SR22 fuel burn rates?

Howdy all,

What’s the gph range for typical cruise power settings? Including ROP/LOP?

For my SR22 G2, the typical fuel flow at cruise is 14.5 gph at say 6500’. At 9500’, it is around 13.8 gph. Speed is typically 172k TAS.

I do not fly ROP much, so I don’t remember any typical numbers.

What’s ROP? [8o|]

At about 10-12000 ft, I would usually run it at about 13.4 GPH (65% power) and get around 170 KTS

Coming back from COS at 15,000’ burning 12.8 and 170 KTAS. Not bad.

Im usually running 13.8-14.5 down where the air is.

Who needs it?

This is from today’s flight to San Antonio. Only doing 174k TAS LOP. Flying ROP might get 5k more while using much more fuel.

Doesn’t sound like you want TN, but for comparison, I flew from KTRK to KSMO today, at 15.5k MSL, at about 16.2 GPH and 192 KTS true. No recent ROP (in cruise) experience.

Hi Will,

I did some ROP flying last year when I broke in my new cylinders. I was stopping for fuel ALL the time.

At 75 degrees ROP / 75% power you can expect around 17.5 gph yielding a similar speed as 14 gph LOP… around 5-6K feet. When I ran it at 85% power, I was pushing 19-20 gph at 75 degrees ROP. I was only getting another 7-8 knots for throwing a 5 gallon bucket of fuel overboard every 15 minutes!

Not sure whether you’re interested in TN numbers. But on a cold day 16.0-16.5 gph, 175kts TAS @10000 ft.
In summer it would be 15.5-16.0, 30.0", keeping TIT<1580.

Bernd

Thanks for the input everybody. I guess it’s safe to say pretty much everyone flies LOP in cruise.

How is this affecting top end maintenance? Are the lower CHTs resulting in few cylinder replacements before TBO?

Will:

You are asking a question that is pretty much impossible to answer. Every airplane engine is unique in that it is used by each pilot in a very variable manner such that no two are exactly alike. So, unless you had a way to do a study where each pilot could run his engine twice; once ROP and then start over and run it LOP, you really have no reliable way to know if running LOP versus ROP “saves” the cylinders. The problem is compounded further by the fact that the turbo engine are all run LOP so there is no ROP equivalent to compare.

So I can only give you an anecdotal answer based on my observation and experience (which is not real science). My view is that these TCM engines are so fragile that whether you operate ROP or LOP, you are running a high probability of needing significant “top work” well before TBO. In all likelihood, but with no data to back up, which side of peak EGT you operate is not the deciding factor in cylinder replacement need.

8500 ft, 75% power, 50F ROP you’re looking at about 17gph for a TAS of about 175kts in a G2 SR22

Brian,

I suppose what I was looking for, absent any empirical data, was anecdotal evidence that owners who regularly flew LOP were making it to TBO without replacing any cylinders. LOP operations lowers the internal cylinder pressure and CHTs, so it’s a safe assumption that their duty cycle would be lengthened. But I’m curious about your comment about Continentals’ fragility. What issues have you seen?

https://www.jpinstruments.com/wp-content/uploads/2013/05/Mike-Bush-Red-BoxRed-Fin.pdf

This has been discussed numerous times on the Member Forums, but if you want anecdotal evidence there’s plenty.

My plane now has 2650 hours on the original engine. I IRANed one cylinder at 2500 hours because of early boroscopic signs of exhaust valve burning. So my engine, run LOP at 65-75% power in cruise easily made it to TBO with no engine work required. There are many others who have done the same.