Junkers88

I'll be switching the battery and AFM thing this week and opening the intake up to about 3 inches along with a snorkle for cooler air. Is there some formula that I can run with the newly modified intake to figure out how much larger I need to make the exhaust so that it'll match the airflow of the intake?

Thanks.

Targetnut

I'm sorry to report, it's not going to make that big of a difference.

Look at the size of the opening in the AFM and tell me that adding size to the intake tube which is already twice the size of the AFM will make much difference.

Even if you get rid of the AFM and fatten the throttle and intake tube up as big as you want, the head will only flow about 130cfm.

what you really need is to port the head, then open up the intake and exhaust. then you will see some serious gains.

abecedarian

how do you arrive at the result of 130cfm?

Targetnut

Here and there you can find this figure published.

Also I built a flow bench and while it is not specifically calibrated, as best as I can tell 130cfm is about correct. that would be measured at .430" lift (or more if you like) and 28"H2O pressure.

Here's a link to a thread about my flowbench; My flowbench

abecedarian

I was just wondering.