Spec Miata buildsheet/discussion

[fndrbndr]

OK, getting back to the car, I suggested last night to Juan that we could figure out how close this car is to the real thing by comparing laptimes.  We ran (among other tracks) Road Atlanta.  In five laps, I had three that were 1:40.xxx and a low 1:39.  First lap was about 1:45, I think.  I looked online, and...
http://www.trackpedia.com/wiki/Road_Atlanta#Typical_Lap_Times
Trackpedia lists a typical laptime for a spec miata at 1:44.  At first, I was a little frustrated by this, because I was SO careful to be as faithful to the series specs as I could.  Then, I found the problem.  With restrictor plates (required at all tracks), the cars run about 115 hp.  We're running 146.  Bearing that in mind, I guess I know that this isn't as close as I wanted, but I still feel like it's pretty good.  30 hp on that back straight without losing grip is probably worth 3-4 seconds.  That is, after all, a missile track, and by SM standards, we're running loads of power.  Factor in my seat time in miatas in Forza, and I guess I feel OK about this project.  Comments?

[Spiny Anteater]

http://www.carfolio.com/specifications/models/car/?car=126269

This site says that the 2005 (I think that's the year isn't it?) MX-5/Miata 2 litre has a 6 speed box with a final drive of 3.72 and 6th gear of 0.83. Shame it doesn't list the other gear ratios. I wonder how close that is to the game figures?

I can reverse engineer a gear set using those values.  And determine how close Forza is to it.  I'll get 'roun tuit after I get done with these pesky Mustangs.

$

A bit more hunting and I found the 5 speed (1.8 litre, 2005 model) so that might save you a bit of time

1st: 3.136:1
2nd: 1.888:1
3rd: 1.330:1
4th: 1.000:1
5th: 0.814:1
Reverse: 3.758:1
Final drive ratio: 4.100:1

And then the current 6 speed 2 litre MX-5 which seems to use the same ratios as in the first post soon after...

Gear ratios:
1st  3.709
2nd 2.190
3rd 1.536
4th 1.177
5th 1.000
6th 0.832
Reverse 3.603
Final gear ratio 3.727

What really intrigues me though is the reverse gear - a total gear reduction of 15.41 for the 1.8 but 13.42 for the 2 litre. I guess that means they expect the 2 litres to be raced in reverse too!

[bimmerlovere39]

In my five laps, I managed consistent 39-40s with one 38.668. No clue what the first lap was.

I think 4-5 seconds faster isn't a big deal, considering the 30hp difference, plus the fact that there's no OMIGAWDIMGONNADIE factor in Forza

[BarbecuePete]

OK, getting back to the car, I suggested last night to Juan that we could figure out how close this car is to the real thing by comparing laptimes.  We ran (among other tracks) Road Atlanta.  In five laps, I had three that were 1:40.xxx and a low 1:39.  First lap was about 1:45, I think.  I looked online, and...
http://www.trackpedia.com/wiki/Road_Atlanta#Typical_Lap_Times
Trackpedia lists a typical laptime for a spec miata at 1:44.  At first, I was a little frustrated by this, because I was SO careful to be as faithful to the series specs as I could.  Then, I found the problem.  With restrictor plates (required at all tracks), the cars run about 115 hp.  We're running 146.  Bearing that in mind, I guess I know that this isn't as close as I wanted, but I still feel like it's pretty good.  30 hp on that back straight without losing grip is probably worth 3-4 seconds.  That is, after all, a missile track, and by SM standards, we're running loads of power.  Factor in my seat time in miatas in Forza, and I guess I feel OK about this project.  Comments?

I think you've done a great job putting these specs together Fndr, Im looking forward to some real good close racing with them tomorrow.... I thought also you might like a look at this... I found the site below which has specs for the UK version of Spec Miata called, MaX 5

In the UK version you are only allowed to run the Mk1, 1.6L versions which have less power than the new one that is in the game so the hp advantage was always going to happen beacause we can't run restrictor plates and we don't have the older version available... One slight differance I did notice between your cars and the UK version is that you are free to change the clutch as long as it still fits the standard flywheel..

I remember seeing someone saying about the slow shift times with standard gearbox, under these regs a clutch upgrade would be allowed and help with the slow shift change of the standard geabox.. Do the American regs actually say that the cars must run a standard clutch?

Website - http://www.max5racing.com/index.html

Full Tech Regs - http://www.barc.net/competitors/regulations/Max5Regs2008Ver01.pdf

[bimmerlovere39]

The shift time doesn't seem that bad with my car... 

I kinda of like it, it adds a little bit of punishment for unneeded shifts 

Anyway, I just dynoed the SM Fndr sent to me (measurements taken in ~250rpm increments):

[fndrbndr]

Yeah...the OMIGAWDIMGONNADIE factor probably isn't as much of a factor at RA as it would be elsewhere, though.  The runoff areas are all pretty generous.  I'd be far more worried on two wheels than four, but that's probably true at most tracks.

