are posted:
http://www.scca.com/.../cars-and-rules
January 2016 Prelims
#1
Posted 12-07-2015 04:30 PM
#2
Posted 12-07-2015 04:42 PM
http://cdn.growasset....pdf?1449506044
NOTE: This preliminary version of the Club Racing Technical Bulletin is provided at this time as a service to the membership. These items may be corrected and will not be official until published on the Fastrack page of the scca.com website on or about December 20.
Spec Miata
1. #17927 (Dan Tiley) Please Add Tolerance Specification to Engine Stroke Requirement
In SM, make the following changes:
Mazda MX-5 / Miata (90-93):
Bore x Stroke: 78.0 x 83.604 1597 or alternate 78.25 x 83.604
Mazda MX-5 / Miata (94-97):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
Mazda MX-5 / Miata (99-00):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
Mazda MX-5 / Miata (01-05):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
#3
Posted 12-07-2015 04:46 PM
Recommended Items for 2016
SM
1. #18236 (Jason Isley) Update the Muffler Rule
Thank you for your letter. Change 9.1.7.C.1.m.4.c:
No expansion chambers. A single Up to two muffler(s) may be added. The muffler(s) shall not exceed a maximum length (parallel to the longitudinal centerline of the car) of 34 inches. The muffler(s) shall not exceed a maximum width of 24 inches (parallel to the lateral centerline of the car). In addition, the sum of the length and width of the muffler(s) shall not exceed 40 inches.
What Do You Think ?
SM
1. #18342 (Ralph Provitz) Allow Turn Signal Removal in the 94-97 1.8
The CRB is seeking feedback on the following. Please respond through the CRB letter system, www.crbscca.com.
Input is requested from racers on parity for the 94-97 model year cars. Is there a parity issue? Are the cars currently competitive?
Option of weight/restrictor plate adjustment, and/or allowing similar changes as the 1.6 cars recently received, but only if needed.
#4
Posted 12-07-2015 04:54 PM
In addition, the sum of the length and width of the muffler(s) shall not exceed 40 inches.
Ok, who's got their 40" wide muffler at home ready to go ??
J~
#5
Posted 12-07-2015 05:45 PM
Ralph - When Bruce ran both NA/NB cars, did the data suggest the NA1.8 needed some help on straight line performance? I really can't comment because my car isn't what it could be and well, yours is.
#6
Posted 12-07-2015 06:49 PM
#7
Posted 12-07-2015 08:26 PM
V2 Motorsports
#8
Posted 12-07-2015 09:31 PM
Spec Miata
1. #17927 (Dan Tiley) Please Add Tolerance Specification to Engine Stroke Requirement
In SM, make the following changes:
Mazda MX-5 / Miata (90-93):
Bore x Stroke: 78.0 x 83.604 1597 or alternate 78.25 x 83.604
Mazda MX-5 / Miata (94-97):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
Mazda MX-5 / Miata (99-00):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
Mazda MX-5 / Miata (01-05):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
It looks like an intended "inch" tolerance spec allowance of 0.004 was mistaken in the above as being a metric (mm) specification.
A 0.004 mm allowance is less than .0002 inch whereas a 0.1 mm tolerance would be 0.0039 inch. This would in reality round to .004 inches in all practical tech shed measurements (example 85.000=3.346447 inches, while 85.100=3.350384 inches and 85.004 mm = 3.346604 inches).
The 3.346447 would round to 3.347 (as would the 3.346604) while the 3.350384 would round to 3.350 for a net dial indicator tolerance allowance of 0.003 inches on the typical 0.001 inch graduated dial indicator found in tech. Having a rule that only allows for a .0002 inch (rounded) allowance on a specification measured with a tool typically having 0.001 inch graduations does not make sense.
While 0.003/.004 may seem as a overly generous allowance, it is not out of the reality of what can and has been seen to occur in the field with the undersized crank journals which are allowed.
Rich Powers
- Johnny D likes this
#9
Posted 12-07-2015 10:31 PM
#10
Posted 12-07-2015 11:22 PM
Ok, who's got their 40" wide muffler at home ready to go ??
J~
DDG probably still has a "suitcase" muffler lying around from the last time i was there.....
Marc Cefalo
www.planet-miata.com
570-262-1013 direct
#1 source for new and used Miata parts and accessories.
#11
Posted 12-07-2015 11:49 PM
DDG probably still has a "suitcase" muffler lying around from the last time i was there.....
I was thinking more folding card tableish, no legs
Are they going to have a max thickness of 40" too
And it's a muffler, not a diffuser, those fins every 5" are to strengthen it.
J~
#12
Posted 12-08-2015 08:49 AM
East Street Auto Parts
Jim@Eaststreet.com
800 700 9080
#13
Posted 12-08-2015 11:13 AM
#14
Posted 12-21-2015 03:18 PM
Official Jan
http://cdn.growasset....pdf?1450468295
Recommended Items for 2016
SM
1. #18236 (Jason Isley) Update the Muffler Rule
Thank you for your letter. Change 9.1.7.C.1.m.4.c:
No expansion chambers. A single Up to two muffler(s) may be added. The muffler(s) shall not exceed a maximum length (parallel
to the longitudinal centerline of the car) of 34 inches. The muffler(s) shall not exceed a maximum width of 24 inches (parallel to
the lateral centerline of the car). In addition, the sum of the length and width of the muffler(s) shall not exceed 40 inches.
