What parts to build a full-race 13B?
12-19-2005, 06:05 PM
#21
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Posts: 524
Originally Posted by Lynn E. Hanover' post='787982' date='Dec 19 2005, 05:01 AM
That is close to what the rule reads now. Do you work for SCCA?
Ouch.
In a 4 port engine to feed each housing through one butterfly you need a plenum so as to feed both the primary and secondary runners. If they were to enforce that rule we would have to pick which runner would be abandon. In a 6 port you have three runners for each butterfly.
Ah, but then the plenums would not be common to both rotors, they would be separated, one per rotor.
This also works for any piston engines that have multiple ports per piston, such as a multivalve with two separate intake ports per cylinder. I do not know if there are any in common use, though.
The problem is, of couirse, the factor of plenum size. Where, and how, do you draw the line between a simple Y branch close to the throttle plate, or a large open space, say a liter in volume, that happens to feed only one rotor and is fed by one throttle body.
I know their rules suck, but if we can't think of a good, fair, enforceable rule (like Mazdatrix's street port definition) then how can we complain about what the SCCA writes up?
12-20-2005, 01:25 AM
#22
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Location: Central Ohio (Hebron) Zephyrhills Fla.
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Originally Posted by heretic' post='788140' date='Dec 19 2005, 04:05 PM
Ouch.
Ah, but then the plenums would not be common to both rotors, they would be separated, one per rotor.
This also works for any piston engines that have multiple ports per piston, such as a multivalve with two separate intake ports per cylinder. I do not know if there are any in common use, though.
The problem is, of couirse, the factor of plenum size. Where, and how, do you draw the line between a simple Y branch close to the throttle plate, or a large open space, say a liter in volume, that happens to feed only one rotor and is fed by one throttle body.
I know their rules suck, but if we can't think of a good, fair, enforceable rule (like Mazdatrix's street port definition) then how can we complain about what the SCCA writes up?
All of the cars that run stock or stock like intake systems have a log that all of the runners draw from, with a throttle body on the end or middle of that log. That log is a plenum.
The 4 valve engines have a short runnner leading to each valve from a single runner. That single runner is a plenum. The two runners of a rotary joint before the butterfly. Where they join is a plenum. Since nearly all of the cars have plenums anyway. As soon as you write up one idea, you notice that there is a car a plenum in stock trim. Or one with two plenums (rotary) or, no plenums (two valve engines) or 4 plenums 4 valve engines. On newer cars, plenums are almost universal.
They must sit down and just specify what they want on each engine. After it has been pointed out a number of times, and they do nothing, then it just makes me wonder about the personell. They make a rule that says all cars have to have the front plug in line with the centerline of the front Wheels. I would have to move my engines forward 5 3/8" and rebuild the front of the chassis. Mid and rear engine cars?????
Then they start changing the words to allow all of the cars they outlawed with the rule, instead of thinking it through first. So now years later, am I illegal with a (stock) 5 3/8" setback? No exceptions in the book for Mazdas. Are they all illegal?
At the last meeting I attended with the comp board, at the runoffs, I discovered that only one of them raced at all, and he knows nothing about cars. He rents his. So, what did I expect?
Lynn E. Hanover
12-21-2005, 07:20 AM
#23
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Location: Dillsburg, PA
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Originally Posted by Lynn E. Hanover' post='788118' date='Dec 19 2005, 05:45 PM
I have no experience with notched rotors. I have never seen them in a race engine. If I saw a back to back on the dyno, then I could comment beyond just speculation.
=====> It seems to me that beveled rotors would dramatically lower the compression ratio (I could be wrong). I wonder if the gains in breating would offset the reduction of compression.
The flywheel we use is 4 pounds.
<snip>
Look in the flywheel and clutch section.
Item three is the one we use. They sell a Quartermaster 5 1/4" two disc clutch pack, but we have a Tilton.
Just about identical, and bolts to the same flywheel. The center of the wheel is steel. You have to drill and tap the counter weight for a smaller bolt circle, but no big deal at all.
=====> Lynn, I can't find a 5 1/4" clutch at Mazda Comp. Please take a look at the parts I found and tell me if I am looking at the right stuff.