My original reading of the rules was that the only clutch allowed is either the stock one or the Mazdaspeed replacement.  I may have gotten that wrong, or be confusing it with the flywheel regs.  I'll check later, but I'm pretty sure that, at the very least, it wouldn't be a racing clutch.

[bimmerlovere39]

I don't know.  From the Chicane to the finish would be frightening, especially the last turn.

[fndrbndr]

True, but didn't they re-do the last turn specifically so that bikes can take it faster?

[fndrbndr]

http://forum.specmiata.com/cgi-bin/ultimatebb.cgi?/topic/39/90.html

I posted this in the lounge, but it has implications here, too.  The tire is still a DOT Toyo, spacer rules have changed to allow for a slightly wider tire.  When I get home, I'll check on whether this means adding a tire width upgrade.  That said, any ideas/preferences on the possibility of allowing a +1 to tire width?

[Fit4aking]

As I stated in the commentary section of Spanky's Speedshop, I've been going through and trying to decide what to do with my prize cars from my Asian career.  I have a good plan for most cars but I was unsure about the MX-5.  I like my Tiny Terror version in D-class but I don't want to replicate all of my Fit profile cars on the offline account.  What could I learn from that??  So I've been working on different things for most of the cars. 

I built out a Spec Miata per the build sheet on page one.  Only thing I changed were the wheels.  I used a set that was the same 25 lb lighter as were the Enkei's.  Can't remember which.  I didn't run the car after the upgrades so I don't have any practical input on it right now but I wanted to feel a bit more involved in the goings-on of the site and this project is right up my Asian alley.  I'll take a crack at Road Atlanta since that is the only track with lap times.

I know that this isn't a competition or an official challenge but in a spec series it could serve well to keep track of lap times.  Either as a way to see if the drivers are getting better or if the cars get tuned to the point that they are "perfect".  Not that any real spec series racers would share setups or laptimes but we're a different breed and I believe that the desire to improve everyone is the point of the site.  Also it may give those of us that are following offline the opportunity to have a line in the sand to aim for.

My 2cts on the trans discussion is to leave it totally stock.  I personally would love to have the ability to fine tune each gear for all the tracks and make the most use fo the cars limited powerband.  However, if the rules for the real series require the unit to be "sealed" than it should remain virtually "sealed" by keeping it stock.  I'm sure everyone here would play by the rules but it would absolutely remove any possibility of any questions.  Kinda like an ounce of prevention.

[fndrbndr]

Thanks for the input.  I'll check for some laptimes whenever I can, but here's what I can tell you from memory about mysetup:

Springs are as close as I could get to the real SM ones:  700 front, 350 rear, 27/19 mm's for ARB's.  (used those settings for in-game ARB settings.  I know it's not a precise conversion, but oh well)

At first, you'd think this would turn the car into an understeering pig.  However, it's still surprisingly drivable.  It has a little understeer, but it's very predictable, which is good for longer races, and probably not a bad idea for online races in general.  I think Bimmer uses settings from the Flyin Miata site, and his is pretty quick.  Let me know what you think about the car.

[bimmerlovere39]

FLYIN MIATA FTW 

[fndrbndr]

I saw a writeup recently of a turbo installation on a miata (I think it was an FM kit) that took the car to over 250hp.  That sounds insane, until you remember that this puts it in the same ballpark as the S2000.  I think the idea was to make the car competitive with corvettes and the like.  I forget which class the guy planned on running with it.

[Fit4aking]

Painted my spec'd out Miata last night and gave it a go.  Its a handful stock.  Not enough rear grip, pushy at speed, and the alignment is way off.  It desperately needed a tune.  The defaults were worse than the stock settings if you ask me.

I played with it a while and found a few things out about the monster.  The posted bias is way off.  52% wouldn't be that bad and was my starting point but it still didn't have enough rear grip and the car would turn in like noone's buisness on slow turns and push on the high speeders.  I got the tire temps in order to improve overall grip and get a feel for where the camber and such needed to be, then it was on to spring rates and such.  The SWR on her is pretty low at 66% so I figured stiffening was in order.  I jumped to 70% and made marginal gains, up to 78% and started losing ground.  I ended up back around 70% with a slightly taller car and some rebiasing.  I believe I ended up with 48% front bias to keep the rear planted but still had to change rear toe to -0.3 to balance the oversteer.  She still needs some work but I'm gathering information at this point.  Plus with a test track like Road Atlanta its very time consuming to test and tune.  Perhaps a QR test is in order to get this thing good all around.

I was a bit slower on the initial lap and running in the 1:46's, the high 1:46's but after that I was easily in the mid 1:39's.  The first turn was the meanest as I was either too fast or too slow trying to fight the over/under steer.  The only other problem was the double apex before the back straight.  I lost way too many miles per hour messing that turn up and it cost me dearly at the line.  More seat time on a shorter track is in order.

[fndrbndr]

RAS is a good track.  Road Atlanta full is fun, but definitely a place for racing, not hotlapping, at least in these cars.  The biggest lesson from seat time, at least for me, is to avoid shifting unless you must.