If German have access to high ocatane fuel, how does that impact the performance of their fighters?

[mig-31bm]

I watched a video on youtube, the author explained that, even though BF-109 is lighter and has bigger engine than P-51, the P-51 ended up being much faster because USA has fuel with much better octane rating of upto 150 while German fuel octance rating is around 80-100.
So my question is, what would happen if we give FW-190, Ta-152 150 octane fuel ? Would they get a huge boost in performance? Or their engine can't handle it?

 

[tomo pauk]

I watched a video on youtube, the author explained that, even though BF-109 is lighter and has bigger engine than P-51, the P-51 ended up being much faster because USA has fuel with much better octane rating of upto 150 while German fuel octance rating is around 80-100.

Let me guess: author of the video is Greg?

 

[Snautzer01]

It is not that simple by far. The devil of perfomance is not power alone. Its drag. Wing design, cooling of engine and how.. see drag..
Ohhhh so many little irritating stuff.

No.

It helped. Did a good job, better performance. But ... not a war winner by itself.

 

[Shortround6]

Would they get a huge boost in performance? Or their engine can't handle it?

You got it.

I watched a video on youtube, the author explained that, even though BF-109 is lighter and has bigger engine than P-51, the P-51 ended up being much faster because USA has fuel with much better octane rating of upto 150 while German fuel octance rating is around 80-100.

The DB 605 engine was about the same weight as the engine in the P-51.
A lot of crap is written about the size (displacement) of aircraft engines, which is of interest to engine junkies. It was of zero interest to aircraft designers/makers.
Aircraft designers/makers were interested in how much power the engine made (and at what altitude), How much it weighed and how big it was (width x height X length) they didn't give a rat's hind end about if the engine was 27 liters or 33 liters or 36 liters or.................

The youtuber doesn't understand this and also doesn't understand the difference between lean and rich mixture ratings. Also doesn't understand that the octane scale stops at 100.
Technically there was no such thing as 108 or 115 or 150 'octane' fuel. Anything over "100" was performance number or PN.

1947 Sweden was making DB 605 engines to put in Saab 19 bombers and Saab 21 fighters. They were supposed to have used 91/96 octane fuel in them. They got 1575hp at 7000ft from them and 1475hp at take-off using 6.3lbs of boost.
BMEP was 203psi at 1575hp.
Sweden was building the Saab 90 airliner at this time using P&W R-2000 engines and planning on using R-2180 engines, both using 100/130 fuel. The R-2000 had a BMEP of 211. They could get 100/130 fuel in 1946/47.
A Merlin V-1650-9 running at 1520hp at 14,400ft was running at 243 BMEP on 100/130 fuel. They could make a lot more power using different fuel using more boost and higher BMEP. But if you simply pour in the better fuel and crank up the boost limiter on the DB 605 you are going to break connecting rods, pistons, crankshafts and possible lift the cylinders/head assemblies off the crankcase.
Please note that the RR Griffon VI (single stage, two speed supercharger) was one liter larger ( 2.8%) in displacement than the DB 605 but weighed almost 90kg more (12% more).
Maybe RR Knew what it took to build and engine that ran at high pressure?
DB knew what they had for fuel and designed an engine that would run on the available fuel/s and not be too heavy for the power the engine was capable of making.
A Griffon running on the German fuel would be carrying around about 90kgs of extra weight that it couldn't use because of the fuel.

 

[tomo pauk]

A Griffon running on the German fuel would be carrying around about 90kgs of extra weight that it couldn't use because of the fuel.

What kind of German fuel?

To expand on the (false) notion that the high octane fuel was a thing that trashed Luftwaffe - if that was the case, Allies would've been killing the LW right, left and center with Hurricanes and Spitfires already in 1940, let alone in 1942 when the P-40s and P-39s were available.
As we know, even the bestest fuel was not enough to make Hurricane or P-40 to compete on equal footing, let alone to trash the LW's best.

 

[mig-31bm]

Let me guess: author of the video is Greg?

Ah yes indeed, it greg, he seem to know a lot about ww ii aircraft i think

View: https://youtu.be/OqiG9VHuBbM?si=w7ZY3U19tfUEXC54

 

[Snautzer01]

Greg seems to know a lot about how to click bait, and ignores periode documents like no other.

 

[tomo pauk]

Ah yes indeed, it greg, he seem to know a lot about ww ii aircraft i think

View: https://youtu.be/OqiG9VHuBbM?si=w7ZY3U19tfUEXC54

Problem with him is twofold the way I see it:
- oftentimes he barks under the wrong tree
- any feedback, that is not affirming his conclusions, is often disparaged and ridiculed

Not conductive for healthy discussios at any rate, and especially on youtube.

