R

rv72004

Well Known Member
I am about to order an rv8 and cant decide about the engine.
There are just so many pros and cons.
XP360 180hp or XP400 220hp ???? It seems the weight difference between them is 2lbs to 22lbs depending on model, and as Superior isnt specific this makes it difficult. The RV8 also has a FWD CofG im told so a heavier engine is not a good thing. But all that extra performance!!! Im sure 40hp will be noticable . Kinda between a Rocket and a 8.

Has anyone flown both?? HELP!!
 
Heavier Engine Compensation

EJ,

For an RV-8/8A application, you can mostly compensate for the heavier weight of the 220 hp (angle-valve) engine by: (1) going with a composite prop (the Whirlwind 200RV prop is 18 pounds lighter than the typical metal Hartzell and can handle up to 250hp) and (2) going with a dual electronic ignition, eliminating 10 to 12 pounds of heavy, and less reliable, mags from the engine. After adding back a dedicated backup battery for the dual electronic ignition and considering the weights of the individual electronic ignition components, the overall weight savings is not much, (on the order of a couple of pounds or less), but electronic ignition does have the effect of effectively shifting the engine weight aft which is a very good thing from a moment perspective. Only the crank sensor(s) and coils must be mounted on the engine itself.

The main downside of the heavier engine is additional cost for the engine itself and compensating mods (composite prop and electronic ignition). Also, for an RV application, the main benefit of the more powerful engine is some additional climb rate (see Van's performance numbers). You don't get a lot of additional top cruise speed (just a few knots, if that) due to the aerodynamics of Van's airfoil. Also, even if you employ a lighter prop and dual electronic ignition, the RV empty weight will still be a few pounds heavier (on the order of 5 pounds) than the same RV with the 180hp/Hartzell combo.

In my opinion, the 180hp parallel-valve engine with a Hartzell prop is the best-value engine combo for the RV-8/8A. It's a lot less expensive and provides nearly the same performance as the heavier 200hp+ angle-valve engines. As noted before, the top cruise speed hardly changes. With the 200hp+ engine, you pay "through the nose!" for the additional climb rate!

In my case, I happen to be installing a 200hp+ angle-valve Lycoming in my RV-8A simply because I got a deal I couldn't refuse on one (110 hours since new and in great condition for less than $10K - - don't ask me how I managed this - - it's too long a story!). In other words, I can afford the composite prop and dual electronic ignition because I got such a good deal on the 200hp+ angle-valve engine itself. If I were buying a new engine/prop combo from scratch for an RV-8/8A, I would definitely purchase the 180hp/Hartzell combo.

Well, anyway, this is my "2 cents" opinion as a contribution to your engine deliberations!

Best Regards,

Bill Palmer :rolleyes:
RV-8A Still In-Work!
Chino Hills, CA
 
I pretty much agree with everything Bill said.

Don't know for sure if it could be a problem, but the XP400 is a tad wider than the other angle valve choices...by about an inch. The RV-8 cowl is already kinda tight along one side with an angle valve 360 or 390. Anybody stuffed a 400 in an RV-8 cowl yet?

The 390 with a BA Hartzell is a surveyed, no question, no restrictions combination, and most folks believe the Hartzell wins the thrust test. I don't know if a propeller vibration survey has been done on the 400/BA combo yet. It was a factor in my choice; although I cheerfully fly a lot of experiments, I want this particular airplane to be as non-experimental as I can make it. The mission is super-reliable cross country with my wife.

I believe it when folks tell me the best RV-8 "flying feel" combo is a light parallel valve 180 horse with a light prop. It is also less expensive.

Always a lot of talk about top speed, but like fast cars, we rarely use it. I wanted climb rate far more than anything else; with trees in the windshield I don't care how much fuel it burns. Cruise fuel burn is pretty much the same for all engine choices, assuming an equal HP setting. At 22/2200 LOP the 390 only burns about 7.6 gph. Low compression means reformulated fuel or auto gas will never be a problem.

All things considered, for me the choices were a stock parallel valve 360 (180hp) or the IO-390 (210hp), both with a non-restricted, vibration surveyed propeller. Had I been on a tighter budget I would have gone the 180hp route. I bought a Barrett IO-390 for the climb performance. Same dimensions as an angle valve 360, so I know it will fit. The only trick will be cooling for sustained climb, and I think a big oil cooler will get that done. I won't use a prop extension, as I need to keep the heavy Hartzell as rearward as possible.
 
