speed

[Mike Coady]

I am contemplating the engine for my set up. I want cruise speed! I also think I will choose a fixed pitch Sensenich prop. Can some of you give me cruise speed figures you have for the O-320 160 hp engine and the O-360 180 hp engine. Is 190-200mph possible with either of these with a fixed pitch??

 

[Jeff Vaughan]

Speed

0-360 8000' WOT
Sensenich 72FM8S9-1-83
196 MPH
RV7A 1120 lbs

 

[frazitl]

I'm getting consistant 170-173 kts TAS

on my Superior IO360 180hp / with the cold air sump turning 2400rpm on a Hartzell BA prop. Seems no matter how high I go (up to 17.5 so far), the TAS hangs in there, but the fuel flow drops...

I've not done much optimizing of cooling air flow (probably on the high side now with extra outlets on a standard Vans cowl).

My personal opinion is that you can get between 190 and 200mph CRUISE speed with 180HP, but I'm not so sure about 160HP. The fixed pitch prop shouldn't make much difference if pitched properly. You will give up some climb performance, but with 1600 to 1700 fmp at GROSS wgt., you have some pitch options to work with...

Lots of smarter speed freaks here to listen to.

Best of luck...

 

[Mike Coady]

0-360 8000' WOT
Sensenich 72FM8S9-1-83
196 MPH
RV7A 1120 lbs

Thanks. The 180 would work great! Still waiting to hear about the 160. I gave a 160 in my warrior and I get a buck and a quarter out of it....hahha

 

[Mike Coady]

on my Superior IO360 180hp / with the cold air sump turning 2400rpm on a Hartzell BA prop. Seems no matter how high I go (up to 17.5 so far), the TAS hangs in there, but the fuel flow drops...

I've not done much optimizing of cooling air flow (probably on the high side now with extra outlets on a standard Vans cowl).

My personal opinion is that you can get between 190 and 200mph CRUISE speed with 180HP, but I'm not so sure about 160HP. The fixed pitch prop shouldn't make much difference if pitched properly. You will give up some climb performance, but with 1600 to 1700 fmp at GROSS wgt., you have some pitch options to work with...

Lots of smarter speed freaks here to listen to.

Best of luck...

Thanks. The 180 will work nicely as I figured. I will se what I hear about the 160. I have a warrior now with a 160 and I get a whole buck and a quarter out of it.

 

[hevansrv7a]

Some data points and a recommendation

My 7A with a Superior 180 HP (FI), James cowl, plenum and pants, Catto prop trues out (NTPS 3-way) at 174 kts at 8500' DA = 200 mph using best power mixture. For the sake of discussion, assume that's 75% = 135 BHP. Therefore a 160 HP would only produce 120 HP. With all factors except BHP equal, the lower HP would give me 192 mph. For the math behind this, see links under my signature.

I have reason to think that my actual BHP is higher, but the relationship between engines and TAS would be pretty much the same. Your airframe may be a little better or a little worse than mine, but this is a good prediction within those fuzz factors.

Note that if you decide to cruise at 160 kts, then either engine will perform approximately the same, even on fuel flow.

The big difference would be in climb. An extra 20 HP lifting a 1600# airframe would give you 20 * 33000 / 1600 = 400 feet per minute. If you are only producing 75% after losses for prop, angle of attack and density altitude then it's still 300 feet per minute extra. That's a big difference on short strips, high DA takeoffs, etc.

Since the 180 HP costs very little more, does not add complexity and weighs almost the same, the climb alone is worth it. IMHO.

 

[Mike Coady]

My 7A with a Superior 180 HP (FI), James cowl, plenum and pants, Catto prop trues out (NTPS 3-way) at 174 kts at 8500' DA = 200 mph using best power mixture. For the sake of discussion, assume that's 75% = 135 BHP. Therefore a 160 HP would only produce 120 HP. With all factors except BHP equal, the lower HP would give me 192 mph. For the math behind this, see links under my signature.

I have reason to think that my actual BHP is higher, but the relationship between engines and TAS would be pretty much the same. Your airframe may be a little better or a little worse than mine, but this is a good prediction within those fuzz factors.

Note that if you decide to cruise at 160 kts, then either engine will perform approximately the same, even on fuel flow.

The big difference would be in climb. An extra 20 HP lifting a 1600# airframe would give you 20 * 33000 / 1600 = 400 feet per minute. If you are only producing 75% after losses for prop, angle of attack and density altitude then it's still 300 feet per minute extra. That's a big difference on short strips, high DA takeoffs, etc.

