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RV-7 cowling exit bump

crabandy

Well Known Member
Seeing other posts on VAF has motivated me do do some smoothing on my RV7 O-360 cowling outlet.

I can make it two ways, first is more of a bump on the bottom of the firewall. Screws/ nutplates on the bottom of the firewall and riveted to the firewall.
Poster board mock-up:
4C6F9D3C-C9E7-4FEB-BB80-D99EED6A2749_zpsxicqhjxy.jpg

C95FA88A-4895-413B-8C92-86A88ABC0B46_zpsj9l4qkoa.jpg


Choice #2 is more of a ramp directing air into the exit. Screws/nutplates for the bottom and adel clamps to the engine mount for the top.
4ABA1ABA-9A93-4BB9-B0E5-18AE1D889860_zpsg0v0uwhg.jpg

0EEF3966-2374-4FD1-A5AE-3153E061F915_zps4bwlthrg.jpg


#1 is more permanent leaving less room for experimentation than option #2. Hoping to start cutting some metal tomorrow and appreciate any input.
Thanks!
 
Looks a lot like mine! Just be glad you don't have the -A model! It was a pain to get the curved aluminum in there without looking horrible. It ended up looking pretty good and has held up well over the past year.

Make sure to report back with your results after a test flight. :D
 
Here is what I am doing. Ready for some screws so it can be removed. I just installed it before mounting the engine so riveting would be easier. I hope it will work :eek:

I made a hole template to make it easier to construct air management radius when the time comes.

IMG_0831.JPG
 
All of the exit ramps I have seen have open ends, do any of you think the ramp would be any more efficient if the ends were closed as much as possible?

Glenn Wilkinson
 
Andy, choice 1 or 2 is probably a matter of convenience. Either way, I'd suggest that you fabricate from stainless sheet and extend it 12 inches aft of the firewall, over the aluminum belly skin.

2uf3ud5.jpg
 
My "firewall fairing" -

152f2tx.jpg


It is .025 aluminum and the nut plates are on the fairing instead of the firewall.

FWIW: My husband has been flying with one similar to your option 2 on his 6 for many years and has not had any issues with the skin just aft of this area. He recently changed to one like option 1...
 
I've been considering this mod. Does anyone have actual before and after data on temps and/or speeds?
 
My husband has been flying with one similar to your option 2 on his 6 for many years and has not had any issues with the skin just aft of this area. He recently changed to one like option 1...[/QUOTE]

Extending the fairing, in stainless, is a fire protection measure.
 
Thanks for the replies, I made the drive to airparts and picked up some .017 stainless from their scrap bin. I like the fire protection.
Melinda, is your fairing only attached at the bottom? The tension in the curve keeps it from rubbing on anything...
 
Yes - attached at bottom only

My fairing is only attached at the bottom. I wrapped some clear duct tape along the upper edge just in case it moves any against the firewall. It sort of curves into the firewall at the upper edge and touches it, so I wanted to be sure it didn't rub.

And yes, I understand the stainless is for fire protection. I guess I'm just sticking with the original Van's aircraft bottom at this point. I am hoping the fairing "smoothes" the exit airflow a little.
 
I've been considering this mod. Does anyone have actual before and after data on temps and/or speeds?
Kent Paser has a nice write up on the mod similar to this that he used on his Mustang II, and supports it with quite a bit of data. It's detailed in his book "Speed with Economy."
 
How do you prevent dissimilar metal corrosion between the stainless sheet extended out along the belly and the aluminum belly?
 
Part 1 mostly complete, part 2 I'm planning on more stainless on the belly.

Lower firewall as it was.
05A0654C-0DB8-40A6-8007-093D603E235D_zpspdnylhvz.jpg


I used posterboard for a template and the shaped it with an old pipe before I cut the relief notches for my control cables. I wanted to make it semi-removable for further modifications.
31651C0E-F702-4445-B42C-F2CB1618C7DE_zps4ccyrb85.jpg

57C0F851-D667-4F29-8862-AD60C953DBD8_zpsruxe8atl.jpg

AC8AFC0C-A6EF-4EB1-9397-09F59AA44077_zpsripnfeqs.jpg

EFD65C5C-00F2-4986-8148-4690781BAC3B_zpslykiqi8y.jpg


Pretty tight between the firewall flange and engine mount so I made a attatch strip that extended forward with nutplates to attatch the lower half. The top half I used a strip of .063 with nutplates and adels to the engine mount.
22563DB4-11AA-4D21-909F-19583E336158_zpsw9o3jcp3.jpg


Underside view, this has got to flow better than before.
2967D2AE-8A8E-4C56-B7C0-200E1E4C99A0_zpstmrfm03r.jpg


We'll see about any results tomorrow.
 
