REFLECTOR: High temps

[Sid Knox]

Hi Jim,
I too have an early '90's 173 RG with a Lyc IO-360 B1B that I bought from the builder about three years ago.  The builder had tried two earlier cooling air schemes and had just completed the conversion to the two top NACA ducts and pressure shroud.  He reported that it was running cooler than previously.  I have been plagued with high cyl temps from day one (" high" for me is anything over 400F).  OTOH, my oil temp runs too low and I have to partially block off the front cooler to ever see 180F.  And yes, all cht temps have been verified with independent thermocouples at the top plugs and oil temp verified by inserting a tc probe directly into the sump (via filler tube) immediately after shut-down.
I balanced my injectors so I can run at least 50F LOP and that along with keeping power below about 60% keeps temps below 380F.  I don't go as fast as most Velocities but running cool, clean and burning less than 7 gph puts a smile on my face.
I did a lot of reading on the reflector about other's experiences regards cooling.  What I come away with is that some have cooling issues, some don't (or won't admit it or don't have the instrumentation to know one way or the other).  Some use the NACA ducts.  Some add VGs at inlet to the ducts and claim a large decrease (one guy at Oshkosh told me he dropped cht by 30F.  I added VGs and saw maybe 10 if that much).

There are times when I would like to burn a little more fuel and go faster so I am still seeking answers.
Two ideas I picked-up (from the reflector) that I will persue when the weather gets better so I can work in the hanger are:
1) verify proper ignition timing with a timing light.  I'm still puzzling over this one as to how to do it without getting chopped-up by the prop.
2) add a scoop to one of the NACA ducts (one side only for initial data taking).  Yes, drag, but don't most of our flying decisions involve trade-offs?

Opinion follows:   if those temps you see are real, you have a genuine cause for concern/alarm.

Sid Knox
Oklahoma

Velocity    N199RS
Starduster  N666SK
KR2         N24TC
W7QJQ




----- Original Message ----- 
From: "Jim & Sharon Beck" <jsbeck at charter.net>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Tuesday, January 11, 2005 10:28 PM
Subject: REFLECTOR: High temps



   I have a 173 RG that was completed in 2001 and then not flown until recently and since I did not build it my questions may seem simple to you more experienced builders & pilots. It has a newly rebuild IO 360 A1B6 that now has about 10 hours on it. The 2 front cylinders are running about 425 to 450 and the oil tem is running about 225 at cruise.  Should I be considering a second oil cooler or might these temps come down as it breaks in. These a winter time temperatures so it seems when summer comes I'll be over redline. Anyone help on this or thoughts would be appreciated.
  Jim


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