Yes, ducting is a BIG factor. The better your ducts are the more you can reduce that 3ci / hp number. I'm closer to 2 ci / HP and it's working ok but did a lot of work on ducts. 3 is ' reasonable' because it is conservative without being almost impossible.
Tracy
Sent from my iPad Thomas, proper ducting can make a world of difference.
Bill Jepson
On Mar 9, 2012 8:40 PM, "Thomas Giddings" < n360tg@earthlink.net> wrote:
Hmmm.....If the 3 CI per HP is accurate then i guess I need to add a trailer to my Questair Venture project to get enough Radiator to cool the HP I was planning.
KIND REGARDS Thomas Giddings
On Mar 9, 2012, at 2:42 PM, Tracy wrote: Ah, I missed the detail of having 2 rads. It was the odd definition of "radiator surface area" that got me off track. Guess that means face area. If the designers of the P51 had used his formula, the rad core would have measured about 5 feet square and would not have fit in the airplane. But I do agree with his basic rule of thumb on rad core volume. 3 CI per HP is a reasonable target.
Tracy
On Fri, Mar 9, 2012 at 11:10 AM, Ernest Christley <echristley@att.net> wrote:
Tracy wrote:
> Sanity check:
>
> 1) Requirement: Radiator surface required is 1.5 sq in of surface area
> per cubic inch of the engine. For example: LS1 V8 Chevrolet = 350 cu in
> x 1.5 = 525 sq in of radiator surface area required. For this purpose,
> this applies only to the surface area of the radiator that the air flow
> first makes contact with.
>
>
> 2) Requirement: Minimum of 3.0 cu in of cooling volume per HP produced.
> For example: We only utilize up to 300 HP of an LS1 for aircraft use.
> Using a dual radiator configuration with two radiators measuring 15” x
> 18” x 2.25” thick = the total cooling volume is 1215 cu in.
> Therefore, our cooling volume to HP ratio: 1215 cu in cooling volume ÷
> 300 HP = 4.05 cu in per HP. With this formula, we have been able to
> maintain climb out temperatures of around 200°F and 190°F at cruise on
> a 100°F day. With a cooling system like this, we could taxi from Houston
> to Dallas with no overheating problems.
>
> Is it just me or is the math here bogus?
>
He's got dual radiators that add up to 540in^2 of surface and 1215in^3 of volume. The math is right.
What doesn't add up to me, is that he says you can get by with 3in^3/hp, but then demonstrates that 4in^3/hp is just
adequate on a reasonably hot day. I would not take issue with the math, just his definition of what constitutes "minimum".
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