350xfire

iTrader: (1)

I am working on porting a 12A and was wondering if both the primary and secondary ports get the same treatment. I have a large street port template from Pineapple racing with just one shape. Just making sure the center iron gets the same shape and port as the side irons.
Thanks

diabolical1

iTrader: (3)

simple answer: yes.

Jeff20B

iTrader: (13)

74spec is better for a lot of folks. This doesn't help you since you already have a streetport template but it's something to think about.

350xfire

iTrader: (1)

So do you port straight down or do you angle and blend?
Thanks

diabolical1

iTrader: (3)

you blend. you want to try to smooth things (airflow). so try to transition changes as opposed to making/keeping them abrupt.

350xfire

iTrader: (1)

Has anyone measured the volume of a large street port after its done? Like taping up one side of the housing and filling with a measured volume of water and seeing what volume the new port holds? Don't want to screw up my porting...
Thanks

diabolical1

iTrader: (3)

you mean like how some people do with cylinder head combustion chambers?

well i can only speak for myself, but no, i haven't. this is just an opinion now, so feel free to do it if you want to, but i don't think the information you would gather translates very well to how a rotary works. combustion chambers are fixed, in both engines (the chambers in the head vs. the peritrochoid and rotor recesses in the rotary), but you can make small changes to affect burn (to a limited extent) and carbon deposits. that's about it.

if you're interested in numbers for the ports themselves, something dynamic (like flow) would be more useful. for example, if you start screwing with transitions to even out a volume number, then you're probably doing more harm than good. does that make sense?

350xfire

iTrader: (1)

OK, thanks. I was just going to use that volume to make all ports equal in volume. Otherwise, I may end up with 4 different volumes.

j9fd3s

iTrader: (3)

i've never heard of anyone doing it with a rotary before, but you might learn something, try it.

i have an engine simulator, and i've got some take aways.

first airflow = hp.

2. the whole combination needs to work together. ports, port runners, intake, carb, exhaust, etc. if these are all well matched, you will have an engine that makes good power everywhere. this is why the 74 spec port works, as it works with a quiet exhaust, and a stockish intake. the less well the combination works together, the less midrange/low end you'll have. or you can actually do something like a full bridge with stock intake/exhaust and probably loose everywhere.

3. you want the smallest port runners that will flow enough air. too big = loss of power everywhere except peak.

four. too big a cam = port hurts everywhere, except peak. for a street car milder is always better. race cars have rules.

DreamInRotary

iTrader: (49)

That's a good question, now I'm curious...maybe when I start porting my setup I'll do that little trick.