231LV

Well, I wanted to give an update on some different settings I used on a cross country trip today. It was not a perfect comparison because the winds were blowing early in the flight and subsided later. Nevertheless, I already know what my speeds are during LOP operations down low. I wanted to try deep ROP down low to see what speeds I could achieve. If you recall, I was seeing speeds of around 145 KTAS below 10,000 ft running LOP at about 10 gph. Today, I was flying at 9,500ft running ROP at 80% power at 13 gph with the hottest jug at about 360 degrees and seeing about 160 KTAS. This is satisfactory and opened my eyes to running deep ROP without generating excessive heat. I did burn more fuel but that's the trade off. I understand that if I elect to run the engine at the advertised 50 ROP, I can get more speed but I refuse to run my engine at the worst settings so I will be happy with deep ROP.

Do yourself and your engine a BIG favor and install an engine monitor...it is absolutely necessary in order to safely run LOP. Without it, you will not know whether you have escaped the Red Box where danger for your engine lurks. The Red Box sits around 50 degrees ROP. Once on the LOP side, there really is no danger.

Well that delta might be worth the extra 5gph!

Tolerating rated cruise power at 10,000 ft is no problem. My engine can easily run higher power settings at higher temps which leads to shortened longevity. I choose to run LOP and I see cooler temps across the board on less fuel and slightly less speed. All in all a good thing.The limit I have to deal with is TIT of 1650....typically I can't get much over 65% power running LOP without exceeding this temp. The newer -LB engine will alleviate the cooling issues with a larger throttle-body and a more efficient exhaust design. The 231 is a wonderful plane and highly efficient and I would never discourage anyone from taking a hard look at one if it fits your mission. I was looking at a way to fly lower without O2 and get better speeds.....one suggestion is to run deep ROP which I will try. The enemy of all our engines...especially turbos is heat and I try to do all I can to reduce it.

Excellent points....thank you. You are right...stepping it up to run deeply ROP will get me faster at a bit more fuel and something I may have to consider for the lower levels. The fuel burn differential between a Rocket and the 231/252/262 is substantial...with avgas at about $6 now...that fuel burn translates into poverty pretty quickly...my 115 cu ft tank is good for about 4 hours with my wife and I at 17k.

Yes, I should have noted that my plane does not fall into the serial blocs...once upon a time I actually did the cost analysis of getting my plane up to the equivalent of a 252...a 262 which was obtainable at a price of $55k. It was cheaper to sell my 231 and buy the 252....my current 231 does have an inter cooler but the old, fixed waste gate and I am still running the original -GB engine which is why I always run it LOP...the GB was a hot running engine....but back to my original question and I thank all the input...it has been invaluable.....sometimes one must go with "the gut"......I'm in no hurry to replace my plane and watching fuel prices climb, I'm still quite happy to be getting 175 KTAS on about 10 gph albeit at 17k ft on O2 so I will sit awhile and watch....and fly east high with O2 in the tank and west low when depleted and be grateful to be in such an enviable position of choosing between two great planes!

not if it means burning up my engine ......wish I could get an upgraded 252 engine....the only engine I can get is the TSIO360-LB...the 252 runs an -MB...not authorized for the 231

I should also say that I fly my 231 LOP....I can get 175 KTAS at 17k on 10 gph...at 10,000 ft, I'm no better than 145 KTAS on the same power set up and I currently use masks above 10,000 ft to keep O2 sat levels in the 90's...we are moving to Sedona, AZ next year which is at 4500 ft and routinely fly to friends located at 7000ft so we need a turbo...I'm curious what kind of sub-10,000 ft speeds the Rocket turns in running LOP?

Thanks all for the posts...I already use a transfill station in my hangar...the problems I am referring to involve the fills during cross country trips...tough to get an FBO to give me a full refill...they simply don't want to wait while the O2 flows into my tank...many FBO's (especially in more remote locations) don't offer O2 refills. The problems I most often encounter involve departing my home airport with a full tank but half way through the trip, my O2 is depleted and now I am forced to find a fill station who will give me a full fill (very difficult) or stay low and slow all the way home...this is the primary reason that I am contemplating a Rocket...I don't have to have O2 to go fast down low

