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bakerde36 wrote:Hi Wes,
That is what I use is the Craftsman deep socket. I have a question what size is your prop? I think I am over pitched as I can only get about 3100 static and 3150 in cruise wot. My prop is Prince P Tip 54x50

I have 95 hours on my 2400 and love it, but still hope someday to have a little more horses.

Hi bakerde36,

BTW, What's your real name?

I haven't flown yet but have purchased a P Tip 54x50. I have no experience with either the Hummel 2400 or Prince props so sorry, I can't comment. I am surprised at the small split between static and WOT RPMs. Maybe that is just the way a P-Tip is. I don't know.

I do enjoy hearing from those that have flown.

Gordon Baxter is flying a Hummel 2400 with a 54x48 P Tip. Some of his reported numbers can be seen here: http://sonexbuilders.net/viewtopic.php?f=5&t=11&p=36973&hilit=speed+run#p36973. Gordon, if you're lurking out there, do you have a number for static RPM?

I have some questions for you.

Can you report TAS at 3150 RPM?

I know all prop manufactures have their own method for specifying pitch. I've noticed over time that with P-Tips it seems to work out that if you calculate TAS with zero prop slip you'll be pretty close.

Ex. (((3150 Rev/Min * 50 in/rev) / 12 in/ft) / 5280 ft/mile) * 60 min/hour = 149.15 miles/hour. Is that close?

What EGTs do you run?

How did you tune the carb? Is it a Zenith carb? I'm thinking I need to tune the Zenith so that EGTs stay just in limits during takeoffs and low level WOT runs.

BTW, cold air induction is the only "easy" way I know of to get more power. I know folks don't believe me (by the awkward silence after I say it) but with cold air induction I could spin the AeroVee powered Sonex I used to have up to 3750 at WOT for right at 150 mph. The arithmetic suggests about a 10% increase in power by not feeding your engine cylinder head heated air.

Any other information you can share would be appreciated.

Thanks,

Wes

My name is Densil Baker and I am located at Pikeville, Ky KPBX. At WOT I am showing 128 indicated
I normally cruise at 105 -110 at around 27-2800rpm. I am not 100 percent sure my rpm gauge is accurate.
I used the areocarb for first 50 hours and the slide stuck on me down at Tripple Tree so when I got back I changed to the Zenith carb. I am running a little rich according to my plugs after my last valve adjustment. I have purchased the Rotec TBI and will probably try that.
MY CHT get close to 400 during climb out on a 90 degree day before I reduce power and push over.
EGT get around 1390 in above scenario. CHT on cruise normally run 320-350 EGT normally run 1150-1220 I always have a difference between left and right. The interesting thing I have noticed is my oil temp will get around 200 on climb out before I start lowering nose. But after 20 min of flying it drops and then it will hardly ever get up that high again even on full power climb. I have also done some WOT for a short time and never see my temps change much though I dont fly WOT much.
I have thought about cold induction but I haven't installed it yet. I will say I have carb heat now but never need it and when I have used it I don't see an rpm drop I think this is due to getting hot air already.
I think I may not be as streamlined as other Sonex I have a friend who has the Great Planes 2275 I think and he is as fast or faster than me with a nose gear.
It is hard for me to pin point the numbers as I change settings and guess I fly little irregular at times.

I just looked at Gordons numbers. His temps are a lot better than mine wonder if he has the temp located under the plug, which is where mine is.

bakerde36 wrote:I just looked at Gordons numbers. His temps are a lot better than mine wonder if he has the temp located under the plug, which is where mine is.

Hi Densil,

Yea, Gord lives in Canada. I don't think our northern neighbors worry too much about engine temps. Don't know where he measures CHT.

Hard to say much about your numbers based on indicated speed other than to say EGTs, CHTs, and Oil Temp look about normal. Do you have gear leg fairings and wheel pants installed?

Wes

Yes, I have the the fairing around the leg and wheel pants.
I have been thinking about fresh cool air if I had an airbox on the firewall and run a scat tub down to the bottom of the cowl for fresh air do you think the low pressure would be a problem pulling in air?

