Page 1 of 1

Radiator Ducting

Posted: 19 Dec 2017, 11:15
by Midlana1
I had marginal cooling issues with Kimini and tried extra hard to do things right on Midlana. I'm happy with the exit-side radiator ducting; the inlet side is dictated by nose cone shape, which leaves one unresolved issue: I never sealed off the radiator so that air couldn't go around it. Midlana has never overheated, but it has an habit of running warm* (high 80s) on the freeway. Since freeway driving only requires enough power to maintain speed, and has relatively unimpeded airflow in that situation, I expected it to run toward the cool side, but it doesn't. Another situation (one which may be entirely normal) is when driving up a twisty road at low engine speed (<4000 rpm). The latest tune seems to have made this worse because the engine makes so much torque that it's not as necessary to use higher engine speed (with its correspondingly higher water pump speed). The tune also runs the AFR a bit leaner, so combustion will be warmer by some amount. Also, I'd been running E85 just because I could, but with the recent tune, I just don't need another 50-100 hp more, so have been running pump gas. E85's cooling properties were no doubt producing a lower coolant temperature *by some amount* but who knows how much.

Anyway, it's just a matter of fabricating a flange and foam or rubber material serving as a gasket. It isn't hard, except someone - me - put the horn ahead of the radiator on a bracket that "reaches around" the radiator. As a result, the horn gets in the way if a gasket is attached to the nose when the nose is opened or shut. An alternative is to have the gasket attached to the radiator instead, so that it doesn't move, but I'll have to see how much space there is around the horn. I suspect it's going to have to be relocated to behind the radiator.

*I admit I didn't know what "warm" or "hot" is with a Honda K-series. I looked up the thermostat and it lists 78 degrees C. I don't know if that's fully open or just when it starts to open.

Re: Radiator Ducting

Posted: 20 Dec 2017, 10:01
by ShadowCat38
I'll start with, "I don't know normal for Honda, either," but this doesn't seem excessive.

every 4 cylinder engine I've driven (Suzuki, Chevrolet, Ford, etc.) always seemed to run hotter than their bigger bretheren. I've always worked in °F for engines, so the 80s in Celsius comes out to between 176°F and 192°F.

I've always had a 180°F thermostat, and my chevrolet engine with a heat clutch fan would even out at 205°F. I upgraded to an electric fan, and it dropped to right where that thermostat was rated.

My Suzuki engine stabilized right at 192°F summer or winter. Always had an electric fan.

My ford engine is all over the place, operating between 176°F and 209°F for reasons God MIGHT understand, but it never boils and performance doesn't seem to change. That one might be tied to vacuum issues.

All that said, these are naturally aspirated. I really don't know how adding a turbo to the equation would change things, but I hope I've added some data points.

Re: Radiator Ducting

Posted: 20 Dec 2017, 13:19
by Midlana1
Good to know. Street cars are always a mystery because while they have temperature gauges, mid-span could be just about any temperature.

Snooping around the Interwebz, "normal" for a Honda K-series seems to be 80-90C (182-195 F), so I guess I'm okay. I'll still add the radiator baffling because that way the radiator's providing maximum cooling and provides a bit of a buffer when running in hot conditions. Plus, there's just knowing that it was done right and is operating at maximum efficiency.

Re: Radiator Ducting

Posted: 21 Dec 2017, 00:34
by ChrisS
90 is normal for an early Ford Zetec, also for the admittedly ancient design Alfa V6 I’m using. For a modern engine like the Honda, I’d say 80 was overcooled?

Certainly can’t argue with the desire to do the entry ducting and make it right though.

Re: Radiator Ducting

Posted: 21 Dec 2017, 20:22
by ShadowCat38
ChrisS wrote:...Certainly can’t argue with the desire to do the entry ducting and make it right though.
I'll drink to that. If it's worth doing at all, it's worth doing right.