Landracing Forum
Tech Information => Technical Discussion => Topic started by: dr j on December 10, 2011, 05:43:39 PM
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I am setting up a small single cylinder 2-stroke engine for LSR.
1. How far away from the cylinder should the EGT bung be centered? Anywhere less than 6"? Or as close as possible?
2. Also what range should the WOT temp be?
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Talk to any good Mazda rotary racer.
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Uh not actually true, about the Mazda info.
The Rotary motor is not a 2 stroke, it is a true 4 cycle motor. If ours was not showing 1700-1750° we took away more fuel. As for using a 2/ expansion chamber, it would not help, the divergent cone might but the convergent definately not.
The problem with using EGT on a 2 stroke is the issue of intake charge contamination pushed into the expansion chamber giving false ex temps. I found the only true way to tune was to read the color off the top of piston, carbon deposit in pipe inlet and transition exit from cylinder.
The spark plug does show some indication but is better suited to reading the timing on the electrode.
Send me an e-mail and I will return a small gif image that is illustrated to show the phases of a 2/ motor.
What motor are you looking at running?
John
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The problem with using EGT on a 2 stroke is the issue of intake charge contamination pushed into the expansion chamber giving false ex temps. I found the only true way to tune was to read the color off the top of piston, carbon deposit in pipe inlet and transition exit from cylinder.
Yes, the cool intake charge going into the header and affecting the temp reading prior to being shoved back into the cylinder by the resonant wave was what I was concerned about.
Send me an e-mail and I will return a small gif image that is illustrated to show the phases of a 2/ motor.
What motor are you looking at running?
John
I have a copy of a gif sequence of a 2 stroke already. It is amazing to watch. Thanks for the offer. I have an RS125 that I ran in Sep and Oct at Maxton. Did fine so far. But I am just beginning to learn about 2 strokes really. Not sure how far I will go with it but it's fun so far. What have you run John?
How about an AFR sensor after the expansion chamber? I know the sensor won't last as long in a 2 stroke but we don't do that many runs anyway.
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The RS 125 is a pretty good motor. Where is the port timing and what ignition are you running?
I mainly ran motors for karting, CR125, CR80, ICC formula and ICA.
Like the camshaft in a 4/ motor, port timing is everything. Of course CR and squish will play big into the final motor configuration balance.
There is much to be found in ignition, especially the digital programmable. I used the Wolfe and SPI units, SPI seemed to be more consistant on the dyno that the Wolfe.
I never tried the AFR in a pipe for the same reason as the EGT, however, if it was placed say near the end of the convergent cone or even in the stinger it may read somewhat correctly for awhile. Like I said before, the color is easily detected in the inlet to the pipe.
How does the top of the piston look? is the kernal burning fully to the edge?
John
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Thanks for your comments John.
So far I am running stock ports and ignition. Thanks for the info on the 2 ignitions. I will check them out. As for the piston top it looked great after Sep but I have not pulled the head since the last runs in Oct. Busy making a living.
As for the AFR vs EGT I am looking for something to watch on the fly to help predict imminent disaster and thus warn to abort the run and make a change rather than seizing.
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Jarl,
You are in a very good place to be, better to start with a stock motor than a mussed-up one.
I notice that you are in Maryland, I just finished talking to my Son, stationed at Andrews AFB.
I don't have any information about this, I recall having conversations with some tuners who were experimenting with microphone pickups on the dyno to detect detonation and or bearing failure before it let go. You might try searching it out.
Happy Holidays, John
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All our 2stroke sleds out here in mountain land have the pyro no more than 1" out from the port. If you go to ebay you'll find an EGT gauge setup with LED's, green yellow red. A lot easier to keep tabs on than a needle or didgets.
Sid.
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According to Eric Gorr (Forward Motion) he reccomends 6" from the piston, which is how I am running my Digatron (YZ250). I wanted to go with a A/F meter also but have heard very little good about the 2 stroke exhaust and the wideband sensor. So I am running EGT and CHT through a Digatron instead
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6 inches is a good distance. The further you get away from the port the cooler the temperatures.
The AFR sensor won't last long enough to get a reading.
Running a two stroke wide open is an easier tuning challenge then a roadracing setup.
The easy way is to lean it out until it melts then back off a little. :evil:
All sensors are relatively slow to react. You can melt it before the reading stabilizes.
1100 on EGT is as much as you want to run. You are approaching the melting point of the piston past that.
I also run a head temperature sensor. The EGT shows rapid changes. The head temperature shows a more stable reading.
At some point the EGT will hit maximum and then drop as you continue to lean it out. If you end up (rare) in that condition you will melt it before you figure it out.
Plug readings and piston inspection are mandatory. The piston and head have to be spotless. Any carbon creates a hot spot. At the end of the run kill the engine. If you run it back to the pits the plug reading is worthless.
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I'm not a 2stroke specialist but on a sled, 6" out would be in the chamber. Sleds spend most of their life at "wide open throttle" with huge altitude changes here in the Rocky's. Lots of guys run nitrous & some guys run turbos.
Sid.
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I'm not a 2stroke specialist but on a sled, 6" out would be in the chamber. Sleds spend most of their life at "wide open throttle" with huge altitude changes here in the Rocky's. Lots of guys run nitrous & some guys run turbos.
Sid.
Not trying to hi jack but you wouldnt have any info on these 2 stroke turbo set ups would you? I wanted to go 2 stroke turbo but found it to be almost impossible, thus why I went to nitrous on my bike instead of the turbo. But if someone has it figured out I am all ears.
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I know that Scott Horner has turboed ATVs and I think he's done sleds. I expect that he's also done two-stroke motors, too, if he's in the snow mobile-modifying business. Contact him via Heads Up Performance in Sandy, Utah. 702 204 4505
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To Dr J
Contact Don Guhl in Ephrata, PA
717-618-4212
He has built many RS125 racing engines
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Jessechop, how about going back to the Profile form that you saw when you were registering - and enter your location in the blank called (for good reason) "Location"? Then we'd have an idea of where to point you towards a shop, for instance. Pennsylvania and Utah aren't next to one another - but if we knew where you're located we could maybe give better help. Thanks.
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Thanks for the info Seldom Seen Slim and I corrected my profile. Sorry for any troubles
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Google Mountain Performance in UT, they lead the pack out here with blown or turbod 2 & 4 stroke sleds.
How about a 300+ horse Yamaha Apex that will just about climb a cloud.
Sid.