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SCCA D Mod build questions
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Author:  Kent2 [ March 3, 2016, 12:19 pm ]
Post subject:  Re: SCCA D Mod build questions
geek49203 wrote:
Kent2 wrote:
Book chassis is what I'll start with, thanks for the info on keeping it small.


The bug fix / update for "the book" is the Haynes book. It has a ton of the common mods done to the Book, as well as fixes a couple of mis-measurments, etc. PERSONALLY I'd use those plans, looking for someone who's got a Honda donor build going along the way. The Haynes is a 221 chassis.

http://www.amazon.com/Build-Your-Own-Sp ... 1844253910

https://haynes.co.uk/forums/index.php

There are plans around (and a few builds done, including at least one here) using the Miata as a donor.



Searching now, I'll take a look at it. Thank you for all the great info.
Author:  horizenjob [ March 3, 2016, 12:32 pm ]
Post subject:  Re: SCCA D Mod build questions
Quote:
Light, that is very light.


Just by door-slammer standards. You can do this, but you can't just throw heavy things at it. Would you run 13" wheels when you compete and can they fit over Miata bits?
Author:  Kent2 [ March 3, 2016, 12:36 pm ]
Post subject:  Re: SCCA D Mod build questions
horizenjob wrote:
Quote:
Light, that is very light.


Just by door-slammer standards. You can do this, but you can't just throw heavy things at it. Would you run 13" wheels when you compete and can they fit over Miata bits?


I'm fine with 13" wheels, I'll end up with wheels based on cost of tires though. 13-15 is fine with me.
Author:  wrightcomputing [ March 3, 2016, 1:07 pm ]
Post subject:  Re: SCCA D Mod build questions
Don't forget minimum weight includes driver. So you need to account for yourself in the build weight.

13" or 15" are the way to go for tires. You can get used qualifying tires (Formula Atlantic, Indy lights etc) from John Burget (JBRacing) for around $400 a set shipped to your home. The ideal size is 10" front and 14" rear as that is what the open wheel cars typically use. Make sure you build the chassis around the size tires you want. I had to completely redo my rear end to fit the 14" tires. The competitive guys typically buy new AVON or Hoosiers or both for Nationals and a set lasts about a year depending on number of drivers and events.
Author:  geek49203 [ March 3, 2016, 1:21 pm ]
Post subject:  Re: SCCA D Mod build questions
wrightcomputing wrote:
I had to completely redo my rear end to fit the 14" tires.


Uh, I hope you're referring to the car, but you did mention driver's weight, so....

At any rate, that 14" is the actual width of the inflated, ready to run tire? Cause I'm building on of Jack's Lola-ish body cars, and I still have time to budget a couple of inches for a possible wide set of tires... should probably figure, what, 15" or so?

Oh, sorry to hijack the thread, you may return to previous discussions about how American bodies don't fit, etc.
Author:  Kent2 [ March 3, 2016, 1:25 pm ]
Post subject:  Re: SCCA D Mod build questions
wrightcomputing wrote:
Don't forget minimum weight includes driver. So you need to account for yourself in the build weight.

13" or 15" are the way to go for tires. You can get used qualifying tires (Formula Atlantic, Indy lights etc) from John Burget (JBRacing) for around $400 a set shipped to your home. The ideal size is 10" front and 14" rear as that is what the open wheel cars typically use. Make sure you build the chassis around the size tires you want. I had to completely redo my rear end to fit the 14" tires. The competitive guys typically buy new AVON or Hoosiers or both for Nationals and a set lasts about a year depending on number of drivers and events.


Yes, was already thinking of going on a personal weight loss plan....... :roll:

Race take offs! Used to do that on the YZF600, I'll be changing my own tires here too soon.
Author:  1055 [ March 3, 2016, 1:28 pm ]
Post subject:  Re: SCCA D Mod build questions
wrightcomputing wrote:
DMod is <2.0L
Forced induction = x 1.4
Therefore the largest turbo engine in DMod is 1.4L (1.4L x 1.4 = 1.96L)
Emod <3.6L = 1700lbs
Emod >3.6 = 1800lbs

Penalty for modified tub (automatic on rube frame) +50lbs
<51% weight on rear tires = -50lbs

Not sure of DMod weights but I think it is around 1200lbs



They don't throw a conniption fit about rotaries anymore? a turbo 13b will make far more power than any naturally aspirated 2.0L 4cyl..
Author:  gregk [ March 3, 2016, 1:45 pm ]
Post subject:  Re: SCCA D Mod build questions
Quote:
Weight w/ driver vs. Displacement
  • Piston engines up to & including 1800 cc.....................................1280 lbs.
  • 12A rotary engines w/ porting restriction....................................1280 lbs.
  • Piston engines 1801-2000 cc...................................................1380 lbs.
  • 13B rotary engines w/ porting restriction....................................1380 lbs.


