a chat to an engine friend of mine reveals
putting higher octane in a lower octane rated engine=minimal difference
putting lower octane in a high octane rated engine = bang
to get the benifit of high octane your engine must be designed to run on it and this involves higher compression ratios be they engine or supercharger/turbocharger
i posted some time ago wep /none wep numbers for some selected engines and the fact that merlins gain power as they go higher (up to a point)due to a feature of thier supercharger design
on MW50 it was often stored in a huge drop tank under the belly of a 109..originally it wes jettisonable but on later models it was not (Irma Behalter tank i think is was called)using MW50 left a charecterisic black trail during use from a 109 due to the engine running rich...fuel use went through the roof and it was a sort of piston "reheat" or "afterburner" in that you got extra acceleration and power at massive fuel use.
on the fw190 it left a charecteristic white plume this time during use(condesation due to presure drop behind engine and over the wing)
from what i have unearthed so far it would appear the rocket firing fw190s had the MW50 system removed
it would also appear that rocket or under wing guns on 109s could not be fitted if GM1 was fitted..i would speculate that the containers(bottles?) ..no doubt presurised ..were in the wings but have not been able to find catergoric eveidence that this was so(or not).
it would also appear that the GM1 versions had lower compression than other versions (not verified/refuted yet)
walter krupinski states that his unit of 109s had "special engines" which while good at altitude with boost were hopeless at lower altitudes..i wonder if thats a 109 with GM1 he is talking about.
my overall impresion is bomber intercepters would use MW50 while fighter interceptors would use GM1 in the case of the 109.
in the case of the 190 rocket armed ones or underwing weapon enhanced ones they lost the mw50 while GM1 was tried but with very little success
in the case of supercharger gears the setting were "M" and "S" on the merlin 61.s..they could be an auto setting but sticking it in high ("S") did NOT give you more power necessarily, LESS in fact due to the extra work the engine had to do and the supercharger waste gate dumped the extra air to save the engine from blowing up.
the time to change gear was "when it made no difference" according to the manual and that was around 20000ft(assuming auto not selected)..if you changed too early the boost would drop as the extra work was done by the engine and any extra air was dumped over the side...too late and you would see the boost rise as the extra air was used to increase performance.
the merlin had automactic boost control and this meant that if the supercharger produced too much air ..it got dumped...as you got higher less air would be dumped and thrust horsepower is a function of true airspeed so as you got higher the engine could do more work and this meant the engine produced more power.
the DB(me109) engine had hydraulic supercharger control and worked similar to an automatic gearbox..as you got higher it "changed gear" (no gears infininatly varible)..increasing hydraulic presure increased the supercharger speed...but this took more horse power from the engine..the DB as fitted to the 109 could maintain is horse power up to about 20000ft and then fell off (unless boosted by an oxident such as GM1)
the standard merlin 61 gained power up to around 15000ft and then fell back to around 20000ft where the 2nd gear ratio now took over and power once more increased to around 30000ft and then fell off.
while the DB engine would have a flat power output up to 20000ft or so the merlin 61 would have two peaks around 15000ft and 30000ft
while MW50 would add 300-500hp the power line would remain similar up to 20000ft
if GM1 was used then it would still be the same but the extra power output would have more effect at higher attitude (thiner less air so less oxygen) becasue it is an oxident(GM1 contains oxygen).
the advantage of the super/turbo chargers is they dont run out while fuel additives do
the merlin on 27 liters capacity could put out 1700-1800hp at its peak without additives..the DB605 was around 1400-1500hp with some thing like 44 liters and the big motor in the thunderbolt got 2000-2000hp on a capacity you could put lake geneva in
think i'll go and plot some graphs on engine performance at various altitudes... (dont know if im a sad case or dedicated..hard to tell
have a nice day
Tomb
