REFLECTOR: High temps

[Jim Sower]

I am running a LIO-360-C1E and even after a lot of work on the baffling 
have CHTs around 375 - 400 with occasional excursions to 425 which I try 
to correct for.  From the beginning, my oil temp never ever budged off 
of 180, but more recently I have had oil temps up to 210 - 220 on 
occasion.  I think part of this might have to do with the firewall oil 
cooler which exhausts right into the plenum - the high pressure air for 
cooling the cylinders.  There can't possibly be much air flow through 
that cooler, and I regard it as a significant design defect.  At some 
juncture (after I get the engine running again and the plane annualed) I 
am going to exhaust it to outside air under the cowl.

Glad I'm not the only one with high CHTs ... Jim S.

Sid Knox wrote:

> 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 <mailto:jsbeck at charter.net>>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org 
> <mailto: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