Well, my exit bump/ramp worked. It was 55ish degrees instead of 85, but my CHT's were significantly lower. I forgot my data card at home so no recorded results.
I noticed on taxi ops my CHT's were about 40-50 degrees cooler. I did multiple heat soaked shutdowns and start ups today, the hot start taxi and takeoff usually yields 410 on #4 on climb-out of 125 IAS. today was a max of 390, #4 is over 100 degrees EGT leaner than any of my other cylinders at full throttle, all other cylinders were 350-375.
I did my first Aerobatics lesson today, 4000-6000 Density Altitude , full rich and 75ish % power yielded CHT's from 326-375 with oil temp 173-182. First flight like this so nothing to compare it too.
I had low 200's for CHT's on landing, I don't remember what they were before but I've never seen that low.

I did notice a different deeper exhaust sound in the cabin, also some constant high frequency vibration on the floor by my feet. I moved the exhaust while installing the ramp and it is slightly different from what it was, not sure if it is exhaust placement or the new flow/sound with the ramp.

I believe I've had a decent baffling seal from the beginning, none of my tinkering with sealing the upper side has produced anything noticeable. I plan on extending the stainless aft of the firewall and extending and narrowing the cowling exit to match the oil/exhaust flows on the belly. Pic from after the -G testing previously.
401142FE-CC3B-48F9-8923-DB4A216CB14D_zpsbzl45mvs.jpg
 
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Yes, from all the oil on that flight I found I may have to remake the trailing edge of my upper intersection fairings.
 
Part 1 mostly complete, part 2 I'm planning on more stainless on the belly.

Lower firewall as it was.
05A0654C-0DB8-40A6-8007-093D603E235D_zpspdnylhvz.jpg


I used posterboard for a template and the shaped it with an old pipe before I cut the relief notches for my control cables. I wanted to make it semi-removable for further modifications.
31651C0E-F702-4445-B42C-F2CB1618C7DE_zps4ccyrb85.jpg

57C0F851-D667-4F29-8862-AD60C953DBD8_zpsruxe8atl.jpg

AC8AFC0C-A6EF-4EB1-9397-09F59AA44077_zpsripnfeqs.jpg

EFD65C5C-00F2-4986-8148-4690781BAC3B_zpslykiqi8y.jpg


Pretty tight between the firewall flange and engine mount so I made a attatch strip that extended forward with nutplates to attatch the lower half. The top half I used a strip of .063 with nutplates and adels to the engine mount.
22563DB4-11AA-4D21-909F-19583E336158_zpsw9o3jcp3.jpg


Underside view, this has got to flow better than before.
2967D2AE-8A8E-4C56-B7C0-200E1E4C99A0_zpstmrfm03r.jpg


We'll see about any results tomorrow.

One would think that this type of setup would actually trap some of the exit air behind it and have less of flow thru the exit. Wouldn?t the ramp provided a better outward flow if the top part of the ramp was attached to the FW and more of a [half] tear shape as oppose to round?

I had and still would really like to build one for mine, but it would be even harder as it is a 7A, so I am very interested in your progress and results.
 
One would think that this type of setup would actually trap some of the exit air behind it and have less of flow thru the exit. Wouldn’t the ramp provided a better outward flow if the top part of the ramp was attached to the FW and more of a [half] tear shape as oppose to round?

Don't know, from the original post I asked the same thing and DanH said either one. Today's flights proved it's moving air more efficiently than the stock set-up. The ramp was more convenient for me to make on the flying airplane, and easier to remove if modified. If you visualize it, both the ramp and teardrop bump are aft of the air exiting the cylinders.

My uneducated guess is I moved the turbulent airflow blocking mess further inside the cowling where everything is swirling around instead of swirling and blocking the exit.
 
Well, my exit bump/ramp worked. It was 55ish degrees instead of 85, but my CHT's were significantly lower. I forgot my data card at home so no recorded results.IMG]
Can you elaborate a bit once you have 85F temps? I have way lower CHTs when it's 55 too. My problems start about 80-85F. This type of mod is on my list too so I'm curious.
 
Well, my exit bump/ramp worked. It was 55ish degrees instead of 85, but my CHT's were significantly lower. I forgot my data card at home so no recorded results.
I noticed on taxi ops my CHT's were about 40-50 degrees cooler. I did multiple heat soaked shutdowns and start ups today, the hot start taxi and takeoff usually yields 410 on #4 on climb-out of 125 IAS. today was a max of 390, #4 is over 100 degrees EGT leaner than any of my other cylinders at full throttle, all other cylinders were 350-375.
I did my first Aerobatics lesson today, 4000-6000 Density Altitude , full rich and 75ish % power yielded CHT's from 326-375 with oil temp 173-182. First flight like this so nothing to compare it too.
I had low 200's for CHT's on landing, I don't remember what they were before but I've never seen that low.

