rich on boost and engine pause after low boost release

[evolution23]

EDIT: fixed it! ended up that it was leaking pressure in the tank from a bad connection or hose. replaced both soft lines in the tank and 4 under the hood. cars running/boosting great now.


1994 gts-25t
walbro 255lph
sard fpr
.8 bar
fmic
stock ecu
HKS SSQV BOV

on the wideband im seeing 14's - 15's at idle and normal driving which is good but under boost im seeing 11's - 12's, is it normal to be running this lean under boost? I tried swapping the stock fpr back on and car was idling in 16's so i put the sard back on. Its set at 35psi with vacuum, 43psi w/o vacuum. It is a rising rate fpr.

other question is since i have installed the fmic i have noticed while cruising on the highway if i give it a bit of gas to pass someone and the turbo spools up just a bit (something like .2 bar) then the bov will release and just after it releases the engine sometimes kind of pauses or almost dies it seems and it feels like i hit extremely strong head on wind. enough to knock your head forward. only pauses for a second and only does this when it releases at very low boost and has only started doing this after i installed the fmic. I have tested and only had 1 intake leak on the fmic intake coupler and it was sealed up immediately and made no difference.

[evolution23]

Updated. Any suggestions?

[Fred-R]

IMO the readings on your wideband seem to be fine. 14-15 on idle is ok. The important thing to watch is when on load/boost. When boosting, you should read 11.1 to 11.6 isshh....

For your other problem, i can't answer that, sorry....

[nimblestix]

Just a guess based on no real thoughts or research but :

If the ssqv is adjustable try tightening the spring to have it release under a higher boost level. It might be dumping ALL of the pressure out of the intake system causing the lag.

I could also be talking out my a$$ lol. Good luck bud!

And as Fred said your afrs are okay, but you might want to inquire further about being above 12 under boost. Healthy is 10.9-11.9
Sent from my Galaxy Nexus using Tapatalk 2

[Skym]

The release part will probably be that BOV needs adjusting, as mentioned above. If use atmosphere BOV with draw through MAF (stock MAF setup) it can make engine stall. Factory recirculate the air from stock BOV, so doesn't reduce amount of air inside intake piping. Atmosphere BOV releases air to engine bay, so reduces amount of air inside intakepiping. If air is removed from intakepiping via atmosphere vented BOV, the engine goes rich and stalls, as ECU has no way to compensate (adjust fueling) for loss of air behind MAF.

Also the slow down of turbo (due to engine running rich, etc) makes air reverse direction from front of turbo (called reversion) and affects MAF (moving MAF further away from front of turbo helps to reduce this reversion effect). Cheaper and easier to just change BOV to recirculate type of BOV like Synapse or similar.

Synapse BOV for R33 -

http://synapseengineering.pinnaclecart.com/products/Synchronic_Single_DV_Kit_for_Nissan_GTS_R32_R33_and_R34_with_Single_Turbo-646-16.html

Neat part about Syanpse BOV is it can be configured to be push type like stock BOV (for overboost protection) or pulltype (boost holds valve closed) like with the BOV you have. Synapse BOV has no diaphram, so engine heat doesn't affect BOV diaphram like with what you have. Also it can be recirculated for a draw through MAF setup and doesn't need any adjustments from factory. It just works.

The lean part might be lack of voltage to fuelpump or have to adjust FPR so injects more fuel (tune on dyno). Aftermarket fuelpumps need more voltage than stock fuelpump. Can hardwire fuelpump so roughly 14-15 volts goes direct from battery to fuelpump via a relay, fuse, etc.

Fuelpump hardwire kit -

http://www.deatschwerks.com/fuel-pump-hardwire-kit

Another way to solve the atmosphere BOV problem is to fit a ECU with MAP sensor, like Link G4 ECU, ViPEC ECU, etc that has MAP sensor on intake manifold, so can compensate for less air inside intakepiping.

[evolution23]

thanks for the replies guys, as for the pause when the bov releases at low boost, it happened more with my stock recirculation bov. it has only happened a couple times since fitting the HKS.

Anyways, i stopped at racing greed today to try and trouble shoot the boost issue. the car would reads 10.75 under 12psi boost (engine starts bogging when in the 10's) but this is where it gets weird.. on the way to RG today i did a few pulls and the car kept running in the 10's and bogging down a bit losing its power. i got to RG and we were looking around to see, i turned down the boost 2 clicks and we took it out for a drive and it started running lean under boost (drops to 10's for a second then rises to 13's) so i wasnt sure why it started rising and going lean so i turned the boost back up and we tried again and it kept running lean now. so i have no idea what is going on. it was doing this all week and the entire way there, it would stay in the 10's on boost and bog down. now it is going lean and losing power. im at a loss. Anyways pressure are set right (35 & 43psi), voltage is good to the pump, new fuel filter, new walbro pump, etc.. but the guys at RG said they think my pump is leaking pressure somewhere as when the key is turned off, pressure drops immediately and when key is turned on it is "slow" to build. and is only spiking to about 45psi under boost then backs off to 40psi. SO either a problem with the FPR or the pump they figure and they said the regulator seems fine. just seems odd that all of a sudden after touching the boost controller the a/f was giving diff readings.. it would drop to 10's under boost, engine would clearly bog down (felt different than leaning out) but now its leaning out. weird.

[speed]

korbin you need a new car!

[evolution23]

korbin you need a new car!

lol no no none of that. most of it is good now. thinking my fuel system is leaking pressure and that it could use new fuel rail/injectors and all new gaskets/fluids then pretty much completely tuned up and back to its former glory.