Sport 76 speed
Jason, can you tell us a little about how you go so fast? Looks like a clean, stock 8, but obviously looks are deceiving! What you got there?
Dan H,
A few big items and then many many small ones that likely would not be possible to independently measure for gain.
I started with a completely stock IO360 engine and stock airframe I built per the plans. In 2010? my friend Seth Baker invited me to a SARL race in West Texas where I posted a speed very close to published Vans numbers...then I got the speed bug. I worked on drag reduction for a few years and increased speed from about 212-225 mph with no change to power or prop. During my rookie year at Reno in 2013 I qualified at 225 mph and then was the first RV to play with Nitrous during race heats. I kept failing solenoid coils and never ran a full race with Nitrous (now I use a trusty ball valve).
Less than two months after 2013 Reno my blended airfoil prop failed which is posted on VAF. The damage from landing in the desert required engine tear down and the entire plane to come apart. I then took lemons and made lemonade.
Here are the major speed mods and I would like to add that I have limited myself to not removing any Vans factory part. I have tweaked and added but still have Vans wheel pants, cowl, wing tips, canopy etc. There is lots of go fast **** you can buy. My goal is to prove you do not need any of it to be one of the fastest.
1. IO-360 parallel valve with Lycon goodies for power. I run slick mags and race with timing at 25 deg. No electronic ignition or fuel control. My master can turn off and engine still runs. I do not need variable timing going in a circle at full power. No one gets brownie points for using a cup of gas less with fancy timing. This base engine is recommended by Vans and I have tried to make it do the best possible and still be a daily driver.
By the way...Sport 39 is at the top, crazy power and he has Slick mags. Pretty sure the top of Unlimited also use mags.
2. Hartzell composite prop which is a speed gain for me. Some have said this is slower but I assume they are less power and slower planes anyway. This prop likes power and appears to be optimized for my race power and speed. I run at 2,700 rpm.
3. Reducing cooling drag is huge as you well know. I supplement water and/or ADI for cooling at race power. My front baggage smoke oil tank now sprays on the oil cooler and inside the intake (downstream of the fuel servo).
4. Tuft testing all over showed areas of drag. Wing root fairing, elevator root fairing, cowl outlet etc. Video of yarn is well worth the time. I do not guess what is going to work.
5. Since the damage from the prop failure I stripped paint and then had the entire airframe smoothed. It is in primer and will stay that way. I can use steel wool, scotch pads or sandpaper to smooth the surface. I have used zero "go fast" chemicals on the exterior.
6. Excrescence drag is a big deal but most folks have no idea it is there. RV's leak all over and I am sealing things up more and more each year. Hard or impossible to measure one improvement to the next but I know the combined result is real. My goal is to open the vent and nothing happens. If I reach that goal then I will make a dedicated outlet.
7. I designed and built my own pitot tube that is also my comm antenna. Basically a home made loaded coil antenna tuned with a VSWM. Nothing hanging out but all of my antennas work good.
8. Nitrous tank size to not run out during a race and jet size to have mixture at full rich. We race at 7,000 ft DA so I am jetted for best power at full rich.
I do not run a wet Nitrous system. Too much risk vs reward. The Glasair I mayday and fire at Reno on Saturday appears to be the result of fuel spraying in the induction system. I am not going to discuss root cause but the fire came from the Nitrous wet system fuel source.
When are you going to try SARL or attend PRS? I am sharing this as a carrot so you will come and play in the sandbox.