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Ferrari Drop Gears http://gemellocattivo.com/forum/viewtopic.php?f=7&t=192 |
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Author: | mk e [ Sun May 01, 2016 7:55 pm ] |
Post subject: | Re: Ferrari Drop Gears |
Welcome Chis...and nice job on reviving the bikini thread Drop changes are not so simple or cheap. Nick Forza was importing a race set I think but they were straight cut so loud and I think I heard around $10k for the set. there was some talk about making a helical set if i10 sets were ordered...again 5k-10k per set is coming to mind. But these were 308 not 328 setups...don't know what's out there for the 328 gear box. What I did was swap the top and bottom gears which was not so easy and I still haven't actually tested it yet. For you I guess besides the money I think it depends on how you drive. I turbo is not going to help you off the line much so changing the gearing will likely slow you down for the fist 100-200 feet....I'd guess. On my supercharged car keeping the wheels from spinning off the line was an issue and I expect the same issue with the 5.4 line V12 so I thinkg the change would help acceleration a bit in my case. After that it shouldn't matter acceleration wise but get you the reduced cruising ropm or higher top speed I'm guessing you're after? |
Author: | 328turbo [ Thu Sep 15, 2016 8:30 pm ] |
Post subject: | Re: Ferrari Drop Gears |
Yes, I'm thinking better overall performance. The car lights up the tires pretty good but not as hard as a big inch American V8 would w the same tires. It's pretty controllable, but it seems to rev very fast & 1st gear feels pretty useless. So I'm really just thinking about longer gears to make the most of the turbo's power. Lower cruise rpm and a higher ceiling for top end would be added perks. But this vehicle can probably already hit a top speed that a car this small and light probably shouldn't ever see. |
Author: | mk e [ Fri Sep 16, 2016 9:06 am ] |
Post subject: | Re: Ferrari Drop Gears |
328turbo wrote: ..... 1st gear feels pretty useless. . That is certainly what I found on the supercharged engine. 1st gear was good for idling around the parking lot, but even look at the throttle and the tires were spinning or you were at redline. I stopped using it for rapid acceleration runs and stuck to 2-5, which also solved the 1-2 dog leg issue. If only new gears weren't so stupid expensive I spoke to someone about making a single new ratio helixal cut set, but even then was quoted $5k each IIRC for 10 sets which I didn't have buyers for so I moved on. |
Author: | TheDarkSideOfWill [ Wed Jan 04, 2017 2:52 pm ] |
Post subject: | Re: Ferrari Drop Gears |
And actually... since the drop gears are a THREE gear set with an idler in the middle... the ratio can't be changed without moving the idler. So it's literally impossible with just a parts swap. Edit: The overall ratio will always be the ratio of input-to-idler shaft center to idler-to-output shaft center. |
Author: | mk e [ Wed Jan 04, 2017 3:02 pm ] |
Post subject: | Re: Ferrari Drop Gears |
They do it by splitting using a new outer cover with more room and outer bearings like the 328, then and inner/outer gear sets with the idler having 2 gear. You get a set with 8 or 12 ratio choices in the $15k kit I saw. or you could simply relocate the idles |
Author: | TheDarkSideOfWill [ Wed Jan 04, 2017 3:10 pm ] |
Post subject: | Re: Ferrari Drop Gears |
Actually, I was wrong about not being able to change the overall ratio... I just wasn't playing with enough variables in my model. If the two shaft separations are the same, the overall ratio will always be 1:1. But if the shaft centers are different, then multiple overall ratios are possible. I'd attach a file, but the form won't let me upload a .xlsx |
Author: | mk e [ Wed Jan 04, 2017 8:03 pm ] |
Post subject: | Re: Ferrari Drop Gears |
you can upload anything as a .zip The idler does nothing in the gear ratio as you say but the centerline location matters. You can't changed the pitch diameter without changing the centerline location. The kit uses an idler with 2 gears is part of the ratio and gives you a lot of options without moving the centerline |
Author: | TheDarkSideOfWill [ Sun Jan 08, 2017 1:27 am ] | ||
Post subject: | Re: Ferrari Drop Gears | ||
mk e wrote: you can upload anything as a .zip The idler does nothing in the gear ratio as you say but the centerline location matters. You can't changed the pitch diameter without changing the centerline location. The kit uses an idler with 2 gears is part of the ratio and gives you a lot of options without moving the centerline Doesn't it need a deeper side cover, then? The ratios can be changed without changing the shaft separations, but the "input" side and "output" side have to change together to make the numbers work out. The range of adjustment ends up being limited for practical reasons. I don't know the original shaft center dimensions from the 308 transmission, so my model is only good as a demonstrator of the math, rather than telling what's workable with the existing metal.
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Author: | mk e [ Sun Jan 08, 2017 8:45 am ] | ||
Post subject: | Re: Ferrari Drop Gears | ||
Your math looks right...but the caution is you end up with unworkable gear sizes pretty quickly so only small changes can be done that way. Yes a deeper cover...found a pic. It looks like they add an outer bearing on the top only but the whole cover looks an inch deeper plus the bearing on top.
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