XP400 in an 8

Hey No. 1. The answer to your question is no. Waiting for Superior to get production units to the market. Should be getting close. Last we heard the XP400 would be available from the engine shops like us and Aerosport, but that could change.
 
Bill Palmer said:
EJ,

For an RV-8/8A application, you can mostly compensate for the heavier weight of the 220 hp (angle-valve) engine by: (1) going with a composite prop (the Whirlwind 200RV prop is 18 pounds lighter than the typical metal Hartzell and can handle up to 250hp) and (2) going with a dual electronic ignition, eliminating 10 to 12 pounds of heavy, and less reliable, mags from the engine. After adding back a dedicated backup battery for the dual electronic ignition and considering the weights of the individual electronic ignition components, the overall weight savings is not much, (on the order of a couple of pounds or less), but electronic ignition does have the effect of effectively shifting the engine weight aft which is a very good thing from a moment perspective. Only the crank sensor(s) and coils must be mounted on the engine itself.
Click to expand...
YES and NO.

Put in a pair of P/E-mags and you save that 10 to 12 lbs but don't have to add in the extra battery and wiring. BTW, the P/E-mags weigh in at a little more than 3 lbs each. (I have no idea how much mags weigh.)
 
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P/E Mags

Bill,

Two Bendix mags weigh between 10 and 12 pounds total, depending on the particular model. The ones on my engine weighed a little less than 6 pounds each (about 11.5 pounds total). If P/E mags weigh a little more than 3 pounds each (6+ pounds total), that saves between 4 and 6 pounds of engine weight compared with Bendix mags. 6+ pounds of P/E mags are still attached at the engine's mag mounts, though.

In the case of dual electronic ignition, only the crank sensor(s) and coils (2 to 3 pounds total) are mounted on the engine itself, saving around 8 to 9 pounds of engine weight. The remainder of the dual electronic ignition (two control boxes/wiring at about a pound each and a dedicated backup battery at about 4 pounds) are mounted behind the engine which shifts the moment aft. To compensate for a heavier engine AND maintain the great RV control feel, the goal would be to reduce engine weight AND shift the moment aft. The dual electronic ignition clearly does this best although it weighs, including a dedicated backup battery, about 2 to 3 pounds more overall than a P/E mag system. The 4-pound backup battery can be placed as far aft as the builder likes to tailor/improve the moment calculations and, thus, RV control feel.

Granted, P/E mags are preferable from an engine weight standpoint compared to the original mags, and they also save 2 to 3 pounds of overall aircraft weight versus the complete dual electronic ignition system. On the other hand, a P/E-mag-equipped engine remains 3 to 4 pounds heavier than one equipped with dual electronic ignition, and the aircraft's moment calculations are better with a dual electronic ignition system. Also, based on reading the various P/E mag threads, the jury still appears to be out regarding the operational stability and long-term reliability of the P/E mag system.

In terms of trying to maintain the great RV control feel with a heavier engine, I still think that a composite prop combined with a dual electronic ignition is the best compensating configuration, but a composite prop combined with P/E mags is certainly another option as you have pointed out.

Again, this is all just my personal opinion ("2 cents!").

Best Regards,

Bill Palmer :rolleyes:
 
Sorry for the thread highjack, but I'm thinking P-mag + electronic ignition (Plasma II?) so that I don't have to carry a back-up battery. This should be the lightest combination, perhaps?

I am thinking that a double independant system failure is probably less likely than a base engine failure in terms of precipitating a forced landing

What am I missing in terms of redundancy and failure modes. Has anyone done this already?

Andrew

(RV-8 in various boxes around the world)
 
Bill Palmer said:
In the case of dual electronic ignition, only the crank sensor(s) and coils (2 to 3 pounds total) are mounted on the engine itself, saving around 8 to 9 pounds of engine weight. The remainder of the dual electronic ignition (two control boxes/wiring at about a pound each and a dedicated backup battery at about 4 pounds) are mounted behind the engine which shifts the moment aft. To compensate for a heavier engine AND maintain the great RV control feel, the goal would be to reduce engine weight AND shift the moment aft. The dual electronic ignition clearly does this best although it weighs, including a dedicated backup battery, about 2 to 3 pounds more overall than a P/E mag system. The 4-pound backup battery can be placed as far aft as the builder likes to tailor/improve the moment calculations and, thus, RV control feel.
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Here is where I disagree. Since the P-Mags don't require that extra battery, battery cables, relays, etc. You not only reduce total weight but complexity as well. Once you figure in all that extra 'stuff', you might exceed the weight of a traditional magneto.

