The modification (reduction) of my radiator inlet duct area from a total

48 square inches to 33 square inches is dedicated to Rusty (for obivious
reasons {:>))  Sorry, just couldn't help myself, Rusty,  - the devil made

do it.

Ok folks, made the first flight today with my reduced/reshaped radiator
> inlet for the left evaporator core.  The right evaporator core was left
> unmodified to  provide a safety net sufficient to do the pattern and

if
> take off temps exceeded expectations.  Fortunately, that was not
necessary.
> OAT on first take off was a humid 85 degrees.  No temperature increased
> noted during ground run up, so launched and made max rate of climb, not
> seeing any abnormal temp increase I left the pattern and continue Max

> climb to 4500 MSL.  Max temp of coolant during climb was 210F (normal

> max rate climb at these OAT temps is 205F), Max oil temp was 200F

> for max power climb. Max temps were reached about 2/3 of the way through
the
> climb.
>
> In level flight, my coolant temperatures normally run 5 degrees colder
than
> my oil temp.  Today my coolant and oil temps were the same.  So average
> coolant temp was increased by 5 Degrees F.  Total radiator inlet duct

> was decreased from 48 square inches to 33 square inches.  24 Square

> for the right inlet duct and 9 square inch inlet for the modified right
> duct (See attached photo for comparision). Probably some drag benefit,

did not try to investigate that
> aspect.
>
> I flew to an airfield 50 miles away to have my transponder recertified

> when I launched out of it, the OAT (ground level) was 92F
>
> After level off I ran at different power settings to see the effect.
>
>  5800 rpm burning 11.9  GPH at 4500  MSL with OAT at 78F My oil and
coolant
> were both 190F.
>
> 5400 rpm burning 9.6 GPH at 4500 MSL with OAT 80F My Oil and coolant

> both 185F
>
> 5200 (Around my normal cruise rpm)  burning 7.25 GPH at 4500 MSL with

80F My
> oil and coolant were both  180F
>
> In summary, the 33 % reduction in total  radiator inlet area appeared to
> have increased coolant temps by an average of 5 Deg above the normal

> old duct).  It could be that both the remaining radiator and perhaps the
oil
> cooler are rejecting any additonal load with no problem.
>
> It appears that smoothing out the path for the air from inlet to

> surface has benefited the cooling situation.  It could be that

> heat may be rejected by the right (second in series) radiator as the
coolant
> it received from the left radiator was probably now a bit hotter. I also
> observed that the plate of the PSRU covers an area 3 " in from top to
bottom
> of the rear of each radiator and the plate is only 2" from the rear of

> fins at its closest, so that is obviously not helping flow, the Ross

> housing did not, so a bell housing might improve flow conditions .
>
>  I strongly suspect I would probably  find that a similar  reduction of
the
> right radiator inlet duct to 9 square inches  would see my coolant (and
> probably oil) temps increase considerable more than another 5 F.

OAT at  ground level was 94F when I landed, so not the hottest of days,

not the
> type I normally prefer to fly in.
>
> >From what I have seen so far, I think it worth pursuing a reduction

the
> right radiator duct.  I will probably not reduce it as much for the

> mentioned above. With some other things to take care of, probably won't
get
> to it until later part of Sept at the earliest.  But, I have no problem
> flying with current asymmetrical ducts, so will leave it as is for the
time
> being and collect some more data.
>
> It it appears that some cooling benefit is derived from providing a
smoother
> transition from duct to radiator (even if far from a perfect
implementation
> of the K&M approach) than my old duct provided.  The volume of the duct
was reduced by at least 60%, so while hard to tell from photos the white
"filler" material actually fills most of the duct.
>
> Oh, yes, as an aside, its been 25 hours since I replaced the spark plugs
and
> right on schedule - on the way back, I got the first SAG (Sparkplug
> Attention Getter)  indication.  So it appears 25 hours on 100LL about

> average time for replacing plugs in my case.  I finally got a spark plug
> cleaner, so need to clean a set (as the electrods do not appear worn)

> see if getting the lead off the ceramic  cone helps any.
>
> Best Regards
>
> Ed Anderson

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

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