I did notice a different deeper exhaust sound in the cabin, also some constant high frequency vibration on the floor by my feet. I moved the exhaust while installing the ramp and it is slightly different from what it was, not sure if it is exhaust placement or the new flow/sound with the ramp.

I believe I've had a decent baffling seal from the beginning, none of my tinkering with sealing the upper side has produced anything noticeable. I plan on extending the stainless aft of the firewall and extending and narrowing the cowling exit to match the oil/exhaust flows on the belly. Pic from after the -G testing previously.
401142FE-CC3B-48F9-8923-DB4A216CB14D_zpsbzl45mvs.jpg
your temp delta may or may not be a result of this mod. With a 30 deg difference in outside air temperature (OAT) between the before and after tests of your temperature readings, your results could be due to the OAT delta alone.

Another measure of the effectiveness of this mod would be speed. If you are successfully reducing cooling drag with this mod, the effectiveness of the mod should be noticeable in a change in cruise speed for example. Although the change due to the mod may be too small of a change to notice a change in speed. However, you would never know for sure unless you did make attempts to measure it. Did you measure your speed at any time during your before and after tests to see if there were any differences in speed?

By the way, one thing I saw as interesting in your oily belly pic was the swirl pattern just to the left of the left exhaust. The air in that area is clearly trying to turn around and go back the way it came. Something inside the cowling in that area is disrupting the airflow before it makes it outside the exit.

Note that my comments below are in bold red after each sentence it is referencing.

Don't know, from the original post I asked the same thing and DanH said either one. Today's flights proved it's moving air more efficiently than the stock set-up. I would not be so quick to say the test(s) you described did 'prove' air is moving more efficiently. There is the OAT variable delta that could be skewing your results.

The ramp was more convenient for me to make on the flying airplane, and easier to remove if modified. If you visualize it, both the ramp and teardrop bump are aft of the air exiting the cylinders.

My uneducated guess is I moved the turbulent airflow blocking mess further inside the cowling where everything is swirling around instead of swirling and blocking the exit. If this is true, mind you I am not saying it is, then the turbulence inside the cowling 'swirling around' would create a worse airflow environment than the 'swirling' air out on the belly. You DO NOT want swirling turbulent air inside the cowling. That is exactly the thing this mod is designed to reduce.
 
Did you measure your speed at any time during your before and after tests to see if there were any differences in speed?

Excellent advice. Seems I meet quite a few builders who have never established an accurate baseline speed (or calibrated the ASI, although that's another issue). As a result, they really don't know if their airplane is fast or slow, and worse, they never really know if a mod made a difference.

The late Bob Axxom was a sterling example of a guy who always ran careful before-and-after speed checks. Learn the NTPS method and be like Bob.

By the way, one thing I saw as interesting in your oily belly pic was the swirl pattern just to the left of the left exhaust. The air in that area is clearly trying to turn around and go back the way it came. Something inside the cowling in that area is disrupting the airflow before it makes it outside the exit.

Steve, best I know it just means the outlet velocity is slow compared to free stream velocity. Ever run your pickup truck up into the wake of an 18-wheeler at 75 or so, and feel it rock back and forth? Google "Von Karman".
 
Sorry, too excited from my flights yesterday, I didn't quantify very well.

" I would not be so quick to say the test(s) you described did 'prove' air is moving more efficiently. There is the OAT variable delta that could be skewing your results."

Yesterday's 50ish degrees was the hot-end (10-50 degrees) of the bulk of my 40 hour test period. I noticed very little difference in CHT's or oil temp during the last couple months of 10-50 degree OAT, the 80 ish degree flight increased CHT's approximately 10 degrees and oil temp 15 degrees.
The CHT's were lower on yesterday's 50 OAT degree flight with the exit ramp as noted than my CHT's at 20 degrees OAT.
I'll try to get a flight in at 80+ degrees OAT and post a screenshot, in Ks I shouldn't have to wait too long.

" If this is true, mind you I am not saying it is, then the turbulence inside the cowling 'swirling around' would create a worse airflow environment than the 'swirling' air out on the belly. You DO NOT want swirling turbulent air inside the cowling. That is exactly the thing this mod is designed to reduce."

