Ok so for those of you who have me on FB know i've been running over this non stop..
But for those of you who don't have me on there, let me gladly explain my situation..
I took my rebuilt (completely rebuilt..) 32 GTS to the dyno the other day. Everything started off great besides my car being on knock maps (Knock sensors were faulty). This was tuned out. The Z32 maf was tuned in, and we were good to go.. A base run showed something in the numbers of 310whp / 280 ft lbs of tq.. This was with VERY safe AFR's (we're talking mid 11's..) and negligible timing. So there was definitely a lot more to take off this motor.. Anyways, as it progressed, we encountered a sudden lean condition. I noticed the FPR closest to the fire wall (since the RB20 has 2 on the fuel rail system for arbitrary reasons..) had lost its boost/vac signal from the plenum. Obviously this promotes the diaphragm inside to close, cutting fuel intake to vac conditions, so it was obvious why we were running into lean spots. I replaced the hose, and we continued, but to my dismay we were still running lean..
So to date, the car idles fantastic on cold start maps. Sees stoich regularly but then drifts into the 15's when the running maps enable.. Now it's not horrible, but the worst part is then whenever the gas pedal is depressed or we give it some degree of air, we run into a total lean condition. Tapping of the pedal goes - 12:1 directly to 16:1 and back. So there is definitely a lean situation involved and from what i can tell on nistune the AFR's should be safely in the 12:1 range with the foot down.
So far i have done this;
1. 150 compression across, cold
2. No exhaust leaks
3. No intake leaks (holds 20 psi steady with a pressure testing system i fabbed up)
4. Plugs are RICH (black but not terribly)
5. New Walbro 255 pump (Edit - pump runs 13.64 V at ALL times .. Is on a direct 12 v feed from battery with relay)
6. New vac lines to FPR's
7. Z32 is clean and runs proper voltage (checked with consult via nistune)
8. New plugs
9. Timing is 25 BTDC (this was tuned)
10. ... and cams are 15 degrees respectively and 5 BTDC
11. Wideband is not faulty - seeing the same readings on both the innovate and AEM respectively
12. New fuel filter
13. Working injectors (checked for pulse)
I bought a fuel pressure tester - this is my next move obviously, as it seems to be the only remaining factor in this mess.
The only thing i cant wrap around my mind is - HOW ON EARTH could my car gone from a perfect running condition, to massively lean on the dyno? And if it is low pressure, why?? What could possibly clog the lines.. I'm aiming at the FPR's being faulty. IF the vac line blew off the plenum then perhaps the diaphragm is cooked inside and is what lead to it blowing off in the first place..
I'm really stumped, this is by far the most confusing issue i've ever dealt with and for those of you following my build and helping me out along the way, you KNOW i've dealt with a lot of stupid, mind boggling problems..
Anything else you guys need, shoot it.. I have endless amounts of data logs sitting here that all lead to dead ends, but i'll gladly supply any essential info!
But for those of you who don't have me on there, let me gladly explain my situation..
I took my rebuilt (completely rebuilt..) 32 GTS to the dyno the other day. Everything started off great besides my car being on knock maps (Knock sensors were faulty). This was tuned out. The Z32 maf was tuned in, and we were good to go.. A base run showed something in the numbers of 310whp / 280 ft lbs of tq.. This was with VERY safe AFR's (we're talking mid 11's..) and negligible timing. So there was definitely a lot more to take off this motor.. Anyways, as it progressed, we encountered a sudden lean condition. I noticed the FPR closest to the fire wall (since the RB20 has 2 on the fuel rail system for arbitrary reasons..) had lost its boost/vac signal from the plenum. Obviously this promotes the diaphragm inside to close, cutting fuel intake to vac conditions, so it was obvious why we were running into lean spots. I replaced the hose, and we continued, but to my dismay we were still running lean..
So to date, the car idles fantastic on cold start maps. Sees stoich regularly but then drifts into the 15's when the running maps enable.. Now it's not horrible, but the worst part is then whenever the gas pedal is depressed or we give it some degree of air, we run into a total lean condition. Tapping of the pedal goes - 12:1 directly to 16:1 and back. So there is definitely a lean situation involved and from what i can tell on nistune the AFR's should be safely in the 12:1 range with the foot down.
So far i have done this;
1. 150 compression across, cold
2. No exhaust leaks
3. No intake leaks (holds 20 psi steady with a pressure testing system i fabbed up)
4. Plugs are RICH (black but not terribly)
5. New Walbro 255 pump (Edit - pump runs 13.64 V at ALL times .. Is on a direct 12 v feed from battery with relay)
6. New vac lines to FPR's
7. Z32 is clean and runs proper voltage (checked with consult via nistune)
8. New plugs
9. Timing is 25 BTDC (this was tuned)
10. ... and cams are 15 degrees respectively and 5 BTDC
11. Wideband is not faulty - seeing the same readings on both the innovate and AEM respectively
12. New fuel filter
13. Working injectors (checked for pulse)
I bought a fuel pressure tester - this is my next move obviously, as it seems to be the only remaining factor in this mess.
The only thing i cant wrap around my mind is - HOW ON EARTH could my car gone from a perfect running condition, to massively lean on the dyno? And if it is low pressure, why?? What could possibly clog the lines.. I'm aiming at the FPR's being faulty. IF the vac line blew off the plenum then perhaps the diaphragm is cooked inside and is what lead to it blowing off in the first place..
I'm really stumped, this is by far the most confusing issue i've ever dealt with and for those of you following my build and helping me out along the way, you KNOW i've dealt with a lot of stupid, mind boggling problems..
Anything else you guys need, shoot it.. I have endless amounts of data logs sitting here that all lead to dead ends, but i'll gladly supply any essential info!
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