Baffles are baffling

[erich weaver]

i am currently diving into the engine baffles task on my -7A. Love the plane, Van. Hate your baffle instructions.

Question: An optional item is installation of some temperature risers in front of the front two cylinders. Apparently these will deflect some of the incoming air from the front cyclinders and divert it more to the back two cylinders where it is more likely to be needed. Instructions say dont do this until proven to be needed. Should I follow this advice? Would seem easier to go ahead and install them and trim them down later, but maybe its no big deal either way. What has been the collective experience with these - needed or not?

thanks

erich weaver

 

[Norman CYYJ]

Wait till you test fly the plane first. I have used that baffle kit on 5 planes and never needed the temperature risers.

 

[Kyle Boatright]

Do you have a system that can measure all 4 CHT's? If so, fly for a while and figure out if your CHT's are relatively even, or if not, which ones are high and which ones are low, then add blockers to fix the problem.

On my airplane, #3 was always the warmest, #1 was always the coolest. A 1" or so air dam in front of #1 brought #3 down and #1 up, bringing the CHT's into much better balance.

Adding cylinder blockers is a 30 minute job if you have the cowl off, a pair of aluminum snips, a drill, a few pop rivets, and some scrap 0.032 aluminum.

 

[Scott Will]

Is there any way to bring CHT #3 up? Here are the numbers from my 3rd flight on the plane. I added some speed tape on #1 and #2 to try to equalize. Looks like I might have to remove a little on #2... but cyl #3 seems off to me.


Min Max Avg
CHT1 276 423 402
CHT2 289 447 424
CHT3 232 346 325
CHT4 289 436 416
EGT1 794 1481 1368
EGT2 793 1519 1407
EGT3 784 1481 1372
EGT4 inop
OilT 195 233 223
OilP 52 87 75

 

[Mel]

Scott, It's very unusual for #3 to run cool on an RV. First thing I would do is swap the probes between #1 and #3 and make sure it isn't an instrument problem.

 

[RV7Guy]

#3

I gotta agree with Mel, #3 will not be the coolest. On my ECI IO360 the order of hot is #4, #3, #2, #1.

Take Mel's suggestion and swap the probes and see what you get.

In an effort to answer the original question, I suggest you find another RV and look at the baffling. I did this and it made the instructions almost worthless. Definitely worth buying a fellow RVer lunch to remove the top cowl. It will clear everything up nicely.

The baffling, like the canopy, is a right of passage.