craigdyer

Hi All,

Could you guys please advise as to what fuel/oil to use on a new revlite Norvel .074 engine? Also what prop sizes are good for this engine and what would you expect in the way of static thrust.

Thanks in advance,

Kind Regards, Craig.

DeviousDave

The Norvel branded fuel the Sig sold was 15 and 35% nitro. The 30% I have laying around has 18% oil, no idea if it's all synthetic or mixed with castor oil. This fuel is still available AFAIK, just don't use it in Cox engines.

The .074 likes a prop in the 7" range, 7-3 to 7-4, possibly down to 6-4.

combatpigg

My Feedback: (3)

Craig, I've tried 10-30% nitro with good results. The oil content should be at least 20%

The 7x3 prop makes the most sense to me...I've used a MAS 8x3 also, but the needle will get more critical, more heat generated. Not good to try this until the engine is broken in.

I've tried smaller diameter props with more pitch, but these engines don't respond well enough to satisfy me for speed, that's why I think they work better for pulling power....like for 1/2A models that got a little bit too big.

The other issue is longevity since this engine is scarce, so 16,000 with a 7x3 prop is a "happy" place for this engine.

Mr Cox

I like the APC 6.3x4 (more pitch means that one doesn't have to run full throttle all the time) and run 10% Nitro and 20% pure castor. This gives a top end of around 16700-17000rpm. Static thrust is around 700g I think.

mtntopgeo

My Feedback: (12)

Most folks go with the 7x3 prop. With this prop, you should get 'bout 17K+ with a stiff shot of nitro. In the Norvel "sticky", someone mentions that the .074 was designed for use with a 6x4 prop. I got to go along with this line of thought. My experience has been that if your plane is big, heavy, & "dirty" enough that your best performance with the norvel is with a 7x3, then you should just bolt an Enya .09 to said plane & really get some extra performance with a 7x4 or 7x5. Remember, the Norvel is rated at 22/23K. I see where CP is coming from 'bout scarce engines, lack of spares, lower RPMs & longer life, but the engine seems to be pretty rugged (once you get the first 10 min. of run-time on it without bending a rod). I take out my my old .074 powered MSS profile almost every time I go to the field. After 4+ years, the only problem I've had is with the carb bolt holes elongating. (JB weld took care of that problem). In fact, the engine has begun to run better this last season. (Don't know if it is just getting broken in, or just getting "well worn". I use Sig 35% nitro, & add enough castor to bring the oil content up to 25%. This lowers the nitro to "bout 33%. RPMs with this fuel usually run near 18,600 with a MAS 6x4. Sounds like it unloads a bunch in the air. Couple of .074 engines that I have run in the mid 19s, but this is not the norm. With a cleaner, lighter airframe, I like a 5.5x4, but then I get to thinking "bout that spare parts, lower RPM, longer life thing. ....................... George K.

hllywdb

I agree with Mr Cox. If your plane is clean and in the 15 to 20oz range, the 6.3 X 4 really works. If you are heavier and dirtier than that, bolt in the Enya.

Mr Cox

Tached mine today, 17200 rpm on an APC 6.3x4, stock head, one shim, 10% nitro, 20% castor.
That is also with a more restrictive muffler than the stock one, trying to improve the low end on my Chipmunk, a real crowd pleaser that flies at near idle...

hllywdb

Nice plane Mr. Cox
How does the 74 do inverted? I almost did that on my Integral to raise the thrust line.

Mr Cox

It runs a bit rich at everything but full throttle, for some reason the very top end is a little lean so when tuned for that the rest is a little rich. Might simply need some more nitro but I like to stick to the fuel I'm using for my other engines.

I ran a stock head today but will go back to a turbo plug and play a bit with the heat range (I have used a P6 before but there are even hotter ones), if only it had an adjustable airbleed I'm pretty sure it would be fine.
As it is now the lowest reliable idle is around 5-6000 rpm, a bit high for my taste.

hllywdb

I've been running 2 shims, but 25 & 35% and getting idle in the high 3k range with that prop and have yet to have a flame out. But I'm not inverted, except of course when the whole plane is inverted.

Mr Cox

It seems that mine was actually a bit overcompressed with one shim, even on 10% Nitro. I added a shim today (to get two in total) and got 17400rpm and a reliable idle near 4000rpm. I need to bring some more shims next time and fiddle a bit more...