Since the 180 HP costs very little more, does not add complexity and weighs almost the same, the climb alone is worth it. IMHO.

Thanks for the detailed explanation. My first inclination has been to use the 180hp. Last year I had heard from a few RV r's that said they were getting good speed from the 160. I will probably go with the 180hp. However, I am almost certainly going with the Sensenich fixed pitch prop. I have had very good luck with these props in the past and am looking for the trouble free low maintence of this type. Thanks again.

 

[vbpiper]

Speed

Mike,
I have the experimental Lycoming O-360 with roller tappets from Van's, with the Sensenich FP prop on my -7A.
I do not have the wheel pants or leg fairings installed yet, and I have been averaging 230 mph so far on about 4.5 gph. It may be worth noting, though, that I have not actually flown the plane yet. These numbers come strictly from the times I sit in the plane, turn off the lights in the hangar, fire up the panel, and dream. I suspect the actual performance numbers may be somewhat different when it is actually airborne.

 

[pierre smith]

Mike, paying close attention to fit and finish...

....goes a long way to top speed. If your canopy skirts and baffling are a really good, tight fit, you add speed....if your landing gear fairings are well aligned and the wheelpants as well...you gain speed. Keeping antennas hidden (Like the Archer wingtip) reduces drag. Building a well rigged, straight airplane will put you at, if not over, the 200 MPH mark.

FWIW, my 0-360 carbed -6A would true 203 MPH at 7500'/2750 RPM with a cruise-optimized three-bladed Catto.

Best,

 

[gclark]

Everything is a trade off. You give and you get. If you want speed go with the 180 hp 0-360. Better climb too, but you will use about 1.5 more gallons per hour. I have 7-A with 0-360 A1A new from Van's. Has about 150 hours now and have flown several long cross countries. I have come to expect
160 K on just over nine gallons per hour. Willl do a little better if you can get above 10,500 both on speed and economy.
Just keep building. You will not be dissapointed. Probably all the speed you want. Too much and you do not get to enjoy the flight as long!
Gclark

 

[hecilopter]

173 knots consistently

I took this screen shot at cruise a while ago because I routinely see this all the time. Density altitude 6770, 200 mph true, wide open throttle, leaned, 2300 RPM. If I push up to 2650 RPM I will see about 208-210 mph true. I burn about 8 gph at the 2300 rpm setting. 180 hp, carbureted, mags, Hartzell 74" blended airfoil. The true airspeed can be seen on the Dynon (mph). The GPS is in knots. 197 that day!

 

[Low Pass]

Mike,
I have the experimental Lycoming O-360 with roller tappets from Van's, with the Sensenich FP prop on my -7A.
I do not have the wheel pants or leg fairings installed yet, and I have been averaging 230 mph so far on about 4.5 gph. It may be worth noting, though, that I have not actually flown the plane yet. These numbers come strictly from the times I sit in the plane, turn off the lights in the hangar, fire up the panel, and dream. I suspect the actual performance numbers may be somewhat different when it is actually airborne.

230 at 4.5?! You got me...

Just another data point. I know I'm mixing models, but I like telling this story. I have a dirt-cheap (subsequently garage overhauled) 160-hp with CS prop on my -8. Gives me ~176-kts at sea level. That's about 1-2 *faster* than my buddies -6A with a brand new O-360 and a FP prop. And I jab him about it often!

If money's no option - go for displacement. Resale will be better too. But in my case, the deal on the engine was right for me.

 

[Christopher Murphy]

real world speeds

You should look at Bob Axsom's spread sheet of air racing results. That will give you an idea of what the differences are between the 2 engine dispacements. The 160hp RV-4s outpace the 180hp RV-4's. Looking at pictures of airspeed indicators and TAS readouts is pretty meaningless info.

ChrisM

 

[hecilopter]

Meaningless?

Looking at pictures of airspeed indicators and TAS readouts is pretty meaningless info.

ChrisM

Not sure why it is meaningless. Real world info for a 180 hp/Hartzell BA setup. It is very accurate in my installation and has been confirmed using the National Test Pilot spreadsheet and GPS data multiple times. NTPS here

 

[slyfox]

I only go by gps ground speed with known calm wind. I guess the only way to really know is a 4 point directional speed check. I'm so use to gps only at high speeds that my asi is worthless, only use it for landing and take off. I'm so good with the gps ground track that I can pick my winds when landing at an airfield without using the sock. with my configuration I can count on 168kts level flight gps at 3000msl. Io360 hartzell, electronic on one side and fuel injection leaned to peak. 27 map and 2400 rpm. have a nice day.