Only N/A rotaries in D-mod.
Author:  Driven5 [ March 3, 2016, 1:58 pm ]
Post subject:  Re: SCCA D Mod build questions
geek49203 wrote:
Cause I'm building on of Jack's Lola-ish body cars, and I still have time to budget a couple of inches for a possible wide set of tires... should probably figure, what, 15" or so?
Nobody says you have to run FA fronts on the front and FA rears on the rear. You could also run FA fronts all around. Beyond that, you need to be able to fit 13" diameter wheels over your brakes, as well as requiring what I believe would be uncommonly high offset for 13" diameter race wheels provided you don't want your street wheels to be so far inset as to look like you're running space-saver spares behind the rear fenders. You're could possibly find a 15" diameter (non-FA) size bias-ply tire size that is more closely matched with your street wheels/tires, or easier yet, simply go to radial DOT-R tires that are available in "standard" sizes. If you're not building a nationally competitive car, you don't actually 'need' a nationally competitive wheel/tire package.


1055 wrote:
They don't throw a conniption fit about rotaries anymore? a turbo 13b will make far more power than any naturally aspirated 2.0L 4cyl..
Rotaries produce one firing event per combustion chamber per revolution, producing power (regardless of the actual combustion cycle used) like a 2-stroke rather than a 4-stroke engine that the displacement structure is based upon...Therefore:

Forced Induction + Magic Spinning Doritos = EMod
Author:  wrightcomputing [ March 3, 2016, 2:50 pm ]
Post subject:  Re: SCCA D Mod build questions
geek49203 wrote:
wrightcomputing wrote:
I had to completely redo my rear end to fit the 14" tires.


Uh, I hope you're referring to the car, but you did mention driver's weight, so....

At any rate, that 14" is the actual width of the inflated, ready to run tire? Cause I'm building on of Jack's Lola-ish body cars, and I still have time to budget a couple of inches for a possible wide set of tires... should probably figure, what, 15" or so?

Oh, sorry to hijack the thread, you may return to previous discussions about how American bodies don't fit, etc.

The 14" wheel is about 15" wide
Author:  turbo_bird [ March 3, 2016, 2:59 pm ]
Post subject:  Re: SCCA D Mod build questions
1420 with driver would be very doable with a car that has a light 4 cylinder drive train if the driver is suitably svelte. I'm not, at 6'2" and about 280lbs, but I still fit in the car ok. My seats are similar in style to the original 7, but I have side bolsters made out of 3/16 aluminum attached to the frame on either side of the seats instead of running the rear seat back all the way across. I even crammed a passenger in my car that was 6'5", 350lbs, and the battery is in the passenger side foot well. My book frame car is street legal, has an iron head/iron block v6, 16 gauge steel floor, small trunk, etc. I weighed it at just a hair under 1300lbs with about 2-3 gallons of fuel in it. My car has decently light 13" steel wheels and no windshield or heater.
Kristian
Author:  wrightcomputing [ March 3, 2016, 6:35 pm ]
Post subject:  Re: SCCA D Mod build questions
geek49203 wrote:

Uh, I hope you're referring to the car, but you did mention driver's weight, so....

At any rate, that 14" is the actual width of the inflated, ready to run tire? Cause I'm building on of Jack's Lola-ish body cars, and I still have time to budget a couple of inches for a possible wide set of tires... should probably figure, what, 15" or so?

Oh, sorry to hijack the thread, you may return to previous discussions about how American bodies don't fit, etc.

You also need to consider the vehicle width. To keep the width down my rear wheels have a 9.5" back space. To accomadate that I have to use push rod suspension.
Author:  Kent2 [ March 3, 2016, 10:56 pm ]
Post subject:  Re: SCCA D Mod build questions
wrightcomputing wrote:
geek49203 wrote:

Uh, I hope you're referring to the car, but you did mention driver's weight, so....

At any rate, that 14" is the actual width of the inflated, ready to run tire? Cause I'm building on of Jack's Lola-ish body cars, and I still have time to budget a couple of inches for a possible wide set of tires... should probably figure, what, 15" or so?

Oh, sorry to hijack the thread, you may return to previous discussions about how American bodies don't fit, etc.

You also need to consider the vehicle width. To keep the width down my rear wheels have a 9.5" back space. To accomadate that I have to use push rod suspension.


I'll get an idea of what I want and mock it up shortly. Thank you again for all the great info. I'm way ahead already

Cardboard aided Design!
Author:  1055 [ March 4, 2016, 9:11 am ]
Post subject:  Re: SCCA D Mod build questions
gregk wrote:
Quote:
Weight w/ driver vs. Displacement
  • Piston engines up to & including 1800 cc.....................................1280 lbs.
  • 12A rotary engines w/ porting restriction....................................1280 lbs.
  • Piston engines 1801-2000 cc...................................................1380 lbs.
  • 13B rotary engines w/ porting restriction....................................1380 lbs.


Only N/A rotaries in D-mod.


Ok, that makes more sense. thank you!
Author:  1055 [ March 4, 2016, 9:12 am ]
Post subject:  Re: SCCA D Mod build questions
Driven5 wrote:
Forced Induction + Magic Spinning Doritos = EMod



This is my favorite thing that I've read on this forum.
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