ive got a line on some gsxr 1000 throttle bodies
but there only 42mm....the busa ones are 46mm but ive seen bored ones for up to 49mm...will 42 be big enough motor is stock at the moment but i do have plans..(bigger cams/prospeed header and more compression).i want to buy some of these before they go up in price

 

You will need the Hayabusa ones. The GSXR 1000's will work for a stock or lightly modified engine, but for anything crazy, you'll want the ones from the 'busa.

 

poop

dam hard to find them

yuo really think 4 mm is going to make that much of a diff

 

up

 

thats 16mm overall! thats huge...its almost 20% of what a normal throttle body would offer!

 

a single itb barrel needs to be sized to handle the max cfm of the entire engine... you should be able to calculate that max cfm potential, based on headflow vs. displacement.

camshafts, headers, etc., aren't gonna change that, but they will get you closer to the ultimate headflow potential, because they increase the efficiency.

i think that the stock h22 came with a 60mm tb? but stock 3800cc mustang v-6's came with 50-60mm tb's, or a 65mm tb for the l36... the little honda motor is more efficient, with a superior head design, but 60mm?

i wouldn't rely on the stock honda tb size to determine what you want in itb sizing... http://www.jenvey.co.uk/ recommends 42mm itb's for up to a ~224hp engine.

the problem with going too big on any tb is something called tip-in, i believe, wherein you have too much flow potential at very small throttle plate openings... and you might see the max flow potential of the engine at only half-throttle... the car would be difficult to drive on the street.


Modified by danimal at 5:00 PM 3/11/2004

 

thank you very much ..thats some of the best info ive ever got here

as far as mods go i plan on using the f20b with the gsxr 42mm(i can always get them bored out right ?)prospeed anr header.2.5 inch exaust /cams jun 3s or corwer equivilent grind and a bvbit more compression 11.5 or more i thikn the 42mm will give a nice midrange as well as some top end ..i dont need to run super high rpm this will be a daily driver/track car..

as far as i see (and im probly wrong) but if the stock throttle body can hamdle all 4 cylinders and produce 200hp then the 42mm per cylinder is pretty dam good ...but then again im new to all this

but thanks for the good info ...ill take more if you got it

 

what's the pricing on boring out the itb's?... if you are close to the cfm limit, you might be able to profile the throttle shafts/plates instead... it would be a small gain(5%?), it's a fairly common procedure on carbs, but i don't know the potential with throttle bodies.

the main thing to keep in mind is that you aren't getting the head ported, so all you need to worry about is getting itb's that match whatever the max hp/cfm potential of the head is.

all that cams, headers, intakes, etc. allow you to do is reach the ultimate potential of the head... unless you can get some serious helmholtz resonator thing going on??

here is some h22 math i posted to another thread: https://honda-tech.com/zerothread?id=698160

try plugging in your displacement numbers, and maybe use the 2200 factor, since you have a real street car.

in a perfect world, you'd get the itb's put on a flow bench, so that you would know the exact potential.

here is a bit more info on flow benches, and a conversion chart: http://www.highperformancepont..._flow/

you'd want to match up the h22 head's 160cfm@10" of water to whatever inches of water measurement you used to flow bench the itb's... that would get you in the ball park.

i can tell you that 48ida carbs w/38mm venturi's flow well over 300cfm@28" of water... your 42mm itb's will easily outflow that, 42mm vs. 38mm... converting the h22 head flow to 28" of water(160cfm X 1.67) = 268cfm@28" of water?? looks like you have some room left.

you can find some headflow numbers in the archives at: http://www.alaniztechnologies.....html

i sure wish that joe posted exhaust port numbers as well!

 

wow is all i can say

 

http://cgi.ebay.com/ebaymotors...=6755

Busa throttle bodies on Ebay.

 

you shouldnt be posting stuff like that onm here grrrrr...i found them yesterday and i am bidding but they have some bent butterflys...dont know how the hell that happened ...hopefully noone else needs then cause i really do ......please think of my family ....my kid needs these to get through all the medical bills