60lbs with ZZP Boost Reference Fuel Pressure System
07-12-2012, 08:08 AM
#51
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You can't rely on a canned tune to be solid. It's only intended to "get you on the road". You need to either find a local tuner or go directly to them for dyno tuning. There's too many things that can throw off a canned tune which is why they are so conservative. Plus every car is different and ZZP nor anyone else can really 100% accurately determine how to set up a tune without physically hooking it into hptuners
07-15-2012, 08:47 PM
#53
Here's what TurboTim said.
60 # injectors are very large and don’t like to work below about 1.2 milliseconds. So since the 2.0L LSJ engine has 60psi of base fuel pressure, at idle the engine needs such a small injector pulsewidth that the injectors can start to cut out and cause idle surge. Lowering the base fuel pressure to around 40psi at idle will remove enough fuel to increase the idle pulsewidth enough to keep the injector pulsing.
Its pretty typical to get idle surge with large injectors. The pulsewidth gets so small at idle that the injectors cant open and close fast enough and then it drops a cylinder here and there and the PCM senses that so it opens the TB and surges up, then back down and repeat.
60 # injectors are very large and don’t like to work below about 1.2 milliseconds. So since the 2.0L LSJ engine has 60psi of base fuel pressure, at idle the engine needs such a small injector pulsewidth that the injectors can start to cut out and cause idle surge. Lowering the base fuel pressure to around 40psi at idle will remove enough fuel to increase the idle pulsewidth enough to keep the injector pulsing.
Its pretty typical to get idle surge with large injectors. The pulsewidth gets so small at idle that the injectors cant open and close fast enough and then it drops a cylinder here and there and the PCM senses that so it opens the TB and surges up, then back down and repeat.
07-15-2012, 11:24 PM
#57
he said he subscribed to the thread. if it were me, i would just throw on the 60s and tune it. if your unhappy with it, then get the boost referenced system. im on 60s that arent flowmatched and i just copied and pasted the fueling values from the spreadsheet on the redline forum and it works fine. i do have idle surges when i drop the car into neutral and decellerate to a stop, but its only minimal. every now and then itll shut off the car at the end of the stop, but its not that big of a deal.
get some matched 60s with a flow sheet. thatll make them run smoother after finer tuning is done to the injector flow rate. and youll have better fuel trims.
i can only get to +or- 5 with my ltft+stft, which is good enough, but im either gonna go with injector dynamic's injectors or order some 60s from racetronix so i can get a flow chart with them. no vendor on here from what i know will give out flow charts
get some matched 60s with a flow sheet. thatll make them run smoother after finer tuning is done to the injector flow rate. and youll have better fuel trims.
i can only get to +or- 5 with my ltft+stft, which is good enough, but im either gonna go with injector dynamic's injectors or order some 60s from racetronix so i can get a flow chart with them. no vendor on here from what i know will give out flow charts
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