M7 235 vs M7 260 Engine horsepower

[Maximus]

Can anyone tell me how they get another 25 horsepower out of this engine- the V4A5, must be RPM? I copied this text below:
"235/235A1235B/235C has Lycoming 0-540-J1A50/J3A5/B4B5 or 10-540-W1A501W1A5 (except MT-7 has 10 only); -260/260C
has Lycoming 10-540-V4A5"

I was wondering if there is a weight penalty but the engine is the same displacement.
Does the M7 on floats perform much better with the 260? Sometimes more horsepower is not always worth the extra expense.

[Kirk]

Can anyone tell me how they get another 25 horsepower out of this engine- the V4A5, must be RPM? I copied this text below:
"235/235A1235B/235C has Lycoming 0-540-J1A50/J3A5/B4B5 or 10-540-W1A501W1A5 (except MT-7 has 10 only); -260/260C
has Lycoming 10-540-V4A5"

.

From the Lycoming Operator's Manual:

IO-540-V4A5D: 414 lbs
O-540-J1A5D: 387 lbs
IO-540-W1A5: 400 lbs

RPM and compression ratio are big variables in the horsepower mix as well as some cam and crank differences. All that is way above my head. Not sure how the soup is made, just know when it tastes good.

Kirk

[Stefan]

A good overview of all 540's can be found here

http://www.lycoming.textron.com/engines ... Insert.pdf

It is basically boils down to Torque x RPM (more RPM at given torque = more HP)

Torque is driven by
- Compression (higher is more efficient - hence more torque)
- Carburated is has to have volumetric losses, otherwise carb would not work - hence less torque than fuel injected
(but only some carb engines can legally us autogas)

I'd take either a carb 235 for $ reasons or if I would want fuel injection, I'd go for 260 hp

Re Stefan

[aero101]

The 260HP is fuel injected, that being the main difference...

[DonMc]

The 260 crankshaft is where the difference in weight comes from. The compression and rpm is where the extra horses come from. I know of guys with the high compression pistons in 235s turning 2700. At sea level, and light you might not see drastic difference in takeoff length. At higher altitudes you will be glad to have the extra horses as well as taking off heavy. The float guys like the carb setup so they can get more dependable hot starts. I have never had an issue with hot start with the 260. The way around this problem if it ever was one was to go to the shower of sparks. I fly a turbo 350 hp lycoming with shower of sparks. It starts the same hot or cold usually coming to life on the third blade. Three things you can never have enough of are time money and horsepower. There are many threads here about how you simply throttle back to the same fuel burn no matter which engine you are sitting behind in your Maule.

DonMc
N260BD

[UP-M5]

example:

i burn 8.1 GPH (on the EI fuel flow meter) following my cub buddies around at 85 mph.

that's about 2100 rpm and 13 in/hg
O-540-J1A5D

[Maximus]

What is this "shower of sparks" you are referring to, I've never heard of it?

[kakkenmc]

burn 8.1 GPH (on the EI fuel flow meter) following my cub buddies around at 85 mph.

that's about 2100 rpm and 13 in/hg
O-540-J1A5D

How much of that low power flying does it take to cause problems? What problems are there? Can you fly two hours straight as above and then clean things up with only a few minutes at high power?

My plane's sitting in Moultrie for its annual.

kakkenmc

[a64pilot]

There a lot of internal differences between the 260 FI and the 235 FI. Be careful of turning up the prop governor in the 235 too much in the quest for power, it's not made for it.

[a64pilot]

If you keep it lean, I believe you can run an engine at low power settings forever, just don't do it until it's well broken in.

[DonMc]

I would not run below 20'' for extended period of time. Especially in cold weather.

DonMc
N260BD

[BUZZ]

What kind of internal differences are we talking about? Obviously the displacement is greater with the 260 opposed to the 235, but where does it come from. Bore?, Stroke?. I noticed that both the T4B5 and the W1A5 have the same 8.5:1 compression ratio. So it seems that the only difference contributing to the extra 25 horse is RPM. Is there disadvantages to turning higher RPM with a shorter stroke or is the stroke on both these models the same with differing bore? Not disagreeing with anyone here just trying to get a better grip on this one.

[210TC]

Nick, the displacement is the same, 540 Cubic inches,bore and stroke the same. The 540 makes between 235 hp and 350 hp with turbos. As others have noted the extra power can come fron an increase in RPM, higher compression, injection and also turbos.
Good example Cummins builds a 855 CI diesel engine. At first this engine put out 250 HP, then 290, 300, 325, 350, 400 and now over 500 hp, all with the same cubic inches. Lycoming has done the same.
In one of my past birds i cranked it up to 3300 rpm with 10 to one compression. Don't know what the HP was, but I would bet it was near 300 without a turbo. Don't ever try to run your engine at these speeds. You need a special small diameter prop to do it. Regular prop will exceed the speed of sound, very dangerous Some of you have seen one of my old videos that got erased. This video would have gotten me in a lot of trouble had the faa investigated it. I was way past the allowed speed below that certain altitude, at an airport in Texas. My VR indicator pegged at 6000 FPM, I went beyond that strait into the clouds at the end of the runway.

[BUZZ]

Ok I'll stop talking. I feel like a bonehead for that one!

[210TC]

Your not a bonehead, its just a lot of terminology that many people don't use everyday. And terminology has nothing to due with understanding.