RV-7A Performance

My mechanic and I have recently completed a very pretty RV-7A. It is also very, very, slow. The aircraft came in at 1,054 lbs., has a fuel injected Superior XP-360 driving a Hartzell constant speed prop. I ordered the LASAR ignition system which was installed by Eagle Engines in California, under sub-contract from Superior.

The aircraft's performance is dismal as compared to other RV's. On a standard day with one person on board, the climb rate is 1,100 ft/min where othere RV's are doing 2,100 ft/min. The top speed is only 180 mph. This aircraft is flying absoultely straight; nothing is dragging.

I suspect that the problem is in the LASAR ignition. During climb, even on a cool day, the CHT will quickly climb to 450 degrees F, at which time only increased speed, reduced power, and full rich will bring it down. We got no documentation on the LASAR from Eagle Engines... and when we called them about the performance and how the LASAR was set up, the mechanic didn't have a clue.

I ordered the special timing box for the LASAR from Van's and it should be here tomorrow. I have also downloaded the service letter from Unison. We will try to set the LASAR up as specified this weekend. Any suggestions and/or recommendations would be greatly appreciated.

Thanks,
Phil Handley
Midland, Texas

Fairings

Hi Phil,
Do you have all the fairings on, including upper and lower intersection fairings? Is the canopy skirt fitting tightly to the fuselage with no air leaks?

We picked up close to 20 MPH with all the fairings and wheelpants. If your timing is way off, it could cost you but I'm not sure how much.
Regards,

I have a LASAR on my older Mooney. I have unfortunately had the engine off twice in the 2 years I have owned the plane...my experience has been that almost no mechanic knows how to work on these things. Even if you give them the manual, they think they know what they are doing and don't read it.

We had similar CHT issues the first time the new engine went back on. At the time I wasn't educated enough to know what the resolution was, but it had something to do with the feedback from the temp sensor.

You may get some diagnostic help by plugging in a laptop with Hyperterminal to the serial port (but you need the cable).

My experience has also been that the system as a whole is darn unreliable, but that the Unison folks are pretty good about support and getting you replacement parts...I guess they have a lot of practice at shipping out replacement mags & controllers for AOG issues.

If I can help, let me know...I have the timing box, PC cable, etc.

Good luck.
John

Fuel flow?

Do you have fuel flow indication?

1100ft/min says lack of power to me...Yes could be the ignition but you will need to check out how much fuel is burned...Thats where the power comes from in any case.

Take it up full rich to say 5000ft...Mine burns in the range of 15 GPH at this point.

Then lean it to peak EGT and go back to 100F ROP...At 2500RPM and 24"MP mine is burning about 12.3 GPH.

It maybe your alradyjust ROP or even LOP and that is where all yer power has gone.

Others may have better data points for you to try...Mine are just from memory.

Good luck

Frank

RV-6A

I have been lucky enough to fly a wonderful 6A for about my last 20 Hours. I helped a friend finish the build. He has an IO-360, ported and polished, balanced, 10.5:1 Pistons with the Lasar System and a Hartzell C/S Prop. It is only about 2 MPH faster than another friends standard O-360 with no mods and the same prop. Climb is usually about 1300 FPM out of our 4700 Foot airport. He was seeing high CHT and oil temps as well.

We put round rings similar to those from James in the cowl and we figured that the cooling was because they were too small but they seemed to be the same size as other 360 inlet rings. We eventually had to tear out these rings and put in the rings sized for the 540. This solved the cooling issue but the performance is still the same.

If we square at 2350 we see about 185 MPH on average and 9.4 GPH.

Can't say that I am a believer in the electronic mags. I have seen so many of the standard mags work so well for so long I am just not convinced of the benefits of the electronic units.

pierre smith said:

Hi Phil,
Do you have all the fairings on, including upper and lower intersection fairings? Is the canopy skirt fitting tightly to the fuselage with no air leaks?

We picked up close to 20 MPH with all the fairings and wheelpants. If your timing is way off, it could cost you but I'm not sure how much.
Regards,

Click to expand...

Pierre,
Yes, we do have all the fairing on. The aircraft is equally slow with or without the wheelpants installe.
Phil

jmbaute said:

I have a LASAR on my older Mooney. I have unfortunately had the engine off twice in the 2 years I have owned the plane...my experience has been that almost no mechanic knows how to work on these things. Even if you give them the manual, they think they know what they are doing and don't read it.

We had similar CHT issues the first time the new engine went back on. At the time I wasn't educated enough to know what the resolution was, but it had something to do with the feedback from the temp sensor.

You may get some diagnostic help by plugging in a laptop with Hyperterminal to the serial port (but you need the cable).

My experience has also been that the system as a whole is darn unreliable, but that the Unison folks are pretty good about support and getting you replacement parts...I guess they have a lot of practice at shipping out replacement mags & controllers for AOG issues.

If I can help, let me know...I have the timing box, PC cable, etc.

Good luck.
John

Click to expand...

John,
We'll make certain that the timing is set correctly on Saturday and see what happens after that. We don't have any of the LASAR service manuals since Superior didn't send them with the engine. Thanks for your help. I'll let you know the results.
Phil

OH yes

On a cool morning at sea level approx I see 2500fpm on the VSI.

You definatly need to know where your engine is operating on the mixture curve.

This assumes you don't find something stupid like your LASER time to 20 deg AFTER TDC or something.

Frank

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 .

Twice I have seen very similar performance from a newly assembled engine.... in both cases the cam shaft gear was installed "off" one tooth. This condition produces low power with few other symptoms. Worth a check?

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!

More on RV-7A performance

rv72004 said:

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 .

Click to expand...

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

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

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

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

I give up, but

Phil Handley said:

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

Click to expand...

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.

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.

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

Max fuel flow at 3,000 feet

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

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.

Tac RPM check

John,
Thanks for the tip. Unfortunately, I had already checked the vaidity of the tacometer and found it to be dead accurate.
Phil

Phil,

It has been a few months since your last post, what ever came of your issue? did you get it resolved? I was considering a LASAR but now am not sure...

- Matt

Performance Fix

Matt,

I had suspected all along that the LASAR was causing the problem, which finally turned out to be true. A fellow named Steve Carter at Unison was most helpful in getting everything right. His email is [email protected], and his cell number is 904 616-7601. After checking that the timing gear was not off by one tooth, and rechecking the timing with a special LARAR timing device I purchased from Van's (found TDC off by 7.5 degrees), the performance still wasn't up to par. Although Steve Carter said that it was indeed rare that the LASAR control box itself could be defective, he shipped a new unit at no cost and we installed it and there was a dramatic increase in performance. Now, at 7,500 feet, I can cruise at 185 mph while buring 9.0 gal/hour.

So, the bottom line is that although the LASAR unit was the problem, Unisom stood behind it and got it fixed.

Phil