That pic was from the 0 G testing prior to the exit ramp, I don't have enough exhaust flow or oil on the belly since I added the ramp.
 
Excellent advice. Seems I meet quite a few builders who have never established an accurate baseline speed (or calibrated the ASI, although that's another issue). As a result, they really don't know if their airplane is fast or slow, and worse, they never really know if a mod made a difference.

The late Bob Axxom was a sterling example of a guy who always ran careful before-and-after speed checks. Learn the NTPS method and be like Bob

Guilty:(......NTPS speed method is my next assignment, I will try to be more like Bob.

My IAS/TAS have always matched Van's numbers, yesterday was bumpy and I had a hard time keeping it level but it was not slower. I believe it was 1-2 knts faster but inconclusive with my improper testing. I did make it removable so perhaps I can go back and test this properly.
 
Can you elaborate a bit once you have 85F temps? I have way lower CHTs when it's 55 too. My problems start about 80-85F. This type of mod is on my list too so I'm curious.

This is truly a big statement. I did rounds and rounds of testing with a lot of small modifications here and there. I can tell you that 55F would definitely show much cooler temps on my engine than 85F. If I didn't match the OAT almost exactly, I would find that I really had no idea if my change actually worked.

The small changes I made (and a couple big ones) are hard to quantify the results if your baseline isn't the same. Especially if you're talking about a net improvement of 5 degrees or so...if the OAT is 30F different than your last test, you really don't know what your results are.
 
Guilty:(......NTPS speed method is my next assignment, I will try to be more like Bob.

My IAS/TAS have always matched Van's numbers, yesterday was bumpy and I had a hard time keeping it level but it was not slower. I believe it was 1-2 knts faster but inconclusive with my improper testing. I did make it removable so perhaps I can go back and test this properly.
I think you are concentrating too much on whether this mod is affecting your temperatures. Yes, a smooth airflow through the cylinders will keep cylinder temps down but this particular mod should have more effect on your airspeed than engine temps. Observing airspeed deltas will give you more info on whether this mod is effective or not.
 
I think you are concentrating too much on whether this mod is affecting your temperatures. Yes, a smooth airflow through the cylinders will keep cylinder temps down but this particular mod should have more effect on your airspeed than engine temps. Observing airspeed deltas will give you more info on whether this mod is effective or not.

Correct, my main goal was to reduce temps. Airspeed deltas will cost a lot of $$ and time, I'm currently rationing both.
 
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The ultimate goal should be to have engine temperatures where you want them both in climb and cruise and also to increase speed.
When I was at this stage smoothing the outlet did a great job of lowering both the engine temperatures and airspeed.
It took many changes to inlets, and a complete bottom cowling rebuilt to get the results that I was looking for. The outlet on this last version, four years now, is quite small and I put a cowl flap on as I felt it would be needed for climbs on hot days. I never have to use the cowl flap and I am ready to bond it in place lose a bit of weight and complexity.
Personally I did not have a lot of luck with individual flight testing as flight conditions were so variable that it was hard to get reliable data with one or two flight tests. Bob Axom and I used to debate this at length what worked for him did not work for me. What did work for me was to fly beside another aircraft before and after a modification. The other aircraft and I would use the same power setting, altitude etc, before and after the mod. Changes, both good and bad, were easily noted.
The best test of all was a few years spent in the SARL racing circuit. It was kind of like playing golf, yes you are comparing your self to others but with a number of races and modifications you were also racing against your own record. Lots of fun and highly educational.
 
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Excellent advice. Seems I meet quite a few builders who have never established an accurate baseline speed (or calibrated the ASI, although that's another issue). As a result, they really don't know if their airplane is fast or slow, and worse, they never really know if a mod made a difference.

Guilty as charged. Although I have done it a number of times for some other testing, but I have not got a kept a good record nor believe my tests were set very accurately.

Would matching density altitude and weight (varied by amount of fuel) be a good way to establish max speed? Of course then you would go WOT and max RPM and try to set the FF or EGTs to the same number as before and after?
 
Great discussion guys. CradAndy, Keep us posted on your changes because, apparently, a lot of us are considering them. :)
 
Don't ignore the possibility that simply adding the exit ramp ('bump' sounds external to me) will likely improve cooling, but will also likely increase drag, as well. You'll be moving more air through the cowl, therefore, high probability of more drag. (Next step: cowl flap to reduce exit area at speed...)

Also,
There's a NACA/NASA paper floating around that deals with inlet lip shape. IIRC, it basically says that if the diffuser uses internal diffusion and the inlet/outlet are sized correctly, the lip can be fairly sharp & that's the lowest drag configuration. If external diffusion is used, the lip should be more blunt and rounded, to avoid separation & turbulence on the outside of the lip.

