flyrotary@lancaironline.net Mailing List Archive

First, I'm sorry the pic of my RV-8 is sideways, something about iPhones...I don't get it.

Today I got the engine cowl on and tethered the plane to my Pickup. I ran it about a half an hour. I richened the Mode 3 mixture as it warmed up. Installing the new turbo caused the engine to run very lean compared to the old one.

When it got above 150F I started adding power and taking pictures of the Engine Monitor to get some data points.

The TO-4E 1.30 A/R turbine housing is not too loose. Today's highest recorded RPM was 4883, 35.0 "Hg manifold, and about 44"Hg turbo boost pressure before the throttle. So this is a huge improvement over the previous turbo, a 60-1 P-trim TO-4 with .81 A/R exhaust housing. Before, I was running about 55"Hg from the turbo, thru part open throttle to get about 38"Hg manifold pressure and 4600 RPM. About 17"Hg pressure drop across the partially open throttle. now with lower turbo boost I get only 9"Hg pressure drop across the partially open throttle, and the engine RPM is higher with a lower manifold pressure. The greater A/R exhaust housing must be reducing the exhaust back pressure, which also reduced the exhaust dilution to the intake charge.

I curtailed the experiment when I noticed the oil temp @ 204F. Water temp was about 185F. When I reduced power the oil temp started back down. I think it will be flyable, with excellent water temp control, and pretty good oil temp control at anything other than high static power.

This prop is a CATTO 2 blade, a left turning prop identical in diameter, pitch and area to that intended for a 180 HP Lycoming O-360. It should turn about 2200 RPM static to be equal to an O-360, which would be about 150 HP. I got 2229 Propeller RPM so that puts me in good company, and I still have more untapped boost pressure.

The 50 trim compressor discharge is smaller than that on the 60-1, so I use a 2" to 2.5" adapter hose to fit it to the existing charge air pipe. I have a Stock Mazda intercooler, the only thing I've found in my on-line search which might fit my airframe, it has a 1.75" inlet pipe.

The turbo's 2" OD outlet is thick wall cast aluminum, so I'm betting the ID is pretty similar to the ID of the 1.75" OD inlet tube to the intercooler. I'm collecting the parts...

Meanwhile, I plan to give the auto-tune program on Tracy's Engine Monitor a try on the next tethered run.

-----Original Message-----
From: Kelly Troyer <keltro@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wed, Oct 30, 2013 4:59 pm
Subject: [FlyRotary] Re: Wrong turbo, maybe better this try

Dave,

What is the A/R ratio of your TO-4E/50 turbine housing??..........My TO-4E/50 (hope to run in this lifetime) has a 1.15 A/R ratio turbine housing. Is your

TO-4 what you were running at Reno ??..............

Thanks,

Kelly Troyer
Dyke Delta_"Eventually"
13B_RD1C_EC2_EM2

On Tue, Oct 29, 2013 at 5:33 PM, David Leonard <wdleonard@gmail.com> wrote:

You are right Scott, that is a much better turbo, though I doubt you were experiencing compressor stall at power settings you would want to use on the ground. I also fly with the TO4E-50, but have used the 60-1 in the past with good success. And yes, your turbine housing should be as big as you can reasonably fit.

Dave Leonard

On Tue, Oct 29, 2013 at 2:41 PM, Scott Emery <shipchief@aol.com> wrote:

Here is a pic of my 13BT powered RV-8. I've already blown & rebuilt the engine, now I've learned from ground running and forums that the 60-1 turbo with .81 A/R housing was not good in 2 ways: the compressor was too large and the turbine housing too small. The resultant increase in exhaust Back pressure rising too rapidly with boost pressure. This held back any hoped-for power gain. Also, the compressor seems to have been on the verge of stall, with fluctuating boost pressure during tethered power testing.
The pictured TO-4E has a 50 trim compressor & 1.30 A/R turbine house. I did run it briefly before I had to return to work, it ran very lean. I'll be reprogramming the EC-2 during the next run. This forum & Ross Farnham over on the Vansairforce were big helps getting me researching in the right direction.
Possible future intercooler location is along the Charge Air pipe on the left side. The hot jacket water pipe will need to be relocated.

Sent from my iPhone
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