"the sum of the length and width of the muffler(s) shall not exceed 40 inches."
J~
#15
Posted 12-23-2015 08:30 PM
Recommended Items for 2016
SM
1. #18236 (Jason Isley) Update the Muffler Rule
Thank you for your letter. Change 9.1.7.C.1.m.4.c:
No expansion chambers. A single Up to two muffler(s) may be added. The muffler(s) shall not exceed a maximum length (parallel
to the longitudinal centerline of the car) of 34 inches. The muffler(s) shall not exceed a maximum width of 24 inches (parallel to
the lateral centerline of the car). In addition, the sum of the length and width of the muffler(s) shall not exceed 40 inches.
OK, I'm a little slow......can someone explain the reason behind this a little more? Just looking for some understanding as to what the benefits might be.
Chris Dilluvio
Farmington Hills, MI
#16
Posted 12-23-2015 08:41 PM
OK, I'm a little slow......can someone explain the reason behind this a little more? Just looking for some understanding as to what the benefits might be.
A few years back, someone built a "muffler" that acted as a diffuser. It filled up the entire area in front of the rear bumper which acts like a parachute. So the next year, the muffler dimensions were spec'ed
Jim
East Street Auto Parts
Jim@Eaststreet.com
800 700 9080
#17
Posted 12-23-2015 09:01 PM
- Jim Drago likes this
Chris Dilluvio
Farmington Hills, MI
#18
Posted 12-23-2015 10:19 PM
Spec Miata
1. #17927 (Dan Tiley) Please Add Tolerance Specification to Engine Stroke Requirement
In SM, make the following changes:
Mazda MX-5 / Miata (90-93):
Bore x Stroke: 78.0 x 83.604 1597 or alternate 78.25 x 83.604
Mazda MX-5 / Miata (94-97):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
Mazda MX-5 / Miata (99-00):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
Mazda MX-5 / Miata (01-05):
Bore x Stroke: 83.0 x 85.004 1839 or alternate 83.25 x 85.004
It looks like an intended "inch" tolerance spec allowance of 0.004 was mistaken in the above as being a metric (mm) specification.
Rich is correct. My intent was to add 0.004in (0.1mm) to the stroke spec, which currently calls for the factory nominal spec of 85.0 & 83.6 as an absolute maximum with no tolerance. Here's the letter to the CRB:
Please Add Tolerance Specification to Engine Stroke Requirement Request:
SMAC & CRB Members,
Our current engine stroke specification is outlined in the GCR on page 752 as 83.6mm for a 1.6L and 85.0mm for all 1.8L. Page 185 states that "unless otherwise specified" stroke is an "Absolute Maximum", defined as follows:"Absolute maximum means tolerances of+0.000 inches or +0.00 millimeters." Therefore, a 99 miata with stroke of 85.01mm is technically non-compliant.Realistically, the 83.6 and 85.0mm specs are nominals from Mazda, which have a small tolerance. Very little discretion is being given in the tech shed (ie. 3rd place runoffs car being disqualified for 1 out of 16 relief cuts slightly oversize). As such our rules need proper tolerancing built in to protect ourselves from ourselves. Mazda cranks are VERY repeatable. Allowing for just +0.004" (+0.10mm) is enough to capture every OEM Mazda crank I've personally measured. Note, our bore spec is already defined with a tolerance of up to +0.006" over nominal.
Thanks,
Dan Tiley
- Johnny D and speedengineer like this
#19
Posted 01-04-2016 11:12 PM
Calling all NA 1.8 owners/drivers. For those that have not seen the request for input in the January SCCA Fastrack regarding the competitiveness of these cars, there is a window for us to submit our requests to bring these cars up to a competitive level with the more powerful NB cars and the lighter 1.6 cars.
Here is the text from Fastrack:
The CRB is seeking feedback on the following. Please respond through the CRB letter system, www.crbscca.com. Input is requested from racers on parity for the 94-97 model year cars. Is there a parity issue? Are the cars currently competitive? Option of weight/restrictor plate adjustment, and/or allowing similar changes as the 1.6 cars recently received, but only if needed.
IMO these cars are very nearly competitive with the others and only need a very small adjustment to close the gap. Weight and restrictor plate adjustments are the easiest for the SMAC and CRB to approve and are also the simplest and least expensive for competitors to adopt.
If you own or race one of these cars, NOW is the time to submit reasonable and well founded requests. It might be wise for those of us who still own or race these cars to pool our thoughts and information and submit it with some collaboration. Anyone that wants to share their thoughts can send me a private message and we can get a group effort started. Time is probably of the essence as the next Fastrack will be published in 2 weeks or less and it’s best to submit requests while we are still on this month’s watch.
- Danny Steyn likes this
#20
Posted 01-05-2016 02:12 PM
I've heard rumor the 47mm plate is nearly no longer the intake bottleneck of a pro-built NA1.8, thus implicating the airbox and intake piping.
I'll have my setup on the chassis dyno this off-season to confirm (yanking the plate outright) but it may not be as simple as we've thought to get "more" out of these motors as others.
None of the allowances for the 1.6L would be a detriment to the NA1.8 IMO and their influence would be minimal in upsetting any apple carts.
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