RV10 Cold Air Induction - Showplanes Cowl

[Richard Connell]

Originally Posted by bjdecker

Is there a snubber or restrictor installed in front of the MAP sensor — and is the MAP sensor a Kavlico P4055-30A-E4A?

What’s going on at 59” into the flight? MAP goes WAY up for quite a while…physics got suspended over Ayer’s rock?

Maybe I shouldn’t bother…
Flight started off at 5k and partial throttle due fzl.
That mysterious jump in MAP is likely due to me pushing the black lever to WOT as I climbed from 5k to 9k
Yes it’s a P4055-30A-E4A with an Omega PS-8G installed at the sensor end of the MAP line.

I should have probably just said WOT rather than specify an actual MAP. Jut grabbed the last flight at altitude I had. I don't target MAP I just fly WOT all the time unless (as in this case) Im held low for some reason. ATC or FZL. In that case I tend to target top of the green arc (which for this flight was around 24.5") at TOC it was 24.5 too.
I really can't be bothered plotting WOT MAP vs PAlt for all the flights I have - but if someone wants to script something up they are welcome to all the data. Im confident its above ambient. How much who knows.

Back to the OPs question tho - you guys have got many hundreds of tens flying around, surely some of you could get together and compare configurations.

My back of the envelope calcs suggest that my 285HP 9:1 with CAI should yield me an extra 6.5kts above the 260HP. People said I'd lose 5-6Kts because of the Hartzell 3 blade (I think that's likely to much). Turns out I'm a few knots quicker than book - so maybe the cowl/induction/larger spinner is worth a knot or two. But who knows without side by side comparisons.

Yes before anyone asks I did the NTPS PEC testing in phase 1 and its small across the range ( +0.6 at 155 KCAS ie quicker than indicated )

[scsmith]

Originally Posted by Richard Connell

https://apps.savvyaviation.com/fligh...7-2ed45a15069a

I have no reason to doubt the instrumentation. Standard Garmin setup.
MAP off the rear of #5

To be fair this was a high QNH day (30.45) so the pressure alt was 8500.

Ps @ 8500 ft Std Day = 21.8 in. hg
V=177 ktas = 298.5 ft/s
rho=0.00184 slug/ft^3

q = 1/2 rho V^2 = 82 PSF = 1.16 in. Hg.

Pt = Ps + q = 22.96 in. Hg. So, if you are getting full 100% ram rise in your induction, the highest your MAP could be would be 23 in. Hg.

We do see some elevation above full ram pressure in cold-air induction systems with tapered runners if the RPM is just right to get some wave augmentation - but not 1.5" I don't think.

[Carl Froehlich]

While there is a bump in HP with the CAS IO-540, my objective for going with the Sam James cowl is drag reduction.

To the OPs question, are there any RV-10 guys out there that have some cruise data that compares the stock RV-10 cowl with a buddy that is flying along side with the Show Planes cowl?

Carl

[Carl Froehlich]

[quote=KatanaPilot;1713814]Seems to me there are so many variables between any two RV's that these sort of comparisons have very little validity.

Perhaps - but even data that needs to be corrected for plane configuration is better than no data.

Carl

[Richard Connell]

Originally Posted by scsmith

Ps @ 8500 ft Std Day = 21.8 in. hg
V=177 ktas = 298.5 ft/s
rho=0.00184 slug/ft^3

q = 1/2 rho V^2 = 82 PSF = 1.16 in. Hg.

Pt = Ps + q = 22.96 in. Hg. So, if you are getting full 100% ram rise in your induction, the highest your MAP could be would be 23 in. Hg.

We do see some elevation above full ram pressure in cold-air induction systems with tapered runners if the RPM is just right to get some wave augmentation - but not 1.5" I don't think.

So that realistically leaves sensor error (unlikely) or the placement of the takeoff. Perhaps the snubber acts as a form of check valve through the intake pulse cycle. Or perhaps it’s linked to the higher idle MAP shown by 540s to 360s.
I’ll put it on the list of mysteries to solve at a later date.

[Kyle Boatright]

Originally Posted by KatanaPilot

The SP cowl is nicely made and does look great. The "duckbill" that covers the nose gear upper mount is also nice and supposedly helps smooth the exit airflow.

Got a picture (or a link to a picture) of this?