There is indeed a big power loss when you go any more LOP than very slightly LOP.
However the “fashionable concept” is that you open the throttle to compensate. The result is the same power as before but with lower temperatures.
Whether one can “open the throttle” depends. On my TB20 it is already wide open, at any altitude above 8000ft. Hence I fly at peak EGT or very slightly LOP the whole time. But on a turbo engine one has more MP to play with.
The power drop by going LOP is measurable, if all cylinders are equally LOP then they should develop the same power. If one or more cylinders don’t develop the same power, you will have roughness. In my own engine the last bit to solve before smoothness were the sparkplugs. I went from Champion fine-wire (good for TBO) to Tempest Massive and the difference was striking. My Champions were still good on the bench, but failed the resistance test.
Setting up the engine to run LOP smoothly is something you have to supervise yourself, most shops don’t have a clue what it takes.
Upload your EDM output to the Savvy website and send the link to John, he will help you get to the bottom.
I don’t have any experience with liquid cooled engines but they should be easier to run once setup properly.
Quote I must find a way to drop my TIT from 1680 to 1650 F – this is the point just before the engine runs rough.
You wont find much written about this subject, but if you have the CHT’s under control, you can trade CHT for TIT(EGT).
By advancing the magnetos 1-2 degrees the balance is changed.
A guru called the Timing Fairy, says it is OK, but depends on how much BHP is taken out of your engine type.
For example. A TSIO-520 comes in a lot of different variants. I dont have the full facts here now, but with no major parts differences, the 520 is certified from 290BHP to close to 385BHP. The high end has the magnetos timed at 29 degrees BTDC.
So say you take a standard 310BHP version, then tweak the magnetos 2 degrees advanced, you probably increase the max BHP by 10(educated guess).
Nothing disastrous, since you will normally only be at this power setting for about a minute or so during take off, each flight.
Trials have showed that about 1,5 degrees advanced change, brings CHT’s from 345 to 375, and the TIT from 1670 to 1625.
This at about 86% climb power, LOP 17GPH. The ROP alternative is 30GPH for the equal CHT number.
You can run your Turbo at 1650TIT all day long. 1750F is more a hard limit.
If you feel that your engine runs rough when LOP(you mentioned 1 cylinder at 150LOP), then I would redo the GAMI test. It should be done frequently to verify your GAMI spread. Anything more than 0.5GPH between leanest and richest is not ok.(in my eyes)
Unless you really need the number of degrees LOP for testing purposes, I would recommend the BMP(BigMixturePull).
Being 10-15degrees LOP is a great place to be as long as you have no issues with CHT.
Quote Its all about how you run your engine hard.
Thank you guys, this is really very clever thinking and I need to digest and see how much can be applied to my engine/airframe.
To answer the question:
The TSIOL-550C is rated at 350 BHP at 2600 RPM and 39.5 inches MP. It is water cooled so that measured CHTs and coolant temps are very low (my coolant redline is at 245 F which is higher than Extra POH but that’s because the EDM930 probe is located at a hotter (hottest?) point ).
People who know these water cooled jugs will point out that not all of the cylinder is water cooled – this is on my to do list:
- how hot does the cylinder get near the crankcase where there is no cooling jacket… I will only attempt adjustments that potentially increase CHT after answering this!
@Spirit 49:
The idea of tweaking timing is well noted – I’ll discuss with John Deakin. Can you tell me more about your 86% LOP climb setting? I am interested in testing it.
The first thing to check is the full rich fuel flow setting during take-off and initial climb. If it is set too low (not rich enough) you will see the CHTs steadily rising; In this case you may temporarily use the fuel pump (if it is not used normally like in the Bonanza) to get a bit more fuel flow. Have your shop adjust the fuel flow at full rich, full power upwards if needed. If you have a readout of the EDM it should be obvious.
@dirkdj – full rich fuel flow is fine. I have been through all of the adjustment pain and now it is finally fine! I just checked my Savvy uploads : somewhere around 145 liters per hour.
In fact it is so rich that upon landing I must lean to avoid choking the engine. Yes I do lean during ground ops. ;-)
Flyingfish wrote:
The idea of tweaking timing is well noted – I’ll discuss with John Deakin. Can you tell me more about your 86% LOP climb setting? I am interested in testing it.
Not much to it really.
Full Take off power is 36.5",2700rpm ROP at around 39GPH(Rich, but no flooding)
Setting climb power at around 34",2600rpm and ROP30GPH. Then doing the BMP to get LOP. Aim for 16.5 to 17.0GPH. Readjust MP to 34" if needed(sometimes drop a bit.)
This power setting is max what I can do LOP.
Its a balancing game really.
Fuel Flow to control the TIT below 1650F. Airspeed to control the CHT’s.
Since the P210 is air cooled, after patching up the baffles, it is possible to keep all CHT’s below 380F and airspeed at around 105-115kts. Climb around 6-700fpm.
On hot days either increase airspeed a bit (115-125), trading vertical speed, or when really hot & heavy I have to go ROP to get into the higher levels. Climb around 7-800fpm.
Since the timing is a bit Advanced, when going ROP you get the opposite effect. So now the CHT’s is higher than they could have been at the correct BTDC. My CHT’s are low enough that I can go about 1,7 degrees advanced. That gives me the possibility to climb LOP, but still the option to climb ROP without busting the cylinders.
My CHT limits are 390(warning on the EDM-830). I try to stay around 385F.
These temps are still low, and is no reason to panic. Just an early warning. On the hot days I accept shorter periods up to 410F, but I normally just level off and do a step climb when temps are back down and some weight has been burned off (after 45 min).
The P210 has a rumour of eating cylinders because of high CHT’s. To be honest, I have flown other aircrafts that have way higher temps, and nobody even lift an eyebrow.
The Cylinder hysteria is more about bad workmanship and suppliers, than effects of misuse.
Ask ANYBODY with a -520/550. Those cylinders from TCM are JUNK. Have a specialist work the valves, seat and stem, and you can go way longer than the factory cylinders.
Chance of getting to TBO on original cylinders are like NIL.
The use of 6 points engine monitors has changed the game. GAMI’s too.
Magneto timing is normally very strictly defined in the TCDS. I would expect that very few IAs would sign off a plane that is more than a degree or so off the value or values in the TCDS…
boscomantico wrote:
Magneto timing is normally very strictly defined in the TCDS. I would expect that very few IAs would sign off a plane that is more than a degree or so off the value or values in the TCDS…
In worst case the engine can EXPLODE.
Aircraft should be marked as EXPERIMENTAL.
No passengers should ever be carried in such a plane.
So on, so forth.
I have studied what the Gurus have to say on engine operations more or less for the last 4 years. I have made my own conclusions
I would never, ever advance or retard my magnetos.
However, I think my IA’s old magneto flowerpot is a bit hard to dial in correctly at TDC…….
spirit49 wrote:
Have a specialist work the valves, seat and stem, and you can go way longer than the factory cylinders.
Who would you recommend in Europe for that job?
