Rb20 blow by / power loss issues - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

steveff · 08-08-2016, 09:30 AM

What's up guys. Having a few issues with my RB (shocker, right?) and wanted some opinions because it's hard to find good information in my area and I'm not finding too much online. I search every day so I'm not being lazy.

Let me start by saying this IS a drift car. Sees street time but it's mainly just testing.

Issue #1:
Having crazy blow by issues with my motor. Running an rb25 turbo at 13psi. Street driving it's fine but at the track last event I was blowing by a liter of oil in 2 laps. Literally rigged a catch can to a catch can just so I can run it more than one lap at a time. Compression is perfect, dead nuts, on every single cylinder. No smoke out the exhaust of any kind or color. Every so often it blows oil out the dipstick too. Going to run a larger catch can with larger ports for more crank pressure release. And potentially just run a drain from the catch can to the sump unless I figure out the issue, if there is one.

Issue #2:
Every so often, when at 13psi I lose power after 5k. Feels like I lift up on the throttle almost like its retarding timing a shit ton. Doesn't sputter or fuel cut or surge. Just feels like I have 50hp. Octane booster helped the issue, made it only happen about 15% of my runs. But it still happened every once in a while. I'd be in 3rd pegging the limiter on one turn and bogging in 2nd, fighting to keep revs up around the next turn. (And no, I wasn't just bogging the motor, it was well in the normal power band)

Before octane booster it cuts power 80% of the time. After octane booster it cuts power 10-15% of the time. Only run Shell 93 v power nitro. And have a walbro 255 pump.

Tuned by RS Enthalpy. Have Splitfire coils so I doubt it's not getting enough spark up top. Putting new plugs in today. Switching from NGL BKR7 to NGK BCPR7 to see if it helps.

Also going to test voltage at fuel pump to see if it's dropping off, but air fuel ratio doesn't lean out when I have the drop in power. Battery voltage and boost pressure read the same as well. Holds 13psi just feels like it has no power.

Picture of my car for shits and giggles.

Sent from my iPhone using Tapatalk

KAT-PWR · 08-08-2016, 09:39 AM

What are the actual compression numbers. Sounds like rings are done-zo

steveff · 08-08-2016, 10:32 AM

Dead on 150 on all 6.

Sent from my iPhone using Tapatalk

Kingtal0n · 08-08-2016, 05:45 PM

sounds like its running lean, you have no wideband or arn't logging it, thus the broken piston(s).

steveff · 08-08-2016, 05:49 PM

Pistons aren't broken? Compression is damn near perfect... FSM states 165 is perfect. So 150 isn't far off. And all 6 are equal at 150 with literally 0psi variance.

Replaced plugs. Power loss is gone on 3 pulls I did. Air fuel is now at 15:1 at full boost at high revs though. Noticed a/f on the 3rd pull.

Trying the fuel pump rewire tonight or tomorrow. Will report back.

Sent from my iPhone using Tapatalk

steveff · 08-09-2016, 10:58 AM

Update:

Replaced plugs with BCPR7ES-11 gapped at .030

Hard wired fuel pump

Still losing power and leaning out around 5k and up in the rev range.

Sent from my iPhone using Tapatalk

steveff · 08-11-2016, 11:16 AM

Dropped boost from 13 to 10psi and raised fuel pressure from 43psi to 45psi without vacuum line and still running 15:1 under boost.

Lower boost should eliminate chance of injectors being the issue?

Pre tune it ran about 13:1 at 13psi with race fuel/ 93 octane mix on track days. And ripped like a bat outta hell.

Now it's running crazy lean at every point other than light cruising. With more fuel pressure and less boost. Timing remained the same @ +20deg.

Sent from my iPhone using Tapatalk

steveff · 08-16-2016, 10:14 AM

Waiting on 550cc injectors to arrive in the mail. Waiting to see if this fixes the issue. Already had Enthalpy send me a new tune for them. Now we wait...

While I'm waiting I'm figuring out how to plumb a new catch can set up.

Probably going to run a closed loop with a drain line doing to the sump. Any idea if I still need to vent the sump and run 2 lines to it? The can will be under vacuum from being connected to the intake tube.

