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Old 01-14-2009, 09:16 PM   #1
chancho
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Default major rpm spike da 170 on ks 95 cans

i purchased the new da 170 and was very excited but now i am sick. i am running it on ks 95s cans with 4.8 nicad in my new 41% wildhare extra 260, i am using a 32-10 bolly wood prop. today was the maiden for the plane and engine. everything started ok. i flew it for about 8 minutes, and while i was flying the throttle was alittle touchy but i thought, no problem just needs a curve. so i brought it in checked out the plane, refueled, visited a little set up my curve base and fired it up this time it was way to low on the bottom and then would shoot up in rpm wildly, long story short i ran a hole tank of fuel trying to correct this condition. at half stick with the best curve i could get was maybe 2500 rpm and then when i moved the stick one dot to dot on the curve graph it would go to 3/4, 7/8 throttle. i have pretty good experience with these engines although this my first set of cans. i tried everything i can with adjusting the carb but i think maybe it is the ks 95s causing the severe rpm spike. i spoke with tony and jeff both at da and they have no answers for me except try a mejlik 32-10 but i just dont think a little less load is going to correct this. i put a short flight with the curve i set and then changed back to the staight line and flew another short flight and i sware the spike got worse , more severe and sharp the more i ran it. any ways if anyone can offer some advice or suggestions or has had or knows some one that has had this problem please reply to this post. i have spent a fortune and as far as i am concerned as severe a spike as this is the plane really is no fun to fly. thanks
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Old 01-14-2009, 09:59 PM   #2
Buzz Lightyear
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Default Re: major rpm spike da 170 on ks 95 cans

Hi Mate

How long are your headers?

A different prop WILL change your throttle curve. As for the change every flight, your motor changes every flight until it is fully run in.

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Old 01-15-2009, 09:00 PM   #3
chancho
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Default Re: major rpm spike da 170 on ks 95 cans

my headers are 11 1/2" , which the guys over at da say that is the best length. i am using a 32-10 bolly wood. how much difference can be seen by just changing to a 32-10 mejlik, it is hard to believe it would change the problem i am having. besides, today a ran a little test by running it on just the headers and it ran excellent, the transition was good with a little tuning the midrange was strong, no jump in rpm. i called tony over at da and he has no idea why this is the case but he said to send them in and he'll run a test on em, if they cause his test engine to run the same, they will send me standard muffs and refund the rest, which sucks but i'll lose a pound and a half and have good linear throttle response.
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Old 01-15-2009, 11:32 PM   #4
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Default Re: major rpm spike da 170 on ks 95 cans

mmm

Different props = different loads = different throttle response

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Old 03-04-2009, 10:55 AM   #5
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Default Re: major rpm spike da 170 on ks 95 cans

I have the same DA170 KS95 combo. I am running a 32x10 mezlik(spelled wrong...I know).
The response is smooth. Just like my DA100(which is on MTW cans)
Are you sure you do not have any radio/servo setup or other issues?
Hard to believe that the KS95s would create a tuned pipe effect....

LJ
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Old 03-04-2009, 11:09 AM   #6
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Default Re: major rpm spike da 170 on ks 95 cans

I know this may sound juvenile, but how long is your throttle servo arm.
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Old 03-04-2009, 11:52 AM   #7
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Default Re: major rpm spike da 170 on ks 95 cans

Customjrod just hit the nail on the head!! this was a problem for me once, if you will run a 1 to 1 arm or less this wont be a problem and you will have more control over the motor and carb
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Old 03-05-2009, 04:14 AM   #8
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Default Re: major rpm spike da 170 on ks 95 cans

32x10 mejzlik or 29x12n 3blade is your ticket.....borrow one and see before you make a purchase
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Old 03-05-2009, 05:11 AM   #9
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Default Re: major rpm spike da 170 on ks 95 cans

If you can afford all this, surely you can also afford another prop .
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Old 03-05-2009, 06:44 AM   #10
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Default Re: major rpm spike da 170 on ks 95 cans

Quote: Originally Posted by bpetty620
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Customjrod just hit the nail on the head!! this was a problem for me once, if you will run a 1 to 1 arm or less this wont be a problem and you will have more control over the motor and carb

agreed...sounds mechanical to me...


and yes, switching to a Mejzlik will make a nice difference
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Old 03-05-2009, 07:13 AM   #11
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Default Re: major rpm spike da 170 on ks 95 cans

Just move the cann back about 3/8" and see if some of the peaky-ness goes away. My experiences with headers and canns has proved to me a correctly lengthened header will produce a tuned power boost regardless of whats on the end. Pipe, cannister, or home made muffler, all see a performance boost. I adjust where I want the peaky-ness, and how much by adjusting the pipe length. Ever notice most Unlimited Race planes have about a 8" header with no muffler or pipe? Thats a typical tuned header length for max power. Never flown one but I suspect they are quite peaky.
You can kill the tuned set up you now have by over proping it. But that doesn't adjust it for smoothness just overload it.
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Old 05-08-2009, 10:49 PM   #12
amatera
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Default Re: major rpm spike da 170 on ks 95 cans

CHANCHO,
Just wondering did you ever figure out the rpm spike?
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