Just say NO to cyberdyne a/f gauge
09-13-2002, 11:00 PM
#16
[quote]And the good thing about that port is it's after the colector so you get the total temp of all the cylinders...much more precise <hr></blockquote>
I question the validity of saying the combined temperature of all cylinders is more precise than reading each individual cylinder. In aircraft, we use a sender for each cylinder and switch between them to find which is lean. I guess if you found which cylinder was lean you could get away with only one sender, but I still think using four would be the way to go.
To tune this way you could have four senders welded onto the header pipes and get a multiple EGT or switchable EGT gauge... The air cooled guys use this often.
Needless to say, in isn't a cheap prospect either way.
I question the validity of saying the combined temperature of all cylinders is more precise than reading each individual cylinder. In aircraft, we use a sender for each cylinder and switch between them to find which is lean. I guess if you found which cylinder was lean you could get away with only one sender, but I still think using four would be the way to go.
To tune this way you could have four senders welded onto the header pipes and get a multiple EGT or switchable EGT gauge... The air cooled guys use this often.
Needless to say, in isn't a cheap prospect either way.
09-14-2002, 01:24 AM
#18
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I had a egt bung welded onto my #4 exhuast header about 5" from the exhaust valve. I did this because I had the header off for some other work and figured then would be the time. The bung is currently plugged, but I do have the egt probe and gauge for when I choose to install it.
Heresay on the board, spark plug reading, and logical airflow consideration all suggest that the #4 cylinder is leaner than the rest of the cylinders, thus that is the cylinder to go by.
EGT probes on each cylinder would be great, at least for when it comes time to tune. With a aftermarket efi that allowed independent control of each injector, you could trim each cylinder individually to get the optimal a/f ratio and egt temps. Of course, careful intake manifold design may be more beneficial and less of a hassle then trying to deal with four egt probes, wiring, and some sort of data logging system.
On another note, egt probes live a very hard life and can be quite unreliable. I probably went through 10 egt probes in less than two years while I was racing karts. Kind of a PITA at $40 a pop!
The guy from socal (can't remember his name) that had a bunch of hot rod 951's and finally gave up and bought a Boxster S had a egt probe. You might want to search here or on Pelican.
Heresay on the board, spark plug reading, and logical airflow consideration all suggest that the #4 cylinder is leaner than the rest of the cylinders, thus that is the cylinder to go by.
EGT probes on each cylinder would be great, at least for when it comes time to tune. With a aftermarket efi that allowed independent control of each injector, you could trim each cylinder individually to get the optimal a/f ratio and egt temps. Of course, careful intake manifold design may be more beneficial and less of a hassle then trying to deal with four egt probes, wiring, and some sort of data logging system.
On another note, egt probes live a very hard life and can be quite unreliable. I probably went through 10 egt probes in less than two years while I was racing karts. Kind of a PITA at $40 a pop!
The guy from socal (can't remember his name) that had a bunch of hot rod 951's and finally gave up and bought a Boxster S had a egt probe. You might want to search here or on Pelican.
09-14-2002, 02:01 AM
#19
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Here's some recorded data from the egt probe of a water cooled 125cc 2 stroke gearbox race kart. This data traces the kart as itenters an extremely tight 170 degree turn, goes down a 500 foot straightaway, brakes, then goes through a sweeping 200 degree turn.
I thought this might be some interesting information to add about egt temps. Keep in mind that this is from a vastly different vehicle, engine etc. in a fairly high state of tune (336+ hp per liter) with the tuning optimized for the relatively short straightaways.
I think the most significant thing to notice is that the egt builds heat significantly the longer that you are running at full throttle. In fact, if the engine is tuned properly, we always see the highest egt reading at the end of the longest straightaway. If we see the egt peak prior to the end of the straightaway, that is usually a sign that engine is going lean.
With these types of characteristics, it seems that egt would be a fairly difficult method to tune with in a non race vehicle, especially without any sort of data logging/playback functions.
I thought this might be some interesting information to add about egt temps. Keep in mind that this is from a vastly different vehicle, engine etc. in a fairly high state of tune (336+ hp per liter) with the tuning optimized for the relatively short straightaways.
I think the most significant thing to notice is that the egt builds heat significantly the longer that you are running at full throttle. In fact, if the engine is tuned properly, we always see the highest egt reading at the end of the longest straightaway. If we see the egt peak prior to the end of the straightaway, that is usually a sign that engine is going lean.
With these types of characteristics, it seems that egt would be a fairly difficult method to tune with in a non race vehicle, especially without any sort of data logging/playback functions.
09-14-2002, 09:26 AM
#20
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[quote]On another note, egt probes live a very hard life and can be quite unreliable. I probably went through 10 egt probes in less than two years while I was racing karts. Kind of a PITA at $40 a pop!<hr></blockquote>
They can be had for different operating ranges and the good ones typically go for much more than that (about 140$ a piece for the sender)
They can be had for different operating ranges and the good ones typically go for much more than that (about 140$ a piece for the sender)
