Just another K swap...
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Joined: Sep 2011
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From: Sierra Vista, AZ
I find that my 10ae downshifting 6-5, or like you mentioned the 4-5-4 shifts to be interesting. Like, if I forget about it, I'll be unable to find 5th in that downshift, or the upshift to it. Or if I think about it too hard, I might miss it too. It's not a bad feeling shift when you nail it, to me it just seems the location of that gate, and my brain being hard wired for a 5 speed, makes it tricky.
With a 5 speed every single gear is a no brainer, autopilot style. I've never had an issue on any of my 5 speeds.
Not to say I think the 6 speed is bad, and that's with a stock shifter. I bought a miataroadster shifter to give that a shot on my new 6 speed in hopes it helps. Also I figure once I get some 6 speed seat time on track I might hammer it into my brain better. I do believe that 6 speed ratio spread is technically optimal over the 5 speed, I.E. using 4/5/6 instead of 3/4/5 has a better (closer) spread for ultimate lap time. But that's older data from some of the CA track guys I read on here years ago, not sure if that logic is still the prominent thought now days.
With a 5 speed every single gear is a no brainer, autopilot style. I've never had an issue on any of my 5 speeds.
Not to say I think the 6 speed is bad, and that's with a stock shifter. I bought a miataroadster shifter to give that a shot on my new 6 speed in hopes it helps. Also I figure once I get some 6 speed seat time on track I might hammer it into my brain better. I do believe that 6 speed ratio spread is technically optimal over the 5 speed, I.E. using 4/5/6 instead of 3/4/5 has a better (closer) spread for ultimate lap time. But that's older data from some of the CA track guys I read on here years ago, not sure if that logic is still the prominent thought now days.
Originally Posted by OptionXIII
Hey Roda, can you point me to where you got that gear ratio plotting tool? I've not found one I really like... one that looks like that!
What I posted was just screen shots of part of the page... some pretty useful tools there.
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Looking at your gearing graphs... is 7400 your redline or the point at which you're actually shifting? I wind my K out to 8000, which may be contributing to my bolts-falling-off problems, but if your redline is really 7400, that seems low for a K. Not sure how much those extra 600rpm would help, but they're worth considering, IMHO.
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Also, I just went back to the MR shifter after losing the pin I had made to lockout extraneous gears with my IRP shifter. I've gotten a lot better at the 4-5 shift - something @codrus said to me about shifting from 4 to neutral and then to 5 has really clicked, only a couple of mis-shifts since then. I kinda bop it into the self-centering neutral, then make the shift into 5. It feels slow as hell, but it's consistent.
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Thread Starter
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From: Sierra Vista, AZ
I have the limiter set at 7600, shift at 7400 +/-
The K24 should rev to 8k, yes. But everyone I see doing it in a Miata swap has eventually had issues. I figured 7500 was a "safeish" limit for a stock cammed engine without balance shafts, and yes I'm leaving some RPM on the table, but **knocks wood** I haven't experienced stuff loosening, or vibration related failures to the degree that others have. I have experienced some issues, but they've mostly been minor, and after the first few heat cycles everything seems to have taken a good set.
It's a trade I'm willing to make.
The K24 should rev to 8k, yes. But everyone I see doing it in a Miata swap has eventually had issues. I figured 7500 was a "safeish" limit for a stock cammed engine without balance shafts, and yes I'm leaving some RPM on the table, but **knocks wood** I haven't experienced stuff loosening, or vibration related failures to the degree that others have. I have experienced some issues, but they've mostly been minor, and after the first few heat cycles everything seems to have taken a good set.
It's a trade I'm willing to make.
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Joined: Jul 2014
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From: Milwaukee, WI
I have a tractive force calculator linked in my signature that can be used to helpfully plot out gearsets and powertrain changes just like this.
