RV-7 180hp vs 200 hp

[Schwemmer]

I have searched for and have not found any information pertaining to the difference between 180 hp and 200 hp powered RV 7's. The Vans website performance specifications show a 7 mph difference. So the real question is;

is it worth the higher upfront cost, and the higher fuel usage, of the 200 hp over the 180 hp powered aircraft?

Rick

 

[Mark Burns]

Fuel burn not a real factor

Dan Checkoway said that when he flew his 200HP RV alongside RV's with 180 hp on trips he would use a little less fuel than them. If I recall correctly.

It's not just the upfront cost. Cylinder repairs or replacement will be more expensive also.

I personally wouldn't do it. If I had plenty of $$$ I might.

Mark

 

[Jerry Cochran]

Cost/Weight

I think I've heard on this forum that the 200HP Angle Valve engine is not only more $$ but 35# heavier... Toss on a CS Prop then you have serious weight up front... I think many just tweak the 180 hp Parallel Valve engine and get 200HP anyway... My stock 8.5/1 IO-360 Superior that I sold to Dale Walter was 186-188 hp on the dyno IIRC...

Go to 9/1 pistons and ypu're prob right at 200 HP...


.

 

[roee]

Fuel options

I think I've heard on this forum that the 200HP Angle Valve engine is not only more $$ but 35# heavier... Toss on a CS Prop then you have serious weight up front... I think many just tweak the 180 hp Parallel Valve engine and get 200HP anyway... My stock 8.5/1 IO-360 Superior that I sold to Dale Walter was 186-188 hp on the dyno IIRC...

Go to 9/1 pistons and ypu're prob right at 200 HP...

Actually, one of the other disadvantages of the 200 HP angle valve IO-360 is that it really requires 100 octane fuel. Same goes for a parallel valve 360 tweaked for extra power using higher compression pistons. This precludes the use of auto gas, as well as some of the proposed replacements for 100LL, which may disappear in the next few years due to political and economic pressures.

The stock 8.5:1 compression parallel valve IO-360 on the other hand will happily operate on most of these fuels. I consider that a major advantage, looking a few years into the future.

BTW, one high-powered variant I am aware of that can still use lower octane fuel is Aerosport's IO-375. Low compression, longer stroke, 195 HP. If you really need that extra power but don't want to limit yourself with fuel availability, this may be a good option.

 

[PIN 37]

Aerosport's IO-375. Low compression, longer stroke, 195 HP.

Yeah, wish I had looked at this option when I bought my engine, but my options were complicated by the fact that I originally chose a FADEC engine (since removed). Mate of mine has the IO-375 engine in his DR9 and it is awesome.

 

[rzbill]

W&B concerns for angle valve.

I have recently done the W&B on a 180 HP (-M1B) CS outfitted RV7A with unadorned cockpit. The aerodynamic W&B window is fine. I would have to do some wierd out of spec loading to bust the W&B envelope.

HOWEVER, nose wheel weight is another matter. If I am solo with full fuel (the worst case loading), I will be @ 365lb on the nose. This is still under Vans specified max of 375 but I don't like it that close. Baggage helps tremendously so I will have a big toolkit

Anyway, the point is that an angle valve will be worse unless other equipment is intentially mounted towards the tail to act as counterweight.

 

[C-FAH Q]

Angle valve

I have the angle valve in my tail dragging 7. It has 8.7:1 pistons, I have never had a weight and balance issue, but that may be different with the nose wheel version. I remember looking at the empty weights of all the 7's listed on Dan Checkoways site when I weighed mine. With the angle valve and the two blade hartzell blended airfoil, my plane came in at 1099 lbs. I would hardly classify that's heavy. I love the performance often 200hp, but the reason I have this is because I was able to purchase this zero timed engine for $21,600. I could not pass a deal like that. If I had to buy an engine again, it would most certainly be dependent on finances and costs of engines at the time, but would buy as much HP as I could. No one can make a better decision with your money but you, buy what you want, build the plane that you want and you will be happy. I know I was.

 

[DanH]

Actually, one of the other disadvantages of the 200 HP angle valve IO-360 is that it really requires 100 octane fuel.

I have no evidence, but disagree anyway

Seriously. can you tell us why you think so? Real detonation data is hard to get.

 

[Sig600]

I have no evidence, but disagree anyway

Seriously. can you tell us why you think so? Real detonation data is hard to get.

I cruised around Google looking for anything that correlates MOGAS STC's to the actual compression ratio of the engine and came up with zilch. The determining factor for each STC seems to be the installation and fuel system specifics.

The only thing I can find about compression ratios is that higer horsepower motors need higher octane. If there's a cut off of say 8.7:1 where mogas can no longer be used, I can't find it written anywhere.


http://www.autofuelstc.com/autofuelstc/pa/Information.html

Installation of an auto fuel STC on a low compression 80/87 octane engine is an uncomplicated procedure. No major modifications are needed on this type of engine. We provide you with the paperwork and placards required by the FAA to make it all legal. An IA mechanic must "install" the STC by adding the new fuel placards and an engine placard. He then fills out a log book entry and form 337. The whole process takes approximately 30 minutes. No additional modification is required on this type of engine.

