IO-360 Generating Proper Power?

MarkChristopher · #1 07-17-2014, 06:54 AM

My RV-7a is only 20 hours old and after doing cruise speed testing I believe that I may not be producing proper engine power.

Here are the test conditions:
- New Superior IO-360, Hartzell CS prop
- 8000 MSL, 50 deg F OAT
- Installed nose wheel pant and leg fairing - no main pants or leg farings
- Running 100 deg ROP, 100LL

Here are the results:
WOT - 22.5 MP, 2620 RPM, 11.6 GPH, 129kts IAS, 148kts TAS
70% - 22.5 MP, 2500 RPM, 10.8 GPH, 127kts IAS, 147kts TAS
65% - 22.4 MP, 2300 RPM, 10.0 GPR, 124kts IAS, 142kts TAS
55% - 19.2 MP, 2300 RPM, 8.0 GPR, 113kts IAS, 130kts TAS

I know there is a speed gain with the wheel pants and leg fairings but it seems like I'm a long way off the published numbers from VANS. Do I have an issue and if so, where should I start looking?
Thanks!

rzbill · #2 07-17-2014, 07:01 AM

Finish your bird first.

N941WR · #3 07-17-2014, 07:08 AM

Expect a 10 Kt +/- gain with gear leg fairings and another 5 with the wheel pants.

Also, your test runs should be done at 8,000' DA, not MSL, and WOT. Indicated AS means nothing, TAS is what you are looking for.

Good luck.

mannanj · #4 07-17-2014, 07:40 AM

Quote:

Originally Posted by N941WR

Expect a 10 Kt +/- gain with gear leg fairings and another 5 with the wheel pants.

Also, your test runs should be done at 8,000' DA, not MSL, and WOT. Indicated AS means nothing, TAS is what you are looking for.

Good luck.

Hard to believe that wheel pants and gear leg fairings will give you a 15 kt. tas gain but it sure did in my RV-8!