Thanks for the preliminary data points Bill......
.....It really would be nice to have a good alternative to the IO-540 for the -10s.
What would the mpg of the Vette be at 185 kt (213 mph)?A C5 vette with a LS1 will get close to 30mpg on the highway... so I don't think these numbers are out of the realm of possibility.
As a comparison, what TAS vs fuel flows have you seen flying Lycoming powered RV-10s?
First,
I know zero about this engine/prop/gear combination.
I would say it is very unlikely you are making 185kts at 11.7 gph in an RV-10.
Looking at all your numbers, none look even close to reality.
What would the mpg of the Vette be at 185 kt (213 mph)?
11.7 gph at 185 kt, as reported earlier, is 18 mpg, which would be extremely impressive, if it pans out. This is very early, raw data, so the reported values may change as better data is obtained. We need to give the builder a chance to get more hours on the aircraft, and to get everything fully calibrated before we hold his feet too close to the fire expecting hard, credible data.
Seems to me there's a guy in Canada doing just that with a Subaru 3.3 engine....
Ross,
I have seen the numbers, but not the FF and altitude for the turbo STI...could you please post them?
.....
My guess is that the turbo STI does very well at high DA, but if you have achieved a quantum leap at cooling drag (which would be evidenced by better FF/AS numbers in the 8,000 DA levels), I suspect you would be posting that long before now.
Anything hs less drag at 17,000 feet than it does at 5,000 feet. Heck, a 4x8 sheet of plywood has less drag at altitude than at sea level.
First,
I know zero about this engine/prop/gear combination.
I would say it is very unlikely you are making 185kts at 11.7 gph in an RV-10.
Looking at all your numbers, none look even close to reality.
As you know, I love this stuff so I've been digging through my archives. Stanford U did some testing on the LS1 many years ago. Brake TE 34% max, BSFC at LBT mixture .39. Pretty darn good and the later LS engines are likely to be better with improved heads, cams and higher CRs. Certainly on par with Lycoming's best engines.
Yes, but I'd make a couple of minor adjustments.While I certainly enjoy the technical engine discussion going on here, isn't this just a simple matter of:
1) Top off the airplane with fuel.
2) Fly four-way GPS runs at various power settings.
3) Enter data into this spreadsheet.
4) Fill the tanks again and compare against FF numbers.
All,
Interesting comments by everyone regarding these PRELIMINARY numbers. Airspeed is true airspeed in knots according to my GrandRapids EFIS. They are not 3 or four-way legs with winds computed by a spreadsheet. Jamie, cool spreadsheet by the way.
Still working the issue to get the numbers labeled FINAL when I have time. Breathe in, breathe out, move on.
Might want to us IAS instead of True - for a normally aspirated engine you should get nearly identical results at all altitudes for the same given power setting (assuming CS prop), with a small dropoff at altitude for prop inefficiency.
Bill,All,
Interesting comments by everyone regarding these PRELIMINARY numbers. Airspeed is true airspeed in knots according to my GrandRapids EFIS. They are not 3 or four-way legs with winds computed by a spreadsheet. Jamie, cool spreadsheet by the way.
Still working the issue to get the numbers labeled FINAL when I have time. Breathe in, breathe out, move on.
At 169 knots TAS @ 4500'. 3800 RPMs and 38" MAP measured exactly 8.9 GPH. I flew exactly 1 hour under the same conditions on this test, then switched tanks, descended and measured the amount to fill.
Call it 194 MPH TAS, 4500' @ 8.9 GPH
At 140 Knots TAS @ 4500', 3800 RPMs and 28" MAP fuel burn came to 6.16GPH. I flew under the same conditions for exactly 30 minutes for this test. Conditions were a bit turbulent along the Cascade Mountains with a South wind blowing.
Call it 161 MPH TAS, 4500' @ 6.16 GPH
geez ross, these are the numbers from the thread I was talking about...I did not see the thread of 213 knots at 8,000 feet on 11.8 gph but to be frank, that is 244 mph, which would take in the neighborhood of 250 horsepower based on Van's design numbers. If you can produce that much power on 11.8 gph it would be truly impressive, and again a BSFC number at or better than stationary diesel....so lets call that number interesting. Perhaps a neutral genius like Kevin can double check my math here, but it seems like we have discovered net negative drag....
Your math is about right, say 240 hp to do this speed at around 8000 feet- with an air cooled engine and standard Hartzell prop.
I told Randy initially it seemed too good to be true but he followed all the proper methodology to the tee and repeated several times to check the FF and the TAS, even not believing the gas pump meter finally and re-checking with Jerry cans. Randy is a straight arrow type who wants to know the real numbers. He is making mods now but welcomes any Lyco powered RV to fly against him to verify. Again, I don't believe the engine is making anywhere close to 240hp at this power setting so, I'll repeat for about the third time here- prop, cooling drag, jet thrust???? He has a fantastic package here. To be fair, the 11.8 GPH figure came from the SDS FF function after tweaking the calibration number through many other fly and fill tests. Could still be off a bit at the higher injector duty cycles due to the delta in response time vs. on time at these power settings. Nonetheless, Randy has by far the fastest stock airframe 7A around to my knowledge and he's certainly not burning 14-15 GPH to do it.
