efi tune up 1.4...

this time we attack the intake side... throttle body...



the original throttle body that came with the injection package had just 46mm in bore diameter... fairly suitable for standard 1.3L engine... but with the current displacement i'm having, i needed something bigger...

i was planning on getting a 50mm throttle body from 4g92p (1.6 wira) but the prices are kinda steep... halfcut shops are selling at approx Rm350 each...

fortunately i found someone selling this particularly rare throttle body from perdana sei which uses 4G63 SOHC engine... it measures 54mm in bore size diameter... price kinda cheap, Rm220 to be exact...



FYI, the ISC for 4G13, 4G15, 4G92p and 4G63 sohc is the same... hence, its plug and play...

installation was done at home by myself... bought new 0.8mm paper gasket to prevent air leak in between throttle body and intake manifold...



installation was abit tough because the coolant inlet and outlet piping is at the wrong position, blocked by the water temperature sensor... the usage of coolant flowing into the throttle body is to actuate the so-called "autochoke" function to ease cold start in the morning... in the end, i forced and twisted the metal piping away and bypass the coolant so that it does not flow into the throttle body...

i also made a crude heat shield protecting the plastic ISC unit from direct contact with the intense heat from the coolant hose running below the throttle body...



fired up the engine... soon after i found my idling rpm is vr high, approx 1.8k rpm... managed to turn down my idle rpm till the minimum by closing tight the idle air bypass hole and throttle spindle hold back screw... yet, my idle still maintain approx 1.2k and fluctuates 1.2k-1.5k when engine warmed up... my mechanic said too much air leaking through, hence causing the idle fluctuation... he suggested me to remove the ISC completely so not much air will leak through...

another problem i'm facing after swapping to larger throttle body is partial throttle response... the TPS that came with the perdana sei throttle body has 3 pinouts while original 1.3 throttle body has 4 pinouts... the previous seller recommend me to use back my original TPS...

the problem is... maintaining the TPS at stock setting, partial throttle has very bad response... as if throttle body isnt communicating with the ecu... this can be solved by advancing the TPS setting, but creates another problem... advance TPS setting will cause high AF mixture, hence deteriorating the fuel economy...

in the midst of giving up, i swapped the 4 pinout TPS with my 3 pinout TPS and see whats what...



to my surprise, the engine runs smoother than before... latest calculation gives me slightly better fuel economy compare to previous original 4 pinout TPS...

due to slightly larger intake, the engine AF mixture would had messed up... and yes it is... oversize throttle body is certainly letting too much air into the engine..



damn, i'm in desperate need of adjustable fuel pressure regulator to bump up the fuel pressure...