bucking when going into boost - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

spools420a · 08-19-2021, 11:23 AM

I dont want to leave behind a dead ed thread so heres the update

the isssue is fixed!!!

thanks again for your help

I cant say for sure which fixed the issue so let me go along the last things i did

I gapped the plugs from .28" to .23" ( I plan on upping the gap till i budget some breakup then gapping down from their to get the best gap possable)

I took out the fuel injectors and noticed one had 2x tears on the bottom O-ring,The tears were in a spot the fuel wasnt leaking out but could have been seeping boost past the the lower o ring.

installed a tomei AFPR and bought a good marshal oil filled guage and set the fuel pressure to this.This was important for me because I had 3 different fuel pressure guages and all 3 read different numbers so I invested in a more expensive guage and went off that,also tested the tomei fpr by adding psi to make sure fuel pressure was rising 1:1 ratio

one of these or all of these seemed to fix the issue as it no longer breaks up under boost.

from here I do see another issue and thats Im reading around a 10.8 afr at higher rpm under boost.

would lowering the fuel pressure a few psi maybe help combat this?right now fuel pressure is 36psi with vaccum and 43psi without vacuum.I really dont want to go safc if i dont have too.Thoughts on lowering the FP to lean out the mix a tad,would lowering the FP even be enough to get me in the 11 afr?

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08-19-2021, 11:23 AM	#28
spools420a Zilvia Junkie Join Date: Dec 2009 Location: phoenix az Age: 43 Posts: 460 Trader Rating: (1) Feedback Score: 1 reviews	I dont want to leave behind a dead ed thread so heres the update the isssue is fixed!!! thanks again for your help I cant say for sure which fixed the issue so let me go along the last things i did I gapped the plugs from .28" to .23" ( I plan on upping the gap till i budget some breakup then gapping down from their to get the best gap possable) I took out the fuel injectors and noticed one had 2x tears on the bottom O-ring,The tears were in a spot the fuel wasnt leaking out but could have been seeping boost past the the lower o ring. installed a tomei AFPR and bought a good marshal oil filled guage and set the fuel pressure to this.This was important for me because I had 3 different fuel pressure guages and all 3 read different numbers so I invested in a more expensive guage and went off that,also tested the tomei fpr by adding psi to make sure fuel pressure was rising 1:1 ratio one of these or all of these seemed to fix the issue as it no longer breaks up under boost. from here I do see another issue and thats Im reading around a 10.8 afr at higher rpm under boost. would lowering the fuel pressure a few psi maybe help combat this?right now fuel pressure is 36psi with vaccum and 43psi without vacuum.I really dont want to go safc if i dont have too.Thoughts on lowering the FP to lean out the mix a tad,would lowering the FP even be enough to get me in the 11 afr?