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Water Cooled vs. Air Cooled- Real Numbers

Woahhhh……I apologize if any engineer was offended at my "Most" comment. No slight intended. I should clarify that I was referencing Innovation/Development of new ideas as applied to engineers. Doesn't mean an engineer is bad or stupid. They may be extremely good at what they do. "Most" stick to what they know and have spent considerable time and money learning. Innovation requires looking outside what is known in ones field. Sometimes it is a new material or science outside their area of expertise. In my case I am not an Engineer. But I have many different areas of knowledge from my line of work. I sometimes apply something new from one field to solve a problem in another. My new awareness of Pourous SS had me calling engineers to see if they could use it to solve a problem I had. Some said NO. I found one who said YES, and was already using it. Problem solved. I've met many brilliant engineers/scientist in my line of work who couldn't see the Forest for the Trees, so to speak. I met Richard V about 28 years ago at a gathering of RV'ers at OSH. Not sure if they still do it or not, now that the RV community is 7000+ flying. Back then there were a couple hundred flying. Richard V is a great success. But even way back then people told me he was "Too much of an Engineer" (have no idea what people say today) That can be a good thing. But innovation is not what "Most" engineers do. Peace :)

Side note: R.V. said back then he hoped to achieve the reputation that GlasAir has. Boy have things changed.
 
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"80 years of time passage has not changed the fundamentals of thermodynamics"


True. The laws of Thermodynamics are the same. But heat transfer has moved beyond Water-to-air in the last 80 years. The laws of gravity haven't changed either since airplanes were invented. But we've found ways to overcome that. Don't you think?

Heres a link to some things that didn't exist 80 years ago. http://en.wikipedia.org/wiki/Coolant There is no reason the coolant system has to be water from the motor to the coolant surface and back in one loop. A Liquid/liquid or liquid/gas exchanger can bring two very different coolant systems into transfer. The surface cooler could for example operate at much higher temps then the water in the motor. Benefitting much like an air-cooled motor. Which can pass more heat for a given surface area, because of water's lower boiling temperature. Use your imagination. I would never state "It won't work" because it didn't work 80 years ago.
 
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.... But innovation is not what "Most" engineers do. Peace :)

Really, I'd say "most" if not all innovation would not be possible without science and engineering. Sorry to dive into the forum on this post, but the anti-engineer speak was driving me crazy. It is not the job of the scientist to write the law, just observe and try to explain it so problems can be solved by engineers. Often our understanding changes, but nature doesn't change. Do you have to be classically trained to solve problems, nope. Having an understanding of how things work helps reduce the trial and error. Thermo is thermo, our understanding and use of it has improved, but pretty sure God or whoever your designer is has not changed the plans on us.

I do appreciate the thread and was looking at it for future plans. Makes sense and looking forward to more test results.
 
Welcome to VAF!

Andrew,
welcome.gif
to VAF:D

Great first post, diving in is just fine.
 
6-8 knots faster at the same power settings and density altitudes than it was before.

Excellent, Ross, just what you estimated way earlier. That 97% momentum recovery is confirmed in the final results. Thanks for posting you project and final results. Happy New Year - !!
 
Fantastic Article in Kitplanes!

Ross, Thanks for the outstanding documentation and very well written article on this project in the new Kitplanes issue.

Everyone should read it to understand the effects. It really makes sense the way you describe the effect. If I get this right, the pressure drop loss of velocity across the heat exchanger is made up by the increase in volume generated by the temperature rise across the same core. When you described it, that made perfect sense of the data! So, it seems a good trade off of core area, pressure drop characteristics, altitude, and BTU's of heat rejected are necessary to get close to the neutral or thrust effects.

This is foundation work for ALL future liquid cooled system designers. Don't just stick a radiator in the cowl! What is really really important, is that it is not necessary to design a completely new airframe to take advantage of this effect. An ill conceived conclusion of mine for many years. Yes, the external drag of the housing still has to be addressed, but your 7 kts increase was well earned, and the external added drag is fodder for another day and thread.

