Speed Mods...are they really worth it?

Fearless Tower

Fearless Tower

Touchdown! Greaser!
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Fearless Tower
So I spent a couple hours hanging out at the maintenance shop today and the subject of speed mods came up.

They were working on a Cherokee 6 and essentially in the process of re-skinning the ailerons. While talking with the shop crew it turns out the speed mods installed were so tight they were literally rubbing the rivets off and resulted in the reskin work.

They were also telling me about another customer with a 182 that had apparently installed every speed mod available....consequently it takes them twice as long to do any maintenance on the airplane because they have to remove and reinstall so much just to access basic components.

I've never given much thought to it, but I'm curious: For those that are speed mod crazy, are you really getting your money's worth.....or is it something where you just enjoy the extra speed and don't really try to look at the overall financial picture?
 
Fearless Tower said:
So I spent a couple hours hanging out at the maintenance shop today and the subject of speed mods came up.

They were working on a Cherokee 6 and essentially in the process of re-skinning the ailerons. While talking with the shop crew it turns out the speed mods installed were so tight they were literally rubbing the rivets off and resulted in the reskin work.

They were also telling me about another customer with a 182 that had apparently installed every speed mod available....consequently it takes them twice as long to do any maintenance on the airplane because they have to remove and reinstall so much just to access basic components.

I've never given much thought to it, but I'm curious: For those that are speed mod crazy, are you really getting your money's worth.....or is it something where you just enjoy the extra speed and don't really try to look at the overall financial picture?
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I think there's a lot of snake oil in supposed speed mods.
 
I take the addtl time in my log book and more flight time. Saving 10 minutes on a XC - not worth it.
 
I have a gap seal kit coming right now. I'm looking for the low speed authority over speed.
 
They may or may not be worth it depending on your goal and how much it costs. They can have other effects than improving speed such as improving climb rate. If you have a plane with marginal summer time take off and climb performance, any improvement is an improvement in safety margin. Any reduction in engine horsepower required to maintain climb speed goes into improving climb performance. The Art Mattson mods for Cherokees were inexpensive and effective. Unfortunately, they seem to be no longer available.
 
I've heard that stuffing the spinner with $100 bills might work. That joke aside, I was shopping Comanches a while back and found that there is a main gear fairing you can get that supposedly does give good "bang for the buck"
 
It takes a lot of clean up on the airframe (sort of like the lopresti reworks of the Grummans and Mooneys) to make a substantial difference. I always find the speed mods on a lot of small planes humorous. It's like my friend in the local VW bug club. They spend a lot of time souping up their bugs, but at the end of the day it's still an old volkswagen.
 
I personally did not put any speed mods on the 310, but it ended up 20 knots faster when I sold it than when it was donated to Cloud Nine. This was basically done by paying very close attention to detail in terms of baffles (big one), antenna drag (removed a bunch of useless antennas), removing the beacons in exchange for wingtip Whelen LED strobes. Even ignition timing (most of us are flying with ignition timing that is wrong) made a big difference.

Attention to detail is the easiest and cheapest speed mod, in my opinion.
 
Hmmm....how did you adjust the ignition timing...so, that it was more better? :D

digital protractor?
 
I'm familiar with a few airplanes with speed mods. The one that I have the most time in was an Arrow with every speed mod Lopresti made for them. It made books speeds, I have no idea what kind of speed it did before all the mods.

I also have a bit of time in a Mooney M20J with a Lopresti cowl and some other mods. This one also does close to book numbers, maybe 5 knots faster.

If I had to pay for the mods on either of these planes I'd say it wasn't worth it. I know the cowls are expensive. The cowls are worth it from a maintenance perspective though. I think the Lopresti cowls are easier and faster to remove than the original pieces.
 
Ted DuPuis said:
Even ignition timing (most of us are flying with ignition timing that is wrong) made a big difference.

Attention to detail is the easiest and cheapest speed mod, in my opinion.
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On my Archer I was moaning about bad starts. 200 hours SMOh. MX found the msg slightly off. After the retiming, holy crap....... Started almost instantly, purred when it idled and I saw about 75 rpm on th tach increase. I'd have to back off in cruise at low altitude because it was in the yellow arc now, which it would do before unless I was in a descent.

So yes, I concur that timing is a very good thing to stay on top of.
 
I would buy an airplane that had speed mods, but I don't think I would pay to add them. I looked at the aft body strakes for my 425, they are about $12-15K installed.:eek: I asked a friend that has them and the "hub caps" installed on his 421C about the speed difference. He said he thought they lost a knot!! :(:eek: They claim 3-5% increase in speed, so 7-10 knots, at 75 hours per year, it would take me until I am 75 to pay for them in fuel savings. :D
 
My Arrow has gap seals, gear lobes and wing root fairings. Had wheel caps, but I lost them in flight lol. In all it's probably good for a 5 knot increase. IOW, not spectacular, and I havent seen much in the way of a significant improvement in climb rate. Flying light does more for my climb rate improvement than anything really. It does stall considerably slower than placard.

