ok guys i have a all new 12app in my s1 rx7. has a mx5 gearbox 5spd behind it.
has 48mm pp ports D shape. with a 48mm ida running 210 mains 120 air and f8 tubes. ( ive tryed 200 210 220 230 mains and 110 120 130 airs and f8 and f11 tubes.) timing is locked elec dizzy set at 20deg. exhaust is twin 2" (94" long) that takes it to diff and then joins into 2.5" over diff into stright through 3" dumpy muffler (yes its loud) its a road car to by the way.
my problem is it starts off key hot or cold no probs. idles mint. from around 4500 to 7000rpm is misses badly if to much throttle is given. you can ease through it then at around 8000rpm stomp on it and it will rev cleanly out to around 12,000rpm (its got 3 window bearings, all lightend and balanced, 6pound flywheel, crossed drilled eshaft etc etc etc) plugs were b9egv i just changed them to b8es to try and see.... no change. coils are bosh gt40 (the square ish ones) leads are all good etc. i was running the dizzy etc on my bridgeport with no problems at all.. the miss is like fouled plug miss. very very nasty... i can get it to do it in netural by free reving it. load etc doesnt seem to change it. HELP I NEED SUM IDEAS please

 

mine was similar, it felt like it hit a wall @3500. i put a wideband O2 on it, and found out that @idle, it gives you a pretty crap number, but @higher rpms, it works. i found out that it was way too rich when the main circuit came on. so i had to go WAY down from the 230mains that the competition book wanted.

since mine just stopped running, and yours misses, it might be that yours is lean, where mine was rich. i'd also suggest testing the fuel pump for volume AND pressure, i think i wound up with weird jets cause i'm running too much fuel pressure.

if you don't have a WB, try some weird stuff. try the biggest fuel jet and block the air. or take the airs out completely.

mine has a stock 12A air cleaner, so its corked up, but i ended up with a 175 fuel and i think 140 air, it drives like a stock FD, i could tow with it. oh i'm running a locked dizzy with an MSD, timing is about 18BTDC L&T together, rx8 leading plugs

 

im using a holley fuel pump (blue) and reg with psi at 3.5psi and the ida has englareged fuel bowl. if it was lean through jetting or lack of fuel im guessing it wouldnt rev out after the missing. from 7500ish rpm on.
i can hold it flat out in 5th at over 9000rpm and its fine. ive tryed uping psi to 5 and down to 2 with no diffrence jetting makes no change to miss if i use 200 or 230 mains etc

 

sounds like you need to bump your idle jet. what size venturies are you running? with a 45 venturies on TII full bridge, I had to use 80 and it wants more

 

i'd agree, but mine was super rich in the 2500-3500 area when the main circuit comes on, after that it leans out a little. also on mine going from 230 to 200, was still like 10:1 afr, i had to go to 175 to get it to mid 11's.

you need to think outside the box a little, that's why i'm suggesting to try as rich and as lean as it can go, it would also help to have some reference too, like a wideband.

 

Thats a huge RPM range to ask for a carb to make it run perfect. 4500-12,000rpm Choose your powerband
So your fine from 8000-12,000rpm
Could u just be way pig rich at the 4500-7000rpm range?

 

i use i on road as a daily driver. need the hole rev range. most of time it driven from 3000 to 7000 rpm round town every now and again it gets a wind up. 43mm venturies. dont think it rich from idle curcit to main as its starts missing bot 5000rpm aprox when im guessing it well on the main jets. cleans up around 8000rpm and runs fine and screams to bot 12 ish

 

http://youtu.be/hUv33Ukicrg

http://youtu.be/5PgdfHigcb4

both these were taken when it was just started up

 

you can test for this actually. take the main jet stack out and try to go around the block, you'll see what the idle circuit does.

to test the main circuit, floor it at an RPM right before the idle circuit dropped off. it'll run on the accelerator pump, and then its 100% on the mains, and you'll see what happens.

for example, mine with the big (150) air. floor it @1800rpm, it'll make it to about 2000 and then the engine shuts off. if i back off the gas the idle circuit will start working, and it'll start running. if i ease into it, and be floored by 2500 its fine.

mine with a 130 air, i can floor it @1800 and will stumble and then go, its rich.

mine with 140 air, i can floor it @1800 and it just pulls hard

 

just to let you all know im now running 180 main jets and 120 airs with f7 tubes and it goes mint, no missing etc. doesnt lean out up top untill 11000rpm. ill try 190 mains next week and see if i can get few more revs out of it

 

see! i'm glad its working! i'm sure its a FUN car...