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Calculating Horsepower on Rocket!

D

Dain

Member
I have an F-1 Rocket that claims to have 330hp. How do I calculate hp without a dyno? I am at 3120' field elevation and at full rich and full power on takeoff I see 26.3gph on the fuel flow. Does this mean I have 263hp at this elevation and if I were at sea level I would have the 330hp?
 
go to the source

Ask the folks who built the engine why it would have such a rating. If it is a parallel valve type, it would need 13:1 compression, or something close, and a 500hr TBO.

If it is a slant valve, well then It would only need 12:1 pistons...

Or, it could be rated at 3000RPM?

If you are referring to the only supercharged F1, the rating I heard was 340hp. @2700/42"....or was that 44"?? Zowie!

Carry on!
Mark
 
YOu need to know a bit more about the engine build, but just using some data you have provided the fuel flow looks to be too low for full rich at 3120' WOT. I would have expected to see about 29-29.7 GPH as a rough guess.

Having said that the HP generated will be unaffected, just the detonation margin is eroded and optimal ICP and CHT would be affected.

Lots of questions ...refer posts above.
 
OK:

I got a call yesterday - seems this plane was originally built by Bobby Hester. I recall Bobby installing either 9 or 9.5 pistons, so that would allow for about 285HP or so.

In any case - a NA 540 with a stock sump cannot make more than 285-290hp no matter what you do. Ya see, the 540 has a built-in NASCAR restrictor plate in the sump. If you want to reach 300 or higher, you gonna need a Barrett sump and an FM350 fuel controller.

The higher compression will give you better efficiency in high altitude cruise, that's for sure.

330HP? Probably not. But, that is a nicely built airplane indeed. Bobby sure liked it - reminded him of his P51, so he said. Well, except the fuel flow.

Speaking of fuel flows, yours might need tweaking down a bit - that much fuel at that altitude is a bit much - should be closer to 22 or so? Set up for 250F ROP EGTs @ FT and see what you flow, and use this number as your full rich flow at your home field.

BTW I am not kidding about an F1 Evo being out there with ~340HP. It's capabilities are nothing short of amazing. I remember seeing 300MPH TAS in level flight at 14,000MSL. No brag - just fact.

Carry on!
Mark
 
Dain's F-1 Rocket builder was Bobby Hester

mrwc2u.jpg
 
I gotta get me some!

Sid Lambert said:
If it says 330HP on the cowling it must have 330HP.
Click to expand...

Yep -- pilots never exaggerate!

I guess I'd better get some similar stickers for my plane!:D Maybe I'd settle for some that express how handsome the pilot is?:eek:

Nice lookin' bird.

Carry on!
Mark
 
Quien Sabe?

I guess I need to find Bobby Hester and get it straight from him on what is under the cowl. I was hoping to find a formula for calculating the hp.

Carry On!
Dain
 
If it's the Bobby Hester that sold engines here in the north Texas area for decades, he is unfortunately no longer with us. Really nice man. I hated to hear of his passing 3-4 years ago (IIRC).

He was a friend of my grandfather.
 
Engine Information?

Ok, I would like to find out all the information concerning my engine. If Bobby Hester is no longer with us, then I need to do some digging in the logs which are in Texas while I'm in California. I guess I'm back to my original question which was, "Is there a formula I can use to find the max hp on this engine without putting it on a dyno?"
 
Unfortunatly, you'd have to know what's in the engine different from stock to get a round about number of HP.

There are some formulas that can get you close by using the baseline efficiency of the 540 and mapping that to peak lean fuel burn. But again, those numbers assume stock engine so they will only get you so close.

May I ask why you need this info? Is it for an EFIS/EIS? If so, I'd just guess using some know numbers for engines close to the same spec.

You have a great looking airplane. Just push the throttle up until you can't afford the fuel burn and fly the snot out of it.
 
Bobby Hester

Bobby Hester, Bladenboro, NC. Try Hester Trucking 1st.

As I mentioned, stock sump = 290HP max. It's an airflow thing. If you have an RSA5 fuel controller (I can't recall on this particular plane), dang sure no more than 285 or so. Heck, Call Rhonda or Alan at Barrett Engines and ask them. That shop is very honest about real world HP. As I recall, 10:1 with a cold air sump is about 305HP, as of about 2 weeks ago. 1000hr TBO at that setup; 1500hr TBO with 9.5 pistons @ about 295HP.

MAX HP is a function of EGT. As I recall - max power is about 75-100ROP. Run the test and see what the FF is. David will step in, but I think FF to HP formula there is about 12hp/gal. Full rich is about 200F ROP, and the HP formula there is 10/1. Stock compression used in these formulas, so yours may be a fuzz higher. Best efficiency FF/HP ratio you can expect is near 14/1 at 10:1 compression on the straight valve Lycs, and that is at 50F LOP. The best NA engine we can buy for turning 100LL into torque is the crossflow TCM IO-550, which is capable of a tad better than 15hp/gal at 50F LOP. This is 225hp @ 75% power! BTW the 550 weighs about 30lbs more than the 260HP 540 when equipped with the small starter and alternator. Just sayin'!

Good luck!

