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  #31  
Old 10-04-2022, 08:54 PM
Thebert Thebert is offline
 
Join Date: Sep 2021
Location: Canada
Posts: 19
Default

Quote:
Originally Posted by Tim 8-A View Post
Ive owned both, the 360 flies lighter to the touch and has better glide, but its hard to argue these #s in cruise.
Whats cruise like at a more average power like 65/75% ?
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  #32  
Old 10-05-2022, 12:00 PM
KGT KGT is offline
 
Join Date: Feb 2018
Location: Rosemount MN
Posts: 33
Default I definitely said it!

Quote:
Originally Posted by rv8ch View Post
To steal Paul's quote with a slight modification:

"I wish I had more weight on the nose!" ...said no RV-8 pilot, ever!
I have an RV8 which I originally built with a Lycoming 0-360 with a Catto 3 blade fixed pitch prop. The CG was so far aft if I put say a 230 LB passenger in back I would add 30 LBS to the fwd baggage compartment. If going x-country heavily loaded I couldn't put much at all in the aft baggage compartment.

I replaced the Lycoming and Catto prop with a BPE IO-360 200HP angle valve engine along with a Hartzell constant speed composite prop. This resulted in a very forward CG which is great for fully loaded X-C putting the CG right in the middle of the envelope. I can cruise 190 knots rich of peak but burning more fuel obviously than lean of peak (I'm usually in a hurry). I do add 25 LBS to aft baggage solo.

It's all about the mission! I don't do a lot of ACRO so I'm not concerned about heavy stick forces. Pro's: I can be heavily loaded in both baggage compartments and go really fast with incredible take off performance.
Con's: I have to add weight aft for solo flights and with heavier stick forces. I probably burn more fuel than most but even that I'm ok with to go fast.

One size doesn't fit all it is mission dependent in my opinion. I would 100% go with the angle valve if I were to build again because it fits my mission. If I were really into ACRO I would probably go parallel valve.
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  #33  
Old 10-05-2022, 12:44 PM
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Tim 8-A Tim 8-A is offline
 
Join Date: Mar 2009
Location: Colleyville
Posts: 318
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Quote:
Originally Posted by Thebert View Post
Whats cruise like at a more average power like 65/75% ?
65% power 165 knots 8.5 gph
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Tim Blake
Colleyville, Tx
RV8a Purchased flying (many changes) Sold
RV-10 Purchased flying.. Panel upgrade complete.
G3X/Dynon/TT all new interior. Flyin like a dream. Sold
RV8a Purchased flying Let the changes begin
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  #34  
Old 10-05-2022, 01:54 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 3,943
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Quote:
Originally Posted by Thebert View Post
Whats cruise like at a more average power like 65/75% ?
Standard I want to get there but not blow too much gas cruise.

IO-360-M1B with AFP FM-150C, standard 74 Hartzell BA prop.
Carl
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  #35  
Old 10-05-2022, 03:50 PM
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DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 11,086
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Quote:
Originally Posted by Carl Froehlich View Post
Standard I want to get there but not blow too much gas cruise.

IO-360-M1B with AFP FM-150C, standard 74 Hartzell BA prop.
Carl
Carl, perfect! Provides a very close cruise comparison with an early 210 HP 390; same prop, both 66% power and ~0.4 BSFC (0.404 vs 0.398).

The math to predict speed based on the 390's extra HP is...

180 x .66 = 118.8
210 x .66 = 138.6
176 knots x ( 138.6 / 118.8 )^1/3 = 185 knots

...and here I'm showing 187 with Ms Patti on board and a bit more gas. The addition is in the scatter, or reflects less drag due to the fastback and a closed cooling outlet, depending on viewpoint.
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  #36  
Old 10-05-2022, 04:43 PM
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Laird Laird is offline
 
Join Date: Feb 2007
Location: SoCal
Posts: 203
Default Manifold Pressure

Carl,

What air inlet system are you running to get 22.3" at 9000'? Ram air of some sort, or the cowl inlet intake with a snorkle? I'm curious.

I know Dan has a pretty well documented filtered ram air system (nicely designed and tested), and you seem to be matching (or beating) his MP.

My poor O-360/carburetored RV-6 can't get anywhere neat that pressure that high.

