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Old 12-10-2010, 05:44 PM   #41
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RJ, the 12/8 setup with RB tubular front and stock rear should be around 57% which imho is great on most tracks. Are you using the tubular setup on the calculator?
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Old 12-10-2010, 08:42 PM   #42
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RJ, the 12/8 setup with RB tubular front and stock rear should be around 57% which imho is great on most tracks. Are you using the tubular setup on the calculator?
Yea, my mistake my current setup is 53.3%. Still hoping to make it to BW on the 19th. May have a splitter added by then... for which I'll have to raise it up the height more.
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Old 12-11-2010, 04:21 AM   #43
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I wouldn't add a splitter to a 53.3...
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Old 12-11-2010, 12:02 PM   #44
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why would you have to raise it up for a splitter? a splitter is at most 3/8'' thick if you went with birch.

drove jakes dad's car with 12k frt. on re-11 and it felt great.
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Old 12-11-2010, 03:50 PM   #45
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Originally Posted by spoolin2bars View Post
why would you have to raise it up for a splitter? a splitter is at most 3/8'' thick if you went with birch.

drove jakes dad's car with 12k frt. on re-11 and it felt great.
Because he'd be scraping... not sure on what, but maybe he uses it as a street car. Mentioned it before.
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Old 12-11-2010, 09:32 PM   #46
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That makes sense. If that is parallel to the ground so is the tie rods.
Not really how that works, sorry.
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Old 12-12-2010, 08:20 AM   #47
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why would you have to raise it up for a splitter? a splitter is at most 3/8'' thick if you went with birch.

drove jakes dad's car with 12k frt. on re-11 and it felt great.
^Good to know. The spring rate change may be necessary w/ the splitter.

Too bad none of you are in SoCal. My lip alone scrapes all day at the bowl of SOW CW as it is. Can't imagine how much more it'd scrape w/ the splitter. I tried to make it as quick release as possible so I don't have to use it on the street (aside from the trip to the track), but I can't find any cheap quick release mechanisms when I have it bolted to the front of the subframe.
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Old 12-12-2010, 08:53 AM   #48
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Perhaps you should raise the car, then. My splitter scrapes in one spot, under compression exiting the Corkscrew at Laguna Seca. Front ride height is like ~11.8".

I also wouldn't add a splitter to any car without a wing/significant diffuser along with it. Splitters create significant downforce and a car with a splitter/no wing will be LOOSE at speed.
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Old 12-13-2010, 03:54 PM   #49
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Perhaps you should raise the car, then. My splitter scrapes in one spot, under compression exiting the Corkscrew at Laguna Seca. Front ride height is like ~11.8".

I also wouldn't add a splitter to any car without a wing/significant diffuser along with it. Splitters create significant downforce and a car with a splitter/no wing will be LOOSE at speed.
I don't know my hub-fender height is off hand, but it is 4.125" at the lowest part of my front beat up pinch welds. IIRC my hub fender is 11.5 ish, but I stopped measuring from there as my fenders are rolled and pulled. My lip is about a cigarette box from the ground w/o the splitter, which is around 4" IIRC

When you say wing/significant diffuser, are you saying AND or OR? I was going to try out an APR wing with the splitter... with and without the wing and see how I like it. My rear bumper is cut, and the rear end is hard to design a diffuser for, without already covering the rest of the undercarriage. I'm mainly doing the splitter for fun/data. If there's too much downforce, I will cut off the front of the splitter. It only extends about 2-3" from my lip in certain areas. My main concern was to start with smoothing out the underside of the car.

I am on stock power btw, and 1.6L at that, so I may get flamed, but with such a high CD (0.38), I'm mainly trying to reduce that-- the splitter is the cheapest option to start.

