VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-7/7A
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 11-30-2009, 03:10 AM
Andrew Hamilton Andrew Hamilton is offline
 
Join Date: Nov 2009
Location: Illabo NSW Australia
Posts: 10
Default CHT variations in Superior 0-360

Cylinder 2 & 4 run @ 185 C
Cylinder 1 runs cooler @ 175 C
Cylinder 3 runs hotter @ 195 C
Is this OK ? Should they all be closer ?
Could it just be differences in the sender units to the Dynon
Older planes only monitor one cylinder so am I worried about nothing.
I would appreciate some thoughts.
Reply With Quote
  #2  
Old 11-30-2009, 03:24 AM
kiwipete kiwipete is offline
 
Join Date: Oct 2007
Location: Birmingham United Kingdom
Posts: 374
Default Welcome

Andrew

Firstly welcome to VAF there's a lot of good info here.

Check a previous thread:

http://www.vansairforce.com/communit...ad.php?t=47542

It should have the info you need.
Looking at the figures you give a small dam in front of number 1 cylinder should even up the temps nicely.
It would be fine to leave it as is but I like having them nearly even as then I can easily spot if somethings changed. Makes it much easier to spot a plug problem etc if you know that normally the're all the same.

Peter
__________________
RV7 G-PBEC Flying
RV10 Finishing

Last edited by kiwipete : 11-30-2009 at 03:24 AM. Reason: typo
Reply With Quote
  #3  
Old 12-01-2009, 08:02 PM
DENMACRES DENMACRES is offline
 
Join Date: Aug 2008
Location: MONTGOMERY, TX.
Posts: 89
Default CYL. TEMP

MAKE SURE THE GAP IN THE BAFFLING AT THE BOTTOM OF THE BARRELS AND HEADS ARE EVEN.
Reply With Quote
  #4  
Old 12-02-2009, 07:33 AM
kiwipete kiwipete is offline
 
Join Date: Oct 2007
Location: Birmingham United Kingdom
Posts: 374
Default gap behind #3

Andrew

Forgot to add it's worth putting a washer between the back of #3 clyinder and the baffle to create a gap which helps cooling and lowers #3 CHT's.

Peter
__________________
RV7 G-PBEC Flying
RV10 Finishing
Reply With Quote
  #5  
Old 12-03-2009, 03:07 AM
Andrew Hamilton Andrew Hamilton is offline
 
Join Date: Nov 2009
Location: Illabo NSW Australia
Posts: 10
Default Gap behind #3 sounds a good idea

Thanks Pete, that sounds a good idea. Without it the area around #3 is a bit of a trap with no where for the air to go. The #2 & #4 side should have better air flow as there is a shallow ramp in and better flow past the oil cooler. On the #1 & #3 side the ramp in is steep (faster flow over #1 making it cooler) and the dead area behind #3 could explain my problem with a hotter #3. It sounds good in theory, I'll give it a try - thats why its called EXPERIMENTAL.
Interesting that in the link you posted a lot of people reported a hotter #1 cylinder which doesn't fit the theory but I'll try the gap anyway.

Many thanks,
Andrew
Reply With Quote
  #6  
Old 12-03-2009, 10:18 AM
instructor_bill instructor_bill is offline
 
Join Date: Jul 2009
Location: Petaluma, CA
Posts: 233
Default forgive me for the simple minded question

for temps that are close-- like these. Why not try changing the location of the cht probes to test whether the temperature (if not at least the trend) moves with the probe?

This type of troubleshooting is routinely done in larger aircraft and works well to differentiate between broken parts, faulty wiring, rigging, adjustments etc.
__________________
Bill Mason

RV7 SB in construction
Avionics, Wiring, FWF, interior, and paint to go.
Reply With Quote
  #7  
Old 12-03-2009, 10:23 AM
andyrv andyrv is offline
 
Join Date: Feb 2005
Location: Leawood, KS
Posts: 275
Default Tape

Andrew,

I had the same situation on my Superior 360. I used a piece of the aluminum duct tape to make a 1" high dam on the #1 cylinder and everything evened out. I already had the spacer on the back on #3. I meant to make a permanent air dam on #1 to replace the tape but that was 200 hours ago and I still haven't gotten it done yet.

Andy
Reply With Quote
  #8  
Old 12-03-2009, 04:17 PM
reak's Avatar
reak reak is offline
 
Join Date: Oct 2005
Location: Loveland Colorado
Posts: 23
Default

I have a Superior O-360 with a fixed pitch prop. My cruise CHT's settle out at at about 330F (165C) for cylinders 1,2 and 4. Cylinder 3 runs about 340F(171C). I do have a 1 inch dam in front of cylinder 1 but no washer behind cylinder 3. Before I put the dam in place the CHT's spread was was similar to yours, although the temperatures were a little lower. I plan to try the washer behind cylinder 3 next week. My slightly lower temperatures may be partly due to my fixed pitch prop not typically making as much power as the variable pitch and I almost alway fly at 7K to 8K ft. where it's cooler. Overall I think your temperature spread is typical.
__________________
-------------
Brad Reak
RV7A Flying, N789W
Loveland, CO
Reply With Quote
  #9  
Old 12-03-2009, 11:04 PM
nucleus nucleus is offline
 
Join Date: Sep 2006
Location: Bozeman, Montana
Posts: 858
Talking 1/4 inch of tape can make a big difference

My number 3 is the coolest right now. The I have some tape on each front cylinder, had been trimming it down on #1 to even things out and went to far. Added .25 inch onto #1 and it is crazy how much difference that made. Don't forget that EGTs are a factor as well.

Hans
__________________
Dr. Hans Conser
Bozeman Chiropractor
RV-6A 195 Hours, up for sale soon?
Reply With Quote
  #10  
Old 12-04-2009, 07:08 AM
N941WR's Avatar
N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,887
Default

Quote:
Originally Posted by instructor_bill View Post
for temps that are close-- like these. Why not try changing the location of the cht probes to test whether the temperature (if not at least the trend) moves with the probe?

This type of troubleshooting is routinely done in larger aircraft and works well to differentiate between broken parts, faulty wiring, rigging, adjustments etc.
Bill,

If you are talking about moving the probes to different cylinders, that is always worth a try. (For those who do not know, the cylinders have a threaded receptacle for the CHT probes, thus there is only place to install them on each cylinder.) However, as closs as the temps are, they are probably OK.

After that, I would try:
1. Cleaning out the flashing between the cooling fins on the cylinder heads
2. RTV any gap in the baffles
3. Add the aforementioned washer behind cyl #3
4. Block the space under the cowl inlet ramps so air cannot pass under them (I used blue Great stuff foam, worked great)
5. Make sure the airseal fabric is sealing (Look at the top of your cowling for where it makes contact, that is a good ?tell?.) and adjust as needed
6. Put some aluminum tape on the front of cylinders #1 & #2. This will force some air up over the front cylinders and into the back.

After going through all that, I was able to get all my cylinders down to between 174 to 178*F.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 03:52 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.