Build Harumi the Rusty Rescue JDM HJ60 - Build Thread

[BrickRunner]

...and then I decided to chase those supposed diminishing returns in sound deadening. This time adding more mat and also including the apparently quite important foam layer. In retrospect, I should have had @kelly saad spray on Lizard skin or similar instead of the bedliner.

 

[BrickRunner]

Finished up the sound deadening this week. It is noticeably quieter around town, we'll see how it does on the freeway.

 

[BrickRunner]

Last weekend we took a drive up to Gaviota, Solvang and then back down to Santa Barbara over the 154. The backside of the 154 is a long grade. Coolant temperature went past the middle mark almost into the red. I pulled off the road, let it idle and the temperature dropped slowly at first, and then off a cliff once I set the idle to 1500 rpm. Once we made it to the top we headed east on Camino Cielo and then down into Santa Barbara for some ice cream. No other issues on the cruise.

It usually gets warm on long grades, but not that warm. Hmmm...

 

[BrickRunner]

After a few days, some reading and thinking I popped the hood to see what the trouble could be since I'd already overhauled the cooling system. There were sizable gaps between the radiator and the core support, and some smaller gaps between the radiator and the shroud. Not ideal for maintaining high pressure in front of the radiator. So, I added some foam tape to fill the gaps.

I imagine there was some there many many years ago?...

 

[BrickRunner]

This got me thinking about how I could improve the efficiency of the cooling system, since I am dumping more heat into it than originally intended via the water cooled turbo.

It gets hot under load at speed when the fan isn't doing a whole lot, as opposed to stop and go traffic or crawling over rocks, so I don't think electric fans are the solution in this particular case. It also cools down reasonably quickly when the load and speed are reduce/removed.

The 12HT has the same cooling setup (I think?), but it doesn't have the water cooled turbo, and it's DI instead of IDI, so it puts the heat into the pistons and oil instead of the cylinder head and coolant. Maybe I'll add 12HT oil squirters to my spare block, but that's a long way off...

One thought would be to plumb the turbo into its own water cooling circuit with it's own heat exchanger, pump and fan. I've got plenty of real estate on the front porch, but that adds complexity.

The radiator has a space in front of it that acts as a ducting to 'hold' the high pressure air (now anyway with the foam tape), but the AC condenser in front of it does not. So, when incoming air passes through the grill, some of it will pass through the AC condenser to the radiator, but much of it will go around it every which way it can. Air is lazy I've often read.

Adding ducting should force more air through both the condenser and radiator, keeping the coolant and possibly AC cooler.
It's also low cost/risk.

Not the final product:

Another thought would be to add these relief flaps seen on many electric fan shrouds, but I have yet to come across anyone using them with a mechanical fan.

 

[BrickRunner]

Yesterday I took the cruiser up and down the Conejo grade several times on my lunch break to test out the addition of the foam tape (but not the cardboard!) Coolant temperature went past half way but stayed away from the scary zone. This was maintaining a max EGT of 600 C and the AC on full blast. If I keep the EGT's below 500 C by downshifting and slowing I can keep the coolant temperatures from rising past halfway.

I finished the aluminum prototype for the front shroud and will repeat the climb up Conejo again tomorrow and see if there is any improvement. If it works, I'll finish it off by filling the gaps with foil tape.

 

[BrickRunner]

Back up the Conejo grade on Friday. Cruising on the freeway, EGT's seemed 25 C cooler, maybe placebo effect. But going up the grade, temperatures climbed more slowly and downshifting was later! I'll call this a win. A more scientific approach would have to picked a specific RPM and gear, instead of pegging EGT's at 600C.

Anyway, I added some foil tape to fill all of the gaps so it should be even better now.
In the future, I may come up with something more elegant, but this will work for now.

And since I had the grill off I finally got around to doing this very important detail:

 

[GLTHFJ60]

25c from just that stuff in front of the core support?! No way. You increased the surface area by what, 10%?

 

[BrickRunner]

25c from just that stuff in front of the core support?! No way. You increased the surface area by what, 10%?

Like I said, it could be placebo, as I haven't been writing down EGT's at specific speeds and gears, etc. More just mental notes. It is curious that it appears to be reducing EGT's as well as coolant temps, but I guess that makes sense.

I actually reduced the frontal area, as the cross section of the front of the duct is smaller than the cross section of the radiator. If I had more nose to work with I would have made it even smaller. It's more about holding the incoming air in front of the radiator to maintain the high pressure area. If it is more scoop-like and larger than the radiator cross section, the air tends to 'bounce' out the sides. If you look at radiator ducting on some race cars and sports cars you will see the air entrance is much smaller than the radiator (1/3 to 1/2 the size).

This book has a good section on radiator flow. Modifying the Aerodynamics of Your Road Car (SpeedPro) - https://www.goodreads.com/book/show/39089242-modifying-the-aerodynamics-of-your-road-car

 

[GLTHFJ60]

I'm familiar with race cars to a point, I have a p-car addiction that rivals my land cruiser addiction. I'm just skeptical/surprised that your small duct modification changed the EGTs by 25c. It's not a huge delta, but it's not bad if it's real.

 

[BrickRunner]

I should also note that the EGT delta isn't across the board, it's only at cruising speeds on flat ground (60 mph is where most of my mental data is). I might be able to cruise at a higher speed now without the temps rising, but I need a longer road with less traffic to test that!

 

[BrickRunner]

I've been trying to de-clutter, but some things you just can't say no to...
Which results in more clutter!

I don't think the winch cover actually helped, it probably made it worse; the winch is much rustier than mine was and we actually had to cut the u-joint spider to get the winch off the truck, and then use a puller to pull the yoke off of the driveshaft. The gearbox turns, but the spool lock is stuck in the unlocked position.

The good news is the chrome filler panels don't have superfluous holes drilled in them like mine so I can swap those over to Harumi.

I also decided to replace the fan clutch for good measure and I'm glad I did. While the old one seemed only slightly less stiff than the new one, it looks like it might have been for something else? The new Aisin one is a whole pound heavier (4# vs 3#), is chunkier and has less fin surface area. The old one says 'MADE IN JAPAN' but has no other markings.