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Old 12-31-2013, 02:39 PM   #121
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Is that sonic restrictor from Rae-tech?
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Old 12-31-2013, 03:22 PM   #122
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It is a Raetech SIR. As there is really no one else but Dave Finch that mass produces them, thats who you stuck with.
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Old 12-31-2013, 08:55 PM   #123
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Damn. Those aren't cheap. I might need to get one myself, not because I am mandated one. I am trying to detune top end only without hurting the low and mid range
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Old 12-31-2013, 09:15 PM   #124
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I was hoping you might have known of a cheaper alternative
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Old 12-31-2013, 11:06 PM   #125
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I was hoping you might have known of a cheaper alternative
I can cad model one up for you, just tell me the inlet ID/OD, the restrictor ID and the outlet ID/OD. And you can have someone rapid prototype it for you. There's a nice spray on amazon for model airplanes that will make your ABS rapid prototyped part sufficiently air tight. Or you could have anyone design that.
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Old 01-01-2014, 03:07 AM   #126
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Chris the car is amazing, you build some seriously nice stuff!!
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Old 01-01-2014, 03:47 AM   #127
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I can cad model one up for you, just tell me the inlet ID/OD, the restrictor ID and the outlet ID/OD. And you can have someone rapid prototype it for you. There's a nice spray on amazon for model airplanes that will make your ABS rapid prototyped part sufficiently air tight. Or you could have anyone design that.
Oh ****, that's the thing. I have no idea what inket or outlet diameters would work for my application. It would cost so much in r&d to figure out optimal.
Unless someone can help me
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Old 01-01-2014, 11:33 AM   #128
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Oh ****, that's the thing. I have no idea what inket or outlet diameters would work for my application. It would cost so much in r&d to figure out optimal.
Unless someone can help me
Well normally the inlet diameter would be the diameter of the filter, throttle body, or tube already in place and the outlet diameter would be the size of the intake tube already in place or the size of the opening to the plenum. But yeah if you were going though a completely fresh intake design around the restrictor then its gonna take some CFD at the minimum.
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Old 01-01-2014, 12:29 PM   #129
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Ya, figuring out the inlet and outlet sizes of the venturis on the sonic restrictor portion are the question. And then having a way for it to connect to a filter and the throttle body... Way over my head.
Who wants to engineer and 3d print it for me? Lol
Or, how do I figure out what system I would need from raetech
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Old 01-01-2014, 02:54 PM   #130
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We found inlet restrictors very effective during our Rotrex development. We ended up using restrictors once or twice on our N/A PT cars. Problem is that a non aero restictor (flat plate) affects the powerband well below the power peak where a well designed aero restrictor doesn't so much. Oscar Jackson hand made us a few custom sized aero restictors that only clipped peak power with almost no effect on torque peak. Turbulence and flow sep are bad.

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Old 01-01-2014, 05:24 PM   #131
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We found inlet restrictors very effective during our Rotrex development. We ended up using restrictors once or twice on our N/A PT cars. Problem is that a non aero restictor (flat plate) affects the powerband well below the power peak where a well designed aero restrictor doesn't so much. Oscar Jackson hand made us a few custom sized aero restictors that only clipped peak power with almost no effect on torque peak. Turbulence and flow sep are bad.
Unfortunately a lot of the SCCA required restrictors are flat plate, at least in the Touring/Super Touring classes.

It seems the SCCA is taking a liking to flat plate restrictors for "performance balancing" in the Touring classes (not GRAND touring) as more and more cars are getting them.

Sort of off topic (well considering this is Miata TURBO.net maybe not), but the SCCA also refuses to try to do performance balancing of turbo cars with anything other than TIRs (Turbo Inlet Restrictors). Other organizations limit boost pressure, but the SCCA can't possibly understand how to enforce that so instead they put tiny TIRs on most of the turbo cars. It doesn't limit the cars to how much boost they can run, just how tiny of a straw they have to suck through. You end up having turbo cars with a bit of advantage, they just have to change turbos every other weekend.

I don't know how reliable GM turbo cars (Pontiac Solstice GXP, Chevy Cobalt SS, etc.) are on track normally, but the ones in SCCA with tiny TIRs seem to blow their turbos almost regularly...


SORRY thread drift, back on topic, NICE GT3 car. Looks spendy...
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Old 01-06-2014, 01:59 PM   #132
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any details on this cooling system?
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Old 01-06-2014, 06:12 PM   #133
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Pretty standard stuff. AFCO Scirrocco style radiator. Fill/purge tank on firewall with cylinder head bleeds to keep air out of head. Radiator ducted to front of car. Its race car stuff but would work OK on the street with a cooling fan. Turbo street cars might want more radiator but keep in mind they use these radiators on 500hp circle track cars.
Chris
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Old 01-06-2014, 06:48 PM   #134
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Very efficient, I did a reroute and had to get rid of the 165 thermostat as the car ran to
cool at race pace. Put in a 185 and now temps are perfect. I did see 200 during one race here in Colorado, but in was 102 at the track and 6,000 feet in elevation so air density was minimal.
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Old 01-07-2014, 10:20 AM   #135
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do you run a rad fan?
I realize its a race car and idling isn't something you normally do.

also, with the purge tank, where do you have the air bleeders set to? Its something Im interested in doing with my track build.
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Old 01-09-2014, 01:38 AM   #136
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I have a fan for the cool down lap and thru the paddock after coming of track. There is a small outlet at the back of the head, it is located on the casting for the thermostat. It is the perfect place to take the bypass as it is located just forward/inboard of the thermostat allowing a small amount of coolant to bypass a closed thermostat.
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Old 01-09-2014, 10:26 AM   #137
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You can run the windshield and hard top if you like, most remove it to reduce frontal area. That being said, the cage creates drag so you need to make it as efficient as possible. You can see the difference in the cages in my car, it was redesigned to reduce drag. I could actually feel a difference when towing the car on an open trailer


I think these pics offer a pretty good comparison of the old cage and the new one. Also in the last pic if you look closely you can see some of the aero features of my new helmet, it is a Simpson Speedway Shark it has eliminated the buffeting that I was experiencing with my old helmet. You can also see the difference in the old windshield and my new one. The new one is much easier to see over, in addition to being lower profile.

.
I have gone back and forth between choosing an open top for lower CG/weight and a hardtop (fastback) for reduced drag. It would be nice to get a cd comparison of the two. I remember reading that the ALMS closed cockpit cars had a lot less drag than the open cockpit cars but then they have to deal with extra weight for the bodywork+A/C
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Old 01-10-2014, 03:39 AM   #138
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Take this for what it is worth, I have a friend that drives a GTL miata. He ran the car in back to back sessions, one with windshield and top and one without, the car was faster w/o the top and windshield. His cage is designed with a halo, and is definitely not optimized to run w/o a top and windshield, with a proper cage is sure the difference would be even greater. There is a huge difference between an optimally designed ALMS closed cockpit car and a miata with its abruptly ending hard top which creates a lot of turbulence.
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Old 01-10-2014, 10:53 AM   #139
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Bill - are you going to post some cage pictures?

In regard to the ALMS cars, a big difference between an open cockpit ALMS type car and a Miata is the placement of the engine or more specifically the placement of the air induction system. The air intake is place up high in the airstream to get a maximum amout of air into the engine, but this would also cause a fair amount of drag - IMHO.
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Old 01-10-2014, 05:11 PM   #140
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Who made your two windshields, Bill?
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