Thanks for sharing this valuable project. I hope to see it at OSH this year.
 
Ross, Thanks for the outstanding documentation and very well written article on this project in the new Kitplanes issue.

Everyone should read it to understand the effects. It really makes sense the way you describe the effect. If I get this right, the pressure drop loss of velocity across the heat exchanger is made up by the increase in volume generated by the temperature rise across the same core. When you described it, that made perfect sense of the data! So, it seems a good trade off of core area, pressure drop characteristics, altitude, and BTU's of heat rejected are necessary to get close to the neutral or thrust effects.

This is foundation work for ALL future liquid cooled system designers. Don't just stick a radiator in the cowl! What is really really important, is that it is not necessary to design a completely new airframe to take advantage of this effect. An ill conceived conclusion of mine for many years. Yes, the external drag of the housing still has to be addressed, but your 7 kts increase was well earned, and the external added drag is fodder for another day and thread.

Thanks for sharing this valuable project. I hope to see it at OSH this year.

Thanks Bill. I mainly did this whole exercise mainly to prove or disprove the theory and all the speculation out there. The side benefit was a simpler setup, reduced weight and a few knots.
 
Thanks Bill. I mainly did this whole exercise mainly to prove or disprove the theory and all the speculation out there.

Funny how folks accept the small exit for least momentum loss on the famous Mustang belly scoop, yet insist on throttled inlets and a large exit for their Lycoming cowl. In terms of underlying theory, there's no difference in cooling with a water to air exchanger, or directly from hot engine parts.

In terms of practical design, the indirect method (engine to water, water to air) adds weight, but allows an optimized heat exchanger in optimum ductwork, with zero leakage. The direct-to-air system is lighter and less complex, but generally suffers from (a) poor sealing, (b) all the engine's auxiliary bits in the airflow, and (maybe) (c) more momentum loss across the the cylinder fins (the exchanger).

Nice job Ross.

Hey, it's been a while since we've seen any updates on the RV-10. I seem to recall a more aerodynamic exchanger housing, as compared to the RV-6 test mule. Did you learn anything that tempts you to go back and rework the RV-10 system?
 
Funny how folks accept the small exit for least momentum loss on the famous Mustang belly scoop, yet insist on throttled inlets and a large exit for their Lycoming cowl. In terms of underlying theory, there's no difference in cooling with a water to air exchanger, or directly from hot engine parts.

In terms of practical design, the indirect method (engine to water, water to air) adds weight, but allows an optimized heat exchanger in optimum ductwork, with zero leakage. The direct-to-air system is lighter and less complex, but generally suffers from (a) poor sealing, (b) all the engine's auxiliary bits in the airflow, and (maybe) (c) more momentum loss across the the cylinder fins (the exchanger).

Nice job Ross.

Hey, it's been a while since we've seen any updates on the RV-10. I seem to recall a more aerodynamic exchanger housing, as compared to the RV-6 test mule. Did you learn anything that tempts you to go back and rework the RV-10 system?

Agreed. I see people trying all sorts of things on RVs to eek out a few more knots when you proved what could be done without a ton of work or expense on a variable exit flap.

The RV10 hasn't been touched in over 18 months. Just too busy with the business in that time and other things in life. We have some new products in the works hopefully to be released over the next few months and have been aligning the future more towards aviation products since 80% of our ECU sales in 2014 were for aviation. The RV10 will likely become a retirement project at this rate...

Actually, outside scoop aesthetics aside, the RV6A scoop internal shape and inlet/ core/ exit ratios are probably superior to the RV10 setup. At least the work on the -6 lets me rest easier that the -10 should cool just fine. I was always worried in the back of my mind that the rad might be too small.
 
