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Old 10-15-2013, 12:13 PM   #1
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Default Planning a FP (F-Prepared) autocross build

Looking into building a Miata for FP autocross for next season. FP is the prepared class for the MSM, but basically I'm looking to build a turbo version of this:



Being that the rules for prepared are so open, the only items that correlate with the MSM are the NB chassis and the BP4W head. Everything else is wide open.


I plan on running MS2
Turbo components are still TBD, but I'm leaning toward a setup built around the EFR6258
6spd with 4.1 or 4.3 and 20x10 slicks (2-3 gear for AX)
I want to use a later NB ABS system. (I've been driving BMWs for a few years now, and I have to say having ABS for autocross is nice.)


I'd like to solicit your opinion on what chassis to start with...

1. NB2 with 6spd and ABS, then retrofit the BP4W head?

2. Start with a MSM and sell off all the extra crap to offset the (smoking crack) price?

3. Start with a 99-00, and add ABS and 6spd if necessary?


I'm really questioning the wiring aspect. I know I could start from scratch and make my own harness, but I'd rather not.


Thoughts?
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Old 10-15-2013, 02:09 PM   #2
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Id probably opt for option one.

It should offer the best blend of low cost of entry, and only having to mess with mechanical bits. I hate electrical, so eliminating the need to retrofit abs and make a harness would be a bonus to me.
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Old 10-15-2013, 05:17 PM   #3
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You posted a picture of an E-Production Club Racing miata. I believe that is significantly different than an F-Prepared autocross car.


OH, and I vote option 1 too. Seems the easiest and most cost effective?

Last edited by Efini~FC3S; 10-15-2013 at 05:18 PM. Reason: T-t-t-t-t-t-typooooo
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Old 10-15-2013, 05:17 PM   #4
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You are going to want wider rubber than those 20x10, I assume on 13s. Gearing is one thing, but my car with the new/more powerful motor was unlaunchable on those FA bias plys. Your quoted tire choice is fine for DP with less power and less weight. You are going to want to plan on 15s or even 16s for wider than 10" wheels. You have several hundred pounds of weight more than DP cars and you better have at least 50% more power too.

My recommendation is either the Avon 10.7x21.5-15 or the Hoosier 23.5X11.0R16 if it comes out in the super secret R75A.

Center of gravity will suffer but I think you'll just end up roasting those 20s. Plus Hoosiers in that size wear horribly on the local (national champion for the last 3 years) DP car.

And on the 2-3 shift, plan on pain. My XP car occasionally has issues with getting 3rd when courses require it. Which is very rarely as I'm geared to 72 in second. And that is even with Delrin motor mounts and solid metal diff mounts (near unobtainium now).

Otherwise, an NB2 and snag a BP4W head would be my vote. ABS isn't too hard to add but you'll have "fun" fab/swapping brake lines. If you want it get it already done. On stock cars it isn't in a bad location so you'll be unlikely to want to relocate it.
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Old 10-15-2013, 05:18 PM   #5
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Quote:
Originally Posted by Efini~FC3S View Post
You posted a picture of an E-Production Club Racing miata. I believe that is significantly different than an F-Prepared autocross car.
He just want to build a windshield less NB with giant flares. :P
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Old 10-15-2013, 05:24 PM   #6
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I would do an NB2 with the ABS already and put on the MSM head, with a 6758. As someone using a 6758 to auto-x, I think the 6258 would only have an advantage if I wasnt able to make as much grip as I do now and had slightly lower cornering speeds. I would be looking at a 15" wheel avon for tires. And I would be paying attention to the Jerico 4 speed thread on here.
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Old 10-15-2013, 06:24 PM   #7
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Quote:
Originally Posted by mcfandango View Post
He just want to build a windshield less NB with giant flares. :P
And I have just the flares for him. Nopro NB's, brand new in their box from Japan. Holla, they're so for sale.
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Old 10-15-2013, 06:40 PM   #8
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Quote:
Originally Posted by mcfandango View Post
You are going to want wider rubber than those 20x10, I assume on 13s. Gearing is one thing, but my car with the new/more powerful motor was unlaunchable on those FA bias plys. Your quoted tire choice is fine for DP with less power and less weight. You are going to want to plan on 15s or even 16s for wider than 10" wheels. You have several hundred pounds of weight more than DP cars and you better have at least 50% more power too.

My recommendation is either the Avon 10.7x21.5-15 or the Hoosier 23.5X11.0R16 if it comes out in the super secret R75A.

Center of gravity will suffer but I think you'll just end up roasting those 20s. Plus Hoosiers in that size wear horribly on the local (national champion for the last 3 years) DP car.

And on the 2-3 shift, plan on pain. My XP car occasionally has issues with getting 3rd when courses require it. Which is very rarely as I'm geared to 72 in second. And that is even with Delrin motor mounts and solid metal diff mounts (near unobtainium now).

Otherwise, an NB2 and snag a BP4W head would be my vote. ABS isn't too hard to add but you'll have "fun" fab/swapping brake lines. If you want it get it already done. On stock cars it isn't in a bad location so you'll be unlikely to want to relocate it.

Hmmm good information.

I ran the 23.5x11x16s on 16x11s on my LS powered XP car. Fitting those monsters took a lot of cutting, but well worth it. I am enticed by the CG of the 13s and was hoping to get them to work. 10in wheel width limits my options, but I guess I have some more homework to do.

2-3 shift does suck, but it was an easy button in regards to gearing. 23.5 with a 3.6 rear gives me 66mph @7800 rpms, but I doubt that will be enough.

Jerico or similar is always an option, I'm not really sure I want to go there just yet.


