M20j 201 top speed

[larrynimmo]

Yesterday tried for too speed of my plane at 1,000’ msl...100 hour engine, fully waxed plane full throttle, full forward prop, full rich and I had a true airspeed of 165k with an equivalent mph of 190. Fuel burn at 18 gph

weight at about 2,350...

with the old engine, not waxed top airspeed had been 161k.

[orionflt]

what was your true airspeed?

[Bryan]

Try you speed test at higher altitudes with less drag.  Also, what you are measuring speed with?  4-direction GPS, or TAS computer?

Most of our birds achieved top speed at the max altitude.  Your bird, in ideal conditions, should be 201mph.  Mine: 252mph, but that was at FL280 or near.

[Jeff_S]

To the OP, I would say that there are still one or two things you could try to increase that.  You could try leaning a smidge to get slightly more power at 1,000' MSL. Also, did you have your vents closed? That's a racing technique that helps reduce drag and may give you a knot or so.  And are you sure your gear doors and flaps are rigged for maximum drag reduction?

As to gaining altitude, Bryan's advice would work for a turbo but not for us NA guys. The performance charts clearly show that TAS will decrease even with full power as altitude increases.  Byron's racing techniques included things (as I recall) that take you close to the edge of the certification envelope, like advancing the mag timing, etc.  Probably not something  you want to mess with unless you're really trying eke out those knots.

But from what I recall of my J-model, the OP is doing pretty well compared to the absolute book values...which as we all know are just for marketing!

[rbridges]

remove your antennas and paint flames on the sides.  I guarantee 200mph.

[Oldguy]

While it does not make as much of a difference as it does in the F, opening your ram air will boost MP a bit. I get about a 2 kt. bump with mine. That would put you even closer to "book" (i.e. marketing) numbers.

[Bryan]

  On 5/2/2019 at 12:56 PM, Jeff_S said:

As to gaining altitude, Bryan's advice would work for a turbo but not for us NA guys. The performance charts clearly show that TAS will decrease even with full power as altitude increases.

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You are correct. I have been flying a turbo for too long, it would be hard for me to come back.

[jaylw314]

  On 5/2/2019 at 11:23 AM, larrynimmo said:

Yesterday tried for too speed of my plane at 1,000’ msl...100 hour engine, fully waxed plane full throttle, full forward prop, full rich and I had a true airspeed of 165k with an equivalent mph of 190. Fuel burn at 18 gph

weight at about 2,350...

with the old engine, not waxed top airspeed had been 161k.

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Try leaning for best power   That would be a little scary, even if they say the IO-360 has a large detonation margin

[gsxrpilot]

  On 5/2/2019 at 12:56 PM, Jeff_S said:

As to gaining altitude, Bryan's advice would work for a turbo but not for us NA guys. The performance charts clearly show that TAS will decrease even with full power as altitude increases.

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While it's true that NA engines loose HP with altitude, there is still a sweet spot where the ratio is optimal. My understanding is that that is somewhere around 8000 ft for the J? 

I've never been to FL280 to try for 252 mph in my K but I've seen 238 mph at FL260.

*all figures in TAS

[Hank]

My C will indicate just above 165 mph wide open at 1500 msl, about 1200' agl around here. Book values are 171 at SL and 174 mphT at 2500 when solo with full tanks [2200 lb].

[aviatoreb]

  On 5/2/2019 at 1:19 PM, rbridges said:

remove your antennas and paint flames on the sides.  I guarantee 200mph.

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Or you could just wear some 3d glasses.

[jaylw314]

  On 5/2/2019 at 4:40 PM, gsxrpilot said:

While it's true that NA engines loose HP with altitude, there is still a sweet spot where the ratio is optimal. My understanding is that that is somewhere around 8000 ft for the J? 

I've never been to FL280 to try for 252 mph in my K but I've seen 238 mph at FL260.

*all figures in TAS

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That's based on the assumption that your maximum sustained cruise power is something like 75% (like it is in the cruise power charts).  So if you keep 75%, your TAS increases as you go up.  There's an altitude where you can no longer make 75% which is around 7-8000' MSL, so that's your altitude for maximum cruise speed.

On the other hand, @larrynimmo was talking about speed at 100% power.  Your TAS will decrease as you climb since you can no longer make 100% power.

Edited May 2, 2019 by jaylw314

[Cruiser]

try putting pressure on the rudder petals and move the yaw slightly to one side and then the other while watching the airspeed. Give it time to react.

Many times the plane is not perfectly rigged and you can get a knot or two from the reduced friction.

This is also a good way to determine if your turn coordinator is aligned properly. 

[Niko182]

  On 5/2/2019 at 9:23 PM, jaylw314 said:

That's based on the assumption that your maximum sustained cruise power is something like 75% (like it is in the cruise power charts).  So if you keep 75%, your TAS increases as you go up.  There's an altitude where you can no longer make 75% which is around 7-8000' MSL, so that's your altitude for maximum cruise speed.

On the other hand, @larrynimmo was talking about speed at 100% power.  Your TAS will decrease as you climb since you can no longer make 100% power.

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For me I'm faster at 8500 WOT than I am at 1500 WOT. I see 182 Knots at 8500 burning 13 gallons LOP and 65% power. I see 180 knots burning 25GPH at 1000FT. I like the first option more.

