Author Topic: P38L Engine Ratings (Read 1015 times)

Raptor · « **on:** September 23, 2007, 02:19:33 AM »

SAPP Relevant

Factory rating for the the P-38L was 1,725 hp at 64 in/Hg. The USAAF derated the engines to increase reliability. Nonetheless, most Ls were rigged for max rated power in the field.

The AH2 P-38L uses the derated power of 1,600 hp at 60 in/Hg.

Therefore I believe the AH2 P38 should have the increased 64in/Hg modelled.

Here is a chart describing the results of a P38L with 64in/Hg WEP performance compared to a P51D.

1K3 · « **Reply #1 on:** September 23, 2007, 03:51:20 AM »

NO to preferential treatment! Should HTC increase P38 boost, they might as well give spixteens the +25 boost, Fw 190A-8's MW-50 boost, 109K's 1.98 ata boost, and so on as this vicious cycle continues.

DaddyAck · « **Reply #2 on:** September 23, 2007, 05:00:41 AM »

Yeah, I agree with ya 100% Raptor. The 38L needs the speed boost, as it is I fly the 38J because there is no dicernable difference onther than the dive breaks and the boosted roll. (I used to be a 38G junkie, that was untill HTC decided to fatten her some 600LBS.)

clerick · « **Reply #3 on:** September 25, 2007, 09:37:50 PM »

4 MORE INCHES!
4 MORE INCHES!
4 MORE INCHES!

Widewing · « **Reply #4 on:** September 25, 2007, 10:45:39 PM »

I think you will not have much success getting a power rating never approved by the USAAF, even if rated by Allison and Lockheed.

However, HTC may be willing to consider offering 150 octane fuel as a perk. Here's Lockheed's speed estimates for the P-38J (in a good state of tune) using 150 octane 44-1 fuel (which was used extensively by the 8th AF from the summer of 1944 on).

My regards,

Widewing

clerick · « **Reply #5 on:** September 25, 2007, 10:53:50 PM »

leave it to WW to poop all over this party with his "facts".

Viking · « **Reply #6 on:** September 26, 2007, 10:03:45 AM »

Widewing, if the USAAF de-rated the engines from 64" to 60", why do you think they would allow 75" just because the fuel could handle the compression? Surely the 100/130 fuel was not the problem.

TUXC · « **Reply #7 on:** September 26, 2007, 11:08:32 AM »

Quote

Originally posted by Viking
Widewing, if the USAAF de-rated the engines from 64" to 60", why do you think they would allow 75" just because the fuel could handle the compression? Surely the 100/130 fuel was not the problem.

"A Supply Division memo dated 11 July, 1944 stipulated the following:"

From this page http://www.wwiiaircraftperformance.org/150grade/150-grade-fuel.html

Captain Virgil Hilts · « **Reply #8 on:** September 26, 2007, 12:37:17 PM »

Quote

Originally posted by Viking
Widewing, if the USAAF de-rated the engines from 64" to 60", why do you think they would allow 75" just because the fuel could handle the compression? Surely the 100/130 fuel was not the problem.

Yes, the fuel WAS the problem. The engines could have been operated at 64" easily, had the quality control of the fuel been consistent. But 64" didn't leave much margin for the fuel to be of lesser quality, nor for maintenance and tuning to be less than adequate. And the fuel quality was anything but consistent.

Simaril · « **Reply #9 on:** September 26, 2007, 01:05:35 PM »

Quote

Originally posted by clerick
4 MORE INCHES!
4 MORE INCHES!
4 MORE INCHES!

Just so we are being perfectly clear: You ARE talking about manifold pressure, not some other measurement, right?

clerick · « **Reply #10 on:** September 26, 2007, 01:08:39 PM »

Quote

Originally posted by Simaril
Just so we are being perfectly clear: You ARE talking about manifold pressure, not some other measurement, right?

I suppose it depends on who you are talking to

Squire · « **Reply #11 on:** September 26, 2007, 01:46:27 PM »

More apples and oranges.

...the MP ratings of the Allisons on P-38s had, NOTHING, to do with 150 octane fuel.

The P-38s were not in service when 150 octane fuel was issued to the 8th AF Fighter Command in June of 1944.

Whatever debates there are re the P-38J/L and its MP ratings, it revolves around 100/130 fuel.

P-51s and P-47s that continued to wars end with the 8th AF, were issued the 150 octane, with the corresponding higher MP ratings ie, 72 inches on the P-51.

Mike Williams · « **Reply #12 on:** September 26, 2007, 03:01:17 PM »

Hi Squire:

>the MP ratings of the Allisons on P-38s had, NOTHING, to do with 150 octane fuel.

I wouldn't be comfortable making such a blanket statement. My understanding is that the 479th FG, 8th AF continued flying the P-38 through the summer of 44, fully converting onto Mustangs in late Sept/early Oct 44. Its possible, if not likely, that they used 150 octane, just like all the other Fighter Groups in the 8th during that period. Certainly the P-38 was cleared to run on boosts greater than 60" using 150 octane. Whether they did operationally is still not settled to my satisfaction. Hmmm, I remember now that some P-38 squadron was using 150 octane in the spring on operational trials, see here for what that's worth.

Mike

gripen · « **Reply #13 on:** September 26, 2007, 03:16:04 PM »

There is claim about the use of the grade 150 fuel in the Caidin's book. But, as most people know here, it is not a particularly reliable source.

Widewing · « **Reply #14 on:** September 26, 2007, 06:41:01 PM »

Quote

Originally posted by Squire
More apples and oranges.

...the MP ratings of the Allisons on P-38s had, NOTHING, to do with 150 octane fuel.

The P-38s were not in service when 150 octane fuel was issued to the 8th AF Fighter Command in June of 1944.

Really? Someone should have told the P-38 Groups that didn't get into P-51s until up to four months after the 150 octane fuel was issued.

Besides, Doolittle already had reformulated fuel issued to the P-38 units beginning in the early Spring of 1944.

My regards,

Widewing