i did a writeup on this a while ago... you won't be able to go much larger than 66mm without welding the iacv ports.

here is a comparison between a manifold that i did to 66mm (right) and one to 70mm that was welded (left).


here is the 70mm, obviously i welded it first, then faced it, bored it and cleaned up the iacv ports.



while i was at it, i shaved all the casting seams.

 

The 27% number appears to be correct.


The surface area of the 62.5mm throat is 4.75 inches square. The surface area of the 70mm throat is 5.97 inches square. The area 5.97 is 25.7% more than 4.75.

He calculated his on 62mm that would result in the slightly larger number of 27%.

 

I knew the area increase % would come up I decided to use the specsmanship method.
Yeah I'm going to do the full makeover on the intake manifold. How did you drop 4 lbs?

Anyone know where the "ecm idle learn" instructions are? I looked through Helms but can't locate it?

Thanks

 

ah, must have missed the area part

 

Great work on that manifold

I especially like the cleanup you've performed on the casting marks...it practically looks brand new!

 

Remove material. Cut away some of the supporting structures underneath. Grind away all the casting marks and unused bosses.

The aft part of the manifold has some major chunks of Aluminum that can be attacked.

Take material off the outside of the entire manifold. I used a flat file to sculpt the plenum.

 

Wow very nice work guys.... the manifold is a fine piece, gotta love the Honda engineering on this car.

BTW Spoon quotes 4whp NA gain across the power band with their 70mm TB. For FI there is no question that the stock TB is a flow choke point.