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Engine specs & equipment
Engine break-in
Injector balancing

Having bought the engine for my RV-8 from Aero Sport Power in Kamloops BC and having had an excellent experience there was little question about who would build the engine for this plane. Aero Sport Power's prepurchase help, the quality of the engine, and especially the post purchase support just don't get any better. Aero Sport Power engines are so popular amoung RV builders especially in the Northwest where I live that we affectionately refer to them as "Bart motors". Below are all the particulars as well some info on engine break-in and operation.

 

Engine specs & equipment

My RV-3 engine is essentially a Superior XP-320 (Lycoming IO-320 D1A clone). Since Superior did not make an O-320 crank at the time I purchased it Bart used new Lycoming pieces therefore I suppose you'd call it a Superior/Lycoming hybrid.
The only difference between an O-320 and O-360 is the longer stroke on the later and therefore the cylinders and heads they share most parts including the case and accessory housing. My engine was therefore built from a Superior XP-360 parts including the case sump camshaft and sandcast cylinders and Lycoming crank and rods.
Why not a factory new Lycoming? Once you take the time to go through a detailed comparison of some of the features of the Superior components compared to their Lycoming counterparts you'll understand why so many RV builders are selecting engines built from these components. Following is a summary of the major components...

• Superior XP-360 crankcase - Includes several significant improvements: reinforced cylinder decks balanced oil delivery system down the left & right sides of case pressurized thrust face bearing lubrication and increased material in areas where Lycomings have shown to be weak.
• Superior XP-360 camshaft - new computer generated profile.
• Superior XP-360 sump - features improved high-flow induction paths.
• Superior sandcast O-320 cylinders
• Precision Airmotive Silver Hawk EX (aka Bendix RSA aka EX-5VA1) fuel injection
• LASAR ignition (ordered w/o the CHT circuit)
• B&C starter and alternator
• B&C 90° oil filter adapter
• Although I considered 9.2-1 pistons I ended up deciding on the standard 8.5-1 compression ratio mostly out of concern for the continued availability of 100LL.

All told Bart predicts this engine will easily make 168-170 hp and should make it so I don't have to worry about keeping up with my buddies in their RV-4/6/7/8s with O-360s. (Note: now that I'm flying there are no worries about keeping up with this plane, in fact I almost always have to reduce my climb rate for my O-360 pals to stay with me, ha!)

Fuel injection
Interestingly I find most folks unaware of what Precision Airmotive has done with their product line. In 2003 they introduced the Silver Hawk EX to the market. This new offering is essentially an improved version of their traditional Bendix RSA system but for the experimental market only and of costs less than the certified Bendix system. Simply put, I think they got tired of Airflow Performance taking most of this market.
For those ordering the Silver Hawk for vertical induction be sure and order the "mixture arm reversal" option so you don't have to carve up your FAB.

Electronic Ignition
There are several significant benefits to replacing the magnetos with an electronic ignition system. Based on my past research and experience with the LASAR ignition on my RV-8 including it on this project was a foregone conclusion. For further reading on the benefits of electronic ignition in general I suggest the Cafe Foundation's three part paper on Ignition Dynamics...

http://cafefoundation.org/v2/research_reports.php

For those interested in more info on LASAR in particular here are links to Part 1 and Part 2 of a series of articles published on AvWeb on the LASAR system... Part 1 and Part 2

 

Oil filter adapter
The RV-3 engine is positioned so close to the firewall that you need to install recess for both an oil filter and a prop governor (if you're installing a constant speed prop). Therefore an oil filter adapter that positions the oil filter at 90° is necessary in order to get the oil filter on and off. When ordering the engine I guessed I'd need the .75" spacer from B&C but when I mounted the engine I discovered this isn't quite enough. The 1.4" spacer is the correct size for the current engine mount.

 

 

For more info on various engine installation systems see the FWF page.

 

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Engine break-in

The break-in process of an aircraft engine is very important. A bit of research will show that much has been written as to the best regimen to use. In studying everything I could find I concluded that the single best overview was provided by a document published by the Cessna Pilots Association: Tech Note #035 (can't publish it here for copyright reasons). It matches Aero Sport Power's recommendations very closely but also provides good background on why they make the recommendations they do. Here are two quotes from that Tech Note that sum it up: “...CPA staff suggests operating at maximum rated continuous power if it can be done without over-temping otherwise reducing power only to the extent necessary to keep temps in the green.” And later just to show how important the first few hours are… “My belief is that if the engine isn’t broken in at ten hours it just isn’t going to happen.”