Every domino can touch every other domino....

Charlie
 
Guilty as charged. Although I have done it a number of times for some other testing, but I have not got a kept a good record nor believe my tests were set very accurately.

Would matching density altitude and weight (varied by amount of fuel) be a good way to establish max speed? Of course then you would go WOT and max RPM and try to set the FF or EGTs to the same number as before and after?

Certainly standardized as much as possible improves accuracy, so yep, all of the above.

You can fly four legs and input different combinations of three into the NTPS spreadsheet as a cross check. If the answers are always close, you didn't have a major variable or error on one leg. It all helps.
 
Ok, I've got the Doug Gray instructions for determining TAS from GPS track and speeds. I may need a little help with the spreadsheet, my laptop doesn't have Excel and haven't been able to find a link to work yet. I'm hoping to record these numbers this weekend with and without the outlet ramp.

I'm also debating if it's also a good time to establish pressures within the cowling , perhaps give me an idea of how well my baffling is sealing. I'm thinking of the yardstick manometer with tubing ran through the heater inlet and on tube in the center of the upper "plenum" and one somewhere in the lower cowling. Thanks for the ideas.
 
Ok, I've got the Doug Gray instructions for determining TAS from GPS track and speeds. I may need a little help with the spreadsheet, my laptop doesn't have Excel and haven't been able to find a link to work yet. I'm hoping to record these numbers this weekend with and without the outlet ramp.

I'm also debating if it's also a good time to establish pressures within the cowling , perhaps give me an idea of how well my baffling is sealing. I'm thinking of the yardstick manometer with tubing ran through the heater inlet and on tube in the center of the upper "plenum" and one somewhere in the lower cowling. Thanks for the ideas.

One of the members here (can'r remember his name) create a free app for iphone and it makes this calcuation very easy. It is called gps2tas and I wonder if it is still available on itune.

On other notes, I am going to try this mod very soon as it is getting time for another oil change. Will report back when I get some thing to show for it.
 
I did between 75 and 100 of these tests and used them to check results of modifications. I used four runs rather then three and then was able to use four separate three leg calculations to verify any error of the data. I always used 6000' PA and the same rpm and mp. After two to three years of this kind of testing I discovered that there is a considerable difference in engine power based on OAT. I guess I should have known this but it meant that all my data was essentially useless unless I just compared those days with the same OAT.
I am not sure if using Density altitude rather then Pressure altitude would have made a difference. I think that density altitude would be better as at least the "air density" should be the same but I am not sure that it would take into account the HP difference in temperature. Perhaps when my EFFIS states 75% power the calculations have a temperature correction but I would doubt that. Years ago one of the rocket guys made a little on line calculator for comparing HP with temperature, it was significant enough to make use of the above method unusable for multiple day/season changes. That is why I went to comparing my speeds based on a chase plane. That takes all the variables out and you can actually see your progress based on the other aircraft using predetermined power settings. Of course this only works if the chase plane is NOT making any changes. We discovered that having a passenger in the back could also change the data, thus every test flight should be a the same weight and C of G.
 
For these reasons, I thought to use density altitude as oppose to pressure altitude.

Also, if we are merely trying to get a comparison of before and after speed, then do we really need to do the four-leg GPS to determine the true speed? Any reason not to use what the EIFS reports as TAS if density altitude is the same? What other factor, beside density altitude is used to draw the TAS? I ask this while I realize each EIFS manufacturer probably uses different formula to calculate their TAS.
 
I did between 75 and 100 of these tests and used them to check results of modifications. I used four runs rather then three and then was able to use four separate three leg calculations to verify any error of the data. I always used 6000' PA and the same rpm and mp. After two to three years of this kind of testing I discovered that there is a considerable difference in engine power based on OAT. I guess I should have known this but it meant that all my data was essentially useless unless I just compared those days with the same OAT.
I am not sure if using Density altitude rather then Pressure altitude would have made a difference. I think that density altitude would be better as at least the "air density" should be the same but I am not sure that it would take into account the HP difference in temperature. Perhaps when my EFFIS states 75% power the calculations have a temperature correction but I would doubt that. Years ago one of the rocket guys made a little on line calculator for comparing HP with temperature, it was significant enough to make use of the above method unusable for multiple day/season changes. That is why I went to comparing my speeds based on a chase plane. That takes all the variables out and you can actually see your progress based on the other aircraft using predetermined power settings. Of course this only works if the chase plane is NOT making any changes. We discovered that having a passenger in the back could also change the data, thus every test flight should be a the same weight and C of G.

