AMT Pegasus SP spool up ???
 

This is a NIB turbine that I just started today in a new Cermark Viper, popped and started as normal first time. It is in a BVM pegasus fully enclosed bypass NOT the factory Cermark one.

My question is what can most likely be causing a very slow spool response on throttle? like 5-6 seconds lo-high
I operate another non SP pegasus in a Kingcat, and it is typical 3-4 second spool.


EGT running 571-635.

Here my list, but what is higher probability.

Bypass starving for air. has some cool sounding whistles at variuos settings
Slow heat seen by Temp probe, maybe put it further in cone?
UAT is notcably sucking in sides, I kept all lines to 5/32" ID.
Pump was not broke in seems a bit high @ 5.6-60Vout on display.
Lines on fuel supply are same as Kingcat so not thinkin this.


Any help would be greatly appreciated.............

RE: AMT Pegasus SP spool up ???
 

Well...if it was the first run-up to max RPM that was so slow...that is normal. AMTs take a few seconds to calibrate max RPM each start, so if you want the fastest response (fast spool) on that TO...make sure you run it up to max beforehand. You'll see 'Max RPM Set' on the EDT.

Ray
AMT USA Field Rep

RE: AMT Pegasus SP spool up ???
 

Thanx Ray,

I am familiar with that feature, I am not new to the AMT lineup I operate 6 of them but this one is puzzling me, since it's in a totaly enclosed bypass kit,

Max set throttle is showing 115K rpm.

As an SP I really expected better performance than the stock one in the KingCat..........

Are BYPASSES known for having negative effects on turbines versus being open air???

RE: AMT Pegasus SP spool up ???
 

I have run both the AMT-280, 280-SP and Pegasus HP in my BVM F-4 (with bypass) and I am now running the 280-SP on my KingCat. Can't say that I have ever noticed any difference in spool up in any of the configurations. The AMTs fit snuggly in the bypass but that really shouldn't make any difference as long as there is adequate air flow into the compressor. You could try running the engine without the bypass cover on and that would surely allow more than enough air.

Since it is a brand new engine I suspect the issue has to do with something else. Ideal sitution would be to run it on a test stand or even on your KC so as to eliminate variables but I know what a pain it is to do that.


Craig

RE: AMT Pegasus SP spool up ???
 

The UAT sucking in the sides and the pump voltage concerns me--I know that this larger engine is going to require more fuel that my Mercury HP, however....My pump voltages for a typical flight are around 3.5 to 4 volts MAX!! That pump voltage does seem high. You could connect the pump up to a 4.8 to 6 volt power supply and break in the pump. Of course you will be breaking in the pump using filtered fuel and never allowing the pump to run dry. Are you running a fuel filter between the pump and engine? (You should) If so, what kind??? I use the high volume clear Festo filters. A small fuel filter can cause a restriction.

Does the turbine spool up freely?? I know that there were some bad bearings in the AT-400's. (Rough/bad/defective bearings can cause high pump voltages.)

As Craig suggested, take the engine out to see if the problem is the bypass. (The only negative thing I have ever witnessed concerning a bypass was that the plane was slower in flight than without the bypass.) Those whistles--Could they be mistaken for a harmonic noise??? My Mercury made a high pitched whistle when new and it turned out to be caused by harmonics...Re-balancing took care of the issue.

Kevin

RE: AMT Pegasus SP spool up ???
 

Thanx for the input guys, I am going to view my pump volts allot closer this thursday on the standard Peggy in the Kingcat. Seems to me that 3 volts is more common. It may be worth a day in a jar for breakin. I also will view uat in KC for deformation. Not quite sure on this since I was certain to have 5/32" ID fittings on tanks.......hmmm

I'll try the bypass cover off........

Aslo I'm using Tams included exhaust tube mated to the BVM Bypass, and now that I think about it there is no flow for air thru the double wall Iguess this is OK???

RE: AMT Pegasus SP spool up ???
 

Got to thinking about the 115K you mentioned for the SP and it didn't sound right. I just checked my 280-SP and it is set for max RPM of 117K. As I recall, 115K was the setting for the "standard" 280. That would at least explain the apparent lack performance.

Well, there has to be air through the double walls. It's either being provided by the air bypassing (flowing around) the turbine through the "bypass" or in some installations the outer exhaust wall is not flush with the bypass and draws air through the fuselage. In any case, you need some small ram air holes or other method of providing airflow through the fuselage and around the exhaust tube as well as between the walls. For areas where the exhaust tube clearance is close to the fuselage or near servos, protect the area with Heat Shield or a piece of heat blanket.

Craig
Craig

RE: AMT Pegasus SP spool up ???
 

Thanx Craig,

Now I'll have to check ECU serial numbers against each other to make sure they have not gotten swapped by myself mistakenly. and max setting on the KC standard peggy.......

The double wall is back from the bypass almost 3" but I do not have any exit holes so it will now based on your advice....

