i have installed a GT35R kit from Rx7Store on a streetported motor. currently running the motor in the using existing fuel maps tuned for 300whp on the original twins. Still running low boost for the run-in time but before i did the motor i was running 11-12Psi max.

planning to up the boost to 17-20Psi max in the near future, but require a fuel upgrade and a new MAP sensor to make that happen. have an upgraded mazdaspeed fuel pump installed.

the exisiting throttle elbow has two spare unused injector ports on it. my question is whether there is any merit in making use of these with a small controller to add the extra fuel or should i rather upgrade the secondary fuel rail to 1680's.

Have seen a similar FD with a set of four extra injectors planted straight into the UIM.

trying to stay on a budget, but i am open to suggestions.

 

just get the 1680s in the rear and put the 850s in the primaries znd you should be fine.

 

darkside, can this be done using the OEM standard fuel rails?

 

well yes and no. You can use your primary rails but you will have to mill it to fit the 850cc injectors. The 1680 will require a new rail. Just buy the cj motorsport fuel kit or the kg fuel kit. This will make your life a lot easier.

Eddie

 

would i be correct in assuming then that no one really likes the idea of adding extra injectors ?

 

It is not common practice to retain the stock injector and add two other additional injectors... Easier...better to just upgrade the stock location injectors first. The car you are refering to with four injectors planted into the LIM was probably using a GZ (Xcessive) LIM. It has ports for 4 injectors. I have this LIM and it was a great upgrade (equal length runners) even though I only still run 2 primary and 2 secondary injectors.

I would just follow darkside's advice and get the KG fuel kit... It is a pretty simple install.. but don't forget you will have to adjust your PFC or other fuel management system according to the injectors you install.

 

850/1680 for that boost level

 

at what boost level (or maybe whp) is it necessary to upgrade to bigger injectors?

i also read somewhere that the stock MAP sensor is ok upto 20PSI..is this correct?

 

The new approach to running 1680s is to use FJO's driver box instead of resistors. In your case, I think running each secondary signal to 2 channels on the FJO and running a pair of 850s as 1700s might work well. This would be much cheaper than running 1680s with an aftermarket rail and the FJO.

Alternatively, I might be tempted to run alcohol injectors in the elbow to complement the stock fuel system.