Deltahawkengines - Page 11

ship · #**101** 08-27-2006, 09:51 AM

Quote:

Originally Posted by rv6ejguy

The SFC on a 2 stroke diesel is really not much better than a high CR gasoline engine fitted with EI and FI running LOP

The more correct statement is to say that a crude 2-stroke diesel such as the DeltaHawk is about on par with the most sophistiated gassers.

apples to apples: DH vs. mag Lyco
apples to apples: subaru vs. diesel w/commonrail & EFI.

DH runs .38 using a very simple single-pulse mechanical-injection system with mechanical injection pumps...about as crude as it gets. This is deliberate. Fully electronic common-rail systems were ruled out for the first generation engines to avoid all electrical dependency FWF.

To rv6ejguy's point, the state-of-the-art gassers are using fully electronic ignition and fuel management. Under the same configuration using piezo pulse-width injectors and common rail fuel at 30,000psi, the DH should achieve SFC in the range of .33. As always, testing will tell the tale.

The current state of the art in gas is high .36's; diesels is .27-.28.

rv6ejguy · #**102** 08-27-2006, 10:26 AM

Quote:

Originally Posted by ship

The more correct statement is to say that a crude 2-stroke diesel such as the DeltaHawk is about on par with the most sophistiated gassers.

apples to apples: DH vs. mag Lyco
apples to apples: subaru vs. diesel w/commonrail & EFI.

DH runs .38 using a very simple single-pulse mechanical-injection system with mechanical injection pumps...about as crude as it gets. This is deliberate. Fully electronic common-rail systems were ruled out for the first generation engines to avoid all electrical dependency FWF.

To rv6ejguy's point, the state-of-the-art gassers are using fully electronic ignition and fuel management. Under the same configuration using piezo pulse-width injectors and common rail fuel at 30,000psi, the DH should achieve SFC in the range of .33. As always, testing will tell the tale.

The current state of the art in gas is high .36's; diesels is .27-.28.

DHs own data actually shows a cruise SFC of around .42 which is about the same as a Carbed Lyco and their comparison to a Lyco in their data suggests they had a guzzler. Given that even a IO-360 with mags can easily drop below .40 in cruise, I don't see all the hoopla about the DH other than it can burn jet fuel which is not available at lots of small airports. Very few small (mobile) diesels have SFCs below .3. With DH not embracing the latest common rail/ ECU technology, I maintain that their SFCs in the real world are unlikely to be much better than an EI/FI Lyco. If you don't use the latest technology available, you cannot reap the benefits of it. They have much to prove in the fuel consumption and longevity/ reliability areas still. I do wish them well. It is a cool concept and they have stuck with it. Kudos DH.

airguy · #**103** 10-29-2006, 06:49 PM

Agreed, they can make better SFC's with some work. But even as crude as the current version is, I am sold on it for two main benefits - I can run standard pump diesel in it for $2.40/gallon, and it's turbocharged to give 100% to at least mid-teens. With the add-on wingtip extensions I can tanker enough cheap fuel to make just about any round trip without having to buy much, if any, Jet A for a top off at my destination. Granted, there may be a small weight/drag penalty to pay for the liquid cooling - but I don't have to worry about supercooling on rapid descent, I don't have to closely monitor the engine to run LOP safely, warmup periods will be nicely shortened in cold weather, and at mid-teen altitude where I like to cruise the high available power will more than make up for the parasitic cooling drag. I'll burn a little more fuel to do so - but at least it won't be $4 fuel!

aadamson · #**104** 10-29-2006, 07:26 PM

Quote:

Originally Posted by airguy

Agreed, they can make better SFC's with some work. But even as crude as the current version is, I am sold on it for two main benefits - I can run standard pump diesel in it for $2.40/gallon, and it's turbocharged to give 100% to at least mid-teens. With the add-on wingtip extensions I can tanker enough cheap fuel to make just about any round trip without having to buy much, if any, Jet A for a top off at my destination. Granted, there may be a small weight/drag penalty to pay for the liquid cooling - but I don't have to worry about supercooling on rapid descent, I don't have to closely monitor the engine to run LOP safely, warmup periods will be nicely shortened in cold weather, and at mid-teen altitude where I like to cruise the high available power will more than make up for the parasitic cooling drag. I'll burn a little more fuel to do so - but at least it won't be $4 fuel!

