Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Where does Carb Temp Probe Go on a MA4-5?
- Thread starter Brantel
- Start date
probe depth
I understand that there is caution on having the probe reach too far into the carb, i.e. will disrupt airflow, etc.. Don't have a pub or any spec on this. Anybody else?
Do NOT drill anything. There is a threaded plug to remove at the top front of the carb, and your probe should screw right in.
I understand that there is caution on having the probe reach too far into the carb, i.e. will disrupt airflow, etc.. Don't have a pub or any spec on this. Anybody else?
Do NOT drill anything. There is a threaded plug to remove at the top front of the carb, and your probe should screw right in.
N941WR
Legacy Member
Sam Buchanan
been here awhile
Before I screw up my good carb, can someone show me a pic of what to remove or drill out in order to install the carb temp sensor in a MA4-5 carb????
I found some post for the smaller carbs but non for the larger ones
Brian, before you go to the trouble of installing the carb temp probe, you might want to search the forum archives concerning temp probes. There was a lengthy thread on this subject in the past year or so.
It seems to be commonly accepted that carb temp probes are pretty much useless because they usually indicate the temp of the carb body instead of the air mass and carb internals. This is borne out by my experience with having a temp probe for the past ten years in my O-320 RV-6. If installing a carbed engine today I would skip the carb temp probe.
N941WR
Legacy Member
I agree with Sam 100% too.
Although the carb probe measures the temperature of the carb body and not the temperature of the air going through the carb, it is the carb body that will accumulate the ice, if the temperature gets low enough and the conditions are right.
It doesn’t really matter if the air temp is 100, 50, 32, or -10. If the air is moisture laden and the temp drops significantly AND the carb is warm, you run very little risk of carb ice.
Radomir is also correct. In my installation the carb temp is always well above freezing and goes up when I close throttle and slow down for landing. I suspect this is because less air is going through the cowling and what air that is in there has a chance to heat up.
If you pull the carb heat on, it only raises the carb temp a few degrees with the stock carb heat muff.
Although the carb probe measures the temperature of the carb body and not the temperature of the air going through the carb, it is the carb body that will accumulate the ice, if the temperature gets low enough and the conditions are right.
It doesn’t really matter if the air temp is 100, 50, 32, or -10. If the air is moisture laden and the temp drops significantly AND the carb is warm, you run very little risk of carb ice.
Radomir is also correct. In my installation the carb temp is always well above freezing and goes up when I close throttle and slow down for landing. I suspect this is because less air is going through the cowling and what air that is in there has a chance to heat up.
If you pull the carb heat on, it only raises the carb temp a few degrees with the stock carb heat muff.
Last edited:
az_gila
Well Known Member
If you do go ahead...
...and install the probe, then the pictures on pages 7 and 8 of the STC installation instructions for the Richter B-5 probe will help.
http://64.13.249.214/images/uploads/B5.pdf
If you have an old Marvel carb. with no plug in it, then the probe hole does exist, but is filled with lead according to the above instructions.
I wonder is some of the problems reported above are due to using non-STC'd probes with possibly different internal heat conduction paths.... The B-5 probe being $200-$300 will cause copying...
Has anyone reported getting really bad (non-existant?) reading with a real B-5 probe?
Before I screw up my good carb, can someone show me a pic of what to remove or drill out in order to install the carb temp sensor in a MA4-5 carb????
I found some post for the smaller carbs but non for the larger ones
...and install the probe, then the pictures on pages 7 and 8 of the STC installation instructions for the Richter B-5 probe will help.
http://64.13.249.214/images/uploads/B5.pdf
If you have an old Marvel carb. with no plug in it, then the probe hole does exist, but is filled with lead according to the above instructions.
I wonder is some of the problems reported above are due to using non-STC'd probes with possibly different internal heat conduction paths.... The B-5 probe being $200-$300 will cause copying...
Has anyone reported getting really bad (non-existant?) reading with a real B-5 probe?
Last edited:
ArVeeNiner
Well Known Member
Don't screw up like I did!!
Check out my post and don't screw up like I did. Actually, the fix worked out pretty well.
http://www.vansairforce.com/community/showthread.php?t=41510
Check out my post and don't screw up like I did. Actually, the fix worked out pretty well.
http://www.vansairforce.com/community/showthread.php?t=41510
Finley Atherton
Well Known Member
SOME PROBES DO WORK
The carb probe that came with my original VM1000C was pretty much useless and I presume was measuring the temp of the carb body as others have described. I swapped the monitor and probes for the newer VM1000C that has the JPI innards and probes (when JPI took-over VM) and this newer probe does seem to accurately measure the carb air temp.
Fin
9A
The carb probe that came with my original VM1000C was pretty much useless and I presume was measuring the temp of the carb body as others have described. I swapped the monitor and probes for the newer VM1000C that has the JPI innards and probes (when JPI took-over VM) and this newer probe does seem to accurately measure the carb air temp.
Fin
9A