[gsxrpilot]

  On 5/2/2019 at 9:23 PM, jaylw314 said:

That's based on the assumption that your maximum sustained cruise power is something like 75% (like it is in the cruise power charts).  So if you keep 75%, your TAS increases as you go up.  There's an altitude where you can no longer make 75% which is around 7-8000' MSL, so that's your altitude for maximum cruise speed.

On the other hand, @larrynimmo was talking about speed at 100% power.  Your TAS will decrease as you climb since you can no longer make 100% power.

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Maybe so, but I'm sure the best TAS I ever saw in my C was around 7000 or 8000 ft. I was WOT, 2500, leaned for best power. Those settings would give me a DMax verified, 152+ knots TAS. I assumed that there was something about it being the best compromise between less wind resistance and enough O2 for power.

[Cruiser]

  On 5/3/2019 at 12:05 AM, Niko182 said:

For me I'm faster at 8500 WOT than I am at 1500 WOT. I see 182 Knots at 8500 burning 13 gallons LOP and 65% power. I see 180 knots burning 25GPH at 1000FT. I like the first option more.

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what RPM are you using and how are you determining power?

[Niko182]

  On 5/3/2019 at 12:31 AM, Cruiser said:

what RPM are you using and how are you determining power?

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JPI 900. It calculates power LOP and ROP for me.
at 1500 ft i was at 2500RPM. at 8500Ft, 2450RPM.
If I went WOT ROP 50, at 8000 ft, 2700RPM, i'm sure
I could see 195knots or more burning probably around 19GPH.
ill give it a shot when I go to Catalina on Sunday and report back.

[jaylw314]

  On 5/3/2019 at 12:22 AM, gsxrpilot said:

Maybe so, but I'm sure the best TAS I ever saw in my C was around 7000 or 8000 ft. I was WOT, 2500, leaned for best power. Those settings would give me a DMax verified, 152+ knots TAS. I assumed that there was something about it being the best compromise between less wind resistance and enough O2 for power.

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You could have gone even faster if you were at 2700 RPM

Notice how each of the specific power settings increases with altitude, as expected.  Notice the "Full Throttle" line, however, increases with decreasing altitude.  It gets cut off where it meets the 75% power line (at 8000' MSL), but I expect that trend continues down through lower altitudes to where it would meet the (not displayed) 100% power point that can only be reached at sea level.

[Niko182]

  On 5/3/2019 at 12:39 AM, jaylw314 said:

You could have gone even faster if you were at 2700 RPM

Notice how each of the specific power settings increases with altitude, as expected.  Notice the "Full Throttle" line, however, increases with decreasing altitude.  It gets cut off where it meets the 75% power line (at 8000' MSL), but I expect that trend continues down through lower altitudes to where it would meet the (not displayed) 100% power point that can only be reached at sea level.

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I usually dont like using that much power. I have a theory that the engine has been working great since new because it only had 244 horsepower for the majority of its life. now that it got upgraded to 310hp, i either run it at 20.5in and 2450rpm rop at 15.7 GPH, or WOT 2450 LOP at 12.8 gallons, both doing 180+ knots. I dont like running how power. It equals more stress. The plane just got out of its first annual and all Cylinders where over 70+ which on a continental that has 1650 hours on it isnt seen too often.

[Cruiser]

  On 5/3/2019 at 12:32 AM, Niko182 said:

JPI 900. It calculates power LOP and ROP for me.
at 1500 ft i was at 2500RPM. at 8500Ft, 2450RPM.
If I went WOT ROP 50, at 8000 ft, 2700RPM, i'm sure
I could see 195knots or more burning probably around 19GPH.
ill give it a shot when I go to Catalina on Sunday and report back.

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240 HP or 310 HP 

two blade or three blade prop?

3200# or 3368# ?

actual weight during flight

[Niko182]

  On 5/3/2019 at 1:22 AM, Cruiser said:

240 HP or 310 HP 

two blade or three blade prop?

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3 blade thick prop 310hp

[MIm20c]

  On 5/3/2019 at 12:32 AM, Niko182 said:

JPI 900. It calculates power LOP and ROP for me.
at 1500 ft i was at 2500RPM. at 8500Ft, 2450RPM.
If I went WOT ROP 50, at 8000 ft, 2700RPM, i'm sure
I could see 195knots or more burning probably around 19GPH.
ill give it a shot when I go to Catalina on Sunday and report back.

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I’ll be looking forward to 3/4 way gps runs with your setup. After thousands of hours with a thick blade and hundreds with a thin blade setup I feel easily over 195 kts is a bit of a stretch but might be possible with one person and quarter tanks. 

[Niko182]

  On 5/3/2019 at 2:24 AM, MIm20c said:

I’ll be looking forward to 3/4 way gps runs with your setup. After thousands of hours with a thick blade and hundreds with a thin blade setup I feel easily over 195 kts is a bit of a stretch but might be possible with one person and quarter tanks. 

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How much speed difference did you notice going from the thick to the thin blade?

[MIm20c]

  On 5/3/2019 at 2:25 AM, Niko182 said:

How much speed difference did you notice going from the thick to the thin blade?

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3-5 kts depending on altitude and prop speed. I will say the paint durability on the thin edges is not nearly as good...

[Niko182]

  On 5/3/2019 at 2:29 AM, MIm20c said:

3-5 kts depending on altitude and prop speed. I will say the paint durability on the thin edges is not nearly as good...

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Okay. But anyhow. Ill be happy as long as i get above 190. Ill update sunday.