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Mazda GT Tube Frame in ST3

Old 05-27-14, 07:07 PM
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Mazda GT Tube Frame in ST3

I've been looking at getting into a purpose built race car and seeing the 7's Only Racing Mazda GT have been moved into the ST and TT classes was wondering what you guys thought the cars chances of being competitive in that class are? The cars use a peripheral ported 13b motor. How reliable are these motors and how long between rebuilds can these engines typically go? What is the cost for a total refresh of one of these engines? The low cost consumables for these cars and relatively cheap upfront cost to get into make them seem like a shoe in for a race car if they can be competitive with a little tweaking of aero and tires. Any insight into these cars is appreciated.

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Old 05-27-14, 08:33 PM
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7s Only will be able to answer all motor, durability, rebuild, refresh questions -- they are the absolute experts on those cars. 7s Only will also be able to tell you the lap times those cars run at all the local tracks, and that will give you an idea of the competitiveness. The only Mazda GT track record I could find (that took place during an SCCA race, anyway, as I know where to find those records) was 1:30.158 for Willow Springs, but considering those cars run rock-hard Nitto NT01s, you could knock a second or two off with a good R Compound, or even more with a slick tire, assuming that record was done on Nittos. 7s Only's brochure claims a 1:27 at Willow.
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Old 05-28-14, 12:18 PM
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I looked into them a while back. I don't know if they have changed over the years, but I've seen them with more than one engine option. The cheaper, more affordable ones being the lesser powered motors. Looking at some of the Buttonwillow times, one could be quite competitive in ST3/TT3. There were a few things that turned me off of them:

* Their site says 350 hp, but most of the ones you'll see for sale are ~250 hp (link)
* I have a friend who races in SCCA and he mentioned those cars are always breaking (no personal experience here)
* I wasn't pleased seeing the suspension setup
* PP builds aren't cheap. I emailed with Daryl Drummond a few years back and he mentioned an expected price for that type of motor was around $8k.

IIRC, we have a member on here (west coast) who has and races one. Maybe he'll chime in with his experiences.
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Old 05-28-14, 01:19 PM
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S1mpsons (hamfist racing) races one in TT3 and seems to beat everyone... but it doesn't look like there are a lot of cars running TT locally.

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Old 05-28-14, 05:29 PM
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we see these things a few times a year, they are pretty quick, i wanna say about 2 minutes flat at thunderhill, maybe 2:02.

since its just a tube frame 1st gen, with a P port, it should be pretty simple/reliable, it doesn't seem like they have problems, but i'm not really paying attention. IE when they go out for a session, they all seem to go out.

how long the engine last probably depends on the apex seals, the carbons will probably wear more quickly, but they are easier on the housings....
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Old 06-01-14, 04:05 PM
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I was looking in to them as well. Tom's a great guy and is straight forward with you. Getting him to sit and talk is the hard part. He is a busy man. Always got something going. But once you get him, he is a fun guy to talk to and helpful.

He is building a new tube frame with IRS that uses the same GT body. Motors are only going to put out as much as you put into them. The more HP the more you need to build/ rebuild.

Bottom line is. They are simple, fast and low maintenance cars. Tom love to keep things simple.

Oh, and if there are a good deal on one (even if it's not his) he will tell you.
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