FB II

anyone know how much cfm the stock intake manifold can flow? i reaaaally think this is what's holding me back on my top end. SEVERELY holding me back at that. i've noticed the car breaks tires loose and pulls SOOOOO hard till around 6,000 at which the boost doesn't drop but the power seems to really level off. i know the stock ports on a 12a are restrictive but i might try something crazy with an intake manifold first.

Rogue_Wulff

I think Sterling and a few others have explored the art of porting the intake, with some success. You are likely spot-on about part of the reason you start loosing power above 6K.
Between the stock ports, and stock intake, only so much air can flow into the engine, even under boost. Those intake runners look rather small to me.

Kentetsu

MSD ignition, from what I understand, gives multiple sparks until you get to higher rpms. Shoulda gone for the transistor trick, for a gauranteed 2ms spark at high revs...

FB II

yea they are, but i gotta be able to get some improvement i want to see how much power i can get out of this stockport boosted 12a. since so far i haven't really seen any dyno sheets of blow-thru stock ported motors. the car is pretty damn quick, gotta be capable of trap speeds around 108 - 110 as is since alot of the cars i'm beating are hitting that this is all still using the stock nikki and intake manifold. i think what's reaaally helping me alot with power is the beast *** turbo header i'm rockin and my very unrestrictive exhaust WOOOT!

i do believe RX7CARL was flow benching some manifolds... i wonder if he found out the max flow possible out of a stock intake manifold. airflow truely is his life woo wooooo!!!!!

FB II

you gotta be kidding me, i know for a fact the msd is making my spark redonkulus alllllll the way to 8,000+ rpms. i noticed it on my wideband the first full 3rd gear pull i did. usually at full boost before the MSD was installed my air/fuels were at 11:1... NOW with the MSD in action, thru the cap at that, it has burned up enough fuel all the way to 8k to make my air/fuels now 13:1. so i had to jet up a tad... THAT = MORE POWER. i did not see any of this happen running the direct fire 2gcdfis. in fact i think it burned less.

REVHED

Wouldn't the stock turbo run out of puff at around 6krpm anyway?

FB II

nah, usually on TII's the boost just falls off around 6k but i'm running a beast *** turbo header that actually pushes the **** out of the turbo. it holds full boost at whatever i set it to all the way to 8500rpms... yes i know this from experience. boost doesn't fall off one bit and i can (unfortunately this happened once) get the boost to go over 20psi easy. so i'm definately not running out of steam there. i know the carb can accept enough flow for up to 550rwhp... robert has proven this of the nikki **** hahaha, so it's gotta be the intake manifold (to an extent), ofcourse porting comes in to play above 7,000 but i know theres gotta be more to get out of what i'm currently running. when i go to the track i want to run knowing it's all i can possibly bring.

Unsupa

iTrader: (2)

i got an extra 12a manifold if you wanna play with porting..

FB II

woooot, i might take you up on that. i got rid of the 3 extras i had layin around a while back. i want to see if it's even worth it tho. i'll wait for some more people to chime in before i start hogging out to all hell.

REVHED

Boost is only part of the equasion. Flow will increase with compressor rpm but after a certain point it becomes a case of diminishing returns.

brandon davis

iTrader: (3)

Just port the secondaries is what i remember reading on porting when I did a search. After I ported out inlet and the Sec. my revs can dance around 5-8 all day till i run outa gas.

85rotarypower

Well, I didn't read the whole thread, but I didn't see any numbers being thrown around. Anyway, I remember reading a post by either RX7Carl or Sterling that the stock 12A intake manifold actually flows LESS than the stock Nikki carb! Its around 300 cfm or something like that. Stock carb flows something like 320cfm. I think this would definately account for some of your power loss.

ApG Spaz

the stock intake mani is very restrictive, any porting in it, even by sumone w/ no idea wat hes doing will enhance the flow. im pretty sure carl was working on finding the most efficient flow for modified stock intake, but since every 1st gen based company just moves onto webers or holleys or the like, theres no research geared in this area.

as far as stock goes, the 79-80 flows considerably better than the later years (idk why, i read it on here for some spec racing or something where you had to use stock intake)

FB II

thanks guys, i'm still searching. i kinda figured it wasn't even good enough for it's own sake... throw a turbo in the mix... hahahahahahah FUUUUUG! might have to get that one mani from unsupa

inuissus_cendi

it mentions intake manifold porting on the pbandjracing.com website. its listed as one of the things they do but theres no other information about it.

I'd be curious too because I plan on sticking with the stock manifold and just getting my Nikki modded, but if the manifold only flows 300cfm anyway...

fcdrifter13

I like my racing beat intake and Edlebrok carb. It seems to flow pretty well. I dont have a turbo though. From what I have heard boost pressure may be constant at a certain RPM but the turbo is not flowing as mush at higher rpms because the compressor wheel is to small to feed the total volume of what is required at higher RPMS.

This is what I heard though the engines I work on everyday dont rev past 2500RPM. Your problem may not be flow but the vloume of air your turbo is puushing

I hope this helps some if not then sry if I got you confused.

ArmySoldier

The stock intake is designed to handle 415 cfm on a NA carb, mine is ported just a bit, I don't like the way it idles, like my carb (stock) isn't taking in enough. No turbo or anything else just straight carb so far, I think its getting to be a matter of a bigger (more cfm) carb. My engine is a 12A with a street port, and there seems to be some arguement about port matching. Sometimes a smaller port on the intake manifold will make the air accelerate into the port on the block, which.....still doesn't really answer your question though does it? Sorry... Im going through the same dilemma on getting the most out of my FB.

cds00bsmg

iTrader: (1)

isnt the stock turbo II turbocharger ouf of its effiency range above 14psi?

FB II

i'm running 10psi at the moment. i turned it down a couple weeks ago and have retuned. it's pretty much as fast now as it was with 16psi. THANKS MSD IGNITION i am about to try some crazy shizzle.... i've had a Holley double pumper i've been playing with and the RB intake manifold. i might try it out and see what the difference is. the RB intake is no joke! LOL no need for porting there

fcdrifter13

the last owner of my intake ported mine it looks wierd though not sure if its to good of a job its all ridgid and had sharp edge i know the runners arnt suppost to be perfectly smooth but i think whoever did mine half assed it.

FB II

still better than stock from what i hear

rotarygod

iTrader: (1)

If this 12A has the large center runners in the engine, DO NOT port the manifold out to that size. You will lose power! Hogging out isn't "always" the best thing to do especially on a street car. Where and how much things are done are extremely important. Sometimes adding material is better. (not necessarily in this case, just an example).

85rotarypower

I wonder where RX7Carl and sterling are? I thought for sure they would chime in on this.

FB II

well, i know in an n/a situation those runners can be a problem if ported out... but my car is pretty much always in boost. even cruising it's at 0 vaccum just waiting to go to positive manifold pressure so i figure this might change things. not sure tho, we'll see

Unsupa

iTrader: (2)

If you're still gonna be in the inman area on the 22nd then I can hook you up with that mani for free.. and perhaps a few other things out under the garage... struts, etc.. things must go.