Primarily for general aviation discussion, but other aviation topics are also welcome.
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By shortwing
FLYER Club Member  FLYER Club Member
#1861474
evening all,

After some advice on the C90 engine in general.

What's the gotchas?
Weak points?
Issues with parts?

This one seems to run about 30psi Oil Pressure when hot which seems low, but google seems to say not - so i'm after some advice from anyone with experience of the C90.

Thanks in advance
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By ThePipster
FLYER Club Member  FLYER Club Member
#1861482
C90 is a great little engine, pretty bulletproof with one main problem, they love to make ice! Copious amounts of carb heat needed, make sure that the carb heat system is kept well maintained.

If you are used to Lycomings then the oil pressure is going to look low, the difference is that the oil pressure on a small Continental is measured on its return to the oil tank not on its outbound journey, i.e after the oil has been all around the engine.

The type certificate and overhaul manual are easily found on the internet and list all the min and max values for temps snd pressures.

The C90 and O-200 are basically the same engine with a different cam and valve spring setups. The C90 is often rated by pilots as the better engine as it produces max torque at a lower RPM, useful during takeoff....


Pipster
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By Cub
FLYER Club Member  FLYER Club Member
#1861486
We operate a J3C Cub with a C90 and it has offered few problems over the past 15 years. It does, as Pipster indicates, generate ice very effectively apparently at all ambient temperatures requiring regular application of carb heat.

We did swap between an 8F and 12F variants at one point and please don't believe that is the straight forward swap on the front of a Cub that you might expect!

PM me if we can help in more detail.
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By Rob L
#1861492
As Pipster suggests, the C90 is better than the 0-200.
Less weight and more torque. All small Continentals make ice, though!

30psi is a bit low but within limits...what's the psi when the oil is hot and the engine at idle?

Rob

Edit: Similar to Cub; I swapped from a -12F to a -8F (the other way around) but on a C-85...I now get 105HP but still the same ice-maker!

Edit2: I have all the small Continental manuals on Dropbox, so if anyone needs them I can post a link.
Last edited by Rob L on Tue Jul 27, 2021 10:36 pm, edited 1 time in total.
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By shortwing
FLYER Club Member  FLYER Club Member
#1861496
Rob L wrote:As Pipster suggests, the C90 is better than the 0-200.
Less weight and more torque. All small Continentals make ice, though!

30psi is a bit low but within limits...what's the psi when the oil is hot and the engine at idle?

Rob



When hot and idling it’s around 30 psi but 40-50 when cold
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By CloudHound
#1861497
O-200 ain't that bad. They need revs to hit the 100 hp mark so my prop limits take off power.

Look at the back of LAA mag for the chap selling spin on/off oil filter adapters.
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By Paul_Sengupta
FLYER Club Member  FLYER Club Member
#1861519
CloudHound wrote:Look at the back of LAA mag for the chap selling spin on/off oil filter adapters.


A friend of mine fitted one to his A65, but had to take it off as there wasn't enough oil pressure to open the non-return valve in the spin-on oil filter for some reason.
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By MichaelP
FLYER Club Member  FLYER Club Member
#1861524
I am not a fan of the spin on oil filter mod.
It can adversely affect the oil pressure, especially on start up.
A friend has had to remove it from an A65 because the oil pressure did not rise within a reasonable time.
Wear and tear is worse when the engine is started, ensure the pressure comes up quick after the mod has been done.

The spin on mod had an adverse effect on a Decathlon we modified to fit the Christen system, and then modified to fit the spin on filter. This was on a crude Lycoming IO 320.
With the screen filter oil pressure was not affected when the aeroplane was rolled to the inverted.
With the spin on mod the oil pressure dropped off when rolling inverted, and then recovered into the low yellow pressure, not into the green :(

I had O-200 engines that went through their lifespans without any bottom end problems using the original oil screen filters, and fifty hour oil changes.
On condition TAU’s O-200 went to 2,796 hours, with good oil pressure throughout.

The centre main crankshaft bearing is a weak point.
Spinning and aerobatics with a metal propeller causes wear in this bearing and subsequent reduction of oil pressure.
Prefer a wood/composite propeller and your engine will last a lot longer.
The Condor used the Evra D11-28-4C propeller.
Prefer a certified propeller with a metal leading edge. In many cases the extra cost is repaid many times over with the extra life.
Before Arrow got a hold of TAU’s Evra, it had gone for ten years and was as good as new.
Recently took a popular uncertified propeller off an A65 and reinstated the Evra. The engine ran smooth, gave another 100 RPM for takeoff, and the cruise was slightly improved. Don’t cheap out on your propeller.
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By MichaelP
FLYER Club Member  FLYER Club Member
#1861530
Use the correct propeller.

A chap was disappointed with how slow his aeroplane was.
The engine had been changed from an O-200 to a C90.
It had the D11-28-4C propeller and he was using the C90 RPM settings!
This propeller was designed to turn to the maximum 2,750 RPM and cruise at 2,550 RPM (75% power O 200).
Torquey C90s don’t turn so fast for their power.
By Crash one
#1861564
I’ve only ever had one or two incidents of ice, backtracking on wet grass, in fifteen years.
What am I doing right?
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By PeteM
#1861566
Maybe just lucky!

Taxiing over grass with dew mine would stall from icing within a couple of minutes.

Max rpm from the C90 is if I recall 2550 and that is time limited. With the right prop I felt the C90 was more effective than the O-200 engined aircraft that followed it.

Mine made 2400hrs before it needed an overhaul and always had good compression. With the oil screen we changed the oil at around 30-35 hours and the pressure never went below 30psi.

Nice engine, simple to work on - but we really only needed to for carb floats which over the years have gone from metal to plastic (several types and then back to metal!)