n395v
Joined: 10 Jan 2006
Posts: 450
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 Posted: Mon Mar 19, 2007 10:16 am Post subject: Not Commander related My Project |
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For those of you familiar with my current project this post covers data gained after about 60 flight hours relative to the M14PF with an airflow performance throttle body.
It is long and may be somewhat boring unless you are a fan of Radials and LOP.
The M14 series engines come with a pressure carbeurator (Kind of a front runner to FI)
I had pressure carbs on my 560 commander and didn't really like em. I prefer to do my own mixture adjustment. And plan on running LOP. As such I replaced my pressure carb with an Airflow Performance Throttle body.This is not what you consider classic FI)
This post chronicles my experience to date. And as mentioned it is long and boring and as mentioned is of interest only if you are a fan of radials and LOP.
Finally have some real data with what I believe are accurate extrapolations.
The data sheets for these numbers can be found at http://www.excaliburaviation.com/al...open&menuID=8~8
Under either the M14P forum or the Radial Rocket forum
Bear in mind there will be some degree of measurement and extrapolation error and your results may vary.
My initial estimates of fuel consumption of the M14PF using the AFP throttle body vs the stock pressure carb were overly optimistic and based on skewed data due to incorrectly calibrated gauges and observer bias.
I am running an M14PF on a Radial Rocket http://www.radialrocket.com/
Initially I had a good deal of heat problems (CHTs) due to baffling issues; these have been largely resolved.
Relative to the M14PF
The fuel consumption is statistically no different between the throttle body and the pressure carb when running rich of peak. The AFP fuel flows are what were needed to keep my hottest CHT at or below 380 deg F this was usually 100-150 degF ROP.
Given the engine is boosted there is room for fuel savings with the throttle body but I have not yet experimented with LOP on this engine.
Relative to the Radial Rocket
Wit this engine, prop, and airframe combination running the pressure carb or the throttle body ROP it appears that for a burn of 15 GPH we have a……………………….
185-190 Knot (TAS) airplane below 8000’
205-210 Knot (TAS) airplane between 8000’ & 11,000’
220+ Knot (TAS) airplane depending on how much fuel you want to burn
I have no numbers above 12,00 feet as I am still having a problem with abrupt and significant power loss crossing 12,000’. It appears to be related to either Icing or decreasing fuel pressure.
I am going to crank the fuel pressure on the ground up to 55-60psi and or use the boost pump above 12,000’ to see what this doe. If that doesn’t work I will try ducting some heat into the induction system.
The benefits of the Pressure Carb vs the throttle body are….
1. Ease of operation.. 1 less lever and with the throttle body you need to make adjustments before major power changes and manage it with ascent and descent.
2. Cost (an extra $3000 for the throttle body after you have sold your carb)
Downside of the pressure carb
1. Continued availability of carb, parts, service
2. Cannot run LOP
3. If your application during the early stages requires it you cannot use fuel flow to decrease CHTs while working out baffling issues.
Benefits of the throttle body
1. Availability of the unit, parts and service.
2. Ability to run LOP (maybe) if you are a believer.
Downside of throttle body
1. Initial cost
2. I’ll let you know the rest when I get all the bugs worked out.
As soon as I get this altitude problem resolved I’ll start running LOP and post those results
“carb” fuel flows are derived from Dennis Savareses data found at http://home.elmore.rr.com/yak52worl...%20Settings.htm
Unless labeled ”carb” all fuel flows are for the AFP throttle body.
CAVEATS
I am neither a mathematician nor an engine expert.
There is still some degree of measurement and extrapolation error.
This application required slightly higher fuel flow than optimal for cooling purposes.
Still have a lot of work to do and data to collect.
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