Bill Palmer said:
Granted, P/E mags are preferable from an engine weight standpoint compared to the original mags, and they also save 2 to 3 pounds of overall aircraft weight versus the complete dual electronic ignition system. On the other hand, a P/E-mag-equipped engine remains 3 to 4 pounds heavier than one equipped with dual electronic ignition, and the aircraft's moment calculations are better with a dual electronic ignition system. Also, based on reading the various P/E mag threads, the jury still appears to be out regarding the operational stability and long-term reliability of the P/E mag system.
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??? How is a P/E-mag equipped engine 3 to 4 pounds heavier than one equipped with duel electronic ignition after you add the battery and other 'stuff'?

As for the operational stability, those issues have been resolved with the latest software update. Notice how quiet the P-mag thread has been. There is a reason for that. Not only that but the new P-mag 114 can tell you if you have a fouled plug or a broken plug wire. Check their web site for details: http://www.emagair.com/Series 114.htm

As for long-term reliability, how many people do you know who have had magnetos fail, or better yet, other electronic ignitions fail? I suspect the E/P-mags will be comparable.

Bill Palmer said:
Again, this is all just my personal opinion ("2 cents!").
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Same here. These debates will never end and I hope they don't as they keep us all thinking about options.

Andrew said:
I am thinking that a double independent system failure is probably less likely than a base engine failure in terms of precipitating a forced landing

What am I missing in terms of redundancy and failure modes. Has anyone done this already?
Click to expand...
Andrew,

I think this has been done but why? The E/P-mags are independent of each other and should one fail, the other will continue to work. Any failure issues you have could strike the Plasma II and/or the E/P-mag. Should one loose it's timing you will need to figure out which one has gone Tango Uniform and fix it. BTW, the lost timing issues the E/P-mags suffered has been resolved.
 
A Moment of Clarification!

Bill,

To Clarify (Not to Argue or Disagree!):

The reason a P/E-mag-equipped ENGINE is heavier than a dual-electronic-ignition-equipped ENGINE is that the P/E mags add 6+ pounds TO THE ENGINE, and the dual ignition crank sensor(s) plus the coils only add 2 to 3 pounds TO THE ENGINE.

The weight of a complete dual electronic ignition system, without a backup battery, is between 4 and 6 pounds = 2 to 3 pounds for control/ignition boxes (and associated wiring) installed IN THE AIRCRAFT's FUSELAGE plus 2 to 3 pounds for the crank sensor(s) and coils installed ON THE ENGINE. A dedicated backup battery adds another 4 pounds IN THE AIRCRAFT's FUSELAGE. In other words, the weight of a complete dual electronic ignition system, including a backup battery, is 6 to 7 pounds installed IN THE AIRCRAFT's FUSELAGE plus 2 to 3 pounds installed ON THE ENGINE = 8 to 10 pounds total contributed TO THE AIRCRAFT's EMPTY WEIGHT. Yes, in terms of AIRCRAFT EMPTY WEIGHT, a dual electronic ignition system, including a 4-pound backup battery, only saves maybe 1 or 2 pounds over a Bendix-mag-equipped aircraft (if that!) and weighs about 2 to 3 pounds more than a dual P/E mag system.

AIRCRAFT WEIGHT & BALANCE (MOMENT) is another story, though. The real "PLUS" for a dual electronic ignition system is that most of its components are distributed in the fuselage instead of bolted to the heavier, angle-valve engine. 2 to 3 pounds of control/ignition boxes and wiring are installed in the fuselage BEHIND THE ENGINE which is a positive contribution in terms of balancing a heavier engine. More importantly, the builder can locate the 4-pound backup battery ANYWHERE ALONG THE LENGTH OF THE FUSELAGE to tailor/improve the aircraft's moment and, thus, balance the heavier engine.

With a dual electronic ignition system, the builder can tailor the moment contribution for the heavy engine+dual electronic ignition system+composite prop combination to match, or nearly match, the equivalent moment contribution of a dual-mag-equipped 180hp/Hartzell engine. In this way, an RV's control feel with a heavier, angle-valve engine can match, or nearly match, that of an RV with a dual-mag-equipped 180hp/Hartzell engine which is generally accepted by the RV community as the "ideal" combo for an RV-8/8A, right? On the other hand, maybe a dual-P/E-mag-equipped 180hp/Hartzell combo is even better in terms of control feel? (I don't know!)

