At about the time of the Spitfire XIV's entry into service its Me 109 counterpart was the Me 109 G-6 with the DB-605 A cleared for 1.42 ata take-off and emergency. The DB-605 AS, with improved altitude performance, came into service during the spring of 1944. MW-50 was introduced that summer in the Me 109 G-6/R2 and Me 109 G-14 enabling improved low altitude performance.
The following chart demonstates how the Spitfire XIV performed during the first half of its wartime service relative to its Me 109 rival. For more on the Spitfire data refer to the Spitfire XIV section of this site. The +18 lb. level speed performance is from AFDS which is nearly identical to that charted by Rolls Royce. The RAE commented on the Griffon 65 engine in Tech. Note No. Eng. 316 from July 1944 "Due to main bearing troubles, these engines are at present limited to + 21 lb./sq.in. boost pressure although they will be capable of operation at +25 lb./sq.in. boost pressure in the future". The same report gives 393 mph at 3,000 ft. as the total possible a/c speed using +21 lb boost, extrapolating to 377 mph at sea level. Back in June Rolls Royce had obtained 366 mph at sea level. Calculated estimates indicate that actual performance was probably somewhere between the two, or about 370 mph at SL. For comparison, the first production Spitfire 21 with Griffon 61 at +21 lbs. boost achieved 368 mph at SL. Absolute max speed at full throttle height would only have increased a few mph with the increase from +18 to +21 lb. boost. No 610 Operations Record Book shows that by July 18, 1944 their Spitfire XIVs were undergoing modifications to operate at +21 boost.
All Me 109 data used in the following charts comes from German sources. The curve of Me 109 G-5 with DB 605 AS engine at 1.3 ata is the only Me 109 curve below reflecting data from actual flight trials. It can be seen that the effect of the hydraulic coupled supercharger is properly represented (for more Me 109 G curves derived from flight trials see: HERE). Unfortunately this feature is often missing from estimated performance curves. The Me 109 G-5 and 6 curves at Start and Notleistung (take-off and Emergency) shown below are approximations, whereas the curve for the Me 109 G6/R-2 again accounts for the effect of the hydraulic coupled supercharger, although with rather less precision than that of the flight tested Me 109 G-5. The Me 109 G-14/U4 curve is an estimate by Messerschmitt's Projecktburo assumming DB 605 ASM engine using MW-50, Gondelwaffen and weight of 7,817 lbs. The GL/C-E2 for a clean G-14 with ASM engine gives 348 mph at Sea Level and 422 mph at FTH. Messerschmitt's Flugbericht Nr. M 35/25 dated 4 July 1944 determined that the MW-50 installation on the DB 605 AM engine allowed for a brief increase in boost pressure to 1,75 ata/2800 rpm, increasing sea level speeds from 315 mph to 352 mph. This corresponds well with the G6/R-2 curve below, which is equivalent to the G-14 with AM engine.
Unfortunately there is little known documentation for climb performance of the Me 109 G using 1.42 ata. The following charts reflect performance of the Spitfire XIV and Me 109 K from the introduction of the K in mid October 1944 through to VE day. The Spitfire XIV's performance was rather stable, new development going toward the Spitfire Mk 21, whereas efforts were taken to increase the output of the DB 605 D series in order to make the Me 109 K-4 more competitive. Unfortunately, flight trials of Me 109 Ks appear not to exist. The following 109 K curves were produced by Messerschmitt's Project Bureau at Oberammergau. While the curves are rather simplistic estimates (the effect of the hydraulic coupled supercharger being absent for example), they should give some idea of potential, however, they should be treated with reserve.
The Projektbüro estimate from 19.1.45 assumes 9-12159 propeller, and a weight of 7,496 lbs. Documentation listed below demonstrates that the most prevalant configuration for the ME 109 K beginning in around January 1945 would be DB 605 DB engine with 1.80 ata/2800 rpm engine limitations. GL/C-E2 from 1.11.44 gives 360 mph at SL, 441 mph at 24,606 ft. with production 9-12159 propeller. Various engine and propeller configurations were experimented with. The 9-12159 propeller was the standard production propeller but various German curves are extant showing estimated performance of the 109 K4 with 9-12199.10 and 9-17018.10 thin blade (Dünnblatt) props and Projektschraube with 4 light-metal blades. The 452 mph figure often cited as the top speed of the Me 109 K-4 derives from an estimate assumming an experimental 9-12199 Dünnblatt propeller. The DB 605 DC at 1.8 ata without MW-50 was tried but did not find favour. (Die E-stelle hat Bedenken gegen den Betrieb mit 1,8 ata Aufladung ohne MW mit C 3 Kraftstoff.) The DB 605 DC at 1.98 ata with MW was tested but seems not to have made it into service (Nach Mitteilung der E'Stelle sind 1,98 ata gesperrt.)
The November 1944 edition of the Bf 109 K-4 Flugzeug-Handbuch states:
which translates to: The MW installation serves to increase the emergency power of the engine. With 1,75 ata boost pressure, additional injection of MW increases emergency power (special emergency power) and can occasionally be used to increase level speed and rate of climb. The MW additive serves for the interior cooling of the engine and for the avoidance of overheating during flight with special emergency power. The use of the special emergency power without MW injection is forbidden! The engine is endangered without MW injection. The withdrawal of the special emergency power is done via putting the throttle lever forward on 1,75 ata boost pressure (number of revolutions 2850 U/min).
Aspera G.m.b.H., Kamenz on orders from OKL Chef TLR F1. E. 3 V reports in Geschwindigkeitmessungen mit 4 VDM Luftschrauben auf Me 109 K4 mit DB 605 D dated 4 January 1945 that full measurments could not be reported due to engine damage at 1.98 ata. Trotz mehrerer Stunden schonenden Einfliegens des Motors mit Dauerleistung vor den Messreihen mit Kampfleistung stellte sich bei den ersten Prüfläufen nach der Umstellung auf p = 1,98 ata ein Motorschaden heraus, der einen Motorwechsel .
JB12