They came with. No way I go through the expense of it all. On a fixed gear pre-78 Piper, I would be willing to upgrade the gear fairings and wheel pants however. That speed mod is significant in my opinion, close to 8 knots from the old pants. The howl cowl is also another one that adds speed, but I consider that one too expensive for the improvement.

In all, a stock RG airplane with big tanks is the best value compromise imo when it comes to speed mods.

So in general I'd say with the notable exception of new style wheel pants for the old FG planes, speeds mods are not worth it.
 
Checkout_my_Six said:
Hmmm....how did you adjust the ignition timing...so, that it was more better? :D

digital protractor?
Click to expand...

Digital mag timing device with metal thread-in TDC finder. Ends up fining TDC precisely vs the "feel it" an gravity needle that most A&Ps use. My A&P had set it 2 degrees retarded from spec via his method. Set properly, I gained 5 kts @ 11k MSL and way easier starting.
 
N747JB said:
I would buy an airplane that had speed mods, but I don't think I would pay to add them. I looked at the aft body strakes for my 425, they are about $12-15K installed.:eek: I asked a friend that has them and the "hub caps" installed on his 421C about the speed difference. He said he thought they lost a knot!! :(:eek: They claim 3-5% increase in speed, so 7-10 knots, at 75 hours per year, it would take me until I am 75 to pay for them in fuel savings. :D
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He's the first I've heard to report a loss with strakes. I'd not bother on a 425 I think, but I do want them on the 414 mostly for better climb.
 
Ted DuPuis said:
He's the first I've heard to report a loss with strakes. I'd not bother on a 425 I think, but I do want them on the 414 mostly for better climb.
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The guy can be a bit of a smartass, so he may have actually gained a little, but he was not impressed with the speed gain. He runs the FBO where I'm based and they use 421C's for their own transportation, he did mention that it climbed quicker, I don't recall the increase.
 
Ted DuPuis said:
Digital mag timing device with metal thread-in TDC finder. Ends up fining TDC precisely vs the "feel it" an gravity needle that most A&Ps use. My A&P had set it 2 degrees retarded from spec via his method. Set properly, I gained 5 kts @ 11k MSL and way easier starting.
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yup....got the threaded suppository....and the app for the cell phone. :D

E25-14.jpg

btw....with the correct timing vs retarded...I bet your CHTs went up too.

Also...the best free speed mod is a correctly rigged aircraft. Cherokee's can gain +4-5kts with correctly setting the flaps up -2 degrees and aligning the ailerons....also, keeping the ball centered with rudder trim helps.
 
N747JB said:
The guy can be a bit of a smartass, so he may have actually gained a little, but he was not impressed with the speed gain. He runs the FBO where I'm based and they use 421C's for their own transportation, he did mention that it climbed quicker, I don't recall the increase.
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Given the anemic climb performance of the 414, that'll be the real benefit for me. I'm hoping for speed, too, but not expecting much there.
 
So how many minutes would some of you venture to guess you save on a full fuel max range cross country trip with all of these speed mods?
 
Checkout_my_Six said:
btw....with the correct timing vs retarded...I bet your CHTs went up too.

Also...the best free speed mod is a correctly rigged aircraft. Cherokee's can gain +4-5kts with correctly setting the flaps up -2 degrees and aligning the ailerons....also, keeping the ball centered with rudder trim helps.
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All correct, and part of how I gained speed on the 310. CHT increase was minor, about 10F.
 
Ted DuPuis said:
Digital mag timing device with metal thread-in TDC finder. Ends up fining TDC precisely vs the "feel it" an gravity needle that most A&Ps use. My A&P had set it 2 degrees retarded from spec via his method. Set properly, I gained 5 kts @ 11k MSL and way easier starting.
Click to expand...
Plus it's just fun to set timing.
 
Ted DuPuis said:
I personally did not put any speed mods on the 310, but it ended up 20 knots faster when I sold it than when it was donated to Cloud Nine. This was basically done by paying very close attention to detail in terms of baffles (big one), antenna drag (removed a bunch of useless antennas), removing the beacons in exchange for wingtip Whelen LED strobes. Even ignition timing (most of us are flying with ignition timing that is wrong) made a big difference.

Attention to detail is the easiest and cheapest speed mod, in my opinion.
Click to expand...

That.

