Exhaust Gas Temperature Numbers

[etemplet]

Hello All,

My engine shop (cars and trucks) owner cousin was asking me about exhaust gas temperatures on the Rotax engines. I know a few member here either have installed this equipment or have used EGT probes in the past. I am interested in setting up a ski with the instruments. Would anyone care to share the desired and danger temperatures related to operating a Seadoo? I told my cousin we might need to blow one up to find out what "not to do." Ha ha.

I told my cousing in my airplane full power climbing I see about 1420 degrees and at cruise I like to keep it 1320 or below. The temperatureis always related to how hard I push the engine. With regard to automobile engines for him 1420 degrees and he shuts down and figures out what is going on. I'd be interested in hearing from knowledgeable people concerning this. I always wonder how "fat"my skis are but being an old two stroke guy... I'd rather give up some top end performance for engine longevity. Help is appreciated.

 

[tobytd]

Matt Braley knew all this stuff , Unfortunately I have not seen him for a while. I could be way wrong but if memory serves me correct I think about 1000 1100° is the max. Like I said I could be WAY wrong.

 

[glsmohio]

Your right! 1100. Is the kill point. I run the koso egts on all my skis

 

[etemplet]

Your right! 1100. Is the kill point. I run the koso egts on all my skis

Can you tell me where I can purchase what I need to set this up on a GTX? I'd love to see where my GTX is running. I'd like to goto a smaller main jet. Both my GTXs do not get high RPMs and both have new engines and I've checked everything 5 times. LOL Fun skis but neither one hits 50mph and I'm at 6700 on the RPMs.

I was thinking the temperature on the aluminum engines would be less than the 1400 we see on the airplanes. That is great info !! Got any pictures??

 

[fatblockabody]

I'm interested in the gauge as well, would like to install in my SPX

 

[etemplet]

I'm interested in the gauge as well, would like to install in my SPX

For some reason this kind of info appears to be "secret stuff" and people don't volunteer much info on it. Matt Braley would never tell me about what he used. There are threads where the parts are mentioned but only in passing. I did a parts search at the time and it came right up on Ebay. One thing for sure, if I decide to do it, the whole world is gonna know. It's all about helping one another.

All that said, set up is pretty simple as you may know. We drill a couple of holes in the exhaust pipe a specific distance from the manifold face and insert the probes. Then just mount the read-out where you can see it. We'll get it done.

 

[fatblockabody]

For some reason this kind of info appears to be "secret stuff" and people don't volunteer much info on it. Matt Braley would never tell me about what he used. There are threads where the parts are mentioned but only in passing. I did a parts search at the time and it came right up on Ebay. One thing for sure, if I decide to do it, the whole world is gonna know. It's all about helping one another.

All that said, set up is pretty simple as you may know. We drill a couple of holes in the exhaust pipe a specific distance from the manifold face and insert the probes. Then just mount the read-out where you can see it. We'll get it done.

I'm not worried about setup. I'm a drag racer for my other hobby and have messed with them in automotive applications (I've built my own turbo setups and I do my own EFI tuning on standalone ECU's), just want to make sure I get what works best for two stroke/water injected exhaust.

I agree, these 2 strokes are old enough now that keeping this stuff a secret isn't really giving away an edge in racing. I just want my stuff to run the best it can and live... at least until I decide I'm ok with more risk. EGT appears to be the best tuning metric, like a wideband AFR in a 4 stroke.

 

[etemplet]

Automotive is my cousin's area. He can build anything.... except a jet ski. I gave him a SPX 657X and it ran for about 4 minutes ever trip. It would blast off from the dock and then you'd see him on a sand bar messing with the carbs. I swapped him out a running GTX that did great for a few tanks of fuel then blew up. I rebuilt an engine for him last year and went through the whole ski. A few months earlier I went to his shop to work on a GTS. The engine would hardly turn over. After I pulled the engine one guy kicked the PTO and the engine spun. Freakin ROPE around the drive shaft. I said Roe, " crawl your azz under that ski and look !" His wife ran over a rope. LOL I did the top end anyway and lined it all back up, PM'd the pump. Too dang funny. He is a terrific automotive guy. A man's got to know his limitation.s

 

[glsmohio]

Matt is an awesome dude. I learned it all from him actually. Koso egt is what I used. I got them off ebay. If you go over to the seadoo forum you can see the whole build for my 97spx and it shows step by step in there how to do it. If I get some time tonight or tomorrow I'll put a link up

 

[glsmohio]

Nm this is the seadoo forum lol...dang tap a talk

 

[glsmohio]

97 Seadoo Spx build

 

[mandriva]

1120 f is maximum
I seized piston at 1160f on my seadoo 787

 

[fatblockabody]

Thanks, bookmarked!

 

[etemplet]

Thanks for sharing guys. This is great stuff. Yessir !!!

 

[ckirby]

Can you tell me where I can purchase what I need to set this up on a GTX? I'd love to see where my GTX is running. I'd like to goto a smaller main jet. Both my GTXs do not get high RPMs and both have new engines and I've checked everything 5 times. LOL Fun skis but neither one hits 50mph and I'm at 6700 on the RPMs.

I was thinking the temperature on the aluminum engines would be less than the 1400 we see on the airplanes. That is great info !! Got any pictures??

Koso makes a daul egt gauge that does awesome comes with everything you need

 

[Itmac79]

I use EGT temps to tune my engines. It’s not that the numbers guys use are a secret, it’s more that it can very widely depending on many variables. Sensor placement, fuel/octane type, ambient temp, etc all have a huge impact. With 2-stokes, you kind of have to just figure out each individual engines sweet spot. My 787 for example has the temp sensor tapped into the manifold and 900-940° is it’s sweet spot.

 

[POPPS]

During our racing careers, 1000‘ish was max. EGT. Our philosophy was to “win“ with the darkest plugs and coldest motor, it goes without saying, to finish first, first you must finish. In havasu in 2004 and 2005 (800cc LTD expert) we never had an engine failure, plugs were the colour of a light ale.

 

[etemplet]

I use EGT temps to tune my engines. It’s not that the numbers guys use are a secret, it’s more that it can very widely depending on many variables. Sensor placement, fuel/octane type, ambient temp, etc all have a huge impact. With 2-stokes, you kind of have to just figure out each individual engines sweet spot. My 787 for example has the temp sensor tapped into the manifold and 900-940° is it’s sweet spot.

LOL.... I asked people that I knew, knew. People that used these set ups and all I got back was crickets. Which is fine. No one is obligated to give information they learned through experience and trial and error. I'm glad this thread got some responses..

Does the kit instructions recommend a distance from the exhaust gasket surface for probe installation.

I think this set up has a lot of potential not just for just tuning.

 

[etemplet]

I see the KOSO set up for $350. I'd only do a permenant mout set up if it was about $125 or so. I'll see what I can come up with for a test rig as there are instruments for Less than $50 with the probes.