RV-7A Performance

[Low Pass]

Hmmm... Might make sure the throttle linkage is opening the FI mechanism fully. I.e., full throttle setting is full power on the engine.

I "have a friend" who managed to install the linkage out one hole on the carb throttle arm after removing the assembly for other maintenace issue. It resulted in something less than full power operation for a while. Couldn't understand why other RV's were climbing at 1500-2000 fpm and I, er... "my friend" was only getting 1200 -1400 fpm.

Gives you very serious appreciation for "RV" climb rates versus average spam can climb rates!

[Phil Handley]

Originally Posted by rv72004

Let me join in and say I had similar issues. High cht and irregular/odd mag drops with a extra rise in rpm when back to both.
Lasar [Steve] sent me a email manual of the system. After checking it out the left mag was timed about 30 degree out. The system was also installed by Eagle. Seems they made a mistake or just careless ?

In any event things seem better now but further tests will tell.

One good thing , Ive never had an engine start easier. Just like a car .

I hope I am replying to all of you guys that submitted replies to my Mayday call. I'm not sure any of you will get this since I don't know how this forum works. Here's what has happened:

I bought the special LARAR timing box and we checked out the timing of the LASAR mags. They were absolutely correct. Here are some other data points:

1. When I do a runup at 1700 RPM; left mag shows drop of 80 rpm; right mag shows drop of 230 rpm... then over a 10 second period, crawls back up to a drop of 70 rpm. Then when the mag switch is turned to both... the rpm goes up to 1740 rpm. (Go figure)

2. During the same sequence, performaing the same checks with the LASAR circuit breaker pulled, you can't see the RPMs, but I can't decern any difference in the drop offs when going between left and right mags.

3. In flight, say at 23/23 squared. If you pull the LASAR circuit breaker (which would make the system switch to convential mags and bypass all of the magic advance the LASAR box is supposed to be providing).. there is not one bit of difference in EGT, RPM, or anything I can see.

4. One of you gentlemen said that at 5,000 feet, 2350 RPM and 23.5" manifold , you were seeing 185 mph and 9.4 GPH. This morning, on a relatively standard day, the same parameters yielded a sizzling 144 mph at 8.8 gal/hour.

5. I was hoping that after spending $250 on a LASAR timing box, that I would find that Superior had screwed up the timing. Not so. I can now only conclude that the LARAR brain box is faulty. Otherwise, why would I not see ANY DIFFERENCE when I pull the LASAR circuit breaker in flight?

6. Someone gave a telephone number for Steve Carter at Unison. I called and left a voice mail message. Hopefully he will return my call on Monday. I certainly hope that Unison will not try to charge me for a replacement controler box.

7. I realize that this ain't rocket science, but it is really beginning to iritiate me that a 1054# airplane with a 180 hp engine driving a constant speed prop has performance comparable to a Cessna.

Thanks for the help you have provided. I hope you all get this mesage.

Phil Handley

[Radomir]

Phil, I'd follow "Chickenlips'" recommendation and check the crank-to-cam timing.

[Scott Diffenbaugh]

Phil,
Not sure where to start other than we went down possibly a somewhat analogous path with high temps and LASAR problems. Although we were carbureted, trying to separate the fuel problems from the ignition problems was time consuming and frustrating particularly since our root problem was fuel, yet our engine builder refused to acknowledge it until it was too late, and the engine was damaged. Also the LASAR system is difficult to figure out and test without specialized equipment and has a checkered history as you are finding out. By turning off the LASAR during cruise you should be eliminating it from the equation so long as you are absolutely sure both L & R mags are dead-on 25 BTDC. There still could be something wrong with the mags/wiring/plugs due to the strange readings when doing the mag checks. (Note that the LASAR turns off automatically for about 20 seconds during mag checks so if you try the mag check with the LASAR disabled there should be no difference in readings with it on or off). Although I don't know the solution to your problem, my advice is to not allow the CHTs to get above 400 degrees or the oil temp above 200 during the initial break in period or you could risk glazing the cylinders, or worse. Please refer to a great article titled "Temperature, Temperature, Temperature" by Mike Busch (www.avweb.com/news/savvyaviator/193242-1.html ). Once you have ruled out all of the obvious items (on the ground), I would insist the engine builder send out an expert armed with Slick mags and all new fuel injection parts for starters. If I were you, I would agree to pay for the expert if it is determined it is something you did wrong.
Regards,
Scott Diffenbaugh, RV-7A, N814SD, grounded pending resolution with engine builder

