Are Speed Mods for Real?

[17031]

I purchased my Comanche (a '67 PA24-260) with the only mod being wing tips that the previous owner changed to help with landings. I don't know if it really makes a difference or not since I have not landed with the factory wing tips. The other mods I read about make some nice claims about speed increases that if true, could increase cruise speeds to 200mph or more which places it in up there with twins. Is there anyone out there that can say they are seeing those kinds of cruise speeds (around 200mph) with these mods?
(Currently my Comanche cruises routinely over 180mph and frequently approaches 190mph {TAS} even at over 10k msl, confirmed with my gps. Is this normal?)

[N3322G]

Nah, you are just a superior pilot ...

Actually, based on 260's I've seen race, I'm not surprised at the performance you see. Some are just faster than others. Obviously you keep yours in good condition from an engine perspective and it is in good rig. Way to go - always happy to hear about good flying Comanches.

[Zach Grant L1011jock]

Speed mods work...but they are not additive. It is a percentage game. Reduce a more significant percentage of drag and you will get a larger gain. First thing to do is to get your speed as fast as you can go with stock airframe, make sure it is rig, no stupid antennas/mountings, clean aircraft, smooth paint, properly rigged landing gear, good baffling and cowling seals. It sounds like you are running pretty well right now. You can always do a quick TAS check with your gps. Fly a big circle at no more than 15 degrees bank. Note the heading and the highest and lowest groundspeeds. You can stop there and just average the high and low and you will be close to your TAS, but if you want to be more accurate, fly directly upwind for 5 miles, and then directly downwind (lowest GS heading, and highest GS heading respectively from the circle) and do this several times and average the data. Many of the Airspeed indicators are a bit off these days, as are the thermometers to get OAT at altitude so it may be a bit of scientific sluthery to get the real speed of the plane.

With all that said, once all that is done, then check out the speed mods. Depending on your average flight length, the best speed mod may be more fuel. Cutting out a stop will cut your block time by about 45 minutes or more. Next, put hubcaps on your plane if you don't have any. Add the Lopresti Speed Spats and Slipper. Add K2U gap seals for the flaps and Ailierons. If you have a 3 bld prop, add the wing root fairings. All of that will get you another 5mph top end, but it will get you more if you slow down your indicated airspeed. Where the speed mods shine are mostly at high altitude where the IAS is lower, and TAS is higher, and the percentage gain is greatest. That is the efficiency gain.
-Zach

[Tony Scarpelli]

Early 260's and 250's can benefit by having the brakes moved to the other side and allowing the gear to go higher into the wing. Or put the single tine forks on with that switched brakes. I have heard this is good for 2-5 knots.

What have you heard about rigging the alerons and flaps to -1 or 1.5 degrees? Cost nothing and is supposed to increase speed a bit.

[N8632Y]

the discussion on speed mods has slowed up some
Funny, for a while, i put most of the mods on, but still flew at peak, limiting my airspeed.
Lately, I've ran at 75 ROP on the leanest cylinder, and speeds increased more than any of the mods could do...
just a thought, spend money on fuel, keeping temps cooler at same time, and go faster.
steve

[nbaker]

I've had PA24-260B's with and without speed mods. Zach's earlier analysis spells it out. The touted LoPresti cowl IMO does not come close to the claims and requires major changes in the engine compartment plus repainting to match. The add on that makes sense are fairings (Spats) behind the main gear since they do not retract completely. First check your rigging. When straight and level hands off is the ball centered? If not, check the rigging and/or adjustable trim tabs.

Dave Pyle ICS 730

[9089P]

Hi Tim,

We have a 260B with the Johnston tips and no other mods. The paint's good, tires fair..........sorry that's another song......anyway we have a new airspeed indicator as well. First, I think an accurate air speed indicator does more for consistent landings than the tips. Speed, speed, speed....We fly long legs at 9500-10500 all the time and we are usually about 450 lbs under gross at take off. On level off at cruise (2300rpm, wot, 100 rop, 12.5gph) we see 185 mph with standard or near standard conditions. As the fuel burns off we do see 2-3 mph increase. We often fly these legs with twinco friends who have the same tips, and all the k2u gap seals, and they are loaded the same (except they have to fill their aux tanks) trust me they are no faster and they are burning 2-3 gph more.

Good luck, Don

ps Steve what's wrong with you, you're gonna get the LOP police after you with fool talk like that.....

[Jody Brausch]

Don,
Your PA30 friends should double-check that the gear selector is in the "retract" positon .......54Y typically trues out around 195 mph at 8000 ft with the throttles fire walled and the props set to 2400, 75 degrees ROP, just a shade under gross. I've seen TAS as high as 200mph. These speeds are verified by the air data computer.

[N8632Y]

Jody,
impressive!
I've run peak, and ROP, and the difference is about 5-7 kts....fuel of about 0.5-1.0 GPH
Running 75 ROP at 6500ft 24"2450rpm 30.52 1C 9.0/side GPH i have IAS 158 TAS just over 171 kts or 196 MPH...
big difference is a combination of the sun and the moon, temps, fuel, etc...it's nice to get there, never fast enough...
steve PA30

[9089P]

Hi Jody,

I think we are talking apples and oranges here, at 8k and your settings you are at 75% or perhaps more (I don't have a twin power chart), at 9500 and 2300 rpm we are only making 65% and I sure my friend was doing the same. By the way what are you burning at your settings?

Don

[Jody Brausch]

Don,
No argument there....the 260 wins hands-down on the fuel efficiency meter. My Dad had a '65 260, and that was one sweeeeeet airplane. Fast, efficient, great ailerons, not to mention the beautiful lines. Can't ask for much more than that. To be honest, after having flown behind one fan for twenty-some years, I just had to have a twin, and I must say that the twinky could not have been a better choice for me, and my family. Now if I could only get those arrivals just right.....

Steve,
54Y's fuel burn is just a little higher than what you experience, burning just about 9.2 to 9.3 gallons/side 75 ROP @ 8000. Not as efficient as what you're seeing, but it knocks the snot out of feeding a 310 or a Baron.

[Kristin Winter]

Don,

For fun we will have to compare your plane to Maggie. At 10K is am burning about 14 gph and would expect 185-190 mph.

[jeffrey aryan]

Don,

I have my twin tricked out thanks to Mr. Speed King, "The Great HANSMIESTER". They seem to work for me. I now claim to be faster than him. This is because I just installed a new set of LoPresto nose bowls. I have copied almost all his other mods. I can honestly say I am getting 174 knots TAS at 75% pwr. My plane still needs paint and a couple of other things.

Jeff

[DBpa30b]

All,

I have a PA-30B with approx 5800 TT. I currently have all speed mods on it as well as tip tanks. There is a slight vibration at as soon as I rotate and it continues during cruise. any thoughts?

[N3322G]

Dean,

Welcome - I saw this is your second post. You might want to start a new thread with this as the topic.

Just click on Board Index in the upper left, then click the category and then click on NEWTOPIC which is just below the category. This way it will get the focus you want vs being under the Speed Mod discussion.

I have some thoughts and I'm sure others will chime in as well.