Stock throttle body or stock-sized throttle body?

[TomL]

The ST rules allow the use of an OEM fly-by-wire throttle or the conversion of the fly-by-wire to manual. Is there any reason to not allow the use of an alternate throttle of the same size? In some cases it may be a lot easier than trying to convert the stock unit to manual operation. I know that there is language allowing alternates on a case-by-case basis. However, I don't see any obvious reason that such a swap shouldn't be allowed automatically as long as the throttle body diameter is unchanged. Am I missing something, or was there a specific problem that was being addressed by the more restrictive language?

[Rabbit07]

The language is a carry over from W/C rules.

What engine specifically are you concerned with?

[TomL]

I'm using an RX8 rotary. I would have to cobble together a way to install both a throttle cable attachment and a TPS adapter,which won't be easy given the way it's constructed. It would be a lot easier to install an aftermarket throttle body of the same size (a common 70mm) and only have to (maybe) modify the bolt pattern.

I can understand why it was written that way if it was just carried over from WC. However, unless there is a technical reason (not readily apparent to me) that one 70mm throttle body would provide an advantage over another 70mm throttle body, I would recommend that aftermarket throttle bodies of the same diameter also be allowed.

[Greg Amy]

I think the spirit of the idea is within the philosophy of the regs, my only concern (as a National Scrutineer) is how to tech it. It is very uncommon for factory shop manuals to list the throttle body bore size, so how will Tech police it?

Note that within the regs you can use an alternate TPS, you're not limited to the factory part. Especially given open ECUs, there's a lot of leeway in there for creativity.

I think that would be considered a rule change, so not possible to implement it until 2014. If it's something you feel strongly about, send in a request. It would be very helpful to address my concerns about scrutineering.

- GA