Tom,
That's a lot of testing! I assumed the test were all using Density Altitude.

I originally made the cowling bump/ramp only to see what it would do for my CHT's, I was going to see if it did anything to my IAS and leave it at that. I've never done the 3 or four leg TAS calculation because of all the variables involved, I assumed my results would probably end up inconclusive.
My homemade pitot and static test passed with flying colors. I've flown with numerous aircraft and found my IAS/TAS displayed on the EFIS to be within 1-2 knts of aircraft that had performed the 3 leg TAS calculation and have current Altimeter Static checks.

Thanks for the tips, probably easiest to do every test solo starting with full tanks for consistency. I will try to incorporate another aircraft when I can, but sometimes hard to fit schedules. I'm going to give the 4 leg NTPS thing a couple shots and see if it shows something definitive between the cowling ramp and no ramp.

Do you by chance have any photos of your foam seal behind the spinner? I saw a post where you glassed in the cowling behind the spinner but the pics disappeared that might've shown how you finished sealing it off. DanH's seal looks great, but because of my landoll ring I'm going to have to do a little glass work to make it work. The more options to look at and copy off of the better!

Thanks,
Andy
 
I'm also debating if it's also a good time to establish pressures within the cowling , perhaps give me an idea of how well my baffling is sealing. I'm thinking of the yardstick manometer with tubing ran through the heater inlet and on tube in the center of the upper "plenum" and one somewhere in the lower cowling. Thanks for the ideas.

This is the standard piccolo tube installation we used in previous data gathering. Information is more global when everybody uses exactly the same setup.

There are two piccolo tubes in the upper cowl and two in the lower. Each pair is tee'd together. The goal is an overall average pressure for each space.

IMG_0194%20600w.jpg


IMG_0196%20600w.jpg


It's easy to drill all the little holes if you make a drill jig:

Drill%20Jig%20745w.jpg
 
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DanH, leftover brakeline/fueline material or hardware store stuff for the piccolo tubes I'm hoping is "similar" enough....

Adels for attaching the Piccolo tubes to the push rod tubes, what's handy for attatching the lower Piccolo tubes? Large Adels to the intake tubes?

I'm on kiddo duty tomorrow and need to get my shopping list in order!
 
DanH, leftover brakeline/fueline material or hardware store stuff for the piccolo tubes I'm hoping is "similar" enough....

Use the exact spec tubes, installed per the spec, if you wish to have reasonably global information. If you don't care about the ability to make reasonable comparison to others who did the same test, do what you want.

The thinwall K&N tube was available on Ebay, etc. Hardware store vinyl tube seemed to work fine for hookups, although yellow tygon is more heat resistant.

Adels for attaching the Piccolo tubes to the push rod tubes, what's handy for attatching the lower Piccolo tubes? Large Adels to the intake tubes?

Don't need adels. Safety wire and some tubing standoffs are fine. In my case the uppers were wired to padded fuel injection lines.

9lh6wl.jpg


r89edu.jpg
 
Ok, my helper and I got her tore apart and found the exact K&S tubing at Hobby Haven 50 miles away.
3F7B1F1F-E7A4-4444-A71B-1BC3EA776D14_zpsgwtkvqbg.jpg


Time to take mama to town for dinner, just happens Hobby Haven is just down the street from a lot of restaurants!
 
OK, slightly embarrassed to show pics of anything of mine next to DanH's but I should get a B- for effort (It started feeling like work and I got in the get-er-done mode).
Piccolo tubes made as specified, mounted close to specs +/- 3/8 inch for various mounting issues.
9811D6A6-406C-4945-B96F-15684805592F_zpsd1zhlovj.jpg

37FF9F5A-AFF0-44CD-BE70-339AFBFC8931_zpsgh5h6bco.jpg


I forgot to get a photo but I routed the tubes through the heater inlet on the firewall and zip-tied the tubes to a meter stick in the cockpit. Here's my measurements of the homemade manometer all in inches while flying and removing shoulder harness to try to read meter stick correctly:
Static: Upper tubes-11/78 Lower tubes-12 1/2
Idle RPM: Upper tubes-12 Lower tubes-12 1/2
130 IAS: Upper tubes 17 1/2 Lower tubes-15 1/4
160 IAS: Upper tubes 20 Lower tubes-14 1/2

Not sure the 160 IAS lower tube measurement is accurate, I recorded it as such but it doesn't fit the trend. Any feedback on my pressure differentials is greatly appreciated.

