OK guys its been a while but im ready to get back on the rx7 again.
I recently bought a webber IDA carb thats boost preped and has a carb hat.
The car runs great when i put the carb on but i didnt have the piping made up yet
. When i put the piping all in and took for its madain voyage underboost. it fell flat on its face. As soon as the engine sees any kinda boost it leans way out and starts backfireing and stuttering. My fuel pressure is around 9 psi. Im not sure if this is enough or not but seems good. Now last time i talked to robert and gave him the numbers on the jets and e tube. he said he was gonna send me knew ones but he never told me what sizes.
I dont know much about the carb but im reading as much as i can.
Here are the sizes.
The top jet. is a 160
The e tube is a F7
and the bottom jet is a 180

I dont know what sizes i need and how the numbering system works
If and of you guys have any suggestions on what jets to get let me know please.
I have a 12 a with a mild street port and a t3/t4 turbo. MSD efi fuel pump with a
mallory FPR that can knock down the fuel pressure to about 3 PSI if needed.
like i said before my fuel pressure at the carb is about 9 PSI.
I would like to boost about 10 psi maybe 15 at max.

Please ley me know if you have any suggestions on what size jets and e tube to use.
Thanks again,
old tex

 

please

 

F11 or a F16 e- tube will richen up the bottom end so it dosnt fall on its face.. if you slowly roll on the throttle it should accelerate.. a wideband O2 meter would help tons, we are just gussing otherwise.. your ignition might need work too.. what plugs are you running?

 

i have some ngks you told me to get with gap you said to set them at. i have a wide band
in my car and when i get to boost the gauge says the car leans completely off thye charts
lean. but when the piping is not connected the wide band says the car runs fine. right at about 13.5:1.
You say either a F11 or F16. Im guessing there is now F12,13,14 or 15?
Thats a big gap between 11 and 16 but then again i dont know much about this carb yet.

 

You have your base fuel pressure set at 9 psi, why?

 

Because thats what some one told me to set it at. What should it be set at?

 

3.5-4.5, iirc. If you're running the Mallory 4309 fpr, it should raise the fuel pressure 1:1 with boost when the port is connected.

 

your fuel pressure should be at 4 psi. #1 question what fuel pump are you running. If you're running a fuel pump that supplies any ess than 35 psi it WILL NOT work. sounds like your problem to me. Also you might want to get some smaller air correctors those are way to lean and you'll detonate on those. the sizes on the jets simply are size. 170= .17mm

 

I assume you are running a blow thru setup?

The float bowl vent, the screen covered thing you pull off to change jets, must see full boost pressure. Your air box on top of the carb must also pressurize that screened cover. The reason why is that the fuel delivery thru the fuel jets is determined by the pressure differential between the float bowl to the main carb throat venturies. If the boost pressure in the venturi is higher than the pressure in the float bowl, then the fuel will not flow thru the main jets and into your engine.

Also, in order for the float bowl to be able to receive fuel into the float bowl when under boost, then the fuel pressure must rise from 5 psi at idle no boost to boost + 5 psi fuel pressure when you are under boost. You must have a fuel pressure regulator that will vary fuel pressure with boost pressure. So if you ran 9 psi boost, then your fuel delivery system must deliver 5 psi fuel to the carb at idle and 14 psi fuel pressure to the carb when under 9 psi boost. The fuel system must always run at 5 psi above your boost pressure.

All of the above comments apply to a blow thru, not a suck thru, carb system.

 

yeah its a blow through system. I have a mallory 4309 FPR and the fuel pressure does increase like its supose to. Im running a MSD efi pump that puts out about 45 psi i beilive.
I will look up the part number when i get home from work.
But as far as my jet sizes and e tube do they sound correct.