I'll be as low as I can, so to keep it somewhat on topic, this just points out that the optimal height is the lowest you can go dependent on your setup.. that doesn't bottom out anything.
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Old 12-13-2010, 04:24 PM   #50
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I was going to try out an APR wing with the splitter... with and without the wing and see how I like it.
Don't do a splitter without a wing. If you want to try combos, try no aero (you already have), try just wing and then try splitter and wing.
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Old 12-13-2010, 10:54 PM   #51
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greentreee-what springrate are you running. At 11.5ish I hope your at 700# or so.
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Old 12-13-2010, 11:35 PM   #52
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Wing OR diffuser. I added the APR wing first and the car pushed really, really badly. I then added the splitter and the car was balanced again - the assumption I take from that is that the splitter makes as much downforce as the wing does, or at least fairly close to it.

I wouldn't put aero on a stock 1.6-powered Miata - the additional drag will absolutely kill any cornering speed improvements you end up with.
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Old 12-13-2010, 11:52 PM   #53
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My main priority was to decrease DRAG, reduce lift. As of now I am not seeing any speeds above 90mph at SOW or BW. I made a splitter diffuser in my other car-- without them, the rear would get twitchy at the front straight of SOW CW, at the slight R... the splitter did not extend past the lip, and the diffuser was elementary-- simple, flat bottom, minimal angle (never measured the exact angle) and 2 fins... the rear was stable when I tested it.

For the splitter I was trying to DECREASE drag primarily... adding tire spats out of rubber mudguards for example. (and I also added some blockers under the splitter in front of the tire). It may not be the same at all, but I pay attn to S2000s (especially when they zoom by me all the time) and aero does wonders for them w/ stock power. I was thinking small aero improvements wouldn't hurt... and if anything, I can trim down the splitter to be flush with the lip, and so at the very least, it'd be a functional undertray. Am I going about this the wrong way? I've already laid down some coats of paint on the splitter so it's too late to turn back... I figured I can just cut if it's too extreme.

Eventually I want the entire undercarriage to be smooth, so I started with the splitter...
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Old 12-14-2010, 05:02 AM   #54
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A diffuser mostly reduces lift at the front ..thats where the velocity stays highest and pressures low.
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Old 12-14-2010, 11:11 AM   #55
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What effect does a small trunklid spoiler have?
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Old 12-14-2010, 06:11 PM   #56
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A diffuser mostly reduces lift at the front ..thats where the velocity stays highest and pressures low.
A diffuser at the end of the splitter maybe. A diffuser in the rear would help with the rear.

I just measured my hub fender. Slightly on unlevel ground as I am at work, but my pinch welds are still the same measurement as in my garage, 4.125F 4.375R, but hub to fender height shows greater front to rear height variance with 11.25"F and 11.875"R. As previously stated, my FR and RR fenders are rolled AND pulled ridiculous amounts which is why I stopped measuring at hub-fender.

I also use 20mm adaptors with the 6ULs, so that inevitably messes with the wheel rate ratio... probably making it worse than the "1.6:1" ratio I've previously read.

EDIT: Was doing some M.net reading and found this:
http://forum.miata.net/vb/showpost.p...2&postcount=63

Last edited by greeenteeee; 12-17-2010 at 03:13 PM.
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Old 12-14-2010, 06:45 PM   #57
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Why in the hell are you running 20mm spacers?
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Old 12-14-2010, 07:06 PM   #58
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Why in the hell are you running 20mm spacers?
Last bit of "form>function" left on my car.

Plus I have a rear stud I need to replace. For now, having the 20mm spacers w/ fresh studs is better than mounting/dismounting wheels all the time on the damaged stud--threads are somewhat damaged, it was a used hub, lug nuts still thread on, I'd rather not swap wheels using that 1 stud. Won't be necessary once I try some x9s. Yea yea, who needs x9s with stock power. But with the same weight as x8s, how can it hurt?
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Old 12-15-2010, 12:10 AM   #59
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Too much tire=too much grip=slower times
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Old 12-15-2010, 12:20 AM   #60
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Originally Posted by wannafbody View Post
Too much tire=too much grip=slower times
Grip = good.

Rolling resistance = bad.

Might as well buy the 9's if you ever plan on making more than 130whp.
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