Um and what do you do, when in the mid teens, and the oat is 0 or less, and you are using auto diesel? Better plan on using some sore of "anti-gel", *and* you better make sure the engine will not have a problem with it. Also, don't forget, the engine needs to run "low sulfer" as diesel as we all know it is *about* to change. The 2007 and newer autos all have to use it and they *won't* run on the old #2 diesel.

There more to this diesel thing that meets the eye, at least with Jet A, all of the above is taken care of.

airguy · #**105** 10-29-2006, 07:48 PM

The reason the auto diesels get cranky about the new low-sulfur diesel is due to the fuel's lowered lubricity giving the old injectors problems. The new injector pumps will handle it, and if operating with an older injector pump a lubricity additive may be needed. As for the fuel temps, you are correct that long cruise periods in cold altitudes might be an issue. A fuel temp gauge would be a requirement, as the fog point of #2 road diesel is -20C. Additives can be used to reduce the pour point of the fuel, but the fog point is what will kill you by clogging the filter, and additives won't affect the fog point.

I'm also still turning over the thought in my head of a small fuel/coolant or fuel/oil heat exchanger, to warm the return fuel line from the injectors on the way back to the tank, to keep fuel temps nice and toasty.

rv6ejguy · #**106** 10-29-2006, 08:26 PM

Might want to check the installed weight of the DH. I don't think you will be tankering much fuel with 2 people aboard unless you raise the gross.

airguy · #**107** 10-29-2006, 09:01 PM

Quote:

Originally Posted by rv6ejguy

Might want to check the installed weight of the DH. I don't think you will be tankering much fuel with 2 people aboard unless you raise the gross.

Good point, and it's been considered. My wife hates anything smaller than a 747, we don't (and won't) have kids, so my right seat is for my flight bag and maybe my dog. I'm mostly after fast, economical XC with good performance, and don't need acro. Hence the 9A, versus a 7 or 10.

rv6ejguy · #**108** 10-29-2006, 09:23 PM

Quote:

Originally Posted by airguy

Good point, and it's been considered. My wife hates anything smaller than a 747, we don't (and won't) have kids, so my right seat is for my flight bag and maybe my dog. I'm mostly after fast, economical XC with good performance, and don't need acro. Hence the 9A, versus a 7 or 10.

If you fly solo XC, no worries. I'd love to see one of these flying in an RV so we can see what kind of numbers it turns in. Keep us posted.

ship · #**109** 10-30-2006, 05:48 AM

Quote:

Originally Posted by rv6ejguy

DHs own data actually shows a cruise SFC of around .42 which is about the same as a Carbed Lyco and their comparison to a Lyco in their data suggests they had a guzzler. Given that even a IO-360 with mags can easily drop below .40 in cruise, I don't see all the hoopla about the DH other than it can burn jet fuel which is not available at lots of small airports. Very few small (mobile) diesels have SFCs below .3. With DH not embracing the latest common rail/ ECU technology, I maintain that their SFCs in the real world are unlikely to be much better than an EI/FI Lyco. If you don't use the latest technology available, you cannot reap the benefits of it. They have much to prove in the fuel consumption and longevity/ reliability areas still. I do wish them well. It is a cool concept and they have stuck with it. Kudos DH.

Not to quibble, but the only diesels making below .3 are massive 2-stroke marine and locomotive diesels.

At this stage of development, DH routinely sees SFC's in the high 30's. This may be "nothing to write home about vs. Lyco", but it should be kept in perspective.

As stated before, DH injectors are single-shot units, and the pump is 100% mechanical. It's about as crude as it can get.....and still it's as good as "real world" Lycoming SFC's. As future generations incorporate common-rail and pilot injectors, SFC's will rapidly drop into the mid 30's.

Hopefully DH will survive long enough to incorporate c-rail, etc.

bumblebee · #**110** 10-30-2006, 09:43 AM

Quote:

Originally Posted by rv6ejguy

I'd love to see one of these flying in an RV so we can see what kind of numbers it turns in. Keep us posted.

FWF is an issue that DH has yet to address, despite several serious offers from myself and others to develop a FWF for RV's.

IMO this is THE biggest stumbling block for DH by not having a flying RV. Who the heck cares about a Velocity? Put the engine on the Chevy of experimentals..... swinging a metal prop in a fast tin tractor will prove once and for all if the diesels will work.

The cooling drag in a tractor configuration will be larger than DH anticipates....as the Subie folks can readily attest.