Thanks for the input....You guys have brain cells stirring.
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Old 10-15-2013, 06:57 PM   #9
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Quote:
Originally Posted by fourwhls View Post
I am enticed by the CG of the 13s and was hoping to get them to work. 10in wheel width limits my options, but I guess I have some more homework to do.

2-3 shift does suck, but it was an easy button in regards to gearing. 23.5 with a 3.6 rear gives me 66mph @7800 rpms, but I doubt that will be enough.
Then build a VVT powered DP if you want 13s. I'm not sure that is the "right" option in DP either. My 15x10 6UL's really don't change the width of the car over the Spinwerk 13x10's I ran. Grip is a huge part of autocross.

FYI- There is a new tire coming out from American Racer. 23.5x10-15. Based off the asphalt slick they currently make. It currently is in the system as "autocross special". I have a set on order to compare to the Avons I listed above (in A15 compound). It has a stiffer sidewall construction and "more rubber". Not sure what the more rubber means. Just what I was told when I talked to the regional distributor about ordering some.

Most of the local FP contingent is highly interested in the R75A coming out next year.

Only reason I haven't build an F Prepared Miata is I'm too lazy to find a new chassis.
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Old 10-15-2013, 10:57 PM   #10
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Old 10-16-2013, 06:50 AM   #11
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Originally Posted by jacob300zx View Post
I seriously considered building an Exocet. I even picked my options and colors and was to the point where I just need to hit the submit button, and pulled the plug.

I've driven a 500hp/tq 2200lb Miata. I couldn't imagine how insane that combination would be at 1500lbs.
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Old 09-07-2015, 01:58 PM   #12
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Time to revive an ancient thread. I opted out of the FP car in '13 and decided to play in the Street Touring world for the past 2 years. It's been fun, but my desire to tinker is back, so I'm looking at options for '16.

I've stumbled across a '04 MSM for a really good price. It is not a show car and IMHO, a really good candidate for a FP car.

Did the American Racer autocross compound ever materialize? I ran the softer road race compound on my LS6 car and they worked great for local events and were CHEAP.

EFR6258/6758 still the goto turbo?
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Old 09-08-2015, 10:15 AM   #13
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Quote:
Originally Posted by fourwhls View Post
Time to revive an ancient thread. I opted out of the FP car in '13 and decided to play in the Street Touring world for the past 2 years. It's been fun, but my desire to tinker is back, so I'm looking at options for '16.

I've stumbled across a '04 MSM for a really good price. It is not a show car and IMHO, a really good candidate for a FP car.

Did the American Racer autocross compound ever materialize? I ran the softer road race compound on my LS6 car and they worked great for local events and were CHEAP.

EFR6258/6758 still the goto turbo?
Look at the new Trackspeed manifold for the EFR turbos. I'm part of the original group buy for it, but it looks AMAZING. Trackspeed EFR Turbo Manifold 1.8L
All the important stuff is at the end

I looked up the weights for prepared cars and if you were to keep the stock displacement of 1839cc, you end up with a final weight of 2206.8 lbs, assuming you use 10" wheels, otherwise, add 100lbs. (0.75 piston engine+0.45 FI)x1839cc. Right now, my full interior car with leather weighs 2390. Looks like you can basically gut the car to the extent of the rules and add your ballast back in the ideal spots.
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Old 10-20-2015, 01:05 PM   #14
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Planning, planning, planning.....

Not happy about this and have submitted a letter to the SEB to allow coolant re-routes on the Miata engines.

O. Cooling System
5. The direction of water flow through the engine shall not be changed from that which was original for the engine unless authorized in Appendix A.
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Old 10-20-2015, 01:08 PM   #15
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Quote:
Originally Posted by fourwhls View Post
Planning, planning, planning.....

Not happy about this and have submitted a letter to the SEB to allow coolant re-routes on the Miata engines.

O. Cooling System
5. The direction of water flow through the engine shall not be changed from that which was original for the engine unless authorized in Appendix A.
I don't see how that makes the reroute illegal, its still a standard flow direction coolant system.
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Old 10-20-2015, 01:53 PM   #16
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The hot water exit the front of the head to the radiator in stock configuration. It exits the rear of the engine to the radiator when rerouted.

Are you saying that it's not illegal because the coolant paths inside the head are not changed?



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Old 10-20-2015, 02:16 PM   #17
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Coolant still goes from the bottom of the block to the head. Direction is still the same. Front or back of the head doesn't matter. Heck even stock coolant flows out both ends so even if you take the rule the way you are then it's still fine.
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Old 10-20-2015, 02:20 PM   #18
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Hmmm, I was just looking at flow path to/from the radiator. Situation averted....Back to planning.
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Old 10-20-2015, 03:22 PM   #19
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First stab at engine specs:

I plan to run E85 and will be building the '04 MSM Engine

What am I missing? Comments/Suggestions?

Bottom End:
Supertech 11:1 Pistons
Manley Rods
ACL Main/Rod bearings
Billet Oil Pump
Supermiata/ATI crank damper
Crank scrapper
ARP Head / Crank studs

Top End:
Supertech Valves (+1 S/S intake, +1 Inconel exhaust)
Supertech Valve springs (double spring)

Fuel:

IDI 1000 Injectors
Walbro 416 Fuel pump

Turbo:
BorgWarner EFR6758
Trackspeed manifold

Management:
MSPNP Pro
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Old 10-21-2015, 11:57 AM   #20
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That was my build for 5 hours.. why go oversize valve with turbo ? Little more boost will do.

BTW I might have 11:1, Manley rods for sale if the plan works out... And check my head in FS section, could save you some $$$
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