M20F Temperatures?

[Lood]

I own a '67 M20F and I am not totally happy with the oil temp and CHT in the cruise. It still uses the original factory installed gauges so I suspect they might not be very accurate anymore. When cruising with closed cowl flaps, the oil temp rises to a tad above 200 deg and the CHT moves up to 400 deg plus. Although both stay within the green arc, it seems a bit high to me. As a result, I almost always fly with the cowlflaps partly open. This usually brings down the CHT immediately, but once the oil temp gets high, it stays high.

Another thing that bothers is that sometimes, the oil temp stays lower - around 180 deg - even with closed cowlflaps. I would appreciate to hear from other owners on how their oil and engine temps behave and if I should have any reason to worry? Also keep in mind that the average temperatures in South Africa is probably substancially higher than in the US. I would guess it to be around 70 deg F in summer and about 50 deg F in winter - at cruising altitudes of 8000 ft.

[KSMooniac]

You should aim to keep your CHTs below 380 dF for optimal cylinder life.  If you cannot do so, I suspect you have some baffling issues that should be addressed.  I fly in the plains and south to TX in the US year-round and it gets as warm or warmer at altitude and can keep my CHTs in check.  A buddy with an E model can too.

You didn't mention what kind of power/mixture settings you use.  If you're cruising around at 50 dF rich of peak on the EGT, that is just about the spot that gives you the absolute highest CHTs possible.  You could try 10-20 lean of peak at 8000' or 100 dF rich of peak.  Either of those settings will help bring down your CHTs.

[TurboExec]

My '67 F model has Oil Temps around 160-175 dF and CHTs from 300-380 dF (depending on how I run it.)  If I run LOP my CHTs stay down at 300 dF, but at Altitude when using my Turbo (no intercooler) temps under the hood rise and my CHTs run up to about 370-380 dF....this is the "go fast mode" too so I'm using higer power settings.  All my cruise settings are cowling flaps closed.

I'd +2 to what Scott said, it may be a baffling issue....(pun intended, haha)  Have a mechanic look at it, some of it may need to be replaced.  Are you turbocharged?  At 8000' you can't be pulling much power and your temps should be considerably lower than if you were cruising around at 2000 or 3000'.

[Lood]

Thanks for the feedback.

I don't have a turbo charger installed - all stock standard. I must add that the EGT connecting terminal on no. 1 cylinder did not make good contact. So the readout for no.1 on the E4 EGT gauge was non-existent. I used no. 3 for leaning purposes and leaned it to 100 deg ROP. I fixed the contact problem in the meanwhile and found that no. 1 actually runs about 30 deg hotter than no. 3. So I was probably flying at around 70 deg ROP which is then why the CHT and eventually the oil temp rose. I will go for a testflight asap and I am pretty sure that things will improve. My gosh, I should have fixed that EGT terminal a long time ago.

[KSMooniac]

Your individual EGTs may or may not peak at the same temperature, so you can't compare the peak temp for #3 to that of #1.  Do you have an engine monitor that displays all 4 EGTs and CHTs? 

[Lood]

My EGT does indeed display all 4 cylinders. It is an E4 from EI and you basically have to manually switch from no 1-4 to get each cylinder's reading. As I mentioned earlier, no 1 was'nt working and only after I fixed it did I discover that it is indeed first to peak! I've only done a quick flip after that to check if the temperatures displayed are stable. Well they are and an early diagnoses tells me that I did run a bit on the lean side. If I set the mixture 100 deg ROP on no 3, no 1 runs at least 70 deg ROP or maybe even closer to 50 deg - which is not good. I'll go test it again at the first oppertunity and give you some feedback on what the temperatures did. At the mixture setting that I used to fly, the fuelflow computer (FP5 from EI) normally indicates 10 gal/hour.

I am waiting for a more advanced engine analyzer though and once I receive it I will have it installed by someone that knows what they're doing and I'll also have the whole system tested out and inspected thoroughly.

[KSMooniac]

Lood, have you done a GAMI lean test by chance?  Since you have fuel flow installed, you could do it with your E4 but it would likely require a helper to record the data.  That will tell you a lot about your engine and injectors.  A more modern analyzer would be great too...I consider them required equipment and would not want to fly without one!  One more question...do you have the fast response or slow response EGT probes?  If they move quickly as soon as you move the mixture then they're the fast ones...which is what you want.

[Lood]

Scott, I'm sure I have the fast response probes because the EGT's change almost instantaniously when I change the mixture. Would you mind elaborating a bit on the Gami check you mentioned - or you can post a link where I can read up on it? It sounds interresting and I would definately like to look into it. Gami's are quite high on my wishlist, but the current R/$ exchange rate makes it too expensive at this time.

[KSMooniac]

Lood, here ya go:  http://www.gami.com/gamijectors/leantest.php  You can download a data form there too.  Definitely take someone with you to record the data while you fly and look for traffic.  You may or may not need GAMIjectors, but in any case doing this test is the first step.  My 201 runs great lean of peak with factory injectors.  A buddy's E does as well.  Many Lycoming 4-cylinder engines will do so without GAMIs, so you might find you don't need them.

You can record the data by hand, and then enter it into Excel or another spreadsheet program to plot the results.  I can help you with this if you need it.

[mooniac58]

I have a M20J but my A&P recently re-did my baffling with some silicone feeling gray stuff (it was about $270 per roll and I used about 40% of it) and my cruise temps lowered by about 120 degrees!!  Amazing really, I can now cruise climb at 105KTS with the cowl flaps closed. and temps around 360F.

 

[Yannis]

On 2/14/2009 at 6:16 AM, mooniac58 said:

I have a M20J but my A&P recently re-did my baffling with some silicone feeling gray stuff (it was about $270 per roll and I used about 40% of it) and my cruise temps lowered by about 120 degrees!!  Amazing really, I can now cruise climb at 105KTS with the cowl flaps closed. and temps around 360F.

 

 

 

Could you share before and after photos, please? this would be interesting to see.