 

[videobobk]

I have a 160 hp 9A, so your speeds won't be all that much different. I cruised 187-188 with Slick mags, 192 with electronic ignition, all WOT at 8k'. Three blade Catto optimized for cruise. If you went with the SJ cowl, 190+ should be easy.

Bob Kelly

 

[Christopher Murphy]

not good comparison tools

Not sure why it is meaningless. Real world info for a 180 hp/Hartzell BA setup. It is very accurate in my installation and has been confirmed using the National Test Pilot spreadsheet and GPS data multiple times. NTPS here

Of course that info is meaningful when it comes to flying the aircraft but I don't think its the best way to compare performance. My point is that your system might be right on the money but the guy making a comparison to his airplane might have a huge error in his. Just not the best data for comparsion in my opinion.

ChrisM

 

[slyfox]

I have a 160 hp 9A, so your speeds won't be all that much different. I cruised 187-188 with Slick mags, 192 with electronic ignition, all WOT at 8k'. Three blade Catto optimized for cruise. If you went with the SJ cowl, 190+ should be easy.

Bob Kelly

but your 9A can't do a yank and bank like my 7A can and that's more important to me than speed.

 

[trg 854G]

Caution! Many of us like to round up.

 

[slyfox]

I have yet to fly along side another rv. I have flown next to a cessna, ah er ah, at least for a couple seconds anyway.

 

[alcladrv]

At WOT, the best TAS I've seen is 168 kts. on my -7A with a carbed ECI O-360 and Sensinich. Too much fuel flow for me. I usually look for about 2550-2600 rpm at 8-9000 ft. and lean for 8 gph or less. TAS then is about 155 kts.

Mike

 

[David-aviator]

I took this screen shot at cruise a while ago because I routinely see this all the time. Density altitude 6770, 200 mph true, wide open throttle, leaned, 2300 RPM. If I push up to 2650 RPM I will see about 208-210 mph true. I burn about 8 gph at the 2300 rpm setting. 180 hp, carbureted, mags, Hartzell 74" blended airfoil. The true airspeed can be seen on the Dynon (mph). The GPS is in knots. 197 that day!

Rusty,

How did you get the GPS 295 signal to work with the D10A?

I have the same panel arrangement with a Garmin 295 and tried every way to get its signal to work for the wind direction arrow but finally gave up as it appeared to be an incompatible format from the 295. I e-mailed Garmin tech help regarding the problem but they did not respond.

The D10A does work with most Garmin inputs but the 295 was not on the list.

Thanks. I'd really like to get the wind indicator to work.

dd

 

[hecilopter]

Garmin 295 settings

David, this worked for me...

Garmin 295

Make sure you have downloaded and installed the latest firmware for the 295 from here.

The Garmin 295 requires a power/data cable (Garmin Part Number 010-10082-00) to provide data output. The Garmin 295 must be configured to provide the correct output.

Press the MENU key twice. Use the rocker keypad to select the ‘INTERFACE’ tab.

Press the down portion of the rocker keypad to select the ‘FORMAT’ field.

Press ENTER and a popup window will show the available settings.
Use the rocker keypad to select ‘NMEA OUT’ then press ENTER. Select 4800 for the baud rate.

Make sure the D10A is setup on AUTO baud rate or 4800.

 

[David-aviator]

David, this worked for me...

Garmin 295

Make sure you have downloaded and installed the latest firmware for the 295 from here.

The Garmin 295 requires a power/data cable (Garmin Part Number 010-10082-00) to provide data output. The Garmin 295 must be configured to provide the correct output.

Press the MENU key twice. Use the rocker keypad to select the ?INTERFACE? tab.

Press the down portion of the rocker keypad to select the ?FORMAT? field.

Press ENTER and a popup window will show the available settings.
Use the rocker keypad to select ?NMEA OUT? then press ENTER. Select 4800 for the baud rate.

Make sure the D10A is setup on AUTO baud rate or 4800.

Thanks, Rusty. I already have it set up to provide NMEA OUT to the NavAid auto pilot and probably have to go back and select the rest of it and also get into the 295 to check the firm ware. I am hoping there is not a problem running the data parallel to 2 devices. We shall see.