RE: AMT Pegasus SP spool up ???
 

Max set throttle is showing 115K rpm.

As an SP I really expected better performance than the stock one in the KingCat..........

Are BYPASSES known for having negative effects on turbines versus being open air???

>>>>>>>>>>>>&g t;>>>>>>>>>>>> >>>>>>>>>

1) as per before 115 is not an sp.....it is a standard 28lb peggy

2) breaking in fuel pumps is very important to set the gears...30 to 45 mins in your furl can is fine

3) for added power cut five holes the size of a nickel at the rear of your by pass ( spaced evenly ) where it tapers down near the exhaust cone

4) v-max can differ in 3 ways on your edt.....a) temp outside....30 to 50 degrees .... b) fuel filter clogging ...kero doesnt have the anit biologics that jet a does so it can be a problem if you run kero with growth...c) pump wearing out

to check a pump you need a variable voltage source.....run the voltage to 6v....then pinch off the line going out of the pump...if the voltage doesnt drop below 1.25 then fuel is slipping passed the gears and the fuel pump is dying ...a new pump would bring the engine back to life again

...dying fuel pumps...they useally dont drop dead they slowly die....and it is harddr and harder to make rpm....and you know someting is up

hope this helps

hornetdriver

RE: AMT Pegasus SP spool up ???
 

Read the ensuing posts...all good info. Hornet driver is right on re the pump testing...though it is new...but that voltage at max seems 15-20% high for a broken in pump (shouldn't be caving that UAT, either!) If max RPM for an SP is 117, and you are not making it, but still seeing 'Max RPM Set' on your EDT, then the ECU max RPM (ECU parameter 'M') has been factory set incorrectly. If you never see 'Max RPM Set, then that is another problem...but, regardless, max RPM will not affect spool-up times (and I now assume it is not the first calibration run to max RPM you are talking about?). Spool-up is another ECU parameter (TLT, which might be 017 for your engine) and that may have been set conservatively, too.

Take it out of the model, put it on a free-air test stand, use a single large tank w/ a Festo filter in the pump intake line. By now (and if you have run in the pump for 20-25 minutes before any installation- a good idea to eliminate any possible pump-source contamination-) then the pump can be run w/ a direct line to the engine. (Matter of philosophy here...that's the way I've run all my engines for years. It eliminates any after-pump added connection leaks and any possible pressure-side restriction.). Good spool-up, Max RPM set at 117K tells you the engine is fine...it's yer on-board fuel system that is defficient.

Finally, and candidly, AMT may have installed bearings in your engine that were from a 'bad' batch.....and all this in the middle of sale to new owners at a new location. The new factory in Cincy is now open for business and you should first (before any more engine runs) call John or Norm (513-769-4539), tell them your S/N, and determine whether your 280 needs to be looked at. Questionable bearings, you will return the engine. Good bearings, try the test stand; check the ECU parameters if you have the software. If still no joy re spool up (about 4-seconds) and/or 117K, yer gonna have to send the ECU back to AMT to verify the parameters.

Unfortunatley, all at a bad time....the middle of flying season! Patience is needed at the moment....I have every faith AMT USA will be a more respondant, better organization w/ 21st century engines in the very near future. Get back to me w/ a PM ([email protected] or call at 508-457-2325) if you wanna converse directly.

Ray
AMT USA Field Rep

RE: AMT Pegasus SP spool up ???
 

WOW,

Thanx so much for the info, the nickel holes idea sounds like a winner.

I am sure with all that has been presented here I will find out what is the culprit and report back.

It won't be till Thursday but now I'm REALLY curious as to what the max set rpm is on the standard peggy in the Kingcat.
I'm almost certain it is the 117K and I have inadvertanely got the ECU mixed up.

I will also breakin this pump on the bench.......It was not done, I had been doing even though it is not in the instructions, ever since I had a Mercury that would shut down prior to max throttle setting and a high amperage pump had been the culprit.

RE: AMT Pegasus SP spool up ???
 

way to go ray

good job with a great explaination

one more note

max rpm drops out the egt ( exhaust gas temp ) setting thus your engine will not shut down on a spike reading which can happen in obvious manuevers...so its important to set it.....i have seen guys not set it and fly which i never do

also always look at your vamx that you mentioned before because it will tell you about issues that are going on...for example i know of a old salt flyer who swithed to jetcat and he crashed his plane....after 150 flights he got so lazy he just auto started everytime and his fuel filter glogged and shut down his jetcat..upon inspection it was filled with gunk and if he were amt and using his edt and reading it he would of seen his vmax going up and up....you can also see the vmax on a jetcat edt but then you have to touch your jet ....personally i like touching mine and in doing so i have piece of mind of it`s present condition

one thing an amt wont do is

start in your trailer and then burn down your trailer because you forgot to shut off your plane and someone else on the same channel started his...ouch....i think they got the dumb ***** award of the year for that one

hornet driver