The International Cessna 170 Association

No, not referring to Viagra , but our favorite airplane's performance.
Question to our learned membership :
In the order of Cessna 170 performance improvements in cruise flight from greatest to least, what modifications have proven beneficial???

Reason for asking is: When I bought my 170B, it cruised 2400RPM at 108 MPH indicated. I since shaved about 40 pounds off the empty weight, removed an ADF antenna, installed 15-600X6 tires in lieu of the 800X6, installed Bartone exhaust/sealed the old cowling cutouts and installed aileron gap seals. Result, today's cruise is 2400 RPM and 108 MPH . One would think reducing the mlg tires equivilent flat plate area by 30% would have shown some improvement, but nothing measurable.

I'm considering adding strut fairings, wheel fairings, flap gap seals and, as a last resort, a JATO bottle on each side. But loathe to spend the money if there is no improvement. Incidently, It's diffcult to justify an engine change (IO-360 or O-360) to pick up 10 MPH in view of increased fuel consumption.

So, I am very keen to hear suggestions/ideas/results/thoughts/discussions if anyone has time to comment.

Run it at the recommended 2450 rpm and get 110 IAS. Based upon your previous experience, the added cost (due to increased fuel burn), will be the cheapest gain in mph you will ever get.

What's your hurry . Speed up your airplane and you spend less time flying.

I've heard a lot of forum talk about running the engine at full throttle and leaning as required. Full throttle in level flight gives me almost the 2700 rpm red line. Here in the flatlands I rarely get above 1500 asl as most flying is along the coast. 2500 asl is waaaay high here. After leveling off I reduce the throttle to bring the MP to 23 or 24" and let the prop settle usually at 2500. Is there a better way? My prop is 53 pitch and I usually fly just under 400lbs passengers and full tanks.

Sounds like you have a good performing airplane and a good technique, Jim. If you really never plan to fly differently, it might improve fuel burn/speed slightly to go to a cruise prop (7655). That way you'd be more likely to cruise at full throttle and still remain near 2450 rpm....which would be a slight efficiency increase. (Not sure it'd be worth the expense of a prop changeout tho', and the short field performance would suffer slightly.)

N170CT wrote:So, I am very keen to hear suggestions/ideas/results/thoughts/discussions if anyone has time to comment.

Why spend hundreds / thousands of dollars to gain a few measly MPH. If you really want to increase your speed, best bet is to buy a different/faster airplane. The 170 is a great airplane, but it never has been nor will be a speed demon. In the grand scheme of things, does 5-10mph really matter?

Put one of those F200 aeromatic props on there and let us know how it performs.

Remove your venturis and install the belt-driven vacuum pump mod. That might get you 1 mph per $1000 spent. On cross countries I run mine at 2500 rpm, that gets me about 68% at 2500 msl and about 119 mph true at light weight and in smooth air.

Buy one of those little stick-on instrument covers that instructors use to hide an instrument while simulating instrument failure. During cruise, stick it onto the airspeed indicator so you can't read the instrument. Look outside the airplane and enjoy the view. Relish the joy of flying along in your 170 again! (And for only a couple of bucks! Great value!)

Deleted

Mr. Riley??

Thanks for that comment...I used GPS to confirm IAS and it was almost dead on. Actually have two, one panel mount and a hand held. Interesting comment on prop. I believe I have a 53" pitch screw on the front and have considered going to a 56" but the cost seems too high for the gain not to mention the potential loss in TO and Climb neither of which is exciting.

BTW..I used to live in Westpark near Harvard and Alton directly across the street from Irvine City Hall. Currently have a/c hangared at SNA and CNO. Where are you based?? I rarely see any 170 types at SNA other than George Sandy's.
chuck

Over thirty years and four engines I can argue that the C-145 (one was an O-300A) engine likes to run at 2650 or above and hates 100 octane. Only one engine failure out of four engines and that was because of "LEAD" deposits on the back of the exhaust valve. Each one has run to TBO and only the one, the one on my plane now, as had a problem with oil consumption.

I expect to see near 130 mph (Standard/Standard) true and burn around 8.5 - 9 gph. At today's prices for avgas it is a little more expensive per hour but getting there quicker makes the trip cost the same. She is a stock airframe with the "Cal-Twist" prop and no wheel pants over the 7:00X6 tires.


Save your money for gas!!!!!!!!!!

So CT you've got one of those 170s like mine that just won't go anywhere fast.

Sounds like your on the right track trying to clean the plane up. As for the wing strut cuffs I did the opposite. Mine had them and they were getting ruff so I took them off. Plane didn't go any slower. I wouldn't expect yours to go faster with them though theoretically it should.

While I wasn't trying to make my plane go faster when I did it, by re-rigging my wings to center my plane picked up about 8 mph. My wings were adjusted to correct for a heavy wing condition I think. One wing was all the way up the other all the way down. The heavy wing condition still existed with the wings twisted and didn't change after the adjustment so I left them neutral and put up with the heavy wing condition while I go faster.

I have a 76/54 inch prop according to the prop shop that twisted it and run about 2600 rpm and about 22.5 mp. I've got 8x6 tires and routinely get between 110 and 115 mph out of it.

Another thing you can do for free is do an accurate W&B. I'm sure you'll find the CG way forward. Add a sand bag to the luggage compartment. that might gain you a few MPH as well.