The same holds true generally for the higher compression Lycoming 0-360 and 0-320 engines depending upon the airframe in which they are installed. Generally speaking when these engines are mounted in an airframe equipped with a gravity feed fuel system (no fuel pumps), installation of the STC's consists only of paperwork and placards, with no modifications made. Some people then reason why buy an STC if it's only paperwork and placards. Installing the STC makes it possible for you to use an octane different than what was called for on the original Type Certificate while remaining in compliance with FAA regulations. Insurance companies expect you to be in compliance with the FAR's and we are able to contact you if we become aware of any changes in the fuel which could effect your airplane. Using auto fuel without an STC puts one in violation of FAR's: Part 43, App. A (2) (vi), 43.3 (a), 43.12.

In some airframes equipped with suction lift fuel systems (pump fed systems), different electric fuel pumps may need to be installed to insure adequate fuel flow, and/or the fuel pump locations must be moved. The STC for the PA-28-160, -161, -180, -181 requires the removal of the factory installed electric pump. This pump is replaced with two completely different pumps and a revised fuel system forward of the firewall. Installation on this airplane takes between four and six hours, approximately double that on 24 volt PA-28's. Click here for more info on the Piper PA-28, -160 thru -181

 

[MikeR]

Not enough difference in horsepower to worry

When independent testers reviewed the Mooney M20C (O-360 180hp) and Mooney M20E (IO-360, 200hp) for the same year model, they came up with a scant 7 horsepower difference, not the 20 horsepower advertised.

With the extra expense, extra weight of the IO series, hot starting problems and "technical" inablility to run MOGAS in the IO, I'd stick with the straight O-360. With a moderate increase in compression (9:1), a good job of flow balancing and an aftermarket throttle body injection system, you'll have as much power as an IO-360 with less cost, less weight and no concerns running MOGAS if you want.

......just my $.02

 

[Scott DellAngelo]

I would make a compression decision based on fuel I buy today not what might happen someday.........even in airplane engines pistons are cheap and very easy to change. Put what you want in now and when the fuel problems actually happen spend a few hours and change them.

 

[Jerry Cochran]

Option: 92-93 ethanol -free mogas

http://pure-gas.org/

Right now one can buy this stuff for $4.15/gal around here, including S30. Worked like a dream last time I used it, no issues. Tried it in one tank first and switching showed not a whit of diff in EGT/CHT/MAP IO-360 & Harzell

IMHO, YMMV

 

[RV7ator]

If you're debating, buy the horsepower and you won't be disappointed, especially for climb.

First off, avoid the angle valve engines; big bucks and heavy. Then, yes, it's worth it because that additional 20hp is relatively low priced on a parallel. Don't buy a box-stock Lyc, they're doggy compared to custom engines which are easily tricked. Check with Aero Sport or LyCon.

Consider port/polish, electronic ignition, what's known as the "old part number" cam. With that LyCon gets 200hp. I'm flying one now in a -7 and it flies like 200hp. I've owned and flown other -7s, one an ECi 360 with the 9.2:1 pistons/EI/cam and it flew like 200hp. A 375 with 9:1/EI/cam/rollers was strongest of the bunch (cubes, cubes, cubes!), a tad faster, slightly better climb; what else would you expect? All had carbs, all ~8gph at 9-10K altitude cruise behind a CS.

Compression and 100LL: Stop worrying. All the above were happy on 91 mogas. 9:1 seems the cutoff (ask ASP). Don't base your decision on what might happen to 100 availability. Nobody knows. It's also a good argument for a CS. Max MP @ 2700 is less likely to detonate if that's your worry than max MP grunting behind a 2200 rpm FP on the roll.

John Siebold

 

[roee]

I have no evidence, but disagree anyway

Seriously. can you tell us why you think so? Real detonation data is hard to get.

I haven't seen any hard data myself, but I've been so advised by two different highly reputable engine builders. Not ideal, admittedly still anecdotal. But barring solid evidence to the contrary, that's the most credible recommendation I have to go on.

 

[CDRDATA]

detonation in cruise???

Seems to me the most vulnerable time for detonation is climb, i.e. high MP. While its nice to avoid obstacles and at least reach pattern altitude, do you HAVE to do it at Vx? At some airports, yes. At most, no. So, if you have a low compression engine and no need to push MP which risks detonation, you could plan for gentle departure and use cheaper gas with a cheaper engine that uses cheaper parts and is lighter. Also, running excessively low RPM stresses the engine and risks detonation with low octane. So, X-country and watching sunsets shouldn't be cause for alarm. This is 100% theory on my part, so feel free with rebuttals.

Also, I haven't asked my insurance agent, but if you are over 200 HP then its a high-performance engine with required endorsement and probably higher premium, though I don't know how much.

My point is that while we all like performance (after all its a Van's), you can get to cruise without heavy acceleration. The excess power is there when you need it, but carries risks. I think with sufficient planning you can make the choice whether mogas fits your situation.