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Post by duckhnter83 on Jun 23, 2014 8:04:23 GMT -6
When going up one gear ratio at the same track say a 600 to a 620 how much rpm can one expect to gain?
Next is when adding rear percent how much is needed to feel a change? Half a percent a whole percent? Thanks guys
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Post by startnonthetail on Jun 23, 2014 8:46:28 GMT -6
Roughly, you can divide your rpm by the old gear ratio and then multiply by the new gear to get the new rpm. e.g. 6600 rpm รท 600 = 11 11 x 620 = 6820 rpm
If I was adding weight, I'd make it at least 1% until you feel like you're really close to where you want to be. I'd shoot for some proven weight percentages for your chassis and then fine tune handling with springs, crossweight, shocks and suspension geometry.
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Post by oldtrackchamp4x on Jun 23, 2014 18:05:16 GMT -6
Typically speaking, for every .10 on the ratio you gain just over 100 rpm.JMO
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Post by flipflopoo1oo on Jun 23, 2014 22:09:32 GMT -6
Depending on a cam' peaking out you may not gain rpms and top out at the flag-stand! Pulling ranges per gear change for us requires a total look at cam degree, fuel and timing to make the most of the change! In some cases more gear on under powered engines will free up power to speed up to a 1,000 more rpms if faster even off the corner adding to top speed also! I go the other way and peak the engines max pulling range to the load! This seems to hold torque longer within a shorter range and more pickup of speed! I look at total weight to choose gear per track length before the cam and degree choice! Match timing to stroke and fuel to compression and with no power valve to shut back the fuel on top end to get a false plug reading, then you can improve jetting to match! I have came from 713 to a 526 and turn the same rpms but the car was faster by far! Weight would depend on where you are now and bar angles! I shoot for 61-63 to hook the beast but some may only need 54-58 with excessive bar angles! Most of these top out and over steer in the process trying to achieve traction with a spoiler that creates uneven variables of loads! I do tune my spoilers to a gear change in going the other way to lessen the load to go faster as well! Solid cams can be tuned by lash to preform to various loads with out degree changes that do not change the profile! We have turned 8300 but 6400 was faster with the same engine, cam, carb, and dist. tuned to work together! What weight car, length track, and rpms are you now? Do you want to run the bottom or use all the track? I would be looking at less spoiler, more rear percent, timing and fuel as well as fire power up grades instead of gear changes! Improve your vacuum but idle it up to keep from stretching or stressing something in the motor when lifting!
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Post by phantom309 on Jun 23, 2014 22:52:43 GMT -6
I agree with all answers. Just thought I,d throw in a couple tips you probably all ready know. when choosing gear= Divide R.P.M. you want to turn by current R.P.M. then multiply by current gear. 6800 divided by 6600 times 6.00 = 6.18. Rear % effects corner entry,exit & throttle. Less rear loosens entry, more rear tightens throttle / exit. To much, i.e 4 link 57%, 2link 58% has a negative effect. Maybe this will help somebody Phantom309
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Post by duckhnter83 on Jun 24, 2014 8:27:37 GMT -6
I don't mean to be a dick but I can't understand any of your gibberish flipflop. Its just so many ideas thrown in together that has no direction or clear answers.
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Post by flipflopoo1oo on Jun 24, 2014 23:31:25 GMT -6
Sorry guys but after 35 years it does get technical! Trying to give out too much! Keep me in line! I never minded any of our cars starting in the rear! So you want easy answers to the direction of getting to the front! Please point out anything not clear! Most is just not believed to happen in this manner and can't with most setups! Happy to help simplify any you cant understand!!! Most have trouble keeping up with my train of thought! I know of two that can and many who don't care to even try as long as the are still winning! About tenth place they start to ask simple questions again! More questions should create shorter direct answers! You guys are holding back! If you have input, answers or questions throw them out there! I do give one on one help in messages! Most seem pleased as they got faster! Grammar is not my strong suit, winning differently is!
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