I had 6spd/4.3 in my K24 (rev limit at 8500 for excursions, but typically would shift at 8k). I transitioned back to the 5spd/4.3 combo and liked it much more due to being less busy with the shifter at my tracks as well. The car had plenty of power to pull through the small powerband segment where the 6spd had an advantage over the 5spd on paper. I think you're making the right move here overall Roda.
I had 6spd/4.3 in my K24 (rev limit at 8500 for excursions, but typically would shift at 8k). I transitioned back to the 5spd/4.3 combo and liked it much more due to being less busy with the shifter at my tracks as well. The car had plenty of power to pull through the small powerband segment where the 6spd had an advantage over the 5spd on paper. I think you're making the right move here overall Roda.
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Thread Starter
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Joined: Sep 2011
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From: Sierra Vista, AZ
I have a tractive force calculator linked in my signature that can be used to helpfully plot out gearsets and powertrain changes just like this.
I had 6spd/4.3 in my K24 (rev limit at 8500 for excursions, but typically would shift at 8k). I transitioned back to the 5spd/4.3 combo and liked it much more due to being less busy with the shifter at my tracks as well. The car had plenty of power to pull through the small powerband segment where the 6spd had an advantage over the 5spd on paper. I think you're making the right move here overall Roda.
I had 6spd/4.3 in my K24 (rev limit at 8500 for excursions, but typically would shift at 8k). I transitioned back to the 5spd/4.3 combo and liked it much more due to being less busy with the shifter at my tracks as well. The car had plenty of power to pull through the small powerband segment where the 6spd had an advantage over the 5spd on paper. I think you're making the right move here overall Roda.
Good to hear your actual experience matches my sim experiments.
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Thread Starter
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From: Sierra Vista, AZ
Ordered a Miata Roadster shifter for the 5 speed. I looked at the CAE and a couple other 'billet' options and decided to go with what I know (and have been happy with). Would have been nice if they could have made the 6 speed and 5 speed shifters the same... LOL.
Now that it's here, and the NC is mostly wrapped up, I need to motivate myself to swap the transmissions....
Now that it's here, and the NC is mostly wrapped up, I need to motivate myself to swap the transmissions....
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From: Sierra Vista, AZ
Still haven't started the transmission swap. Too damn hot in the shop lately to get much done.
0600 this morning...
I did start fiddling with some ideas for Splitter V3. On V2 I wanted to incorporate a rounded underside on the leading edge to discourage flow separation, and I did it free hand. I have no way to quantify any improvement, but I didn't like the uneven results of sanding it freehand. So, I bought a Harbor Freight cordless router and a 'thumbnail' router bit. I'm already invested in the HF 20v ecosystem (and most of the tools are pretty good), so the router fit right in. The 'thumbnail' bit gives a curved edge with an 'oval' profile, with the long axis horizontal.
Router
Test on a piece of 3/4 ply
Test on my old V1 splitter
I also intend to incorporate splitter ramps in V3, though I still need to order a set. Probably going to end up with the 9 Lives version, but $200+ for some molded plastic is a little irritating.
Also noodling diffuser ideas for the rear...
0600 this morning...
I did start fiddling with some ideas for Splitter V3. On V2 I wanted to incorporate a rounded underside on the leading edge to discourage flow separation, and I did it free hand. I have no way to quantify any improvement, but I didn't like the uneven results of sanding it freehand. So, I bought a Harbor Freight cordless router and a 'thumbnail' router bit. I'm already invested in the HF 20v ecosystem (and most of the tools are pretty good), so the router fit right in. The 'thumbnail' bit gives a curved edge with an 'oval' profile, with the long axis horizontal.
Router
Test on a piece of 3/4 ply
Test on my old V1 splitter
I also intend to incorporate splitter ramps in V3, though I still need to order a set. Probably going to end up with the 9 Lives version, but $200+ for some molded plastic is a little irritating.
Also noodling diffuser ideas for the rear...
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Ooooh, looks like I have to grab myself a router here soon. End result looks clean.