Run engine at least 50 minutes out of each of the first 10 hours at 75-100% power. An easy guideline when flying is to use the "rule of 48": never let power go below 24/24 (24" of manifold pressure and 2400 rpm) which is very close to 75% on most engines. Of course you'll need about 10 minutes of every hour for stall speed checks and pattern entry.

Oil/filter change schedule :

0-10 hours

20-50 mineral oil (Exxon or Philips)

10-25 hours

20-50 mineral oil (Exxon or Philips)

25-60 hours

any AD oil NOT semi-synthetic yet

60-100 hours

any AD oil NOT semisynthetic yet

100+ hours

Exxon Elite 20W-50 or AeroShell 15W-50

To the right is a table that recaps what seems to be the common ground in all of them and the regimen I use.

And yes I'm a fan of multiviscosity oils the pros quite clearly outweigh any cons IMHO further comments here.

 

Engine cooling
Comments on cylinder and oil temperatures can be found on the FWF page.

 

Injector balancing

Lycoming injector nozzle inserts

One of the advantages of a fuel injection system over a carburetor is that it has inherently more even fuel distribution. Better still, because there are individual nozzle inserts at each cylinder, the opportunity exists to improve the balancing the fuel flow to each cylinder by adjusting the size of the inserts. The objective is to get them to peak at the same time and thus provide consistent cylinder-to-cylinder operation at LOP settings. While GAMIjectors have had much press in this area Don Rivera at Airflow Performance can handle the task on experimentals for a significantly smaller investment.

Conventional wisdom regarding cylinder balancing is that you want to simply get a small EGT spread. The real objective should be to get the cylinders to peak at the same throttle/mixture setting so that they are at the same point LOP or ROP. That way you can run further LOP yielding smoother and more efficient operation. This is what both of the above mentioned programs aim to accomplish.

The first step is to get the correct sized inserts in place to start with. Apparently Precision Airmotive ships all Silver Hawk EX systems with .028 inserts regardless of application (O-360 or O-320). Don advises putting in .022 inserts to start with for my IO-320 application to keep the pressure up in the flow divider (aka spider) and prevent that from becoming a factor.

 

10/15/07 — I received the .022 inserts installed them and obtained the following initial flow/temp data...

 

Altitude 6000'

MAP: 20.5

RPM: 2400

 

 

Cylinder 1 EGT

Cylinder 2 EGT

Cylinder 3 EGT

Cylinder 4 EGT

Restrictor:

0.022

0.022

0.022

0.022

7.9 gph

1231°

1284°

1268°

1223°

7.7 gph

1252°

1308°

1291°

1245°

7.5 gph

1266°

1326°

1309°

1261°

7.3 gph

1276°

1334°

1317°

1270°

7.1 gph

1295°

1342°

1335°

1292°

6.9 gph

1301°

1335°

1341°

1298°

6.7 gph

1292°

1297°

1328°

1300°

6.5 gph

1282°

1283°

1307°

1289°

6.3 gph

1251°

1259°

1278°

1259°

Note that there is a .4 gph spread, not bad for starting values. This info was sent to Don Rivera for review and recommendation. The ideal goal is a .2 gph spread, we'll see how close I can get as the process proceeds.

10/16/07 — Don reviewed the results and recommends a .0225 insert for #2 as the only change. That will cause that cylinder to peak later and should bring it closer to the others. The insert was ordered.

11/3/07 — Installed the the new .0225 #2 insert and collected the following data...

 

Altitude 6500'

MAP: 22.0

RPM: 2400

 

 

Cylinder 1 EGT

Cylinder 2 EGT

Cylinder 3 EGT

Cylinder 4 EGT

Restrictor:

0.022

0.0225

0.022

0.022

8.0 gph

1293°

1310°

1333°

1289°

7.8 gph

1308°

1324°

1346°

1302°

7.5 gph

1307°

1345°

1345°

1312°

7.3 gph

1296°

1341°

1333°

1305°

7.0 gph

1273°

1321°

1304°

1286°

Indeed, the slightly larger #2 insert brought that cylinder's peak temp point down relative to the others and now there is only a .3 gph spread. In reality it might be closer than that but my data points are fairly course. In all, mission accomplished, this is a tighter spread than many achieve and I can now run as much as 90° LOP if desired.

 
Engine operation
Comments here on engine operation principles

 

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