I think just "cleaning up" a plane and zeroing and rigging it properly is the best bang for your buck speed wise, well outside from picking good cruise altitudes.
 
jesse said:
Plus it's just fun to set timing.
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It is. The very observable improvement from something so simple is also nice.
 
flyingron said:
It takes a lot of clean up on the airframe (sort of like the lopresti reworks of the Grummans and Mooneys) to make a substantial difference. I always find the speed mods on a lot of small planes humorous. It's like my friend in the local VW bug club. They spend a lot of time souping up their bugs, but at the end of the day it's still an old volkswagen.
Click to expand...

My first car was a 68 Beetle. Put an extractor exhaust on it right after I bought it and suddenly it would actually go up hills. Some Bug mods are worth the money and some ain't. I suspect its the same with planes.
 
Fearless Tower said:
They were also telling me about another customer with a 182 that had apparently installed every speed mod available....consequently it takes them twice as long to do any maintenance on the airplane because they have to remove and reinstall so much just to access basic components.
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This sounds like they went from having a normal conversation to making up crap.

There aren't that many 182 speed mods out there. The only one I can think of that's hard to remove, is the goofy nose gear fairing. Even that thing isn't THAT hard.

Others are fairings on the struts, and wheel pants, and plenty of us still have the factory wheel pants on.

None of the stuff I've found adds any appreciable speed to cruise flight either.

I have a reverse speed mod, in the Robertson kit. Ha. Those stall fences on top of the wing and the cuff, knock off about 5 knots from most of what I hear for cruise speeds from other 182 owners. We're also slightly out of rig, and one of these days we'll figure out how. We get a slight ( very slight ) roll to the right if everything is left alone, ball centered. You can make it go away with light aileron pressure or tweaking the rudder trim so the ball is a tiny bit out. Could even be the TC isn't installed perfectly level. It'd be a project to figure it out, especially with the droopy ailerons. We may be slightly dragging one all the time, hard to say without a lot of labor and detailed measuring and messing around.

And none of us make book speeds from the 1970's wishful-thinking POHs, ever. Hahaha. Marketing fodder.

I met a guy who had a 182 with all conceivable speed mods on it at OSH and talked to him about it. He said it didn't make the airplane any faster, but he bought it from the guy who wasted all the money for them on it, because he wasted money on everything on that airframe and had top of the line everything done to it and on it and maintenance...

The speed mods were just leftovers from the former owner who had money to burn on the airplane and did so, and the new owner hadn't had a significant squawk in a number of years of owning it. He hated the nose gear fairing thing and said he'd probably pull it off.
 
POHs performance numbers are under nearly ideal conditions: std temps, low humidity, perfectly clean plane, engine making book numbers, balanced weight, no minor hangar rash, no add on antennas.
You got to know your limitations, also, checking speeds via 4 cardinal ground speed check will always be lower than actual TAS, how much depends on the wind speed.
 
So how many minutes would some of you venture to guess you save on a full fuel max range cross country trip with all of these speed mods?
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Each speed mod gets you 5kts (according to some claims) so 5 of them gets you...um, the joy of noting all the speed mods in your TradeAPlane ad.
 
Let'sgoflying! said:
Each speed mod gets you 5kts (according to some claims) so 5 of them gets you...um, the joy of noting all the speed mods in your TradeAPlane ad.
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I've wondered about different mods interacting in ways that may be "aerodynamically undesirable".

Each mod has a separate STC, presumably based on that one modification being installed on an otherwise stock, certified airplane.

I think there's an argument that in some instances combining a whole series of individual external airframe modifications together may make the plane a quasi-experimental in terms of how it might behave at the limits. Certainly there's no requirement for the suppliers of these modifications to test their products in combination with anyone else's mods - a standard that would never have been allowed for the original manufacturer.
 
When it comes to performance STCs, with STC layering you get a smaller ROI for each subsequent mod if any real gain. For the best result possible to enhance marketing/sales, an STC applicant will typically do their testing on an aircraft that only has their STC on it. So there may be a 5 knot increase when STC 1 is put on a clean airplane or when STC 2 is put on a clean airplane but when 1 & 2 are both put on, you will not normally gain 10 knots. Usually nothing close to that.

STC layering can also be dangerous. This article by AOPA explains it pretty well.
 
teejayevans said:
POHs performance numbers are under nearly ideal conditions: std temps, low humidity, perfectly clean plane, engine making book numbers, balanced weight, no minor hangar rash, no add on antennas.
You got to know your limitations, also, checking speeds via 4 cardinal ground speed check will always be lower than actual TAS, how much depends on the wind speed.
Click to expand...

I've heard this OWT forever but believe the numbers fib more than these items factor in.

