Thread: EGT probe location difference.
02-18-2007, 08:41 PM #1
EGT probe location difference.
Here's my results on the question of my probe location.
I tapped my spec 2 mani again in the location where everyone else taps 'em. On the side about 3/4" up from the cyl.
In the pics you'll see my original mounts located on the mani bosses next to the carbs which are temps #1 & #2. I have 3 probes so I used temp #3 on the PTO side since it's the hotter of the 2. I ran WFO for over 1 minute & got these temps:
A 148 degree difference!!
I ran this several times & were within 10 degrees of the #'s posted above.
I found though as the temps rise from idle speeds to top end the difference in temps increase also.
So now my question is: If i'm running 1300 degrees in my regular location that would put me about 1152 temps on the new spot. What is the safe temps to using the location on the side of the manifold?
02-18-2007, 09:48 PM #2
1300* seems moltent
All engines I have used egt on where down at at 1100*, 1200* max
The correct location for probe is to be at the tip of the flame front. Some say 6" from the center of piston.
A simple analogy would be to compare the exhaust flame front, to the tip of an oxy acetylene torch.
When the mixture is set correctly on the torch the flame has a sharp point. This is where you want the probe.
After looking at your pics, see you have a 2 into 1 exhaust manifold.
On 2-stroke with expansion chamber and 2 into 1 manifold...can EGT be used correctly without separate pipes?
Doesn't exhaust reversionary wave from the other cyl affect the temp of the adjacent cyl probe giving inaccurate readings?
Last edited by allcool; 02-18-2007 at 09:53 PM.
02-18-2007, 10:17 PM #3
The hotter location is the one I would go with.
If it is hotter it has to be closer to the tip of the flame front and thats where you want to be for egt.
02-18-2007, 10:29 PM #4
This is a hot subject. Literally. Everyone says you should run this temp or that temp. In actuallity, I was taught differently. On my XPL I could run temps of 1250 all day long at wide open throttle. Where as some other tuners could only run their skis at 1150 or less. Why? Location of the probes. Your situation is a perfect example. EGTs aren't exactly the same for each boat, only way to know what EGTs you can run at is by doing plug chops. Its not a tuning device persay, but its a good warning device. You'll have to tune your boat in and see where your EGTs consistantly run. If you ran you ski at WFO for a minute and it didn't blow, your rpms stayed consistant and so did your temps, I would assume that you are safe at the moment. Meaning you can run those temps safely, if not, you would have seized already.
I have ran mine close to 1300 before. But I knew that at 1250 I was safe to hold my ski wide open for over 5 miles with no problems. I also ran wiseco pistons which can handle more heat over OEM pistons.
02-18-2007, 10:30 PM #5
I have ran the ski into the low 1100's & it is just sloppy! I get 7400 rpm at best & a mess on the rave caps from what i'm assuming is unburnt fuel creating sludge. It runs best at high 1200's & has been running that high for over 40hrs so far.
I have a fresh miller rec ported top end ready to bolt on when this top end goes & i'm tempted to run it hotter just to see the melting point.
02-18-2007, 10:36 PM #6
02-19-2007, 04:17 PM #7
The racepak is just a guide really, you get to the point where you melt a piston and basically see where the temps were. Then you know you can't go any higher. I've run mine close to 1300 before, but opted for a little more richness for my style of riding. I like to hold mine wide open for miles and miles. I may give up a little on the top end, but how many rec racing skis do you see do that?
A buddy of mine always said, you need one ski for racing and one for riding, hahaha.
02-21-2007, 08:40 PM #8
Shooter's the MAN! He's a wealth of knowledge that I'll be taping more of as the weather warms up!
02-22-2007, 05:17 PM #9
nah, I know quite a few guys that know way more than I do. I sometimes have to call them up to get info on simple ****. I know 10% of what most know, but I've experienced just about every problem there is to experience with a ski.
I was told about the racepak from a buddy of mine that owned a shop here. He told me to use it as a guide, not a tuning tool. So ever since I started listening to him, I quit blowing skis up.
02-22-2007, 07:37 PM #10
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