Heres a link to some things that didn't exist 80 years ago. http://en.wikipedia.org/wiki/Coolant There is no reason the coolant system has to be water from the motor to the coolant surface and back in one loop. A Liquid/liquid or liquid/gas exchanger can bring two very different coolant systems into transfer. The surface cooler could for example operate at much higher temps then the water in the motor. Benefitting much like an air-cooled motor. Which can pass more heat for a given surface area, because of water's lower boiling temperature. Use your imagination. I would never state "It won't work" because it didn't work 80 years ago.

I originally used Evan's Coolant - instead of water - for my LS1 radiator set-up. It worked fine, but I was worried about exceeding 235 degrees. The Evan's could handle that just fine without a pressure cap, but 235 degrees is where the ECU decides to go into limp home. Mixing old & new technologies has unintended consequences....

John
 
Evans

I originally used Evan's Coolant - instead of water - for my LS1 radiator set-up. It worked fine, but I was worried about exceeding 235 degrees. The Evan's could handle that just fine without a pressure cap, but 235 degrees is where the ECU decides to go into limp home. Mixing old & new technologies has unintended consequences....

John

In my experience I found nothing has better heat transfer then 95% distilled water and 5% Dex Cool anti freeze.... That is my summer time cocktail.. Winter it's 60% anti freeze and 40% distilled water..... And this potion is cooling a 400HP motor.. Every time I experimented with Evans, it just didn't transfer heat very good at all.. YMMV.
 
thread revival

Reviving an old (and very interesting) thread

Hello Ross,
How's the long term performance looking? You previously noted a 6-8 knot increase. What was the actual performance before or after? Are you near Vans numbers compared to a Lycoming?

Do you think you have all your cooling drag minimized? Since you have an intercooler to deal with, is that still a large drag point?

Since I?m considering a similar project, I wonder if I could get some numbers to start planning?
Radiator specs: length, width, thickness, rows, other?
How did you Calculate/determine your inlet and outlet size?

Here?s where I?m coming from:
RV7, Subie H6 3.0 (was an Eggenfellner conversion), Electric CS 4 blade prop. (no turbo or Supercharger)
At one time it had 5 small radiators. 3 for coolant and 2 for oil. I have since changed out the cowling and have 2 larger radiators for coolant and 1 for oil. Cooling is actually too effective and it?s been difficult to keep the temps up. I?ve added thermostats for the oil cooler and before each radiator. I still have to partially block the oil cooler. All the radiators ram air through them with no consideration as to where the air goes afterwards other than a couple holes on the bottom of the cowling. I think this is typical of radiators buried in the cowling; so cooling works, just pretty draggy.

Cruise speed is about 150-155 knots, 2300 prop rpm and 23? MAP, burning 10.5 GPH between around 5-8000?

I would like to create and attach a scoop, with a properly sized radiator, to the bottom of the fuselage, located between the baggage bulkhead and the next bulkhead. (this is a bit further back than yours.)
Relocate the oil cooler or have ducted air from another source.
Redo exhaust to have a single muffler inside cowling and have exhaust exit out of the way of the scoop.

I think this would allow streamlining the cowling significantly and minimize the cooling drag. I would hope to pick up 10-15 knots cruise at 75% power.

Here?s what the cowling and exhaust look like:

Here you can see the 2 coolant and 1 giant oil cooler openings:
REwualrArkNvrR4sEZ1qYdYvaUGTQkupue2D3EkHEBmzuLgqsu5zThtcw-ekmw5-J9X1iZjuatMIUgmy9x6CJ4GNA1UPOBhCoQEF9T3Qf1LMcNvKO8y0H6RiLlXFik4KiP8RLaO1WtMJT1YOuN2BVyR8aYgSzSDREgiI5mieQbKUcUomdn_ryRrRZwv4w9D6hD18dnc4SmcKSVE2ORxCskyIM1WVGvTKEqz4F9S_dXdH3fK4kHZ-xTe28v8E4gYbh5G2NDX_Ksw4Y7Hwx65zlVTURtM3iynOhxxwU9y3Q1UlxLzCq1rrgRjfCH9F9N7Mc_MMQRv1z0ySzlbzfsf-WwJmxo4kAastPo7_lCzneFS8aNL9I9hKdkRGeH__JDwPwm5dLEVBkZa9wzS9a1zcKvy-anyi3w78UUmEBZwp2ufvM69NyHvclubSPITFIEhV3g9X64mffxSHkfIjcWt2OqRBGtRqBtC40Ut5yd98iWxZ6d_ugQ2QmQ7Cf9Nj-iJty69b8AqXjpm9ZEHNYDSdpJEd-p2P6p-Yekr8gaiHg8o-MexT9BcNYxEhFFUhf4DPXq8ZUd0v41T8Kz5MPM4ALe_NHPX_Xmx4xzvwxPk=w425-h225-no