Hummel Numbers

My Onex/Hummel 2400 is presently "out of service" while I make the switch from the Zenith carb to the Revmaster RevFlow throttle body injector. I have never been comfortable with the carb ice issues and the lack of a "standard mixture control" with the Zenith carb. Having said that......the engine runs really well and puts out a lot of power judging by the speeds and climb rates I am getting.

The Prince 'P' tip 54x48 at WOT is showing 3510 rpm, I can't give a static rpm because the Sonex hydraulic brakes won't hold it. Once I get the new TBI installed I will tie the tail to a post and do some testing and come up with a number. Lonnie Prince recommended a 54x50 prop for my Hummel but I decided on a 54x48 and I am happy with that choice. I am seeing climb rates of around 900 fpm at 3180 rpm. The CHT's are around 240 F and the lead wires are attached to the cylinder fin according to the Sonex Aerovee instructions. I have never seen CHT's higher than 300 F. Oil Temps are running 180 F to 195 F and oil pressure 70-78 psi. I am using the oil that Scott Casler recommends......Shell Rotella T4 15w40. I have been using Shell 91 octane mogas. I have never had a "vapor lock" problem so far...…….the fuel line is "fire sleeved" and I run 2 cold air blast tubes to the Slick magneto like it did on my Lycoming/RV setup.

I don't have near as many hours on this airplane as I thought I would due to a lot of MGL radio problems. I fly out of a VERY BUSY towered airport and radio issues are unacceptable. My MGL V6 com failed at 12 hours and the replacement V16 (MGL) only lasted 4 hours before failure. Rather than have another 3 month long fight with Matt at MGL I decided to forgo the warranty and switch brands to a Flightline 760 which is excellent.

Gordon...…..Hummel 2400......Onex

Hi Gordon,
Do you think the 2 inch pitch difference is causing me 400RPM difference? Or would you suspect a timing or fuel delivery issue?

bakerde36 wrote:Yes, I have the the fairing around the leg and wheel pants.
I have been thinking about fresh cool air if I had an airbox on the firewall and run a scat tub down to the bottom of the cowl for fresh air do you think the low pressure would be a problem pulling in air?

HI Densil,

I really don't understand the question. What low pressure?

Have a look at Gord's numbers. Notice the split between his climb RPM and WOT RPM. That what you expect with a fixed pitch prop. Something is wrong with your instrumentation or something else. If I were your I would get that sorted out before I made any changes.

As far as cold air to the carb is concerned, it's obvious to me that the power benefits are real. I spout off about it a lot but remember, I'm no expert. What I can say is I had a successful one off set up and the performance was significantly better than what others were reporting with the standard setup.

Cold air induction comes with some added complexity and at least the possibility of carb ice. I haven't done extensive research, but I doubt any carb manufacture would claim their carb is immune to carb ice if supplied with ambient air rather than heated air.

Here are a couple of examples of slide type carbs that the manufacturer requires carb heat.

Have a look at this video (BTW Ellison carbs are back in production). If you don't want to watch the entire video skip to about the 4:45 point for the relevant content.
https://www.youtube.com/watch?v=4szv3ZBSJjw.

And here is some more from Ellison: http://ellison-fluid-systems.com/faq-carburetor_heat.shtml

Have a look at this web page: http://revmasteraviation.com/?p=206
You can see that the induction system for the Revflow switches to "under cowl" air for carb heat/filtered air.

And of course, since you are using a venturi type carb, you absolutely have to have carb heat.

Wes

Just a side note. Talking about performance, cold air, different carbs, etc. etc. Seems there is no perfect carb. But there does seem to be a viable alternative.

I just listened to to Jeff's podcast Episode 58 "SDS EFI for your AeroVee". Ref. http://www.sonexflight.com/58/index.html. Interesting stuff. Someday ...

Fun to open the podcast and listen while browsing the links included on the main podcast page.

Wes

FYI-- I had the opportunity to compare a P tip to my Sensnich. I was told that the P tip was designed to be flexible near the tips so it would un-pitch under load, then re-pitch at cruise rpm. They were both 54 X 44. I ran both props within an hour of each other. At WOT the static rpm with the P tip was 150 RPM higher than the Sensenich. I did a short flight with the P tip and couldn't tell the difference. Not very scientific, but I guess the P tip does change pitch under load.