 

[Engineman]

1947 Sweden was making DB 605 engines to put in Saab 19 bombers and Saab 21 fighters. They were supposed to have used 91/96 octane fuel in them. They got 1575hp at 7000ft from them and 1475hp at take-off using 6.3lbs of boost.
BMEP was 203psi at 1575hp.
Sweden was building the Saab 90 airliner at this time using P&W R-2000 engines and planning on using R-2180 engines, both using 100/130 fuel. The R-2000 had a BMEP of 211. They could get 100/130 fuel in 1946/47.
A Merlin V-1650-9 running at 1520hp at 14,400ft was running at 243 BMEP on 100/130 fuel. They could make a lot more power using different fuel using more boost and higher BMEP.
But if you simply pour in the better fuel and crank up the boost limiter on the DB 605 you are going to break connecting rods, pistons, crankshafts and possible lift the cylinders/head assemblies off the crankcase.

Some of this is correct, but your words about the DB 605 are not completely correct. The Swedish DB 605 was operated on Flygbensin 100/130 and they did indeed just "crank up the boost limiter on the DB 605". There was an option of the original 1.42ata limit or an increased 1.65ata limit that gave an increase of 15% power at altitudes up to around 10,000'.
However, all engines do require to be built to match their operating loads and demands so, there are limits if you do not improve the design when increasing the boost loading, or
you will suffer increased wear and tear on the engine. So, just as the various versions of Merlin engines were able to operate on different fuel at different boost levels and power ratings, so could different versions of the the DB 605.

Eng

 

[Peter Gunn]

I watched a video on youtube, the author explained that, even though BF-109 is lighter and has bigger engine than P-51, the P-51 ended up being much faster because USA has fuel with much better octane rating of upto 150 while German fuel octance rating is around 80-100.
So my question is, what would happen if we give FW-190, Ta-152 150 octane fuel ? Would they get a huge boost in performance? Or their engine can't handle it?

It wasn't just the fuel the Mustang was using, the P-51 was aerodynamically superior to any piston engine German fighter that saw service.

And Greg is far from an authority on WWII aircraft.

 

[Shortround6]

Some of this is correct, but your words about the DB 605 are not completely correct. The Swedish DB 605 was operated on Flygbensin 100/130 and they did indeed just "crank up the boost limiter on the DB 605". There was an option of the original 1.42ata limit or an increased 1.65ata limit that gave an increase of 15% power at altitudes up to around 10,000'.
However, all engines do require to be built to match their operating loads and demands so, there are limits if you do not improve the design when increasing the boost loading, or
you will suffer increased wear and tear on the engine. So, just as the various versions of Merlin engines were able to operate on different fuel at different boost levels and power ratings, so could different versions of the the DB 605.

Eng

Thank you for the correction.
But it does show that 100/130 fuel would not give the amount of improvement than many people think.

 

[Engineman]

Thank you for the correction.
But it does show that 100/130 fuel would not give the amount of improvement than many people think.

You are correct that it is not just a matter of using a higher Octane fuel in an engine designed for lower Octane. In the case of the DB 605 A there was obviously the capability on engines built after about Autumn 1943 to have been uprated to about 1.65ata MAP using 100/130. However, the Germans did not take this option until the later introduction of MW50, in early Summer 1944, when they linked that with the mandatory use of C3 fuel to give an emergency limit of 1.7ata MAP for a relatively long-duration 10min period, with 5min recovery between use.
It is interesting to consider the results that Rolls-Royce achieved on the smaller late-war Merlin compared to DB with their late DB 605. Using 100/130, RR achieved rating at 18lb boost. Whereas, using a similar late C3 fuel, DB achieved rating (without MW) at 1.8ata MAP (11.76lb boost).

Eng

 

[Galahad]

You are correct that it is not just a matter of using a higher Octane fuel in an engine designed for lower Octane. In the case of the DB 605 A there was obviously the capability on engines built after about Autumn 1943 to have been uprated to about 1.65ata MAP using 100/130. However, the Germans did not take this option until the later introduction of MW50, in early Summer 1944, when they linked that with the mandatory use of C3 fuel to give an emergency limit of 1.7ata MAP for a relatively long-duration 10min period, with 5min recovery between use.
It is interesting to consider the results that Rolls-Royce achieved on the smaller late-war Merlin compared to DB with their late DB 605. Using 100/130, RR achieved rating at 18lb boost. Whereas, using a similar late C3 fuel, DB achieved rating (without MW) at 1.8ata MAP (11.76lb boost).

