RV-8 oil cooler recommendation

Scott Hersha · #1 06-10-2009, 10:42 AM

I know this has been discussed before, but how about this specific question. I have the Van's FWF oil cooler II mounted on my baffle on my RV-8 (ECI Titan O-360 w/9.0 to 1 pistons). My oil temp is running a little hot - 200 to 210. My oil cooler is a Niagra. Jon Thocker has a SW 8432 and is running about 20 degrees cooler (CHT's also a bit cooler). We have the same FWF setup except for props - mine is a Whirlwind. Will I see a difference with a Stewart Warner cooler instead of what I have? Anybody have any experience with Positech? I want to keep it in the same location - no firewall mount and don't want to re-engineer a totally different setup, like a Setrab. Are other direcr replacement coolers more efficient than my cheap Niagra?

Thanks,
Scott
RV-8 Fastback

jthocker · #2 06-10-2009, 01:07 PM

Scott,
My cooler is the 8406R.

DanH · #3 06-10-2009, 02:17 PM

Scott,
Is this Vans "EA Oil Cooler II"?

http://www.niagaraairparts.com/20002...ifications.pdf

If so, compare with Jon's SW 8406.

@50 lbs/min oil flow, oil pressure drop across the cooler is about the same for both, 5.3 (20002a) vs 4.6 (8406) psi.

Assume 5" H2O across the baffles:

20002a: 25 lbs/min air flow, about 240 BTU/min

8406: 21 lbs/min air flow, about 280 BTU/min

Notes; the Niagara chart lacks detail, and it doesn't say what oil and air temperatures were used (unknown delta T). The SW chart doesn't have a 50 lbs/min oil curve, but it's not hard to pick an approximate.

Scott Hersha · #4 06-10-2009, 08:48 PM

It is an EA OIL COOLER II, which is a 20002A. It doesn't sound like the difference you mention (Dan) would make much of an improvement. Jon's temperature differences are a little more significant though. I guess the SW is just more efficient.

Scott

DanH · #5 06-11-2009, 12:50 PM

Scott,
Just for fun I pulled up a Positech chart. It plots the 20002A and the 8406R against Positech's 20002C (and an Aero 8000075, whatever that is), and does list delta T (125F).

Again using 5 inHg drop across the baffles (apples to apples), the air mass flow plots for Brand N and Brand SW correlate well with the previous post, with slightly more airflow for the Niagara 20002A. The plotted BTU/min values are slightly higher, but there is still a 40-45 BTU spread between the two.

The Positech airflow is 1/3 higher than the SW (31 vs 21 lbs/min). Right offhand that doesn't strike me as a good thing, but my reservation would be about speed, not cooling. It means an increase in total air mass through the cowl.

Positech does claim about 15 more BTU/min compared to the 8406R. They do not plot oil pressure drop.

About the same cooling on a lot less air? You know which I'd pick <g> Your installation being identical to Jon's (except for the prop) sets the stage for an interesting report after you switch.

APACHE 56 · #6 06-11-2009, 05:50 PM

has an article on this topic entitled "Cool Runnings." It can be found on page 41 along with a sidebar called "Let's Do the Math."

DanH · #7 06-16-2009, 01:15 PM

Quote:

an article on this topic entitled "Cool Runnings." It can be found on page 41 along with a sidebar called "Let's Do the Math."

A note about the math example. It suggests you'll need a cooler about twice the size found on RV's and most GA aircraft. In fairness the author calls it a worst case; 230F in, 190F out. I suspect he got drawn into the example values by information from an old Lycoming reference (third paragraph) stating "heat rejection will not exceed 750 BTU per minute". I was curious and emailed a Lycoming rep. The current will-not-exceed value for an angle valve 4-cyl is 475 BTU at 7 gal/min.

That said, has anyone here ever made a good measurement of cooler in, cooler out temperatures?