was able to replace at a pick-n-pull in Las Vegas.

Coolant Temps never went above 205F and the oil usually hovered around 220F with some time around 250F during mountain highway driving.

It was pretty peppy at the upper altitudes (Above 4,000 feet) for an NA diesel, but it was noticeably slower than at sea level and some of the mountain driving was pretty much capped at speeds around 55mph.

Oil consumption averaged 1,333 miles per quart (total of 6 quarts added, most of which burnt off in the mountains)

So this brings up a couple of thoughts...

Would it be advantageous to add an oil cooler to a NA engine for mountain driving to keep oil temps closer to 200-220F?

Would adding a turbo be a good idea for cross-country driveability or is adding a turbo to an NA engine likely to cause rapid piston, ring, bore and/or other wear and tear?

[ngoma]

Originally Posted by DieselScout

Would adding a turbo be a good idea for cross-country driveability or is adding a turbo to an NA engine likely to cause rapid piston, ring, bore and/or other wear and tear?

+T would immensely improve driveability in most all conditions you can imagine!

Properly tuned, the lower end should be OK if it already in good condition, and you keep up on maintenance, run full synthetic oil, keep the cooling system in tiptop condition.

For frequent mountainous high-load driving you can install a lower temperature thermostat to help the cooling system get a head start keeping the temperatures lower during high load conditions.

[DieselScout]

Originally Posted by ngoma

+T would immensely improve driveability in most all conditions you can imagine!

Properly tuned, the lower end should be OK if it already in good condition, and you keep up on maintenance, run full synthetic oil, keep the cooling system in tiptop condition.

For frequent mountainous high-load driving you can install a lower temperature thermostat to help the cooling system get a head start keeping the temperatures lower during high load conditions.

Apart from modifying the oil pan with an oil return port, would any other modifications/fabrications have to be made, or are the rest of the parts swappable/bolt-on?

Can the oil pan be tapped for a port, or does it require a port to be welded in place on the passenger-side?

[ngoma]

Main items are:

• Turbo IP w/ LDA
• Turbo oil feed (part of the oil cooler/heater assy)
• Turbo oil return

The oil return line is not pressurized so can either drill/tap a fitting into the N/A pan or can weld one on. Here is an example:

https://d24t.com/showthread.php?t=41

[v8volvo]

Great to hear of the success on a very long and ambitious journey with a classic car. Must have been fun and gotten a lot of good reactions along the way!

Staying cool in the mountains is always a task with any IDI type diesel. Prolonged operation under heavy load results in a lot of heat entering the coolant through the prechamber in the head. I would say your cooling system performed very impressively based on the numbers you saw.

As ngoma said, the turbo addition will result in an engine that is more satisfying to operate in every condition, with no cost to fuel economy. If you have concerns about durability, you can always tune your boost and fuel according to conservative limits you choose. Even a few PSI of turbo pressure will give a nice power benefit, and will also have the result of compensating for thinner air at high altitudes where the NA engine will struggle to breathe well, as you noted.

The turbo engines require an oil cooler in particular because they use "squirters" in the block that shoot an oil jet up at the undersides of the pistons. That oil spray helps cool the piston, but the counterbalance is that it pulls a lot of the pistons' heat into the engine oil, necessitating the cooler to remove that heat to the radiator. The squirters also increase the oil volume demand, hence the use of a higher volume oil pump on the D24T and D24TIC engines.

If you're adding a turbo to a NA engine without squirters, you may be able to get away without adding an oil cooler, because you don't have those squirters. The turbo itself may add quite a bit of heat, though. The good thing in your situation is it sounds like you have an oil temp gauge installed. Thanks to that, you can just keep an eye on temps before and after adding the turbo. I'm no expert but from what I've heard, up to around 250F is fine for a good synthetic oil. Not sure you'd want to see much higher than that. But you can do some testing and decide from there, right?

Adding a turbo to a NA engine does increase the demands on it, but whether or not it'll cause issues will depend a lot on how hard you push the engine with the turbo on it, and how sensitive you are to backing out of it when necessary. Given how many miles you just drove successfully in an old IDI diesel car whose engine you rebuilt yourself , I think you wouldn't have a hard time keeping things in the safe zone. VW did add those squirters to the engine for a reason -- the added fuel and air from the turbo create a lot of additional heat. But most of the heat comes from the fuel, not the air.

If it were me, I would do the +T, but then tune the engine conservatively, in terms of running full factory turbo boost (~10.5 psi), but then turn the fuel down a little from stock D24T level (on a D24T IP with aneroid of course). This will result in an engine with more power than a stock NA D24, and MUCH more flexibility and better resilience to high altitude, but a little less power than a stock D24T. The upside is that with a lot more air but just a little more fuel, you'll have an engine that makes the additional power without a lot of additional thermal stress. That will mean you will have less concern about overheating the pistons without the factory D24T squirters, less (or maybe no) need to add an oil cooler, and less heat input to the cooling system, which on a 240 is more limited (less radiator size) than on a 7 series -- the reason Volvo never sold factory 240 TD's.

A nice, clean, smoke-free exhaust will also be a side benefit of this approach, since you'll be adding a lot of oxygen but not as much fuel. Just to be extra safe, also adding an EGT gauge would be a smart idea, and set very conservative limits for where you want it to see run. That will give you the best immediate feedback to know how hard or how long you can push it on hills and/or in hot ambient temps. But keeping your fueling turned down a little should go a long way to keeping EGT within very safe bounds while still getting a very nice power boost.

I bet you would be very happy with this result on a car you're intending to put a lot of reliable miles on.

Let us know how it goes!