Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

[aaaprod]

I have always had this happen particularly at higher altitudes where the air is colder and I am using more turbo. I always thought that I had poor sealing on the baffles but now that I have a fresh motor with fresh baffles the issue is still there. Before we start looking at poor baffle sealing is this normal for HS equipped planes? Anyone else see differences in CHT on 2 and 4 from 1 and 3?

 

[neald]

Re: Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

I have always had this happen particularly at higher altitudes where the air is colder and I am using more turbo. I always thought that I had poor sealing on the baffles but now that I have a fresh motor with fresh baffles the issue is still there. Before we start looking at poor baffle sealing is this normal for HS equipped planes? Anyone else see differences in CHT on 2 and 4 from 1 and 3?

Mark,

That is not normal (at least not on my plane). There are a lot of "opportunities" on the 112 baffling, so there may just be a couple of minor sealing issues on yours. But before you start throwing money at the baffling (which if often a time/money sink), it is probably worthwhile to double-check your probe accuracy.

Happy Hunting.

Regards,
Neal

 

[pjdavis67]

Re: Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

My CHT's in my HS were 333 (coolest) and 338 (hotest) on my flight home from DC, 7000', 25.5", 2400rpm, 11gph, 1495 TIT, 208 Oil Temp.

I've found the above to be typical in my non-GAMI a/c.

 

[N4843W]

Re: Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

5 degrees difference between 4 cylinders? That is damn near miraculous. You are runing 4 intependent engines side by side, all experiencing different mixtures, different cooling air patterns. Lucky guy!

 

[bhogue]

Re: Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

Mark
My experience is close to yours. I have always had #2 running 20 to 30 degrees hotter, both on the climbout as well as cruising with the Hot Shot in use at high altitudes. I've been told that one solution might be to check the injector to see if the same amount of fuel is going into the cylinder. Gamis maybe?

 

[aaaprod]

Re: Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

Mark
My experience is close to yours. I have always had #2 running 20 to 30 degrees hotter, both on the climbout as well as cruising with the Hot Shot in use at high altitudes. I've been told that one solution might be to check the injector to see if the same amount of fuel is going into the cylinder. Gamis maybe?

Thanks Bob. We did check fuel metering and it is perfect over all cylinders. Nearly exact amount.

 

[wab003]

Re: Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

Easiest step Mark might be to swap probes between sides and see if the difference follows. Question answered. If the diff stays in the original locations, then pursuing bafflesmay be order.

Having "equal" fuel metering doesn't guarantee identical CHTs. Effective cylinder fuel charge depends upon several factors, actual cylinder size, valve condition/dwell/etc. As a very simplistic test, you can take the injectors from the highest and lowest temp jugs and swap them to look for impact. (do NOT overtorque those rascals during the install and remember to keep the vent holes up) Little more interesting experiment is to test each cylinder for indicated fuel flow when it individually peaks and swapping the highest and lowest (first and last to peak) to see if you can pull the peaks closer together. This is what GAMI does by matching the nozzles to actual cylinder conditions so that all the jugs peak close to the same overall fuel flow. That should create appx equal CHT's as each jug will be close to its stoichiometric optimum at indicated peak or close to peak. (sf - there's your word for the day. ;-)

Note the above is only to create the matched heat input for all the jugs. You may still have to deal w/ sensor differences or heat dissipation (cooling) differences to account for your observations.

 

[aaaprod]

Re: Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

Good thoughts Bill. Will look into this stuff. I have a feeling my issue is from very poor fitting landing gear doors that are just channeling in cold air. Baffles do look good and this only happens at high altitude. Down low everything is pretty even.

 

[Jeffrey Boccaccio]

Re: Cylinders 2 and 4 run about 40-50 degrees cooler than 1 and 3 in CHT?

My #2 has been always hotter than the rest. Been that way for years