Today's Message Index:
----------------------
1. 08:04 AM - lean of peak injector balancing (Frazier, Vincent A)
2. 08:40 AM - Re: lean of peak injector balancing (Michael W Stewart)
3. 02:59 PM - Re: Update on Jim's Rocket (Don)
4. 07:59 PM - Re: lean of peak injector balancing (Jim Stone)
Message 1
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| Subject: | lean of peak injector balancing |
Jim,
Read this.
http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20O
peration/Pelican's%20Perch%20Mixture%20Magic.htm
It will tell you what you need to know.
To balance your injectors only requires a few flights to get 'em pretty
close. More if you really want excuses to test fly.
The injectors that came with your engine are most likely all the same
ID. But each cylinder has different flow patterns. IOW, the injectors
should be matched to the flow, but they aren't.
Assuming that you have a 6 cylinder EGT monitoring capability, fly at a
fixed throttle and prop setting and altitude, start rich of peak and
begin leaning and record the fuel flow vs. EGT every 0.1 gph. Just
record the stuff near the peak EGTs, not all the way down from 28gph. No
need for that much data! You're just looking for the peaks.
The first cylinder to peak is the leanest, and so on. When you get back
on the ground, call Don Rivera at Airflow Performance and tell him what
you found. He can send you new injectors of varying ID to replace your
existing ones. It's not that expensive and you'll easily save the money
back in fuel savings.
Basically, you're going to swap the leanest injector for one with a bit
larger ID. Changing one injector changes the flow to the others since
they're all drinking from the same well. So, you will have some trial
and error involved, but not too much.
You might need to swap the injectors around a bit, but when you get the
peaks to happen within a GPH, or better yet, 0.5GPH you should have a
smooth running, LOP, gas saving, clean plugs, cool temps engine.
This is all from memory... hope I remembered the high spots.
Vince
P.S. Make sure that your EGT probes really are in the cylinder that you
think they are or it'll get real interesting.
Message 2
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| Subject: | Re: lean of peak injector balancing |
You may find this useful.
MIke
http://www.mstewart.net/super8/nozzles/index.htm
"Frazier, Vincent
A"
<VFrazier@usi.edu
To
> <rocket-list@matronics.com>
Sent by:
cc
owner-rocket-list
-server@matronics Subj
ect
.com Rocket-List: lean of peak inject
or
balancing
10/05/2007 10:59
AM
Please respond to
rocket-list@matro
nics.com
du>
Jim,
Read this.
http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20
O
peration/Pelican's%20Perch%20Mixture%20Magic.htm
It will tell you what you need to know.
To balance your injectors only requires a few flights to get 'em pretty
close. More if you really want excuses to test fly.
The injectors that came with your engine are most likely all the same
ID. But each cylinder has different flow patterns. IOW, the injectors
should be matched to the flow, but they aren't.
Assuming that you have a 6 cylinder EGT monitoring capability, fly at a
fixed throttle and prop setting and altitude, start rich of peak and
begin leaning and record the fuel flow vs. EGT every 0.1 gph. Just
record the stuff near the peak EGTs, not all the way down from 28gph. N
o
need for that much data! You're just looking for the peaks.
The first cylinder to peak is the leanest, and so on. When you get bac
k
on the ground, call Don Rivera at Airflow Performance and tell him what
you found. He can send you new injectors of varying ID to replace your
existing ones. It's not that expensive and you'll easily save the mone
y
back in fuel savings.
Basically, you're going to swap the leanest injector for one with a bit
larger ID. Changing one injector changes the flow to the others since
they're all drinking from the same well. So, you will have some trial
and error involved, but not too much.
You might need to swap the injectors around a bit, but when you get the
peaks to happen within a GPH, or better yet, 0.5GPH you should have a
smooth running, LOP, gas saving, clean plugs, cool temps engine.
This is all from memory... hope I remembered the high spots.
Vince
P.S. Make sure that your EGT probes really are in the cylinder that you
think they are or it'll get real interesting.
========================
============
========================
============
========================
============
Message 3
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| Subject: | Re: Update on Jim's Rocket |
To chime in here, Jims comment/dissertation on nozzle tuning is mostly correct.
At peak EGT the engine is not necessarily running at peak efficiency. If you
talk to people that have the equipment to actually measure efficiency, that
is outfits that have dynos that measure air flow, fuel flow, torque, etc; not
just a prop stand, BSFC and BSAC will give the efficiency of the engine. The
point at which the EGT peaks is a specific fuel air ratio. This is what were
trying to match. There are curves that show (Lycoming data) that even with different
engines, naturally aspirated and turbo charge, the point at which EGT
peaked was the same F/A for each engine and the F/A changed a specific amount
to the change from peak EGT. This was again true of any engine they tested.
Obviously the EGT number was different for the turbo charged engines and the naturally
aspirated engines at peak EGT, but the F/A was the same. So a given
change form peak EGT results in a specific F/A. For instance running 200 rich
of peak EGT results in a F/A of .086. Peak EGT is a F/A of .065. This is pretty
much true for any Lycoming engine, and probably most engines. So what Jim
said is were adjusting the fuel flow to the cylinders air flow so that all the
cylinders run at the same F/A.
An important consideration when gathering the data is to not exceed 25MAP, keep
the fuel flow above the point where the flow divider influences the flow division
and let the EGT stabilize before changing fuel flow to get a new line of
data. This means that if you use a data logger to capture data, slowing leaning
the mixture control while gathering data will result in mostly worthless data,
as the EGT does not respond as fast as the fuel flow indication.
If you need more instruction on this process give me a call or email me off line.
Don
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=138379#138379
Message 4
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| Subject: | Re: lean of peak injector balancing |
Great stuff, thanks Vince,
Jim
----- Original Message -----
From: "Frazier, Vincent A" <VFrazier@usi.edu>
Sent: Friday, October 05, 2007 10:59 AM
Subject: Rocket-List: lean of peak injector balancing
>
>
> Jim,
>
> Read this.
>
> http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20O
> peration/Pelican's%20Perch%20Mixture%20Magic.htm
>
> It will tell you what you need to know.
>
> To balance your injectors only requires a few flights to get 'em pretty
> close. More if you really want excuses to test fly.
>
> The injectors that came with your engine are most likely all the same
> ID. But each cylinder has different flow patterns. IOW, the injectors
> should be matched to the flow, but they aren't.
>
> Assuming that you have a 6 cylinder EGT monitoring capability, fly at a
> fixed throttle and prop setting and altitude, start rich of peak and
> begin leaning and record the fuel flow vs. EGT every 0.1 gph. Just
> record the stuff near the peak EGTs, not all the way down from 28gph. No
> need for that much data! You're just looking for the peaks.
>
> The first cylinder to peak is the leanest, and so on. When you get back
> on the ground, call Don Rivera at Airflow Performance and tell him what
> you found. He can send you new injectors of varying ID to replace your
> existing ones. It's not that expensive and you'll easily save the money
> back in fuel savings.
>
> Basically, you're going to swap the leanest injector for one with a bit
> larger ID. Changing one injector changes the flow to the others since
> they're all drinking from the same well. So, you will have some trial
> and error involved, but not too much.
>
> You might need to swap the injectors around a bit, but when you get the
> peaks to happen within a GPH, or better yet, 0.5GPH you should have a
> smooth running, LOP, gas saving, clean plugs, cool temps engine.
>
> This is all from memory... hope I remembered the high spots.
>
> Vince
>
> P.S. Make sure that your EGT probes really are in the cylinder that you
> think they are or it'll get real interesting.
>
>
>
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