smokyray(at)yahoo.com
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 Posted: Mon Jun 09, 2008 2:14 pm Post subject: Rocket-List Digest: 5 Msgs - 06/08/08 |
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Lee,
I don't know the (Harmon)Rocket cowl numbers but I will find out and get back with you. I have found that both my RV4 and Rocket have had about a 1.5 to 1 exit to inlet...
Yep, talked to Festus and he informed me of the Piet project...cool! BTW, I run one mag and one Rose EI, makes a big difference...
RR
--- On Mon, 6/9/08, Rocket-List Digest Server <rocket-list(at)matronics.com> wrote:
| Quote: | From: Rocket-List Digest Server <rocket-list(at)matronics.com>
Subject: Rocket-List Digest: 5 Msgs - 06/08/08
To: "Rocket-List Digest List" <rocket-list-digest(at)matronics.com>
Date: Monday, June 9, 2008, 1:57 AM
*
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Rocket-List Digest Archive
---
Total Messages Posted Sun 06/08/08: 5
----------------------------------------------------------
Today's Message Index:
----------------------
1. 03:59 AM - Re: CHT's and Fuel Flows (Rob Ray)
2. 06:28 AM - Re: CHT's and Fuel Flows (Lee
Logan)
3. 08:36 AM - Re: CHT's and Fuel Flows
(CalBru(at)aol.com)
4. 11:33 AM - Re: CHT's and Fuel Flows (Tom
Martin)
5. 04:22 PM - Re: CHT's and Fuel Flows (Lee
Logan)
________________________________ Message 1
_____________________________________
Time: 03:59:42 AM PST US
From: Rob Ray <smokyray(at)yahoo.com>
Subject: Re: CHT's and Fuel Flows
I have a 13 year old HR2 with the stock Harmon cowling and
a LyCon flowed 10.4:1
comp engine. Summer temps reached 400 CHT in extended
climbs with oilreaching
245.Cruise was 350-380 and 210 oil. I have read thatcowling
outlet area should
slightly exceed inlet area by 10%. I measured my HR2's
cowling and trimmed
6 inches off the bottom lip of the cowl.Now my CHT's at
altitude running at peak
range between310 and 348 with 180-190 oil temp. I have
experimented with LOP
and see 288-315 with oil at 170. During extended climbs in
90+ degree FL weather
I never exceed 380 CHT (oil has reached 230 butquickly
cools to below 190
when level).
Lycon frowns on LOP operations for the 10.4:1 comp engines,
but it cools all temps
another 20 degrees with a 5% FF reduction.
I have found even with my RV4 and 2 other Rockets I have
helped with that cowling
exit area needs to be opened up. My Dos Centavos...
Rob Ray
--- On Sat, 6/7/08, psiegel(at)fuse.net
<psiegel(at)fuse.net> wrote:
From: psiegel(at)fuse.net <psiegel(at)fuse.net>
Subject: CHT's and Fuel Flows
On one of my early cross country flights, I had to pull
back the rpm's a
bit when I noticed one of the CHT's was getting close
to my personal upper
limit of 400'.
Back home after pulling the cowl and plenum, I noticed that
some of the paint
on the cylinder heads had flaked partially blocking air
flow, particularly on
the hot cylinder head.
I took great care to completely clean out all the cooling
fins of any paint
flakes or casting flash and I was amazed to see a dramatic
drop in the formerly
hot CHT!
I am also amazed at how operating lean of peak in economy
cruise ( I NEVER run
LOP at high power settings) drops CHT's! Bart did a
nice job right from
his shop on my fuel flows to each cylinder...I sent my data
to GAMI and they
responded that my numbers were so close with the stock
injectors that there was
nothing they could do for me!
A good rule of thumb with the IO-540's is at full
power, take your fuel
flow in gph and multiply by 10 (add a zero at the end of
the fuel flow) and
that will give you a pretty good idea of the horsepower you
are getting. So
depending on compression ratio, it is normal to see takeoff
fuel flows at sea
level in the 26 to 29 gph range.
Paul Siegel Evo N4XU
________________________________ Message 2
_____________________________________
Time: 06:28:38 AM PST US
From: "Lee Logan" <leeloganster(at)gmail.com>
Subject: Re: CHT's and Fuel Flows
Rob: Do you know what the "official"
measurements are with a Rocket cowl?
