I have an old Ram 750F that’s been sitting in a box for a few years.........bought it used and have never lit it off. But now that I’m finally ready to start it I have a couple of questions:

1. The ECU battery has a sermos connector to fit the mating connector on the ECU. Did these use any kind of switch between them? ........or was it customary to just unplug it between flights? In looking through the list of included items in the manual there is no mention of a switch........or does the ECU not draw a significant current unless there’s a signal from the throttle channel in the radio receiver?.......what gives?

2. About that start box.........do you have to use it to start these up? The reason I ask is because I have a friend with a AMT Mercury that he starts manually, triggering his own air and propane with a standard glow lighter. Can the Ram be started the same way or does the start box have to be used (assuming everything is properly configured )? I don’t mind using the box but was wondering if it was truly necessary.

Thanks,

John Fangohr

Hi John,

It is a good engine. There were no switches involved since the ECU needs a signal from the RX in order to turn on and as long as the RX is off, so is the ECU. However, it is a good idea to unplug the battery for storage and charging etc.

I guess you don't have to use the start box but why won't you? You would still need the propane and air supply so you might just hook those up to your start box and not have to worry about lighting the glow plug manually etc. Also, the start box will tell the different stages the engine is on not to mention the fact that you need the start box to set the idle of the engine - I remember you needing to push the ignition button momentarily if the idle was above a set pressure.

Hope this helps.

Adil

I still have a RAM 1000ES with the same box. The ignition is started from the start box, so, YES you must use it. The Start box also plus into the ECU to monitor/run the engine during start up. The propane is regulated by the start box, but I am sure there are ways around that, so read from that what you will. I am sure you can just plug in a battery to the starter motor and have it spool the engine (don't know if there would be any greater damage to your starter motor that way) and I am sure you can just plug a propane bottle directly to the engine, but that also leaves you with more external things to try to control.

Turbulence

Adil and Ralph,

Thanks for the replies. The primary reason I was asking about that start box was because I wanted to know if I could get it started (using my friends gear) if I left home with my brain in neutral and no start box.

Hey Ralph (Turbulence), remember that Futaba 9VAP I bought from you a few years ago? It's still going strong........sent it off to Futaba earlier this year for a check up. I've attached a photo of the check sheet.......thought you'd find it interesting.

John

The ECU are interchangeable with the start box with some problems. If you are
using the newer Air or electric start ECU the older start box will not display you glow plug
adjustment and CP setting that you power adjustment.

The older ECU and start box only set your throttle adjustment and pump prime.

RED -BATTERY

BLUE- GLOW PLUG

YELLOW- PUMP

To let you in on a simple mod to turn your 750f 17 pounder to a 21/23 pounder
only change the older fuel pump the the latest fuel pump (simjet/ jetcat/ FTE)
all can work

good luck

Unknown

They are great engines! Probablly the best one ever made by RAM. I just sold 2 that I had with many trouble free flights between them. I just needed a larger engine and needed the funds. I hope my 2 new jetcat's live up to the reputation, Im sure they will.

What Unknown said here is NOT true: The RAM 750F was controlled by the ECU sensing CP (Compressor Pressure). 1300 mb of pressure was full thrust (about 17 pounds). If you use a different pump (assuming one that is more efficient), all that will happen is that the ECU will reduce the voltage to the pump to keep max throttle at 1300 mb. You will not be putting out more thrust.

The way you do that is to operate the engine at 1400 mb max instead of 1300. That should give about 21 or 22 pounds. I ran one at 1400 for quite a while. Of coarse at a higher power level, the engine will not last as long. You need someone like Andy Low (the designer and builder of the old style RAM ECU) to reset the ECU to 1400 max. At 1400 you can use any pump that works.

Hey wokeman i guess you never used the older pump on your Andy Ecu . You con not get more than 1000 to 1200 mb out of the older pump i'm very sure about that try it.