What AOA are you running your wing at currently? The ~10% DF increase with ramps in the front seems like it would be enough to noticeably change a car's aero balance, although I haven't seen any accounts I can remember of folks adding ramps then saying they needed to make changes to the rear.
I plan on adding ramps after our last race this season but am curious on how much tinkering that will trigger. I've got my wing set at 0* AOA currently, so I can nose it down a bit if need be. However, the wing did feel like a parachute on the straights at anything above 2* on when I first put it on. You're pushing more power than I am, though, so maybe having to steepen your wing wouldn't be as big of a deal.
What AOA are you running your wing at currently? The ~10% DF increase with ramps in the front seems like it would be enough to noticeably change a car's aero balance, although I haven't seen any accounts I can remember of folks adding ramps then saying they needed to make changes to the rear.
I plan on adding ramps after our last race this season but am curious on how much tinkering that will trigger. I've got my wing set at 0* AOA currently, so I can nose it down a bit if need be. However, the wing did feel like a parachute on the straights at anything above 2* on when I first put it on. You're pushing more power than I am, though, so maybe having to steepen your wing wouldn't be as big of a deal.
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Thread Starter
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From: Sierra Vista, AZ
I'd have to check my notes, but I think I'm already at ~4-5* on the wing. Anything I do to the rear will be in a diffuser, which I hope will be enough to balance the front without more wing, or will even allow reducing wing angle. I really should do the rear diffuser first (and I probably will), as I don't want to push my balance any further forward than it already is. The main thing I'm looking for with ramps is more efficient wheel well evacuation and reduced drag... but I do think I need to do some serious fender mods to see real gains there.
For the rear, I'd like to raise the trunk floor and muffler to gain space for the diffuser, but I'm worried about heat management around the muffler... still noodling that one.
And then there's barge boards to consider...
It's all a package, but difficult to do everything at once. LOL
For the rear, I'd like to raise the trunk floor and muffler to gain space for the diffuser, but I'm worried about heat management around the muffler... still noodling that one.
And then there's barge boards to consider...
It's all a package, but difficult to do everything at once. LOL
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Newb
Joined: Apr 2024
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There is a company local to me, RGR Engineering that also sells some splitter ramps. Link below for reference. He also sells a diffuser, however I don't think it'd be so applicable for you if you're willing to chop up the trunk.
https://www.rgr.engineering/product/...splitter-ramps
https://www.rgr.engineering/product/...splitter-ramps
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Thread Starter
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From: Sierra Vista, AZ
I like a lot of RGRs stuff, and saw some in person at FM this summer. I don't like that their splitter ramps mount from the bottom... otherwise, they're probably the most affordable I've found.
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From: Sierra Vista, AZ
Took about a month off from the Miatas... we were attending a friend's daughter's wedding in MT, so we decided to make a 3 week trip out of it, spending time in MT, WY and CO. A few pics...
Would have liked to have had the NC along for this road (Chief Joseph Scenic Pkwy), but the Jeep was needed for most of what we would be doing...
Would have liked to have had the NC along for this road (Chief Joseph Scenic Pkwy), but the Jeep was needed for most of what we would be doing...
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^^ 
When's the NA's next event? Interested to hear if your times and general enjoyment on track improve from the lessened amount of shifting.
I'm still sitting on the 5 speed for my car as well. Kinda curious if swapping that in will be faster once I add power next year...
When's the NA's next event? Interested to hear if your times and general enjoyment on track improve from the lessened amount of shifting.
I'm still sitting on the 5 speed for my car as well. Kinda curious if swapping that in will be faster once I add power next year...
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Thread Starter
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From: Sierra Vista, AZ
Originally Posted by Z_WAAAAAZ
When's the NA's next event? Interested to hear if your times and general enjoyment on track improve from the lessened amount of shifting.
Five speed is in... need to fill fluids, install exhaust and shifter and it should be good to go. Now I just need to remember the 5 speed shift pattern...
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