[Phil Handley]

Gentlemen,
Here's a follow up on my performance problem. We replaced the LASAR control box and it has made a lot of difference. However, I still don't believe that I'm getting the performance that one would expect. The climb rate at 25 squared is now up from 1100 fpm to about 1500 fpm (taking off from a field that is 3,000 elevation.) The true airspeed has also improved to this extent: 7,500 feet; 23 squared; 74% power; 9 gal/hour; CHT 440 deg; oil temp 151 deg = 185 mph true. Is this what I should expect?

I am very troubled by the 440 deg CHT. Could this possbily be an accurate reading when the oil temp is showing only 151 deg? Even taxing out to the runway, it seems terribly high to me. This morning the ambient temperature was about 55 deg, and the CHT was already up to 345 deg while the oil temp was at 100 deg.

I really appreciate all your adivse.

Phil Handley

[gmcjetpilot]

Originally Posted by Phil Handley

Gentlemen,

I am very troubled by the 440 deg CHT. Could this possibly be an accurate reading when the oil temp is showing only 151 deg?
I really appreciate all your advice.

Phil Handley

No advice but I am troubled tooo. 440F CHT will destroy your engine sooner than later. 500F may official red line, but running over 435F at any time, from what I have read, is bad for your engine in a big way. Good Luck. Also your OIL temp is silly low and below what it recommended.

Recommended by Lycoming (Ref. Key Reprints from the "Flyer":

Oil temp - 165F-220F acceptable range. (I like nominal/optimal 185-195F)
CHT - 400F or less for continuous, max 435F "for long life"
(RV'ers don't ignore or accept high CHT, it is the KEY to Lycoming life)

Plane slow, CHT high, Oil Temp low? I give up.

[jmbaute]

At the risk of stating the obvious, is your CHT probe on the hottest cylinder wired back to the controller box as well? On some (certified) installations you are allowed to run the system open loop (no feedback to the controller), but on others, you need the sensor. The system is supposed to sense high CHT and adjust appropriately. There should be a dual point CHT probe- one set of leads back to the controller and the other to your engine monitor.

[Phil Handley]

Gents,
Checked the cam timing today to make certain it was not off by one tooth. It was right on. Checked fuel flow at full power and full rich on takeoff. It was 15.2 gal/hour. I am told that it should be approximately 1/10th of the rated HP of the engine, which would put it at 18 gal/hour at a minimum, assuming that the Superior is not cranking out a vew more HP above the rated 180. We'll turn up the wickk on the fuel, and also check the CHT prob accuracy.
Phil Handley

[Phil Handley]

Following up on the maximum fuel flow for my 180 hp Superior f/i engine, I stated that it was 15.2 gal/hr at takeoff. Since the airport from which I fly is 2800 ft elevation, can anyone tell me what their max fuel flow is at 3,000 feet? I don't know how much difference it would make were I checking it at sea level.
Thanks,
Phil Handley

[RV7AV8R]

Phil, I recently discovered my Van's tach, running off the P lead, was reading 200 rpm high at 2500 rpm. I checked it with a good optical tach (PropTach). This measn I was not using 200 rpm that I could be using or about 13 knots where being left on the table. I am waiting for CAVU to go test again to verify my finding. Anyway, check your tach. This could explain the low speed but doesn't explain your high CHT however.
John Adams, RV7, O-360, Sensenich.