You guys that "fly" at sea level get all the breaks!! If I tried to run mine at that P2, it would surely over-rev and grenade. I need to run mine at 1100 or less. Oh well. My 750F still runs like the proverbial Energizer Bunny ... too many cycles to remember

Mike

Unknown, what in the heck are you talking about. The old 750s are limited, by the ECU to a certain Compressor Pressure. You are not going to get more out of it with a different fuel pump unless one of the following scenarios is the case: A) you somehow change the max CP allowed by the ECU at the same time you change pumps or B) the first pump you try is worn out or otherwise defective and the new pump allows the full CP (allowed by the ECU) to be realized (in which case any working pump would allow that full CP to be reached). In either case, to get higher than the 1300 mb of pressure originally programmed into the RAM 750F (and hence, more thrust), you need more than some different pump (unless you have a crappy pump). You need to reprogram the ECU. Now stop smoking that wacky tobaccy before posting to R/C U!!!

P.S. The ECU will allow the engine to overshoot the set max CP, sometimes by quite a bit, but it is a closed loop system. When the ECU sees higher than 1300 mb, it reduces voltage to the pump to try and bring the CP back down to around 1300. The overshoot is temporary and that overshoot amount might very well vary quite a bit pump to pump, but I do not think that is what you meant.

I'm not talking about limiting the engine to 1000 mb and installing a new pump to producing 1400mb. I'm talking about having the ecu max cp 1400 and can not get more than 1200 /1000 with the older pump. I am willing make a wager my p120 for your jet

talk to andy or carlos.

Oh oh, your story is changing (more of that wacky tobaccy perhaps?)! You originally said "To let you in on a simple mod to turn your 750f 17 pounder to a 21/23 pounder only change the older fuel pump the the latest fuel pump (simjet/ jetcat/ FTE) all can work". Now you are saying that you need not ONLY use a new pump, but also a modified ECU that allows a CP Max of 1400. That's not what you said in your 12/27 post.

I will take your bet and everyone here ion R/C U can be the judge. I have already won as the RAM 750F can indeed produce "more than 1200 /1000 (CP) with the older pump". Heck, it was a 1300 mb CP max engine stock in 1999 (with the "older pump" that it originally came with)! I know, I had one. And then I ran it for quite some time at 1400 CP max with the same "old pump" design! And I am certain that if I talk to Andy (whom I talk to by e-mail all of the time) or Carlos they will indeed confirm what I am saying.

What are you trying to claim? That all of those happy early RAM 750F owners were getting screwed out of 2 or 3 pounds of top end thrust (1000 - 1200 mb CP max instead of the 1300 mb they paid for) and no one complained? I can assure you that those engines ran very well at 1300 mb (about 17 pounds of thrust).

Please send my P-120 today. I will pay for overnight Fed-Ex. PM me for the address. Thanks.

I've got a 750F with both the RAM labled ECU (as shipped with the 750) and one of the Electrodynamic (Andy) labled ECU for the 750.
Andy's ecu allows CP to be set by the user to a max value of 1413 mb. The OEM RAM is set to limit at approx 1260 mb.

With the standard (speed400) RAM pump assembly and Andy's ECU the 750 will run at 1400+ mb all day.

W.G. Hunter

Woketman is correct!
I had 2 750f's straight from RAM and they would both put out 1300mb all day long. And if it was cold just under 1350.I say send Mark the motor.

The verdict is indeed in! Unknown, please PM me before Fed-Ex closes today as I want to be test running that P-120 for the first minute of 2004, tomorrow night. Thanks for the free motor Unknown and happy New Year to all!!!

How about i hand deliver the engine at F/J under one condition i will bring my 750 air start with five of the older pump and two of the new pumps and after i proved my point leave the receiver in my jet

I email Andy waiting on is response

No no! Don't try wiggling out of this! This was a generic question about the RAM 750F, not about a particular 750F that you may have that has a few old pumps that can not perform up to spec. The fact that many many people ran stock 750Fs for years at 1300 mb of CP proves the point. Please ship the P-120 today... I WANT IT NOW!!!!!

Happy New Year!!!