Note: The backup battery "cables" are only No. 18 wire. Each control/ignition box draws less than 1.5 amps continuous (less than 3 amps total). The backup battery is only a 5AH battery. In other words, the weight of the dual electronic ignition's wiring, including the backup battery "cables," is fairly small; on the order of half a pound, if that.

Well, anyway, in terms of compensating for a heavier, angle-valve engine and maintaining the great RV control "feel," it still seems like a dual electronic ignition system is the best ignition option, at least at this point in time. Of course, the weight savings and moment improvement associated with a lightweight composite propeller are even more important. Compared to the P/E mag option, the dual electronic ignition system is heavier and more complex in terms of installation, but that's also its main advantage in terms of compensating weight & balance for a heavier, angle-valve engine.

Again, it's all just my "2 cents," and that's about what it's worth! (. . . just trying to help a fellow builder!)

Best Regards,

Bill Palmer :rolleyes:
 
Bill Palmer said:
Bill,

To Clarify (Not to Argue or Disagree!):

...

Again, it's all just my "2 cents," and that's about what it's worth! (. . . just trying to help a fellow builder!)

Best Regards,

Bill Palmer :rolleyes:
Click to expand...
Bill,

I agree with each point, even the last one about helping a fellow builder.

Your comment about moving the weight of options to improve handling is more important than some people appreciate. It is also the reason I put my strobe power supply and ELT under the baggage compartment floor and my plane isn't even an acro bird.
 
Dan,

I'm wanting to check out the IO-390 engine application for an RV-7. Are you flying your 390 yet? Do you know anyone else flying the 390 I could ask about performance?

Thanks,

Hank Avent
 
havent said:
Dan,

I'm wanting to check out the IO-390 engine application for an RV-7. Are you flying your 390 yet? Do you know anyone else flying the 390 I could ask about performance?

Thanks,

Hank Avent
Click to expand...

Sorry, I'm not done building yet. Email Rhonda and she can connect you with some flying 390 owners: [email protected]
 
RV-7 with IO-390

The link posted above has two contacts for you. Travis Hamblin and Marc Ausman (Vertical Power) both of whome participate on this list. Here is a recent email from Bill Gill regarding his first flight the weekend before last.

Ross Schlotthauer (SD) was the first to put our 390 in a -7, but he has since sold the airplane. Also, Jean-Louis Tricoire in France ([email protected]).

Hope this is helpful to you.

-----Original Message-----
From: Gill, Bill [mailto:[email protected]]
Sent: Tuesday, November 06, 2007 9:48 AM
To: BPA
Subject: RV-7 IO-390 first flight

Hello Allen & Rhonda,

I have not had any over-heating issues with the 390 after four hours ? running 24? X 2500 as you suggested. The highest oil temp was 209 degrees which occurred during a steep/aggressive climb to 5500 feet. I have leaned to get CHT?s up to around 380 degrees which yields EGT?s in the mid-1300.

This thing can really climb. I can rotate to about a 45 degree pitch attitude and maintain a 3000 ft/min @ 90 knots (indicated, but I have an airspeed error). Shortly after I landed, a Varieze pilot approached me and asked, ?Wholly ****, what the **** do you have in that thing?, as he witnessed the takeoff. I was over 2500 above the runway before I got to the other end of the 4000 feet runway! Did I say this thing can climb?

Did I say it?s fast? The 180 hp chase plane could not keep up and I was only at 24 X 2500. I flew to Ottawa Sunday afternoon at 4500 feet and returned at 5500 feet. My ground speeds were 158 knots going out and 220 knots coming back. Did I say this thing is fast? At these speeds, it will be hard to keep paint from sliding off...ha ha. ****, I lost the paint already.

Allen, no major squawks ? I think I have the mixture and idle zeroed in (won?t know for sure until next flight). I adjusted the high rpm stop set screw on the governor in an attempt to prevent operation above redline. Aero Technologies said that each turn results in about a 25 rpm change. I was able to get 5 complete turns which should get me real close to 2700 rpm. I also have the common heavy left wing, but will look into that later (when it?s raining/snowing and can?t fly).
 
<<I can rotate to about a 45 degree pitch attitude and maintain a 3000 ft/min ......2500 above the runway before I got to the other end of the 4000 feet runway! >>

Ooooo baby, yes, yes, YESSSSSSSSSS!
 
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