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-   -   RV-14 Engine choice (https://vansairforce.net/community/showthread.php?t=98748)

Kyle Boatright 05-24-2014 07:48 PM

Quote:

Originally Posted by propsync (Post 882502)
Any idea why so much heavier?

Diesels run at far higher compression ratios than gasoline engines and the firing impulse is much more violent. This drives a need for beefier components, which weigh more.

Mike H 05-25-2014 12:30 PM

In addition to the reciprocating assembly weighing more due to the stresses of higher compression ratio and torque, the combustion pressures are much higher than gas engines and this requires a much stronger cylinder head and cylinder walls to contain the pressures. Light duty Diesel engines such as the Mercedes and Volkswagen aluminum block engines weigh roughly twice what a similar sized gas engine weighs. Light industrial application diesels such as the Cummins 6B series weigh three to four times of a similar displacement size gas engine.

Wolf 01-04-2015 11:23 AM

Quote:

Originally Posted by Aerosporty (Post 763421)
The Superior XP 400 makes 205 HP on auto gas. If you get the high compression version it is 215, but Avgas only.

I was just on the XP website and they say auto fuel is prohibited in the XP-400. They also only list a 415 HP version. If you are correct with auto gas currently at $2 a gallon and avgas still over $6 a gallon, sign me up for the XP-400. On the XP engine portion of the website they say XP engines are certified for auto gas and they don't make an exception for the XP-400 as the Home page does. Has anyone talked to Superior about this and have a definitive answer?

Relentless 01-05-2015 06:33 PM

R409 Efii is the perfect Rv14 engine
 
Although my R409 is 45lbs lighter than 390 or 400 put two alternators instead of two backup batteries and you will have an engine that was designed to run as low as 90 octane fuel. Ethanol? NO problem new chamber in AX50 cylinder running at 17 degrees advance, will eat it up!

If you want to see how sweet this engine runs come to San Luis Obispo KSBP and we'll go fly my RV8 with R409 and 91 pump gas all you want.:D

Price is still a bit higher but hey, 230 hp and over 40lbs lighter than a Lycoming 390 or Superior 400 doesn't come for nothing! Price with Dual Efii fuel and ignition R409 $47,850.00.

@ $2.oo per gallon savings over 2400 hours @10 gph, just paid for the entire engine?..:cool: Did I mention 230hp!!!



Tomcat RV4 01-06-2015 08:54 AM

Unfortunately IMHO mogas with 10% alcohol is what is going to be used to save GA. Any special fuel will not be cost effective in future,with various EPA and transportation issues. Tomcatrv4

kamikaze 01-06-2015 11:30 AM

How picky would the aiframe be in terms of where the weight goes?

I mean, if I put an R409 in, and want to make up some weight, does the position matter a whole lot?

Can you hang weights in strategic locations to make up enough weight for example? A second battery could give you 15-20 pounds, but obviously the mass isn't centered in the middle of your engine ...

Relentless 01-07-2015 07:33 AM

R409, Angle 409, 91 auto fuel form local shell?
 
Quote:

Originally Posted by kamikaze (Post 947844)
How picky would the aiframe be in terms of where the weight goes?

I mean, if I put an R409 in, and want to make up some weight, does the position matter a whole lot?

Can you hang weights in strategic locations to make up enough weight for example? A second battery could give you 15-20 pounds, but obviously the mass isn't centered in the middle of your engine ...

Yes it matters, but in my experience adding weight is far easier that removing. Until the first RV14 is completed we won't know exactly the flexibility we will have on the engine. My R409 weighs 285lbs compared to 331lbs for lycoming 390 we tested in the same configuration. (btw, the 390 only made 205hp on the same dyno we saw 234hp on my R409) I have only the rear 20 amp alternator so the first thing I would add would be the 40mp alternator up front. This 12 lbs right behind the prop maybe all that is needed to keep cg well forward. Build a nice cooling plenum instead of the rubber baffles and I cannot imagine you wouldn't be right there.

Keep in mind that if the RV14 MUST have a 330lb engine to make it work we can still kick Lycoming and Superiors arrrrssses with angle valve cylinders and the same beefed up 409 lower end. Yep, 230+hp:D, but lets start with 285lbs and all the benefits of AX50 technology first.

I hadn't actually flow the latest version of the AX50 cylinders and optimized pistons with 91 auto fuel so yesterday I climbed up to 6k and stabilized at 24' and 2400rpm on left tank full of 100ll and then switched over to right tank with 91 auto fuel from local Shell. Just as we saw on the dyno the only noticeable change was a slight increase in cht's, 6-8 degrees. This made sense since the lower octane fuel has more btu's. I increase the EFii mixture 3% and everything stabilized back to original temps.

I never lost one knot of airspeed………offer is still available to come fly this monster with me anytime until I sell her.:cool:

rvbuilder2002 01-07-2015 08:34 AM

Quote:

Originally Posted by kamikaze (Post 947844)
How picky would the aiframe be in terms of where the weight goes?

I mean, if I put an R409 in, and want to make up some weight, does the position matter a whole lot?

Can you hang weights in strategic locations to make up enough weight for example? A second battery could give you 15-20 pounds, but obviously the mass isn't centered in the middle of your engine ...

It is nothing more than a basic weight & balance calculation.
If you reduce the arm distance by 1/2, you need to double the weight value

If you install an engine that is 35 lbs lighter than recommended, you have to make some level of adjustment if you want to have the same handling and baggage utility that the prototype RV-14 has.

If we assume that the engine weight reduction is centered on the engines CG (about 36 " fwd of the wing leading edge), then you would have to add about 70 lbs, centered on the firewall battery location (about 18 " fwd of the wing leading edge) to get the empty C.G. back to being similar to what it would be with the recommended engine.

N941WR 01-07-2015 09:02 AM

Sounds like a four bladed metal CS prop is called for to help with the CG and to absorb all the extra power. ;)

kamikaze 01-07-2015 01:52 PM

Certainly sounds like less weight further forward would be easier than more weight further back ... not sure I'D want 70 pounds hanging on my firewall!

A heavier propeller, alternator(s), a front mounted governor maybe (I'm no expert I'm this stage, just guessing).

Opens up options at least ... But I'm not sure I could afford an R409 :P By thew time I get around to it, the R410 will be out anyways!


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