First off, thanks to CRABANDY for his original work 5+ years ago.
This past week, I decided to add the firewall bump to my RV-7 (as depicted in builders manual, section 12, page 12-2, figures 12-1 and 12-2.)
I've been gathering test data for over 2 years now, and have a pretty solid data set for a variety of operating conditions, power settings, etc.
With the "bump" installed, there appears to be an increase in TAS of 3 kts. This was measured at 6500MSL, 2500RPM, 24.1" MAP, 9.7GPH - 50°lean of peak, 5°C OAT, 30.20"inHg. TAS was 168kts.
CHT's and OT was a few degrees warmer, but all within limits and nothing really concerning:
No Bump - With Bump
285 287
314 314
290 293
276 279
OT:
185 187
I attribute the increase in airspeed to a reduction in cooling drag due to "shrinking the exit".
Next steps -
Change to stainless steel and extend from 15" to ~18" to cover more of the area above the cowl exit.
Cheers!
This past week, I decided to add the firewall bump to my RV-7 (as depicted in builders manual, section 12, page 12-2, figures 12-1 and 12-2.)
I've been gathering test data for over 2 years now, and have a pretty solid data set for a variety of operating conditions, power settings, etc.
With the "bump" installed, there appears to be an increase in TAS of 3 kts. This was measured at 6500MSL, 2500RPM, 24.1" MAP, 9.7GPH - 50°lean of peak, 5°C OAT, 30.20"inHg. TAS was 168kts.
CHT's and OT was a few degrees warmer, but all within limits and nothing really concerning:
No Bump - With Bump
285 287
314 314
290 293
276 279
OT:
185 187
I attribute the increase in airspeed to a reduction in cooling drag due to "shrinking the exit".
Next steps -
Change to stainless steel and extend from 15" to ~18" to cover more of the area above the cowl exit.
Cheers!
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