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Old 06-27-2005, 10:56 AM   #1
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Default slide vs rotory carbs

ive been searching and cant what the pros and cons are for each one. which is better? im not racing as of now so i want something easy to tune. im looking at buying a new engine but dont know what carb to get.
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Old 06-27-2005, 01:17 PM   #2
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Rotary is going to be the most convienent to a newcomer....

Rotary carbs offer a more linear throttle feel. More gentle low-end and just easier to drive. For off-road 10th scale cars, rotary is the way to go. For on-road and 8th scale, you'll be looking for a slide carb as they offer tons of low end power.

An 8th scale car needs the low end grunt and touring cars can handle the low end availibility of a slide because of the useable traction.

While it all depends on the applicatin.....I'd recommend a rotary.
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Old 06-27-2005, 02:03 PM   #3
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thanks mafiaracers.
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Old 06-28-2005, 03:53 AM   #4
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Slide carbs need more attention for tuning also.Go with a rotary.

Sean
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Old 06-30-2005, 01:43 PM   #5
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Quote:
Originally Posted by Team Duratrax
Slide carbs need more attention for tuning also.Go with a rotary.
Sean
If anything a slide carb is just as easy to tune as a rotary carb, if not easier. Don't know where you got this from.

As for more power, once both types of carbs are WFO they make pretty much the same amount. A rotary carb offers a little more intake restriction due to the barrel that rotates within the carb body. Linkages are obviously different, of course.
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Old 06-30-2005, 06:47 PM   #6
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Directly from RCCA.

SLIDE CARBS. These provide more consistent response throughout the throttle range. Their design permits air to flow smoothly through the carb at any throttle setting. A slide carb might make it slightly more difficult to maintain the low-speed mixture when making idle-speed adjustments, but otherwise, they're just as easy to tune.

RCCA also mentions the rotary carb being easier to tune on the bottom,
So i guess you were right about a slide carb being just as easy to tune but aren't they supposed to be more finicky? Like more prone to losing their tune and super fine adjustments.

Sean
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Old 07-01-2005, 08:23 AM   #7
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The biggest trick to slide carbs is getting the linkage geometry right. On smaller carbs, its more critical. The smaller the carb the smaller the travel of the servo and linkage - thus its harder to get good resolution throughout the servo travel.
On my Losi XXX-NT I found the best point to mount the throttle linkage is in the furthest inward hole on the arm. The losi manual shows it in the second hole. In the second hole, I was only using about 50% of the servo travel, and the analog servo I was using had pretty rough resolution when using so little of its available throw. Also, a servo is rotary - and a slide carb is linear. With the servo arm exactly perpendicular to the carb is where its the most linear.(but also the most sensitive) At the extremes of the servo rotation it doesn't create an equal throw on the carb for the same amount of servo rotation.
By adjusting where in the throttle travel the arm is perpendicular you can create a "throttle curve" mechanically. If the arm is perpendicular at idle it will be really sensitive at the bottom end. Not what you usually want in offroad. Having a radio with a programmable throttle curve will let you do pretty much anything you want with the sensitivity of a slide carb - especially if it has 5 programmable points to the curve.
But, I found that once I got my chassis tuned right and found the right tire combo for my track, I didn't really need to soften up the throttle curve anyway! If the track ever gets marble slick - It would be a different story.
Rotary carbs are easier to get a smooth throttle curve out of because the linkage travels in a rotary fashion just like the servo.
Once you get a slide linkage right, I don't really think its any less smooth or hard to tune than a rotary.
The only time I've had to fiddle with my idle mixture was when the air temp went from mid 60's to mid 90's. 1/8 of a turn and that was done.
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