I know variations of this subject have been done many times on this forum but I'm hoping to get some perspective that I may not have contemplated. I have owned my 231 for ten years...flown it everywhere from the Artic Circle to the Yucatan and absolutely love it in all aspects but one....to get the speeds, I have to fly high which means O2. Those of us who routinely use O2 realize its drawbacks...namely unavailability at many FBO's or difficulty getting full fills. I am retiring next year and my wife and I plan to do more flightseeing trips around the US and Bahamas...we will still need turbo performance but don't always want to go up high to get the great TAS. I'm looking hard at upgrading to a Rocket. My 231 has a run out engine so if I sell it, I am expecting a low price. The Rocket can go fast down low and burn a lot more gas than my 231 which is no faster than an E model at 10,000 feet and below. As I watch the price of Avgas climb, I'm wondering whether I should just stick with the 231 and accept the slower speeds down low and deal with the O2 issues when planning for a cross country. Maybe someone who has switched from a 231 to a Rocket can chime in here with their thoughts....

all looks good...don't know what the surge is as I have never had that problem but could be a momentary richening of the fuel flow. LOP equals cooler which equals engine longevity...also lower fuel burn at a slightly slower speed. Exhaust output is "cleaner" than ROP...mechanical advantage of the flame front moving more slowly which allows the power stroke to "push" the piston down rather than suffer the "pounding hammer" when ROP...all in all good...enjoy running LOP...your engine loves it!

Thank you all!!! Excellent suggestions

Patience is the key with buying a nice plane...oh and cash...at the ready. Nice ones don't last long and go fast! I agree with all previous posters and the advice to use LASAR for prebuy. TG does good work but cross check never hurts. Sound advice on the cost of the panel versus the gear ups....sounds like a club plane or school with those hours. Updating the panels are incredibly expensive and everyone loves glass but many, including myself, are content to fly behind steam gauges....good luck

I fly a 1980 231 with the 12volt system. After 7 years, I replaced the battery (the BatteryMinder paid for itself). Shortly after, I noticed the ammeter gently "bouncing" at low rpm. The charge was a typical 14.1 volts right after startup to 13.7 volts in cruise. I never noticed the ammeter even moving during the previous years with the old battery ( which is the same as the old one). I didn't notice any other abnormalities so largely ignored the gently bouncing gauge....until a recent trip. Over the course of the 4 hour flight, the ammeter went from a gentle bounce after startup to a swinging needle from plus to negative. The Hi/lo voltage light never came on. I'm wondering whether this could be the result of a slipping alternator coupler or the alternator itself? I suppose it could also be a poor ground or voltage regulator problem, as well. I replaced the coupler several years ago but don't recall the symptoms which led me to replace it. I plan to take it into the shop but wanted to see if there might be any thoughts which could narrow down the cause before I spend the money on shop time tracking down the problem.

Thanks for the much better explanation than I gave....I thought I understood Tom at Top Gun in Stockton to say that the Merlyn acted like a turbo-normalizer but I could very well be wrong! I may have to revisit the Merlyn. Regarding the Airflow intercooler, check out the other thread...there appears to be a group of 231 owners who can get a batch of the Airflow intercoolers for a minimum order of 10

Well you could be right...however, the price might include superior avionics, low time engine, good interior/exterior ect ect. I have the Airflow intercooler and a fixed wastegate. I spoke with Tom R over at Top Gun a couple years back about upgrading to the Merlyn...as he described it, the workload to manage the engine wouldn't be eliminated (which is what I was hoping for) and the Merlyn basically limits pressure into the engine at sea level and maintains it up to the critical altitude...more of a turbo-normalizer and of the two, the better place to spend money is on the intercooler...for the added cost, I elected to keep my old, inefficient fixed wastegate and enjoy the punch I get on the runway when the engine boosts up to 37 inches....

Getting a K model for less than $100k is certainly doable but your avionics wont be the latest and certainly wont be glass( if thats important) and most likely will have a run out engine...the hot engines of the K vintage are the TSIO-360-GB which have almost all been replaced with the cooler running LB variant. A very small serial block of 231's can be upgraded to 252 but the cost ( I ran the analysis) really doesn't justify simply purchasing a 252 out of the gate. I agree with others..if high flying is in your future, spring for the K and don't look back...the NA planes will make altitude...eventually....but there is nothing like cruising to 18k ft at a steady 700 fpm climb....the down side for a turbo (beside being more costly to maintain and engine management) is altitude....it flies best in the high teens where O2 is mandatory. No O2 and you are stuck down low where the 231 loses all it's speed advantage. It is surprisingly difficult to find an FBO that sells O2 AND will give you a full tank for the $50 or so they charge...most simply don't want to wait while the tank fills so they give it 10 or 15 minutes then charge for a full load....frustrating I started with a C model...loved it for economy...moved up to the K....love it for it's mission capabilities....tough to choose but simply consider yourself blessed to be able to even be in this situation!!...owning the left seat trumps all....