The only realistic mod I can think of that I know “works” for a PA-28, is to install one of the rather common faulty tachometers. I have flown several PA-28s that seemingly performed better than book values, but when I brought my digital optical tachometer and adjusted RPM according to that, the airspeed fell to a few knots below book value in every case. The best “performing” aircraft had a tachometer reading 180 RPM low, and AFAIR that equalled to 7 or 8 knots above book values for the indicated RPM.
Huv.
You make a very good point!
AnthonyQ wrote:
To be fair you should either compare a warrior with a skyhawk OR an archer with a Superhawk (180hp)….then I think most of the pa28 advantages would disappear…
The current production model Skyhawk (172S) has a 180 hp engine. What’s a Superhawk?
The current production model PA28-181 (Archer III) is up to 5 knots faster (book figures) than a Cessna 172S..
The 172S has very slightly better rate of climb.
Both aircraft have the same MTOM. The 172S still doesn’t have rudder trim.
And the Archer III still has just one door…
But that one door means that the pilot stays dry even if the door seal isn’t great.
As this has become a Pa28 v C172 thread, I prefer the Pa28 by far for enjoying flying. But the C172 is the plane I’ve opted to continue flying in the worst weather.
Low hours in both, most of my flying in a Jodel tailwheel.
C172 may have more utility value but compared to PA28 it looks like a fat pidgeon! The fast cherokee 140 160hp goes 160mph aka 140knots! Read all about it! 
!
http://www.aero-news.net/index.cfm?do=main.textpost&id=ab0514bc-2fcb-4c40-9f76-13f1e21d2f97
Given that early P28As always need 5 to 10 hp more than early C172s, I guess some of the mods would make the 145hp C172 a similar 160mph aircraft ;-)
For my experience, the least costly to squeeze a few more knots out of any plane is a good wash, wax and polish. Some speed mods help a little, some just look like they help.
Right now, I would be more concerned about the probability of a burdensome inspection on PA-28 wing spar attachments. That said, The larger tricycle Cessnas have their own SB coming out too. Cessna has parts kits available for sale, I hope Piper comes to the table with parts support for legacy PA-28s, which would offset my poor experience with some Piper primary structure parts availability in the past.
So lets assume these new and old wing spar inspectons mandated are all done and the most common GA types PA28 and C172 aircraft do not fall out of the sky after 60 years in use due to some messages in aviation forum. How would you make them faster? I do like both of the types PA28 and C172 very much. Improving something that has existed very long time should be a goal and appreciated.
