CHT questions

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wjunius
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CHT questions

Post by wjunius »

I just got my 2004 DA40 back from engine overhaul. I’m 20 hours post SMOH. We replaced the baffling but I’m getting, what I consider to be a wide spread of CHT’s. On T/O, as soon as practical, I cut RPM’s from 2700 to 2400 because my #1 CHT will get over 400 and closer to 410 if I don’t. Once I get to around 3000 MSL I can go back to full T/O power and it’s fine.

In cruise I fly between 8000-9000 feet and run WOT with 2200 RPM’s, LOP, TAS around 125-130 kts, and with #1 and #4 CHT’s in the low 370’s and #2 and #3 running 320-330’s.

First, is this a problem? Second, if it is, I think it’s related to the seal between the intake scoops and the cowling. I have GAMI injectors, new mags (not a timing issue), and new baffles so I’m not sure what I’m missing. Any ideas/comments?
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Re: CHT questions

Post by astaib »

Hi,

Have you the Arizona version of the right hand baffle ?

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wjunius
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Re: CHT questions

Post by wjunius »

Yes I do. I’m pretty sure.
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Re: CHT questions

Post by wjunius »

Confirmed. I have the Arizona baffle. I found my invoice but can’t attach a screenshot from my phone.

I spoke to the DOM at Premier and he says I shouldn’t worry about CHT’s even into the 380’s in cruise. I’ve read a lot of Mike Busch and I don’t think he would agree. Maybe I just take things to an extreme.
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Re: CHT questions

Post by dant »

Can someone remind me which cylinder is which? I thought 1 and 4 were kitty corner from each other. If they were the forwardmost cylinders I would say you have a leaky baffle so your cooling air is partially venting prior to passing over the rearward cylinders. I wouldn't expect a 50 degree temp difference in cruise. Looking at a recent log mine are within 10 degrees of each other during cruise.
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Re: CHT questions

Post by wjunius »

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wjunius
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Re: CHT questions

Post by wjunius »

Mine used to be pretty close but it changed within the last year even before the overhaul.
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Re: CHT questions

Post by Rich »

You’re correct in that #1 is front right and #4 is left rear. This is a curious problem. I wouldn’t expect CHTs of 370-ish LOP. The 320-330 seems more like it. Have your injectors been cleaned? Here’s something to think about: You’ve just had an overhaul. Did they put the injectors back in the same place? Another thing about GAMIs: They are custom-fit to allow for the behavior characteristics of each engine. You no longer have the same engine, really. And it’s not necessarily fully broken in.
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Re: CHT questions

Post by wjunius »

The injectors are brand new GAMI’s installed at overhaul about 20 hours ago.

I realize that the cylinders run hot during the break in process but it seems there should be more uniformity.
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Re: CHT questions

Post by Rich »

wjunius wrote: Fri Jun 17, 2022 6:18 pm The injectors are brand new GAMI’s installed at overhaul about 20 hours ago.

I realize that the cylinders run hot during the break in process but it seems there should be more uniformity.
My understanding is that GAMIs are custom-fitted based on testing how the engine behaves. What sort of assumptions were made for the brand-new GAMIs?

Does the CHT profile mirror the EGT profile. i.e., hotter cylinders also have higher EGTs?
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