Full tanks and me yielded a gross weight of 1505 lbs and C.G. of 81.93 in my RV7. The airport weather system reported 30.17 inHg and 59*F, my aircraft altimeter set to field elevation yielded 30.17 inHg and OAT of 64*F. Winds aloft at 6000 in my vicinity were forecast at 4*C (I forgot to record direction), at 6000 MSL my OAT indicated 46*F. Perhaps my aircraft OAT reads 3-5*F high, it's mounted between the 2 and 3rd access bay under the right wing. For the speed test I used 5700 pressure altitude, my best guess at 6000 density altitude. I leaned to approximately 80-100*F ROP on my leanest cylinder (#4) which peaks at 1450*F. I performed 4 runs, heading 360 followed by a right turn to heading 240 followed by a right turn to 120 in an attempt to stay in the same air-mass. I also did a random run a heading 180, I wasn't sure I consistent results were possible with my piloting skill (or lack of) but here goes:
Hdg 360: 160 IAS/ 175 TAS/ 183 GS/ 359 TK
Hdg 240: 160 IAS/ 175 TAS/ 171 GS/ 240 TK
Hdg 120: 160 IAS/ 176 TAS/ 179 GS/ 120 TK
Hdg 180: 160 IAS/ 175 TAS/ 175 GS/ 178 TK

I hope to have Excel on my computer in the next couple days, if someone else could enter my info in the spreadsheet that would be great. The rough avg speed is 177 knt TAS with an IAS of 160 so calibrated air speed should be close to +1 knt at this airspeed I believe.

For my purposes the primary purpose of adding the ramp/bump was for CHT cooling, here's some screen shots of my EFIS during the above test. All screen shots here were without the ramp/bump under the above described conditions.
This shot is after a 3 minute taxi and engine runup after a cold start, CHT's all around 300.
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At level off after takeoff and climb at 130 IAS from 960-6000 MSL.
20140518_095537_zps77732e36.png


Screen shot after all full power runs.
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Screen shot after landing and 3 minute taxi back to the hangar.
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I've re-installed the ramp/bump and hope to get a test flight done in the morning.
 
Hdg 360: 160 IAS/ 175 TAS/ 183 GS/ 359 TK
Hdg 240: 160 IAS/ 175 TAS/ 171 GS/ 240 TK
Hdg 120: 160 IAS/ 176 TAS/ 179 GS/ 120 TK
Hdg 180: 160 IAS/ 175 TAS/ 175 GS/ 178 TK

I hope to have Excel on my computer in the next couple days, if someone else could enter my info in the spreadsheet that would be great. The rough avg speed is 177 knt TAS with an IAS of 160 so calibrated air speed should be close to +1 knt at this airspeed I believe.


Andy, Here is what I got using the NTPS formula. I used 3 sets of numbers in different configurations.

51brsy.png


The average for 4 runs using your numbers is 177.8 ( the same number as a 3 leg 120 degree test)

Hope this helps and keep up the good work.....
 
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....I routed the tubes through the heater inlet on the firewall and zip-tied the tubes to a meter stick in the cockpit. Here's my measurements of the homemade manometer all in inches while flying and removing shoulder harness to try to read meter stick correctly:
Static: Upper tubes-11/78 Lower tubes-12 1/2
Idle RPM: Upper tubes-12 Lower tubes-12 1/2
130 IAS: Upper tubes 17 1/2 Lower tubes-15 1/4
160 IAS: Upper tubes 20 Lower tubes-14 1/2

Andy, I'm not sure what we're looking at here. Some numbers don't make sense.

Let's back up a moment and check the installation. A manometer measures the difference between two points. Your plumbing should be like this, one leg connected to aircraft static and the other connected alternately to upper or lower cowl pressure:

ehnf5y.jpg


Here's your test card. Print it and carry it with you. The text assumes an electronic manometer, and also measuring exit temperature, so ignore those bits.

Zero the manometer before engine start (see the instructions which came with the instrument).

Climb to 3500 feet pressure altitude, i.e. altimeter reads 3500 when set to 29.92.

Set AP altitude hold mode if you have it.

Set AP to heading mode so you can steer with a heading bug.

Set your GPS to indicate track, or find an EFIS page which indicates track.

Set power for roughly 100 knots indicated, the first target airspeed. It does not need to be exact; anywhere from 95 to 105 will do. The key item is stability; we want a nice stable airspeed, meaning you need a stable altitude hold and a locked throttle quadrant.

Set mixture for about 100 ROP, best power, for max heat load to the cylinder heads. Trim when speed stabilizes. Again, no particular exact speed is necessary; just a stable speed which approximates the target speed.

When speed is stable, record GPS groundspeed and GPS track (NOTE: track, not heading).