Eng

Years ago I'read somewhere that DB 605 ASC was able to do 1.98ata MAP even with their bad late-war C3 fuel (max. 98 octane or so). Apparently in March 1945 there were some converted Bf 109 G and K at eastern theatre. And also, that on factory dynos DB 605s were running well above 2.0ata. Sounds like with good fuel this engine would had further potential.

Edit: found this one, is it known?

Kurfürst - Performance of 8 - 109 K4 and K6 with DB 605 ASCM/DCM

 

[Engineman]

Years ago I'read somewhere that DB 605 ASC was able to do 1.98ata MAP even with their bad late-war C3 fuel (max. 98 octane or so). Apparently in March 1945 there were some converted Bf 109 G and K at eastern theatre. And also, that on factory dynos DB 605s were running well above 2.0ata. Sounds like with good fuel this engine would had further potential.

Edit: found this one, is it known?

Kurfürst - Performance of 8 - 109 K4 and K6 with DB 605 ASCM/DCM

Hi.
Of course this is known. You might also wish to read the excellent book "The Secret Horsepower Race" (TSHR) by Calum Douglas, a book that explains much of the detail of WW2 Piston engine development and technology.
As far as "potential" goes, there was further potential in all the engines at the end of WW2. However, the most important potential was in Gas Turbines.

Eng

 

[Shortround6]

The German fuel was rated at lean mixture (or close to it) and it never really got a rich rating which is what the 130 of the 100/130 was. Lean/Rich. A lot of the late war German 96 or C3 fuel was not 98 octane when measured by the allies using Allied testing procedures. It may have been 96-98 lean but it was around 130-140 when measured at rich. However the German fuel injection systems may not have allowed the engines to run as rich as the allied engines

Also note that the 1.98 ata, pressure required both the C3 fuel and MW-50. Without the MW-50 the Pressure was 1.80ata.

For the P-47 with 100/130 the max pressure was 52-53in. With the initial water injection they could use 56in. With the later water injection kits they could use 64in.
Power went from 2000hp to 2300hp to 2535hp all on 100-130 fuel.

As brought out by Engineman, this really needs a book as even dealing with fuel alone needs quite a number of pages to cover what was happing over the years on both sides.
Not all liquid cooled engines behaved the same and air cooled engines behaved very different than liquid cooled engines with the same fuel.

And sometimes engine companies (especially air cooled engines) just threw the existing engine out the door, kept the bore and stroke and changed EVERYTHING else.
And that was how some engines reached their "potential".

 

[spicmart]

Kurfürst is some kind of controversial luminary wrt the Me 109 iirc. Has he ever published articles or books?

 

[Engineman]

Kurfürst is some kind of controversial luminary wrt the Me 109 iirc. Has he ever published articles or books?

Olivier was active on his Bf 109 info site for around 10 years, and the site still seems available.
His information is well presented and I found no problems with his data, much of which is well translated in English.

Eng

 

[Luft.4]

And also, that on factory dynos DB 605s were running well above 2.0ata.

I've heard of this too. Would anyone have a source for it?

All the best,
Dan.

 

[Shortround6]

And also, that on factory dynos DB 605s were running well above 2.0ata. Sounds like with good fuel this engine would had further potential.

There is a story that one P&W engineer ran a R-2800 at well over 100in on a factory dyno. Over 3.0 ata. He was in the next test cell to some guys working on the R-4360 (28 cylinder engine) and he was trying to beat them. He was using enormous amounts of water/alcohol. It was only for a few seconds. The engine survived (as supposed to have been a "B" series engine and not one of the later "C"s.
This is why they have confidence it rating engines they way they do for service in the real world (engines with several hundreds of hours on them maintained by 18-20 year old mechanics, sleeping in tents, eating lousy food.
What an engine did once or twice on a test stand is interesting, what it could do for a number of hours is a lot more interesting.

The US tested a P-47 in Europe using 44-1 fuel (100/150?) and ran it at 65in without water and 70in with water. Things were OK in level flight but in climbs there were problems with both cylinder head temperatures and carburetor inlet temperatures. Low airspeed did not provide enough cooling airflow for either the engine or for the intercooler/turbocharger.
Not breaking the engine on the test stand is step 1.
Keeping the engine alive using the service radiators/oil coolers, etc is a lot harder.

 

[Luft.4]

44-1 fuel (100/150?)

Yes, PFF 44-1 is 100/150 grade.