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Old 03-06-2008, 04:21 PM   #1
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Default 17.5 vs 27t

A lot of guys on here are saying 17.5 is slower than 27t. i know that racing trans am cars (4 cell, 17.5 or 27t), I ran a 58mm roll out. The car was as fast as any other on the track, yet came of at 145* F (0* timing). The only guy who had a better lap was up 1 tooth from me.

Just wondering what rollout and temp everybody is getting to with these motors...and lap time vs, 27t
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Old 03-06-2008, 04:24 PM   #2
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I believe the 17.5 is faster
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Old 03-06-2008, 04:34 PM   #3
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I believe the 17.5 is faster
What makes you think that? The one person at Trackside that has compared feels that his 27T is still a tick faster.
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Old 03-06-2008, 04:40 PM   #4
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I think your going to find that the 17.5 is faster on bigger tracks, that is if you can gear it high enough. On smaller tracks the 27t is going to be faster.
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Old 03-06-2008, 04:43 PM   #5
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on a track 48x70 I have been able to run identical times with a roar stock and a 17.5 so go figure. 17.5 doesn't fall off as much as it should be.
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Old 03-06-2008, 06:24 PM   #6
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Quote:
Originally Posted by robk View Post
A lot of guys on here are saying 17.5 is slower than 27t. i know that racing trans am cars (4 cell, 17.5 or 27t), I ran a 58mm roll out. The car was as fast as any other on the track, yet came of at 145* F (0* timing). The only guy who had a better lap was up 1 tooth from me.

Just wondering what rollout and temp everybody is getting to with these motors...and lap time vs, 27t
track 40x90 esc speed passion, motor 17.5 novak, roll out 50ish thermaled the motor several times, temp around 160 to 175. Timing not 0 but some where around 15 or 18.75. That might be why it over heated 6 cell touring car
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Old 03-06-2008, 06:28 PM   #7
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Forgot to mention, you're not going to be able to gear it to temp with 4 cell T/A. Keep gearing up and it'll slow down long before it gets hot.
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Old 03-06-2008, 11:06 PM   #8
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There's maybe 3 more teeth in it from what i figure for T/A, temp wise. I'll try to find out this weekend...
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Old 03-06-2008, 11:28 PM   #9
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Quote:
Originally Posted by nashrcracer View Post
on a track 48x70 I have been able to run identical times with a roar stock and a 17.5 so go figure. 17.5 doesn't fall off as much as it should be.
Just out of curiosity...what roar stock motor are you comparing to, and how well was it actually built?

From what I have seen at the 120x60 track here...17.5 was overall slower in stock 1/12th than the well built CO27s... 17.5 was faster (slightly) on the straights, but it just didnt seem to cut it in the infield.... I think I am going to stick with a CO27 for now...
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Old 03-07-2008, 04:29 AM   #10
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Well, good thing for everyone there's a little race coming up next week that will pit 27T vs. 17.5 in the stock classes. We'll know what's faster before qualifying even starts
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Old 03-07-2008, 06:16 AM   #11
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Sorry newbee hear that just picked up a 17.5. What do you mean by timing and rollout?

Thanks
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Old 03-07-2008, 07:17 AM   #12
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I think the whole 17.5 vs 27t thing comes down to the class that you're running. That being said, I think that everyone will agree that the two motors can run together in the same class and that's a big step in the right direction.

Things will sort themselves out for each class after a few big races. At a club level, I'll bet that more and more people run BL just because of the maintenance.
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Old 03-07-2008, 02:28 PM   #13
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I had been running a CO27 that I know is fast. What i find strange is that everybody keeps saying how they have no rip, but are fast on the straight. When we first tried the motors, the opposite was true. With the bigger gears out now, we are getting them to run fast on the straight. The thing i am wondering about is timing..what are you guys setting timing at??


Rollout is the mm of movement per revolution of the motor. Easy way to compare gearing between different cars and tire sizes.

Timing is the relation of the stator and rotor (or brushes and/or commutator and magnets) to each other. Changes the powerband and characteristics of the motor.
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Old 03-07-2008, 02:56 PM   #14
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what about 17.5 vs. co27 in 1/10th TC eh? Rubber, asphalt...mmm...

no rollouts for us! FDR ftw!
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Old 03-07-2008, 02:58 PM   #15
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Quote:
Originally Posted by Matt Howard View Post
Well, good thing for everyone there's a little race coming up next week that will pit 27T vs. 17.5 in the stock classes. We'll know what's faster before qualifying even starts
too bad it's less than a week until the race and you can't buy one of the two legal 17.5's yet...
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