RV-7A Performance

[Phil Handley]

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

[pierre smith]

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,

[jmbaute]

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

[frankh]

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

[ww2planes]

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.

[Phil Handley]

Originally Posted by pierre smith

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,

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

[Phil Handley]

Originally Posted by jmbaute

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

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

[frankh]

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

[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 .

[Chickenlips]

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?