52 mm throttle body fitting

Don't knock it till you've tried it John, take a look at the How To I did (linked by David above) and the photos of the difference in space for air flow.

Just on the TB markings

There's loads of stuff on the net regarding this and general consensus is that the 48mm TB restricts the airflow and 52mm is much better. Also 56mm doesn't improve performance further (this could be where John's dynamics bit comes to the fore).

So it appears that 52mm is optimal size.

Although 4mm doesn't sound like much it represents a 17% increase in surface area, and that's without accounting for the wedge.

PQD44 wrote: Don't knock it till you've tried it John, take a look at the How To I did (linked by David above) and the photos of the difference in space for air flow.

Just on the TB markings

Oh, I'm not knocking it Paul, far from it. Excellent how to by the way.
As it is reversible I may just give it a go.
Good point by Laz regarding the apparent lack of gain between 52 & 56.

My brain is probably stuck in the eighties and optimising SU carb airflow!

Both me and Whiz did this inexpensive little mod gain, after tweaking Pauls' original guide to remove the soldering phase and called it 'version 2'. It works well. No issues encountered. Cheers Paul. :broon:

Throttle body 48mm - The original modification guide.
Throttle body 48mm version 2 - Modification guide mark 2.

brilliant Mod, one of the first done on Madam :broon: