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| CHTs during Ground Run http://t18.net/thorpforum/viewtopic.php?f=35&t=7781 |
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| Author: | dickwolff [ Wed May 27, 2015 7:24 am ] |
| Post subject: | CHTs during Ground Run |
I'm looking for the experience of others for comparison. When I ran my engine last fall, I was seeing CHT's creep up above the 400F mark after about 10 minutes. I was running the engine without cowls. OAT was about 70F. I was idling at 1000 rpm, with a couple of mag checks at 1700. I was a little surprised at the temps, but on the other hand they were believable considering there was no air flow through the cylinders. What have others seen under the same conditions? D |
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| Author: | Jim Mantyla [ Wed May 27, 2015 7:29 am ] |
| Post subject: | Re: CHTs during Ground Run |
Dick, I haven't run my engine without cowls but with them on I don't see more than 260F after quite a bit of taxiing and pre take off checks. Jim |
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| Author: | fytrplt [ Wed May 27, 2015 8:22 am ] |
| Post subject: | Re: CHTs during Ground Run |
You will see that on a new/topped engine. Shut it down if ground run gets to 400. There is some good poop on this subject on the engine parts companies web sites. Most CHT gages read the difference between ambient and the probe. The lower the outside air temp, the higher the reading. Since your engine sat for a while, you may have built up some rust in the cylinders. Also, make sure the timing is correct. Change the oil and try again. |
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| Author: | Gary Green [ Tue Jun 02, 2015 11:43 am ] |
| Post subject: | Re: CHTs during Ground Run |
The key to this is running without the cowl installed. You must hold the run time to a minimum or you are assured of getting high CHTs. You must have a cowl installed and good baffles to force the air to flow thru the cooling fins. Look at the design of test stands used for ground running new engines for break-in. They have ducting to force the air to go where it does some good. GG |
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| Author: | dickwolff [ Tue Jun 02, 2015 1:35 pm ] |
| Post subject: | Re: CHTs during Ground Run |
Thanks, all. Indeed, Gary, I figured it was due to running without my cowling in place... I was just looking for validation. I ought to be in a position to run it again in a few weeks, this time with the cowls on and baffles sealed. It will be interesting to see what the difference is. I'll be sure to report back. |
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