i doubt you will have lean issues unles you start changing the C/R.

 

Sorry but.............C/R????????

 

Why do people say that there is a limit? If it's too big, you just won't use the extra capacity. People are talking about running lean...get an safc or else. I don't see why a 62mm tb is the max size on a n/a engine. I don't get why there is a max at all. Unless you mean the max that you can use. An ITB setup would get way more air than a 70mm tb on an N/A

Then again, I am just curious, never heard of a maximum size for a tb.

 

I think what they meant was 62 was the biggest you can go without having to get an SAFC or tune anything at all. Direct Bolt On.

 

That's what I'm talkin bout wink.gif

 

The reason why a N/A tib starts to loose power if you go 63mm or larger on a throttle body is due to the loss of air velocity. It just simply gets too large after 62mm. The exception to this is, of course, if you go turbo. This was already discussed in another site a while ago.

 

C/R = compression ratio

the size also has to do something with a thing called pulse harmonization. this determines where a car hits its powerband. pretty much, it refers to when the air coming into the engine hits the valve when it closes and bounces back, creating negative pressure. this negative pressure causes air to rush in to the cylinders faster when the valve opens, allowing an engine to attain more than 100% VE for a very short time at some rpm.

 

There we go technical speak to explain why not to go too big right away.

Thanks for the C/R explanation.