Zoomed in photo of dual mufflers protruding quite a bit from the cowling.

UxsYVSTeAvTtAckoJ14KiosvdN6wU79JaJEytI6oKXicrGhSNUuYBPUs2-tzHg9b9C6ktNvdsC_UNki1d4TRlm5LG4m5q4ijFQsBv1YnhDSaltEvTQbyNx2OuIWPcsoIGHFUdgxit_jraIPcNSlNv4HaNdwNdGs3ZFE0zphCDeA_JSWZPJxGR0JgjDOUicO68Vz0EdCK7aF6JNW-lcS-jSvsuS_5H4p-nW9Sf2lyMFwYd7V9Y2ozFcGvdslltlN5mj5XhQq3bDB4Rtixqa0gNZAMNBR1VNWLBrzvlssdP3d-wKIVJ8deMXmqLlgvQu0nz7O1yjtJrQOqMRpqPJsYeGco2gjyl2pG-wKCxvdw8ZROFJZd2oByRGANZE8mnGtuvr6_uBwOT_Tkp8V_94OdiXzVyBQAr86TjF4DnRzNQxNduFXAvIl12XQF3IsvtCjVV3Qh2GQ0pEhXN7Mwz4UoVFcJiY3I-1F1hsb2o6RyDDo4Xmm9sbl_7_p27yNEqN4GqXbc7-1o7pc3b3xYSmHSXDPcDIgYElGN8YaXj-CVDTJvJYVvo9NqsskXvWA5ihtMwmWCAEnuGiubQ6k48kMkF2f1dnz6UTC26iTqfI4=w425-h225-no



Thanks,
 
Reviving an old (and very interesting) thread

Hello Ross,
How's the long term performance looking? You previously noted a 6-8 knot increase. What was the actual performance before or after? Are you near Vans numbers compared to a Lycoming?

Do you think you have all your cooling drag minimized? Since you have an intercooler to deal with, is that still a large drag point?

Since I?m considering a similar project, I wonder if I could get some numbers to start planning?
Radiator specs: length, width, thickness, rows, other?
How did you Calculate/determine your inlet and outlet size?

Here?s where I?m coming from:
RV7, Subie H6 3.0 (was an Eggenfellner conversion), Electric CS 4 blade prop. (no turbo or Supercharger)
At one time it had 5 small radiators. 3 for coolant and 2 for oil. I have since changed out the cowling and have 2 larger radiators for coolant and 1 for oil. Cooling is actually too effective and it?s been difficult to keep the temps up. I?ve added thermostats for the oil cooler and before each radiator. I still have to partially block the oil cooler. All the radiators ram air through them with no consideration as to where the air goes afterwards other than a couple holes on the bottom of the cowling. I think this is typical of radiators buried in the cowling; so cooling works, just pretty draggy.

Cruise speed is about 150-155 knots, 2300 prop rpm and 23? MAP, burning 10.5 GPH between around 5-8000?

I would like to create and attach a scoop, with a properly sized radiator, to the bottom of the fuselage, located between the baggage bulkhead and the next bulkhead. (this is a bit further back than yours.)
Relocate the oil cooler or have ducted air from another source.
Redo exhaust to have a single muffler inside cowling and have exhaust exit out of the way of the scoop.

I think this would allow streamlining the cowling significantly and minimize the cooling drag. I would hope to pick up 10-15 knots cruise at 75% power.

Further flying shows 5-7 knots over the previous rad setup.

With the turbo, I can exceed Lycoming speeds at altitude burning more fuel. It's certainly no more efficient but a lot of that is probably the prop.

I don't have cooling optimized, oil cooler and intercooler drag are probably significant. I only wanted to prove you could produce cooling thrust on a decent rad setup.

I don't think you'll pick up 15 knots with your proposed changes. The Egg EZ30s don't produce anywhere near their stock rated hp due to the poor intake manifolds Jan attached to them and poor exhaust systems. I'd address those first since you're cooling ok now. These should cut the FF for the same TAS by improving the volumetric efficiency.

I'll look up my rad areas and volumes for you when I get some time here.
 
Rad Numbers

Ok, here are the numbers on my rad:

Core area 119 in2
Core thickness 2.25
Core volume 268 in3
Inlet area 29.5 in2
Exit area with door in closed position 16.5 in2

I'm making about 150-160 hp at 35 inches MAP and 4600 rpm.

I can ground cool indefinitely at +27C. Coolant reaches about 90-92C and stays there at a 1400 rpm idle (636 prop rpm)

I would not exceed 3 inches of core thickness with the inlet aft of the spar- not enough Delta P to penetrate the core on the ground.
 
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Thanks, Ross. Much appreciated. That will give me good idea of where to start. I figure if gear leg fairings can add 10 knots, cleaning up a wall of radiators has got to be worth another 10.

I?ve know the efficiency of Jan?s intake systems was not good, and I believe the exhaust pipes are probably on the small side. I?ve thought that improving the efficiency would gain some HP, but I would need something like 40hp to gain 12 knots (assuming the drag of a standard RV7, not mine with radiators). I can?t be losing 40HP, can I? (I thought it was closer to 20hp)
I believe Russell S. custom built the intake and his 3.3L Glasair.? I?ll have to look into that.

Would poor VE cause higher fuel flow at lower HP? I have been assuming the BSFC number would not change with a poor intake/exhaust system, I would just have lower HP and therefore lower fuel burn (keeping AFR the same). I will have to do more research.

Can a MAF sensor be connected to the SDS just to read the values and plug them into a VE calculator?

Thanks,
 
Thanks, Ross. Much appreciated. That will give me good idea of where to start. I figure if gear leg fairings can add 10 knots, cleaning up a wall of radiators has got to be worth another 10.

I’ve know the efficiency of Jan’s intake systems was not good, and I believe the exhaust pipes are probably on the small side. I’ve thought that improving the efficiency would gain some HP, but I would need something like 40hp to gain 12 knots (assuming the drag of a standard RV7, not mine with radiators). I can’t be losing 40HP, can I? (I thought it was closer to 20hp)
I believe Russell S. custom built the intake and his 3.3L Glasair.… I’ll have to look into that.

Would poor VE cause higher fuel flow at lower HP? I have been assuming the BSFC number would not change with a poor intake/exhaust system, I would just have lower HP and therefore lower fuel burn (keeping AFR the same). I will have to do more research.

Can a MAF sensor be connected to the SDS just to read the values and plug them into a VE calculator?

Thanks,

From flying in some EZ30 powered RVs and they numbers the put down, most are lucky to be putting out 170hp, so yes, you are down 30-60 ish hp from the stock rating, depending on the engine version you have.

One fellow made a proper exhaust system (equal length headers, proper diameter etc.) and I believe picked up something like 11 knots with no other changes.

The stock EG33 intake is excellent. Russell built his composite one to lower the cowling profile and save a ton of weight. Doubtful it flows any better than the stock one. Jan's twin frypan manifold also has very small runners and sharp bends at the port entrance. Not optimal at all.

