CHT

[plehrke]

Originally Posted by BillSchlatterer

The truth is in the operations manual you got with your engine from Lycoming. Pretty much anything else is educated opinion.... and probably good opinion but Lycoming built it !

Could not agree more. Only Lycoming has decades of data and is financially accountable.

That being said, how to ensure your installation achieves the Lycoming published limits is completely up to builder/owner and has many opinions and options.

Can't end without my opinion; temperature, like a lot of stuff, is not a hard and fast limit but if it gets up in the "hot" range (insert your definition of hot) to many times you can expected you are paying a price in engine life (TBO) and therefore $$$. Therefore I listen to the educated opinions and personally keep my CHTs below 380 in cruise and 425 in climb. Your mission may vary if your priorities are more performance driven and less economy driven.

[DanH]

Originally Posted by Selma

What is the truth with CHT on a Lyc.O320 / 160 HP in a RV9? Is 460 F really too much in a long climb up to the flightlevels? Is 360 - 390 good in the cruise ?

Set aside the opinions and consider the question this way...are you running hotter than the most of the similar installations? If so, then something is not as it should be.

My opinion? I could not accept 460F. I think a good, normal parallel valve installation in an RV reaches a little over 400 in climb and probably cruises about 350.

[vic syracuse]

I agree that 460 is too high. However, all of the RV-9A's with fixed pitch props I have flown seem to have high CHT's on climb out, peaking around 435 before starting to settle back down as the altitude increases. Cruise is also higher, in the 370's. I use a cruise climb at 120 KIAS or better and still see very respectable climb rates approaching 1000 FPM.
As Dan mentioned, do check to see that the cylinders are sealed really well all around the baffling with RTV, especially the front of the engine, the washer is in place behind cylinder 3, the ramps on top of the cowl are closed on both ends, and the rubber baffling is laying properly across the lower cowl ramps when the colwing is on.

Also, make sure the FAB box is properly sealed with rubber baffling to the lower cowl. Any pressurization of the lower cowl will prevent airflow from the top and result in higher temps.

Vic

[MikeyDale]

I took off on my first flight, nervous as ****, got about 400' off the ground, looked down and saw 405 on my #1 and almost crapped my pants! This was a used engine with 75hrs since OH. I reduced power, brought the nose down, and got it coming down after it reached about 415. By then, a couple of the others had reached 400....So began several months of experimenting. I also learned from reading these forums, that 415 on climb out will not cause you to fall out of the sky! I worked on the baffles and sealed gaps, didn't help much but a little. I increased my cowl exit by 1", helped a little but not enough. I resisted trimming more because it will slow me down, and eventually it was gonna turn winter again and I didnt want to be up there cruising with excess cooling. I installed antisplat cowl flap and that helped a little, especially when doing all my slow flight maneuvers in phase 1. Then, after 30-40 hours, I believe, my baffle seals finally got hot and broken in and all of the sudden, I wasn't having any problems anymore! It could have been, my engine loosened up a little since it was overhauled back in 2006 and was run only 75hrs the next few years and my first flight was in 2015. Also, this is the first time I've ever had such good engine monitoring (Skyview) on a plane. My old 59 tri-pacer could have hit 500 and I'd never knew it!

[kai]

Many people here on VAF are talking about a washer for the #3 cylinder. I am not exactly sure were to install it.
Does anybody have a picture or drawing showing were to install it?

[N941WR]

During testing of the Van's RV-9A, the CAFE foundation recorded a CHT of 462 while performing a climb test.

Mu question is, were you full throttle and full rich during your climb? Apparently our carbs have feature that adds more fuel when wide open to help cool the cylinders.

[kai]

Bill, yes full throttle and mixture full open. But we found out that the FF is too low. It?s only 10.8GAL @2350 RPM 29.7MAP 86%.

[N941WR]

Originally Posted by kai

Many people here on VAF are talking about a washer for the #3 cylinder. I am not exactly sure were to install it.
Does anybody have a picture or drawing showing were to install it?

No picture, just a description.

On the aft side of #3 (that is the right rear cylinder as you sit in the plane), there is a 1/4 - 20 bolt (it looks like a hardware store bolt) that screws into the cylinder head just above where the baffles start to wrap around the cylinder. The washer goes between the cylinder head and the baffle.

The cooling fins are not very deap in this area, which is why the extra cooling air is helpful. (There is a corresponding bolt on the front of #1 but no washer is needed there because the incoming air keeps that cylinder cool.)

[WA85]

Be careful in assessing fuel flow when operating with a fixed pitch prop. Fuel flow is somewhat proportional to engine RPM. If you have a FP prop and are in a low speed climb condition with low engine RPM (due to loading the prop), fuel flow is going to lower. Fuel flow is proportional to mass air flow, which is directly related to how fast that engine cylinders can pump air through the engine.

By increasing your climb speed, the FP prop may have less load on it, turn faster, allowing the engine to flow more air and fuel, and higher airspeed means more cooling air. Its a balancing act.

Adding a #10 thick washer between the #3 baffle and the cylinder does have a significant impact on cooling the #3 cylinder. I just did this on a 9A and it took the climb CHTs from 415 down to 390, almost amazing. Did the same thing on my IO-320 powered 8 and it was 20 degree delta after adding the washer.

If you have an AeroSport O-320, which may have an O-360 oil sump, another mod I just did was adding the tapered insert in the sump opeing above the carb per Lycoming SB 258. This also had a significant impact on the rear cylinder CHTs. The #3/#4 CHTs in climb used to be 20 deg hotter than the front cylinders. After adding the insert, the aft cylinders are 5 degrees cooler than the front.

[DanH]

Originally Posted by N941WR

No picture, just a description.

Pictures here, other methods, discussion, etc:

http://www.vansairforce.com/communit...ghlight=bypass