310 - Turbo or Colemill

Topper

Topper

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Topper
going to buy a 310 and really enjoy the extra performance of turbos even though a good deal of my flying is in the middle of the country and not needed. When alone or with one of my sons, I don’t mind strapping on o2 to take advantage of winds.

I recently looked at a colemill equipped 310 (not sure if it was a 1 or 2). What are the pros/cons of the turbo vs colemill. What about the performance differences. Most of the turbo models have been P models and the colemill was a Q.

Thanks,

Jim
 
Ted will be able to come in here with his aeronautical engineer mindset and give you more/better info.

I’ve flown turbo’ed Twin Cessna’s and normally aspirated but never a colemill. I sought-out a NA Q model with full de-ice when I was buying. If I lived in mountain country or had a mission taking me there regularly, I would have opted for turbo’s. I’ll suck O2 if I have to but I really don’t enjoy it and if you find a nice turbo R model, it starts getting you close to that 340 price/operating range and who doesn’t want pressurization? :)

Based on your comparison/question, I’m guessing you want more performance than a stock NA will give you. The colemill is a great conversion but is costly to initiate, demands a premium on a nicer one (harder to find) and the Overhaul costs more. A guy on TTCF (you should join if your serious about buying) just upgraded his Q model and he posted pics of 193kt true at 9000 with the props back to 2300 and 15 per side. If you want to run it up, it makes the 310 a 200kt + plane.

I think you can’t go wrong with any 310...I’m biased obviously. If you want to go fast and you and your passengers don’t mind sucking O2 to take advantage of turbo’s, go that route. If you want to have the speed advantage and stay below O2 levels, I’d go with a colemill. I’m perfectly happy with my stock NA Q model (theoretically the cheapest to operate/maintain), she gives me all the performance I need/want and more.

Good luck! Let us know how the search ends up.
 
Topper said:
going to buy a 310 and really enjoy the extra performance of turbos even though a good deal of my flying is in the middle of the country and not needed. When alone or with one of my sons, I don’t mind strapping on o2 to take advantage of winds. I recently looked at a colemill equipped 310 (not sure if it was a 1 or 2). What are the pros/cons of the turbo vs colemill. What about the performance differences. Most of the turbo models have been P models and the colemill was a Q.
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I used to have a Colemill President 600 Baron and now have a normal B55 Baron. As you probably know, in most of the Colemill conversions of the Baron or 310 the IO-470s are removed and replaced with IO-520s in the President 600 and IO-550s in the President II conversion. The 310 nomenclature is Executive and Bearcat. New props are required too and some other modifications but the engines are the major component of the swap.

http://www.mikejonesaircraft.com/stc.htm

Since Colemill never asked for any changes to the POH, the conversion airplane is limited to producing 260HP, not the 300HP that the new engines produce. Therefore, *legally* you are limited to 260HP in all regimens. You cannot legally use full MP during take-off at sea level, as an example but as you climb and HP is reduced you are legally able to add MP to maintain 260 HP. I’m sure many operators regularly *accidentally* use full MP on takeoff and climb out . . .

That said, the Colemill will climb noticeably faster than the non-Colemill but doesn’t cruise any faster (Baron, I’m sure the 310 is the same). I seem to use less fuel now for the same true airspeeds I was getting with the Colemill, might be the differences in the IO-470 versus IO-520.

Colemill or not, these are great airplanes in the 8,000-12,000 ft range. If you plan to regularly cruise above 12,000 ft, get the turbo.
 
I can’t speak to the Colemill but I fly my turbo in the 9000 to 12000 thousand foot range LOP (GAMI & JPI). Seeing good speed on 26 g/hr, but then I’m not in a hurry to get anywhere. At 29 /2100 it’s as quiet as a 310 can be and will cruise way longer than anyone will want to sit. Push the power up and it’s a true 200 mph cruiser. It also climbs like a home sick angel. I’m in the SE so I ready didn’t need it. For me it was more about getting a good airframe. It just happen to have turbos. Feel free to PM me if you have any questions. I’m happy to share my experience. Good luck with your search and keep us posted.
 