Carry on
Mark
 
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As a point of reference:
In my past I operated a Piper Navajo PA-31-350, at full power near sea level, the engines would consume 40 - 42 GPH a side to produce ~350 HP
 
Thanks for setting us straight Mark

According to a very popular and reputable engine builder a C4B5 with flow balance and 10:1 pistons, dyno's at 320 + HP. Based on my full power rich fuel burn I know it is no where near that. I feel that I am getting a honest 280+ HP based on performance and fuel burn (27 GPH at full PWR 2700 rpm's @ SL). I am happy with it.

Why does the engine builders dyno give higher numbers than real world performance dictates?

Steve
 
Cool! Thank You All for the Help!!!!

Ok, I'll be back in Texas on July 4th, and I will dig in the logs to see if there is anything interesting concerning the engine. I will post what I find then. Thank you all very much.

Dain
 
Bobby Hester's cell phone number is 910-876-2331 in Bladenboro, NC. He is a nice guy and probably would be more than happy to talk to you!
 
There's an old saying that almost all dyno's have this thing called a "happy customer knob" and usually they're cranked all the way up. Sort of like Spinal Tap, my amp goes to 11.
 
As was eluded to in a previous post, "330 HP" must just be a rating on the Handsome Pilot matrix. I don't know if a higher score is better or worse, but I think I'm pretty close to the bottom of the scale myself. Can someone please enlighten us to the scoring on this scale? :rolleyes:
 
Steve Barnes said:
According to a very popular and reputable engine builder a C4B5 with flow balance and 10:1 pistons, dyno's at 320 + HP. Based on my full power rich fuel burn I know it is no where near that. I feel that I am getting a honest 280+ HP based on performance and fuel burn (27 GPH at full PWR 2700 rpm's @ SL). I am happy with it.

Why does the engine builders dyno give higher numbers than real world performance dictates?

Steve
Click to expand...

Could be exhaust fumes in the test cell?
 
Speed varies as the cube of the hp so find out what an average 260hp Rocket does at say 8500 feet DA WOT and the same rpm. You should go about 1.085 times faster if you really have 330hp at SL on a standard day assuming same prop, airframe cleanliness etc.
 
F1Boss said:
...In any case - a NA 540 with a stock sump cannot make more than 285-290hp no matter what you do. Ya see, the 540 has a built-in NASCAR restrictor plate in the sump. If you want to reach 300 or higher, you gonna need a Barrett sump and an FM350 fuel controller...
Click to expand...

Without the benefit of peering inside a stock 540 updraft sump, can you elaborate on this "restrictor plate"... Is this something that can be overcome with a mill or some good old fashioned hand porting? Also, what does an RSA-10 servo buy you over the RSA-5? The -10 features a bigger throttle plate so it should flow more, but that's not going to help much if the induction system is corked up. I was quite surprised to see a -5 on several of the high horsepower "boutique" engines, yet Lycoming installs the -10 on several of their 540 NA engines.

At any rate, I will fully concede that if using strictly stock components, you will hit a wall concerning airflow. However, it seems that time proven automotive automotive modification techniques such as porting, component matching, and exhaust tuning can improve the generally awful aircraft engines.
 
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I Spoke to Bobby Hester on Rocket

I called Bobby and got some pretty cool info. He said with all the extras installed on the engine the hp should be at 330hp. It is by far not a stock engine. However, I would like to know what hp the engine really produces for my own reasons. Details of all the extras to come in a future post. I still haven't had time to go through the books in detail.

Cheers!

Dain
 
impressive

WOW 330 HP with 26.3 GPH. That?s a .478 BSFC. Pretty impressive with a C4B5 up-draft sump and a RSA-5 fuel control.

Now on the other hand a parallel valve 540 with 10:1 and a cold air system with a FM-200 will make 320 HP. Saw it at Barrett?s with my own eyes. More like 29-30 GPH there. Had some nice cold air going into the intake too. Winter time.
 
F1Boss and I have had this discussion about my motor as well. CB45, 10:1, RSA-5, updraft sump. Original dyno from 1998 shows it maxed out at 322 HP. So since its in writing, its even better than handsome pilot stickers saying its so, right! :D I figure the feel good knob was at 11 and the fumes were strong that day too..but who knows...I wanna believe (but know betta).

Another aspect of that dyno measure that may impact the result is the fact its on a test bench, and not constrained by cowl and air delivery inlet and filter imperfections. I'd actually like to see one in action, to see how it works, and see if and how things like 250 mph ram air is simulated (if it is at all).

Like Steve though, I'm happy with the motor, and though I live at 5,000', when down at the coast, I've been north of 27 gph. Will have to get some current data next time I head that way (Steve, wanna play?)

15 years and 1200 hours, and its still a strong runner, but I do covet a cold air sump and FM-350 combo. When Bill Beaton in his Rocket and I did some recent "line abreast formation" testing, his cold air set up was getting 0.8" to 1" of MP higher than mine, same RPM. Very nice!! Perhaps at overhaul time, when there will be lots of mods to consider (and recent cowl mods and sanding elbow have faded out of memory, and I'll be game again!) ;)

Cheers,
Bob
 
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The reason why the cold air sump works better is not because the air is colder (the temperature rise due to traveling thru an oil filled sump is known to be insignificant) but because the intake tubes are longer and skinnier which delays the standing wave effect from direction reversal of the intake air. Lycoming sumps on the 300hp engines like the K1A5 have intake tubes that extend across to the other side of the plenum chamber inside the sump for this reason. They actually overlap the opposite cylinder intake tube by 8" or so.
 
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