Laird

Last edited by Laird : 10-05-2022 at 07:38 PM.
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  #37  
Old 10-05-2022, 06:46 PM
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Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 3,943
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Quote:
Originally Posted by Laird View Post
Carl,

What air inlet system are you running to get 22.3" at 9000'? Ram air of some sort, or the cowl inlet intake with a snorkle? I'm curious.

I know Dan has a pretty well documented filtered ram air system (nicely designed and tested), and you seem to be matching his MP.

My poor O-360/carburetored RV-6 can't get anywhere neat that pressure that high.

Laird
This is the stock snorkel but using the AFP FM-150C. At some point Ill modify the snorkel following the lead of what was done on the RV-14 with the shift over to the IO-390-EXP119. They got a nice bump in MP from this mod. Im using the FM-150C and not the FM-200 like the EXP-119 uses so I suspect Ill not get as much gain.

For vertical intake I enjoyed good MP on my old RV-10. I had a straight in shot from the engine air intake on the James Cowl, but modified the filtered air box to accept the taller K&N E-1000 filter. The mod was simply to flip the FAB top over to have the edge go over the sides of the fiberglass. This provided the extra height for the taller filter.

The new RV-10 project will have cold air sump horizontal injection and Ill be using a new filter box that Jimmy at James Cowl is working on.

Carl
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  #38  
Old 10-05-2022, 08:50 PM
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DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 11,086
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Quote:
Originally Posted by Carl Froehlich View Post
This is the stock snorkel but using the AFP FM-150C.
Carl, might want to check that MP indication.

Run the numbers. At 9000 ft, 176 KTAS, and 54 OAT, pressure is 21.39" Hg and available dynamic pressure (q) is 1.07 Hg.

Can't get 100% conversion of dynamic pressure in an open-ended system. The ballpark is more like 75%, thus q applied to increasing MP would be roughly 0.8" Hg, not the full 1.07".

Next consider manifold pressure loss due to flow through filter, fiberglass snorkel, the FM150, and the intake tract between the throttle and the cylinder head. How much is the loss? My airbox has a larger filter, no duct, and no entry bend. The smaller throat of the FM150 results in 6" H2O more loss than an FM200. The M1B and the 390 have the same horizontal intake sump. Having measured my total intake loss at three altitudes, I'd estimate your 9000 ft loss at about 15" H20, a bit more than 1" Hg.

So, 21.4 + 0.8, less 1 = 21.2", more or less. 22.3 is unlikely.
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  #39  
Old 10-05-2022, 10:02 PM
RV8JD RV8JD is offline
 
Join Date: Jan 2005
Posts: 647
Default

Awhile back Dan saw that my MAP was also reading high. I did the ground calibration (several times on different days) and adjusted it in the Dynon menu:
Ended up adjusting it down by 0.5" Hg:

Below is a screenshot from my RV-8 with the Lycoming YIO-360-M1B, Avstar FI, LSE Plasma III & Slick mag, and Hartzell 72" BA prop. Note that the IAS reads about 4 MPH high, so this is about 200 MPH TAS/173.8 KTAS. Similar conditions as Carl's above, and similar performance.
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Last edited by RV8JD : 10-06-2022 at 10:42 PM.
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  #40  
Old 10-06-2022, 08:00 PM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
Posts: 903
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Quote:
Originally Posted by rv8ch View Post
To steal Paul's quote with a slight modification:

"I wish I had more weight on the nose!" ...said no RV-8 pilot, ever!
Quote:
Originally Posted by Lucmac View Post
Count me as one of those guys that built an 8 with an angle valve IO-360A1B6 that would re-build with a parallel valve, non-counterweighted crankshaft (but still with fuel injection) if I could do it over again. It was a plus when doing cross country with a person and full luggage. But I mostly flew solo and it was a negative for me when doing acro. Heavier stick forces than I like pulling through the bottom of maneuvers.
Would seem that an 8 with one of the new Whirlwind 300 series would be a nice match; 3 blades but only ~35 lbs IIRC. The performance reports here have been impressive. 20 some odd pounds off of that station would be pretty dramatic per what's been stated here. Depending on mission of course, would seem a great match for IO390 powered 8. Anybody?
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