Bring the altitude up and the turbo Subaru gets even better mileage as TAS increases and FF stays about the same. This is where it really shines against a Lycoming.
I've read up on the Robinson LS conversions as well today and the V8 delivers substantially better MPG figures than the Franklin it replaced as tested on the same airframe before and after- 12.9 vs. 10.
Gary Spencer's race winning Long EZ with the Ford V8 did 200mph on 6 gph vs. 175mph on 6 gph with the O-235 Lycoming.
The Vesta FF data is nonsense IMO. We know for sure that no SI engine is going to deliver SFCs of .31. The very best are in the .37 range.
The exuberance regarding the success Randy has had with the STI is understandable, and an unquestioned achievement, but it needs to be tempered just a bit.
Randy has had 4 engine out landings with the STI and the last one really scared him. I congratulated him on the successful flights and that particular landing but also commented that he has been very lucky.
The STI is performing well and will smoke by a Lycoming but until it becomes as reliable as a Lycoming, it is not an apples to apples comparison.
Not many pilots enjoy taking off and wondering if they dare leave the traffic pattern on a day to day basis, fastest airplane or not.
Really not fair to just throw out "He's had four engine out landings" and leave it at that.-----
--I think the guys with a subaru or LS1 or even the rotary engine deserve our respect and support for going where very few have gone before (successfully). I think that will be one of the greatest advancements in experimental aviation in our time- new engine technology.
Really not fair to just throw out "He's had four engine out landings" and leave it at that.....
Danny,
OK, I will fill in the blanks.
There were about 25 STI's sold, as far as I know 2 have flown, Randy Crothers and Robert Paisley. The engine is a technical marvel for producing power but it is complex and prone to not working on a regular basis.
I just can not accept its potential performance based on a few flights as a reason to jump into such an effort. Too many guys have done that and the engine sits in a corner in their hangar. You can not give them away. I spent 4+ years trying to get the 2.5 and H6 to reach a point where I could kick the tires, light the fire and go fly. It never happened.
My point being, the numbers the STI can produce are not the total story.
.....I'm looking at the high speed data point here. If there are any Lycoming powered 7As out there which can true 213 knots on 11.8 gph at 8000 feet, please step up here.....
Danny,
OK, I will fill in the blanks.
There were about 25 STI's sold, as far as I know 2 have flown, Randy Crothers and Robert Paisley. The engine is a technical marvel for producing power but it is complex and prone to not working on a regular basis.
I just can not accept its potential performance based on a few flights as a reason to jump into such an effort. Too many guys have done that and the engine sits in a corner in their hangar. You can not give them away. I spent 4+ years trying to get the 2.5 and H6 to reach a point where I could kick the tires, light the fire and go fly. It never happened.
My point being, the numbers the STI can produce are not the total story.
Ross, are you sure it is 213 knots and not 213 mph?........
Does the ECM have to be mounted ahead of the firewall? I know they do it that way with cars, but cars generally run at lower average power than aircraft, so the engines make a lot less heat. And the consequences if a car engine stops because the ECM overheats are relatively minor compared to the consequences from the same event in an aircraft.A discussion with Bud today leads me to believe that the high engine temperature may have exceeded an operating parameter in the ECM and the engine reverted to a low power setting. This has yet to be confirmed but obviously needs to be addressed if this is indeed the problem.
Ahh. Makes sense. An automotive limp home mode might offer quite a low power - more than enough for low speed ops in a car, but no where near enough for an aircraft. Thanks for the educated guess.Kevin, I don't think he was talking about the ECM overheating but the ECM sensing the engine was overheating and basically sending it into limp home mode. The problem being limp home mode probably doesn't generate enough power to keep the plane flying. I think Bill doesn't know if there is such a thing on this computer though.
Ahh. Makes sense. An automotive limp home mode might offer quite a low power - more than enough for low speed ops in a car, but no where near enough for an aircraft. Thanks for the educated guess.
Too bad GM won't share the detailed design of the ECM. I've done quite a bit of FADEC testing on aircraft turbine engines. We force the manufacturer to do a detailed analysis of the effect of all possible correct and incorrect inputs from each sensor, plus all possible failures of each thing that is controlled by the FADEC. This is followed by a long test stage on a test rig to validate the results of the analysis, followed by a running a sub set of the tests on the aircraft. This process has invariably revealed some cases where the expected response to some types of failures was not acceptable, or cases where the actual response to the failure differed significantly from the predicted response. But if the ECM is just a "black box", with no knowledge of exactly what it does, then you are leaving yourself wide open to cases where the assumptions that underly the design of the automotive ECM are not valid in the aviation world.
I think if you want a reliable system, you need to have simple electronic controls designed specifically for aviation use, and where you are certain that the system has been fully analyzed and tested in an airborne environment.