Twin_Flyer said:
I fly my turbo in the 9000 to 12000 thousand foot range LOP (GAMI & JPI). Seeing good speed on 26 g/hr, but then I’m not in a hurry to get anywhere. Push the power up and it’s a true 200 mph cruiser.
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I would have thought a T310R would be faster than that on that fuel flow. At 10,000 ft (+/- 500 ft), in my bone stock B55 Baron I get about 190 KTAS (218 MPH) on 25 GPH, about 180 KTAS (207 MPH) on 22 GPH and about 175 KTAS (201 MPH) on 20 GPH.
IMG_2424.jpg IMG_8124.jpgIMG_8123.jpg
 
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Twin_Flyer said:
Seeing good speed on 26 g/hr, but then I’m not in a hurry to get anywhere. Push the power up and it’s a true 200 mph cruiser.
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Twin_Flyer said:
I see 190 KTAS at that flow but not at 29/2100
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You wrote that if you push the power up (which means an increase in fuel flow above 26 GPH; increasing power and increasing true airspeed requires an increase in fuel flow), then you get 200 MPH (175 kts). 26 GPH must be a speed below 175 KTAS, then. Am I reading this incorrectly ?
 
KLRDMD said:
You wrote that if you push the power up (which means an increase in fuel flow above 26 GPH; increasing power and increasing true airspeed requires an increase in fuel flow), then you get 200 MPH (175 kts). 26 GPH must be a speed below 175 KTAS, then. Am I reading this incorrectly ?
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That was for people who just care about speed... The truth of the matter is it’s a 200+ knots/ mph aircraft if you want to run it that way. Sorry if you disagree....
 
Twin_Flyer said:
That was for people who just care about speed... The truth of the matter is it’s a 200+ knots/ mph aircraft if you want to run it that way. Sorry if you disagree....
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Not disagreeing at all, just trying to see what your actual speed is for a given fuel flow. As I wrote, it appears I am mis-reading what you wrote.
 
Twin_Flyer said:
I can’t speak to the Colemill but I fly my turbo in the 9000 to 12000 thousand foot range LOP (GAMI & JPI). Seeing good speed on 26 g/hr, but then I’m not in a hurry to get anywhere. At 29 /2100 it’s as quiet as a 310 can be and will cruise way longer than anyone will want to sit. Push the power up and it’s a true 200 mph cruiser. It also climbs like a home sick angel. I’m in the SE so I ready didn’t need it. For me it was more about getting a good airframe. It just happen to have turbos. Feel free to PM me if you have any questions. I’m happy to share my experience. Good luck with your search and keep us posted.
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Thanks for the replies, I think I am where you were, more about the deal and airframe than if it has turbos or upgraded engines.

Main thing is I want to see performance close to the Columbia 400 I fly a lot now. At 8-12,000 I probability average 180knots. At 16,000 I average another 10 knots more.

I used to have a 56 310 and loved it, but with no ap and old avionics it wasn’t worth upgrading.

I will keep everyone posted on what we do.
 
FBO I flew 135 at had a Colemill, might have been an M model but don't recall. They had a T310R and it was a sweet machine. 35+ years ago so I forget the numbers but do remember liking the Colemill 310.
 
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Not sure whether you're looking at a 310R or a short nose (Q or earlier). I flew a 310N Colemill Executive 600 (520s) for about 1000 hours and it was a great performer. Someone on the Twin Cessna forum recently upgraded his 310Q to an Executive II (with 550s).

A stock turbo 310 IR or pre-R) is really not all that much better of a performer until you get to altitude. And even then, it's not great. If you really want a hot rod out of a 310, go with a RAM IV T310R. Now that is a hot rod, and a fun plane. They also have sold very few of them so they're hard to find. I have probably 10 hours in one and it's a great airplane.

Personally I'd go with the Colemill. The performance is about the same for the altitudes you'll typically fly at, the fuel consumption is lower when flown properly, and the engines (being naturally aspirated) are more reliable. Get 550s if you can, but a short nose with 520s will still perform great. I got a lot of extra speed out of the 310 by attention to detail - rigging of control surfaces and removal of unnecessary antennas, etc.
 
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