Standard temps? Easy to find.
Low Humidity? Doesn't get much lower than here consistently.
Perfectly clean plane? Been there done that.
No minor hangar rash? None here.
Engine making book numbers? Hardest one to guess at, but some reasonable science says other numbers would change noticeably like manifold pressure. So a factor but not that big.
No add on antennas? Airplane came with more and larger antennas from the factory, including ADF antenna on the belly and a long wire from mid wing to tail, all removed, including losing the weight of those original radios.
Flying a wind triangle isn't any fancy new tech.

If it's that easy to debunk that list, it's a lot saner to say the book numbers are simply wrong and always were, considering the heavy competition between the manufacturers back then.
 
denverpilot said:
No add on antennas? Airplane came with more and larger antennas from the factory, including ADF antenna on the belly and a long wire from mid wing to tail, all removed, including losing the weight of those original radios.
Flying a wind triangle isn't any fancy new tech.

If it's that easy to debunk that list, it's a lot saner to say the book numbers are simply wrong and always were, considering the heavy competition between the manufacturers back then.
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The factory may have installed the antennas, but the performance is based on bare bones design, done by computer, verified with a prototype, not the factory end product. The numbers were generated before the first plane was ever built.
No ADF, SS, GPS, VOR, ELT, VHF, Satellite TV and whatever else.
Wind triangle will still show lower TAS than actual if you have winds aloft, try playing with your high tech E6B
Saner to say the book numbers are wrong...maybe just easier than trying to understand why.
 
MAKG1 said:
If there is a safe way to adjust it with the engine running, an obvious way is to minimize manifold pressure. That's how it's done on a car.
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nope....the timing has to be adjusted with the engine "off". The key to timing accuracy is having the correct equipment.
 
N747JB said:
I would buy an airplane that had speed mods, but I don't think I would pay to add them. I looked at the aft body strakes for my 425, they are about $12-15K installed.:eek: I asked a friend that has them and the "hub caps" installed on his 421C about the speed difference. He said he thought they lost a knot!! :(:eek: They claim 3-5% increase in speed, so 7-10 knots, at 75 hours per year, it would take me until I am 75 to pay for them in fuel savings. :D
Click to expand...

My PA28 has gap seals, metco wing tips, and a powerflow exhaust...all installed by the previous owner. If these mods improved the performance, I would have hated to have flown it before the mods, because this PA28 rarely makes book numbers. Always best when it's someone else's money buying the mods.
 
tawood said:
My PA28 has gap seals, metco wing tips, and a powerflow exhaust...all installed by the previous owner. If these mods improved the performance, I would have hated to have flown it before the mods, because this PA28 rarely makes book numbers. Always best when it's someone else's money buying the mods.
Click to expand...
No doubt, the good thing about mods is they don't become obsolete, bad thing is they add a little to your empty weight
 
tawood said:
My PA28 has gap seals, metco wing tips, and a powerflow exhaust...all installed by the previous owner. If these mods improved the performance, I would have hated to have flown it before the mods, because this PA28 rarely makes book numbers. Always best when it's someone else's money buying the mods.
Click to expand...

I had a PA28-140 for over 20 yrs. It is definitely not a speedster. More power is going to do very little to speed it up but should be seen in improved take off and climb performance. The Cherokee 140 is a real dog in that area in the summer time south. Max gross take offs at 105 - 110 degrees can be interesting. Probably not a concern where you are. I made it a summer time practice to do Vx take offs for every take off and some times turning back over the field to continue climbing.

At engine rebuild, it got the high compression pistons to take it to 160 HP. Also a prop tip mod that was effectively worth about another ten HP in improved efficiency/thrust. With that combination, I was able to increase prop pitch 4 inches and maintain the same RPM (red line at WOT, S&L). I also put the Metco wing tips on, wing root VGs, and aileron & stabilator trim tab gap seals. That certainly cured my take off and climb worries. I wasn't very interested in speed. When done, the temperature corrected ASI showed 145 mph/125 kts WOT S&L with just me in it and 2 or 3 mph less with 2 people in it. I never tried it at gross. The landings also seemed to be gentler. The pre-mod wing seemed to like to quit flying rather suddenly while in the flare resulting in thumper arrivals (or maybe I just got better at landing). I only spent about $3K but everything was self installed (with A&P supervison) and the mods were bought from Art Matson.

The prop tip mod was really simple. The tips were beveled front to back at 45 degrees. It was described as putting a Hoerner wing tip on the end of your prop. An acquaintance copied it on an experimental and saw about 100 rpm increase in static rpm.
 
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That's a fast Cherokee. Mine, with tips, flap and aileron gap seals, and vortex generators ran about 120 mph at 75% power. The gap seals were worth about 5 mph. I don't know if the vortex generators did anything to speed the aircraft up, but it had the best low speed handling of any airplane I've ever flown. Really good control authority all the way into the stall, such as it was. I could never get a clean break out of it, the thing just mushed along. Probably the one airframe modification I would wholeheartedly recommend.
 
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