mx5cartalk.com

I am currently planning a build of a stronger and more powerful N/A motor for my car and had some questions regarding the allowed modifications in the regulations and my current plans.

3.1 Carburettors may be replaced, provided the replacement(s) are of the same configuration (i.e. downdraught or side draught) and have the same number of inlet venturis as the originals.

I am planning to fit ITB's and while they are not explicitly dis-allowed in the above rule I feel the intent of the rule would not allow them. Would I be correct in my assessment?

3.7 Material may be removed from cylinder bores (for reconditioning purposes) to the limit of manufacturer’s specifications.

I have not been able to find the OEM rebuild specifications so am unsure as to how much of an over bore I am allowed, I am only planning a 1.0 mm over bore which would likely be within the OEM specs but I would like to be sure.
Cams, pistons, head work and balancing are all free in the regs so I have no concerns there.

From the Supersprint regs, Type 2, General
"1.3 The entire vehicle must be as originally specified by the manufacturer except for the specific freedoms allowed herein."
So as they don't say you can replace a STB with ITBs, this clause means you can't in Type 2.

Okay thanks for that, I only briefly read over the general regs so missed that part.
Now I just have to decide what class I'm going to aim for then build to that.

For N/A, type 3 will allow most of the performance mods that are sensible for MX-5s.
Suggest you read the relevant regs front to back, such as the Supersprint Vehicle Regs - Type 3 and CAMS 3J regs if you are considering type 3.

Mike runs his car in SVB for some reason. There are more club points there.

Last time I spoke to Mike on this subject his car is a 2B car. He runs in SVB for tactical reasons.