Turn to a new heading (a 120 degree turn works well). When speed stabilizes, again record GPS groundspeed and GPS track.

Turn to a third heading. When speed stabilizes, again record GPS groundspeed and GPS track. Now record upper plenum pressure, lower plenum pressure, all CHT readings, exit temperature, and OAT.

To make the pressure measurements, simply connect the upper tube to the open manometer port and record the reading. Now swap the lower line for the upper line and again record the reading.

Pay attention to where you are going. The first heading will use some distance because you are setting power. The second goes quickly, just the time it takes for speed to stabilize after the turn. The third heading requires time to stabilize plus time to record the temperature and pressure data.

Now repeat the procedure for the next higher speed, ballpark 120 knots. Then repeat for 140 knots and 160 knots. The airspace required for each three-leg set will increase with increasing speeds; don’t hit anything solid.

When you get home plug the three groundspeeds and tracks for each speed point into the attached NTPS spreadsheet. The result is your true speed for that temperature and pressure data set.


I leaned to approximately 80-100*F ROP on my leanest cylinder (#4) which peaks at 1450*F.

Excellent. Keep doing that, as it nets maximum heat load.
 
Andy,
To follow up on what Dan has said.
Your static numbers should be zero. At no forward speed your pressure would be zero difference between plenum and static.
Moving forward you would have a positive pressure difference between plenum and static.
Looking at your numbers we could take your static numbers and round those to zero by reducing 12.
If we took your 160 kts numbers we could also reduce those by 12 and get 8" upper and 2.5" lower.
They would be zero'd at altitude. And as Dan mentions you need to connect the static port to the ships static system as we all learned from training that the static changes in the cockpit during flight.
 
Doh, seems I've negatively transferred the fuel tank pressure testing setup to my cowling pressures. My upper piccolos are T'd together and is the clear tubing, the lower piccolos are T'd together and is yellow.
70F13380-8F31-4E87-9286-21DE137C150C_zpsb9fbobig.jpg


I charted the initial level and figured the difference between the two would be my differential. I knew the static cabin was different, didn't think about hooking it to the static system.
 
A little bit warmer today, airport weather reported 60*F and 29.86 inHg. My EFIS was 65*F and 29.88 on the ground. Winds aloft at 6000 were forecast at 210@30 and 15*C, When I started my test at 5000 pressure altitude my EFIS was 60*F when I ended it was 62*F. Density altitude was close to 6000.

My RV7 was at the same 1505 Gross Weight with a C.G. of 81.93, with the bump/ramp installed leaned for 80-100 ROP on my leanest cylinder. Gusty winds and low broken layer today, smoother above the layer but I had a harder time getting everything stabalized. (no autopilot) Here's my 4 runs I believe it actually is faster:
HDG 360: 161.5 IAS/ 177 TAS/ 210 GS/ 002 TK
HDG 240: 161.5 IAS/ 177 TAS/ 147 GS/ 247 TK
HDG 120: 161.5 IAS/ 177 TAS/ 185 GS/ 106 TK
Hdg 030: 161.5 IAS/ 177 TAS/ 215 GS/ 029 TK

Not sure about the validity of my pressures now but here they are measured in inches of water at cabin static pressure. Very similar as the readings without the bump/ramp.
Static (zero point): upper 11 7/8 lower 11 1/4
Idle: upper 12 lower 11 1/4
130 IAS: upper 17 3/4 lower 14
161.5 IAS: upper 20 lower 14 1/2

EFIS screenshot after 2 min taxi and runup. OAT on the ground very similar Average CHT without bump/ramp was 299.75, with the bump/ramp 288.
20140519_084003_zpsb92f7b41.png



EFIS screenshot after level off from 130 IAS at 6000 density altitude, about 15*F warmer today. Without the bump/ramp the average CHT was 367.25, with the bump/ramp they were 363.5.
20140519_084555_zps36bb55ad.png


EFIS screenshot after 4 speed runs at 6000 density altitude, again about 15*F warmer today. Without the bump/ramp average CHT was 377.75, with the bump/ramp was 381.75.
20140519_090316_zps67925665.png


EFIS screenshot at shutdown, yesterdays was a low power gliding descent with a 2 min taxi after landing with average CHT's of 297.25. Today I flew level above the broken layer, dove down and flew level to the airport, did a go-around because of winds and a 2 min taxi average CHT was 302.75. I forgot to note the OAT at shutdown, but when I got in the car 30 minutes later it was 75*F.
20140519_091737_zpsfe35be2c.png


Whew, lots of typing now I gotta run!
 
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