RV-7 max cruise speed

[Sylvainsting]

Hello,

On the Van's Aircraft performances table, RV7 with 200 hp fly 180 kt (207 mph) at 8500 ft 75% power, solo weight and 2 blade C/S prop.

I have a brand new RV7 with IO375 (195 HP) from Aerosport Power and WW 200RV prop ( 2 blade C/S).

At 8500 ft, 75% means full Throttle, but I cannot reach those performances, only a little 170 kt (195 mph). I precise I fly LOP ( FF 31l/h)

Is the Van's Aircraft performances table wrong or is it me ?

Is anybody with a similar configuration who reach better results ?

Take a look on the pic, screen shot test at 7500 ft.

In advance thank you
Sylvain



http://img4.hostingpics.net/pics/327...703841enUS.jpg

[AltonD]

What are your numbers ROP? I lose as much as ten knots going from ROP to LOP.

[BobTurner]

Look at your own gauges. They show 66% power, not 75%. Issue is the density altitude (over 9000') along with the LOP mixture (as opposed to best power mixture). IF you could up your power 13% to 75%, speed should increase about 4% getting you close to 180.

[bret]

Not flying yet but a question, if we bring the prop RPM up closer to 2700 will we be making more HP, or will the increase prop drag cancel this?

[BillL]

Adjust your knobs

mixture (richer), rpm (2600-2700), lower density altitude(7500-8000) and see what that yields. Report back.

Bret, it probably depends on the prop. Hydroguy reports best with 2600 on his 180 hp WW200 prop. I plan to explore this and document.

[RV8iator]

Like others have said, push everything up and your speed as well as your costs will go up proportionally. You'll get a little speed for a lot of money.

In my 8 I can cruise along at 176 KTAS at a realistic weight burning just under 10 gph or 165 KTAS on slightly nder 8 gph. That about 6 % slower on 20% less fuel. Depends on airframe straightness, weight, DA, CG, etc.

I guess it's fun to say you can cruise at 180KTAS, but it's expensive..

[Randy]

I have an RV7A with same IO-375 engine from Aerosport, mine has normal or low compression, nice new paint, clean looking airplane.

I also do not achieve Van's performance numbers and have been planning a project to find out why. At altitude, say 8,000', I routinely see 160 knots in cruise at ROP mixture settings and 2400 RPMs. If I go LOP, depending on how far lean I go, I will lose between 5 and 10 knots.

I can count on 150 knots @ 7.5 GPH running LOP at 8,000' and above. This gives me about 4 hrs endurance with decent reserves.

When I see reports of people getting up around 180 knots I can't help but think I must have something rigged improperly. This winter I hope to dig in and learn more about what is going on. At 195HP with a Whirlwind RV200 prop I think I should at least achieve Van's numbers for 180HP.

I look forward to any other reports and what others have found.

My airplane looks very clean as in there is nothing obvious as far as what would cause some lack of speed. I have heard that improper rigging of the wheel pants can cause considerable speed degradation so that is where I will start looking, but it would be great to learn from what others have found.

Randall from Sedona

[MikeyDale]

Not sure if mine is typical. I have IO360 with two Bendix mags, CS prop, 1123 empty weight. At 8,000' I can just reach 200 statute mph (TAS) with WOT/2670 RPM/best power fuel mixture, fairly cool air, no passengers. Cant remember what the fuel burn was but guessing between 9 and 10 gph. Basically, everything maxed out......I typically cruise 180 mph (157 kts)TAS at 2400 rpm, 30-50 deg LOP, burning about 8.2 GPH.

[dlloyd3]

As others said, full performance requires more power. Van's uses 75% at 8000' density altitude. That will take 2700 rpm and ROP mixture. Anything less gets less speed. You will also want to verify your actual speed. My Dynon calculated true airspeed is 3 knots slower than actual.

[brad walton]

Unless we are all talking apples to apples, it is difficult and misleading to compare performance. True air speed and density altitude are the only relevant numbers in my opinion.