Part #: 0000-02-9103
CLUTCH ASSEMBLY, QM 5.5" 1"x 22
QUARTER MASTER 5.5"
Notes:
"5.5" clutch assembly includes a Quarter Master Lightweight aluminum clutch cover, pressure plate, housing, floater plates and 2-disc clutch pack. Requires use of Quarter Master bolt kits, #0000-02-9123 and #0000-02-9128, and Quarter Master release bearing, #0000-02-9122 or #0000-02-9122-PB. Spline size 1'x22. Quarter Master clutches require the use of a special radius-faced release bearing. Do not use a flat-faced bearing with any Quarter Master clutch."
-----------------------------------------------
Part : 0000-02-9203
FLYWHEEL, BILLINGTON 5.5"
BILLINGTON
12A 13B
Notes:
"This unique lighweight flywheel for 5-1/2" racing clutches weighs approximately 4 pounds and features a steel center heat shield for durability. Moment of inertia is comparable to all-alluminum flywheels. The aluminum outer hub can be replaced when necessary. When replacing aluminum hub and/or ring gear assembly, aircraft quality bolts must be used, Part #0000-02-9203-AA."
<snip>
Thanks.
12-21-2005, 12:11 PM
#24
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Location: Central Ohio (Hebron) Zephyrhills Fla.
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Originally Posted by Don1' post='788627' date='Dec 21 2005, 05:20 AM
Thanks.
Lynn, I can't find a 5 1/4" clutch at Mazda Comp. Please take a look at the parts I found and tell me if I am looking at the right stuff.
Part #: 0000-02-9103
CLUTCH ASSEMBLY, QM 5.5" 1"x 22
QUARTER MASTER 5.5"
Notes:
"5.5" clutch assembly includes a Quarter Master Lightweight aluminum clutch cover, pressure plate, housing, floater plates and 2-disc clutch pack. Requires use of Quarter Master bolt kits, #0000-02-9123 and #0000-02-9128, and Quarter Master release bearing, #0000-02-9122 or #0000-02-9122-PB. Spline size 1'x22. Quarter Master clutches require the use of a special radius-faced release bearing. Do not use a flat-faced bearing with any Quarter Master clutch."
-----------------------------------------------
Part : 0000-02-9203
FLYWHEEL, BILLINGTON 5.5"
BILLINGTON
12A 13B
Notes:
"This unique lighweight flywheel for 5-1/2" racing clutches weighs approximately 4 pounds and features a steel center heat shield for durability. Moment of inertia is comparable to all-alluminum flywheels. The aluminum outer hub can be replaced when necessary. When replacing aluminum hub and/or ring gear assembly, aircraft quality bolts must be used, Part #0000-02-9203-AA."
<snip>
Thanks.
That is the correct clutch. I should have said that the same thing in the Tilton part is 5 1/2" and is identical, if you prefer the Tilton. Billington Welding made the setup for Mazda Comp, and Billington used to champaign two CSRs. It is the lightest possible combination, as the bolt circle for the 4 1/2" clutch pack appears to interfere with the counterweight nut. But a machinist could rig up a pin drive nut, and get it to work, for a slightly improved weight.
Clutches come in 4 1/2", 5 1/2" 7 1/4" and 8 1/2" from Tilton.
12-21-2005, 06:45 PM
#25
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Posts: 524
Originally Posted by Don1' post='788627' date='Dec 21 2005, 05:20 AM
It seems to me that beveled rotors would dramatically lower the compression ratio (I could be wrong). I wonder if the gains in breating would offset the reduction of compression.
As a general rule, for a 13B in the range where this concerns, compression drops one tenth of a ratio for every CC you remove. If you cut two bevels 5cm long, .5cm deep, and 1cm wide, then you lose 2.5cc per face, dropping a 9.4 rotor down to about 9.1-9.2. I choose the numbers just as an example, of course, since the math works out in nice round numbers that rarely happen in real life.
12-23-2005, 08:49 AM
#26
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Originally Posted by heretic' post='788849' date='Dec 21 2005, 07:45 PM
As a general rule, for a 13B in the range where this concerns, compression drops one tenth of a ratio for every CC you remove. If you cut two bevels 5cm long, .5cm deep, and 1cm wide, then you lose 2.5cc per face, dropping a 9.4 rotor down to about 9.1-9.2. I choose the numbers just as an example, of course, since the math works out in nice round numbers that rarely happen in real life.
Thanks, heretic. That may prove to be very useful information.
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