What is the inlet area and standard outlet area with the
lower cowl trimmed
to the "factory" trim line? Did you end up with
something like a 1 to 1.1
ratio with your inlet/outlet?
P.S. Don't know if you know it or not, but Festus is
building both an RV-8
and a Pietenpohl!!
Thanks,
Lee...
On Sun, Jun 8, 2008 at 6:54 AM, Rob Ray
<smokyray(at)yahoo.com> wrote:
>
> I have a 13 year old HR2 with the stock Harmon cowling
and a LyCon flowed
> 10.4:1 comp engine. Summer temps reached 400 CHT in
extended climbs with
> oil reaching 245. Cruise was 350-380 and 210 oil. I
have read that cowling
> outlet area should slightly exceed inlet area by 10%.
I measured my HR2's
> cowling and trimmed 6 inches off the bottom lip of
the cowl. Now my CHT's
> at altitude running at peak range between 310 and 348
with 180-190 oil temp.
> I have experimented with LOP and see 288-315 with oil
at 170. During
> extended climbs in 90+ degree FL weather I never
exceed 380 CHT (oil has
> reached 230 but quickly cools to below 190 when
level).
> Lycon frowns on LOP operations for the 10.4:1 comp
engines, but it cools
> all temps another 20 degrees with a 5% FF reduction.
>
> I have found even with my RV4 and 2 other Rockets I
have helped with
> that cowling exit area needs to be opened up. My Dos
Centavos...
>
> Rob Ray
>
>
________________________________ Message 3
_____________________________________
Time: 08:36:02 AM PST US
From: CalBru(at)aol.com
Subject: Re: CHT's and Fuel Flows
Does the theory of a 10% larger exit area vs. cowl inlet
hold true for ships
with pressure plenums?
Thanks, Cal
F1
**************Get trade secrets for amazing burgers. Watch
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Tyler Florence" on AOL Food.
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________________________________ Message 4
_____________________________________
Time: 11:33:57 AM PST US
From: Tom Martin <fairlea(at)amtelecom.net>
Subject: RE: CHT's and Fuel Flows
Opening up the trailing edge of the cowling, or adding
louvers will lower
engine temperatures. I have confirmed this on a
observations that I have
made on my rockets. This allows more air to go through the
system. In my
experience this increased airflow is directly related to a
decrease in
airspeed. A three to four knot decrease in speed is what I
have found when
trimming back the lower cowling.
I was not satisfied with reduced airspeed and an article
in the
august 2003 sport aviation helped me to gain back the lost
speed and improve
cooling. The key to the system is in the inlets. Not so
much the actual
size but the internal shape. The inlets need a straight or
gradually
increasing diffusion zone and then a smooth transition to
the plenum. The
seals between the inlets and the plenum need to be as tight
as possible.
Although I have no personal experience with the round
cooling air inlets
they have two main advantages. Number one is that they are
usually located
further forward and this allows a longer smoother
transition zone. Secondly
it is quite a bit easier to seal the round inlets than it
is the rectangular
style. By improve my inlets I noticed an immediate
improvement in cooling.
The decrease in cylinder temperatures was to a degree that
I was able to not
only return the aft cowl opening to the original size but I
was able to
extend the aft ramp and close the opening from stock. The
lost speed has
been gained back, plus a little (maybe) but the engine now
runs where I want
it;330 to 380CHT depending on OAT and power settings. Oil
temps are in the
190 range.
The conclusion that I have come to with my experiments is
that there
is not much in the way of speed gains to be made with the
stock cowlings but
significant improvements in cooling are attainable. I
believe the stock
rocket cowlings are quite efficient. Some day I will try
some round inlets
just to see if there are any improvements to be had there.
I suspect that
if you have a good stock system then there probably is not
much to be
gained, but I would like to confirm that suspicion.
Currently my combined
inlet size is 37" and my outlet area is 48". I
do have a cowl flap but have
found that it is really only useful in the cold winter
months in keeping the
engine warm during descents. This is the second plane that
I have installed
a cowl flap on and both instances I could find no speed
benefits. (It looks
kinda cool, and that must be worth something!)
Tom Martin
C-GEVO The EVO 1, 230 hours
Checked by AVG.
AM
________________________________ Message 5
_____________________________________
Time: 04:22:17 PM PST US
From: "Lee Logan" <leeloganster(at)gmail.com>
Subject: Re: CHT's and Fuel Flows
Great info (as usual), Tom. Thanks for taking the time to
type that all
out!
Lee...
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