Increased VE means more hp as less energy is going into pumping air in and out of the engine. Likewise, you can reduce rpm and make the same power with improved VE. Lower rpm reduces frictional losses. It's all good for efficiency. BSFC is impacted by lowered VE.

We don't use MAF with SDS. You can observe MAP at WOT and see a loss of a couple inches at high rpm. Jan used some restrictive hoses on the throttle body as well. I was there and suggested he test the MAP loss with the TB coupler removed. Picked up about 1.5 inches if I recall correctly.

Some other points on my rad. I built a test rig to quantify pressure drop through the core vs. heat dissipation. I tested several different rad designs.

My rad uses 2 rows of .080 X 1 inch tubes, spaced .44 inches apart with 14 louvered fins per inch. This offered about the best compromise between pressure drop (drag) vs. heat dissipation.

I would like to see someone fit their EZ30 with proper intake and exhaust systems and see what improvements can be made in TAS vs. FF. An interesting experiment for sure.
 
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Headers



Here's a photo of those RV7A EZ30 headers built by my friend Cliff.

Not sure if you have the single or 3 port heads?
 
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Ok, here are the numbers on my rad:

Core area 119 in2
Core thickness 2.25
Core volume 268 in3
Inlet area 29.5 in2
Exit area with door in closed position 16.5 in2

I'm making about 150-160 hp at 35 inches MAP and 4600 rpm.

I can ground cool indefinitely at +27C. Coolant reaches about 90-92C and stays there at a 1400 rpm idle (636 prop rpm)

I would not exceed 3 inches of core thickness with the inlet aft of the spar- not enough Delta P to penetrate the core on the ground.



How did you choose your radiator? Did you calculate your heat rejection load, then pick a coil, or start someplace else?
 
I am no way even close to the knowledge or experience as Ross, but I "stole"
his dimensions for ducting and rad on my RV4 with2.5 Subaru stock, and mine were crude(aluminun instead of nice glass)and it would idle all day at 190f,and
not even change at full power climb thatwas with stock 190 deg thermostat.It would have a much easier install on any of the side by side RVs,compared to inline like -4 or-8..I believe if more people paid attention to this type setup there would be many more successful auto conversions! Tom
 
How did you choose your radiator? Did you calculate your heat rejection load, then pick a coil, or start someplace else?

Too many assumptions and not enough good data to do calcs from where I started from. I scaled down hp and sizing from what my friend Russell did on his EG33 which worked excellent. Now that we have a couple of successful data points, we know what will work in an RV/ Glasair type speed range.
 
Ross,
I will take your advice and try to improve the volumetric efficiency first. (not sure what I can do about the exhaust… then later the cooling drag)
How did this setup workout? http://www.sdsefi.com/air42.htm

For those that are not familiar, here is the intake manifold used on the H6 3.0L engine (This is mine, but not the one I have installed. The one I have installed is grey and the MP ports are in a different location. Everything else is the same):
W2tCp1Crmh6iEClVypDujMAH-Ii_a6KINJt1vk_zdeCxlIC27M8q4hT0H3eC-VCiVf1t6wngTQCI3TlYI8XImNVXB7-f-1B-uURFFCNfw4mTwvmvbSIXwW3LaU37IyUONpaT5EpxuRVgSw5xdSVq90RASqBYgOTpgxqEzslWT1HYVz9PqdLVNGFvlOod22YohX7IF4HeFvzgFmriemm1rXnA49LJ80Hol0sWkRDVci_dWihs1K9S1TtPzYCcX_qWpUAegrjTm7hWved4-jDVoxtv6IAJM8qx_nBcvFxFpU0GAgngPR_2lCR1jM8mOXqzXj9DbhAhN395sqFdw_M79aWIHpwdsOj2QtRa3G5t-J1l2oczYr2ciY9lWoHJwhPN43A3YEP2TG-facnyxs6R55HQSkJBuzlfxGQjchcxwx_FKAahMH1-jyZVmupweXMPH49l8ZrTO7xXddIptLmtYPYmAg5wkqsmYBZwAA-a92BYKFHFnUWEpw87dtQVohbIl9JMxLaIoM2uuSuLft1MRE0kC8ayuYpZUj3qgW3xoEVKxHhAQkvpcu8SmhLGzXlOFh9xgKVeZyvfp9odsNdaUD54bltafUP-q3AxPA4=w549-h412-no

