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Old 03-19-2015, 05:00 PM
BillL's Avatar
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
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Default Interesting Approach

It looks like you have things well in hand. IIRC, the offset of equivalency ratio to peak EGT is due to latent heat of the fuel, on a natural gas engine it is right on. Again IIRC. For your calculations I would not worry about humidity and certainly not nitrogen. Temperature and In-Man-P yes.
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Old 03-20-2015, 08:47 AM
dhc2jeep1 dhc2jeep1 is offline
Join Date: Apr 2013
Location: USA
Posts: 16

Originally Posted by 1001001 View Post
Anyone have a chemical analysis of 100LL?
Much like automotive gasoline, there is not a single formula that defines 100LL. ASTM D910-14A defines the performance that 100LL must meet, but that document leaves it up to each refiner as to how to achieve the required performance. This means that the chemical composition can vary from refiner to refiner. They will be similar, but just realize that there will be some variation.

This is why isooctane is used in ICE research - to eliminate variability of the fuel composition.
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Old 03-21-2015, 01:44 AM
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rvmills rvmills is offline
Join Date: Nov 2007
Location: Georgetown, TX
Posts: 2,164


Just installed an Air/Fuel Ratio monitor, and have had a few longish legs to do some data collection during leaning (painfully slow leaning to evaluate injectors and learn what AFR is telling me). Lot's of raw data to wade through, as its collected by hand from my VM-1000 :

My first peek at this data seems to correlate well with the charts and numbers Dan shared here. Best power, roughly based on cruise speed during leaning, occurs about 12.5:1, Peak occurs in the mid- to hi- 14:1 range (14.5 to 14.9) and my motor starts to grumble a bit and speeds drop off markedly just before reaching 16:1 (the top of the scale on my AFR monitor). I'm going to try to hand-jam this into a few spreadsheets, and will be happy to share what I come up with. The sensor is on one side of the engine versus each cylinder, the data is eyeball collected, and the AFR reading jumps around a bit, so it may not be at the super-fine data level you may be generating...but if its of value, happy to share.

Its giving me some good data on injector management too!

Interesting thread!


Bob Mills
RV-S6 "Rocket Six" N49VM
Cross Country-Marshall Field (07TS)
Georgetown, TX
President/Sport 49, Sport Class Air Racing
Trustee, Formation Flying Inc (FFI)
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Old 03-21-2015, 06:47 AM
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rv6ejguy rv6ejguy is offline
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 6,324

Bob's numbers are right in line with what you'd expect.

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 460.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016

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Old 08-09-2022, 03:49 AM
Pop Alexandra Pop Alexandra is offline
Join Date: May 2017
Location: Cluj-Napoca
Posts: 48

The numbers look right to me. I get something similar whenever running a dry colorimetry analysis.
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