I don’t know what, if any, consideration was given to the lengths of each runner.
The bends into the cylinder head are too sharp:
8hCHoLNiZu7bt145L0fwKswAKq7eB5kEboAvaJ1ksVs3Exhyw1AxMSAkkXVpQUMnP4bnlvqjznRIrhPkwBNDSoSWchsMYzc9-bFSwUMebrCxnA-naPN1zeFG4AYorWVmaLOslLoGGu7XUaDEPSx8rUSEF_Xjfhsd5EpFuELHc3t0kAzV8Xl2FvwT3QALMzmDRaLjkWA-M6jMkDGt77YMooHcSefwDprDgPfDFqlsWg8Mvj6tJxvyHHl2v_LF6lrwagg07MoBUWx3LhysZH5BPFxDGh8MPC8Qzz9VhvgR6Adi7VCEHGN9gKDEDNVG1raNbmF_BKEvPlAUQoawW98Li3WK93wbvYJXpSKaCdQa46bbso6rs58Iaf5TresNbS47HBc0BFZbTMYjZwNrFaN6PPTOU4fICS6zua_Ty0GieRisexClLYeABotSIICUk-5Vjjw-MCF-DD7lI2S7csbRHsJhLaRChhIDY3wVWKhkkEbWe4IJaAqBIuBUEJw1_PpR_PM645uETwYBZ1hS-NTKyCeYHfDxCmWsfRiluIWsveARTSi7cGewzLDcAiAXHAprcpssnAGuT8-P0T4sxyXwMLdFlHIit-zyxdniWOM=w549-h412-no


The edges of the runners in the center section are too sharp, should allow smooth flow of air into the runners:
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I actually have some extra room in the cowling to make some improvements. And if I have to put a bump in the top of cowl, I'll do it.
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The OD of the runners appear to be 1.75” and the Throttle body opening is 67mm. Maybe need larger runners. The stock throttle body of the H6 3.0 is 74mm.

(Maybe 6 individual Throttle bodies.. eh, eh? :D )
 
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My EG33 never ran but I've built multiple examples of these intake manifolds for various engines. They all worked well.

Your photos don't show up for me here.
 
Ross,
I will take your advice and try to improve the volumetric efficiency first. (not sure what I can do about the exhaust… then later the cooling drag)
How did this setup workout? http://www.sdsefi.com/air42.htm

For those that are not familiar, here is the intake manifold used on the H6 3.0L engine (This is mine, but not the one I have installed. The one I have installed is grey and the MP ports are in a different location. Everything else is the same):
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I don’t know what, if any, consideration was given to the lengths of each runner.
The bends into the cylinder head are too sharp:
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The edges of the runners in the center section are too sharp, should allow smooth flow of air into the runners:
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I actually have some extra room in the cowling to make some improvements. And if I have to put a bump in the top of cowl, I'll do it.
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The OD of the runners appear to be 1.75” and the Throttle body opening is 67mm. Maybe need larger runners. Not sure of the stock /throttle body of the H6 3.0l, but I thought it was closer to 76mm.

(Maybe 6 individual Throttle bodies.. eh, eh? :D )

Pictures . .??
 
Yes, you can see the runners are too small, unequal length, bends too sharp at port and no velocity stacks on the tube ends in the plenum. Overall bad design which is why these engines are well down on their stock output.

A lot of this had to do with the gearbox design having no offset from crank to prop centerlines and trying to squash everything low enough to fit under the stock cowling. One design choice leading to another major compromise. The custom gearbox could have easily incorporated offset.
 
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