Plumbing will go as follows:
-Both valve covers to catch can via 2x -10AN lines
-Catch can (bottom) drain to sump via 1x -12AN line T-d into existing turbo oil drain line on the block
-Catch can (top) routed to intake tube after maf via 1x -10AN line
-Will still be running intake-side valve cover to factory PCV valve
-Air oil separator (for added filtration) in-line with catch can line routed to intake tube

Think this will create an environment preventing oil from traveling from the sump back into the catch can? I'm thinking the -12AN line is large enough to provide enough air to vent the sump while blow by oil travels through it.

The turbo oil drain line isn't vented......unless it's vented through turbo vacuum? If that makes sense. So in theory creating vacuum in the catch can will provide the same effect?

Or am I wayyyy off?
Thoughts?

08-08-2016, 05:45 PM	#4
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	sounds like its running lean, you have no wideband or arn't logging it, thus the broken piston(s). __________________ 5.3/4l80e/turbo 240sx playthrough: tinyurl.com/4l80er

08-08-2016, 09:30 AM	#1
steveff Zilvia Member Join Date: Mar 2012 Location: New Jersey Posts: 295 Trader Rating: (1) Feedback Score: 1 reviews	Rb20 blow by / power loss issues What's up guys. Having a few issues with my RB (shocker, right?) and wanted some opinions because it's hard to find good information in my area and I'm not finding too much online. I search every day so I'm not being lazy. Let me start by saying this IS a drift car. Sees street time but it's mainly just testing. Issue #1: Having crazy blow by issues with my motor. Running an rb25 turbo at 13psi. Street driving it's fine but at the track last event I was blowing by a liter of oil in 2 laps. Literally rigged a catch can to a catch can just so I can run it more than one lap at a time. Compression is perfect, dead nuts, on every single cylinder. No smoke out the exhaust of any kind or color. Every so often it blows oil out the dipstick too. Going to run a larger catch can with larger ports for more crank pressure release. And potentially just run a drain from the catch can to the sump unless I figure out the issue, if there is one. Issue #2: Every so often, when at 13psi I lose power after 5k. Feels like I lift up on the throttle almost like its retarding timing a shit ton. Doesn't sputter or fuel cut or surge. Just feels like I have 50hp. Octane booster helped the issue, made it only happen about 15% of my runs. But it still happened every once in a while. I'd be in 3rd pegging the limiter on one turn and bogging in 2nd, fighting to keep revs up around the next turn. (And no, I wasn't just bogging the motor, it was well in the normal power band) Before octane booster it cuts power 80% of the time. After octane booster it cuts power 10-15% of the time. Only run Shell 93 v power nitro. And have a walbro 255 pump. Tuned by RS Enthalpy. Have Splitfire coils so I doubt it's not getting enough spark up top. Putting new plugs in today. Switching from NGL BKR7 to NGK BCPR7 to see if it helps. Also going to test voltage at fuel pump to see if it's dropping off, but air fuel ratio doesn't lean out when I have the drop in power. Battery voltage and boost pressure read the same as well. Holds 13psi just feels like it has no power. Picture of my car for shits and giggles. Sent from my iPhone using Tapatalk

08-08-2016, 09:39 AM	#2
KAT-PWR Nissanaholic! Join Date: Dec 2011 Location: US Posts: 2,040 Trader Rating: (11) Rides Gallery: KAT-PWR Feedback Score: 11 reviews	What are the actual compression numbers. Sounds like rings are done-zo __________________ MRP Manufacturing

08-08-2016, 10:32 AM	#3
steveff Zilvia Member Join Date: Mar 2012 Location: New Jersey Posts: 295 Trader Rating: (1) Feedback Score: 1 reviews	Dead on 150 on all 6. Sent from my iPhone using Tapatalk

08-08-2016, 05:49 PM	#5
steveff Zilvia Member Join Date: Mar 2012 Location: New Jersey Posts: 295 Trader Rating: (1) Feedback Score: 1 reviews	Pistons aren't broken? Compression is damn near perfect... FSM states 165 is perfect. So 150 isn't far off. And all 6 are equal at 150 with literally 0psi variance. Replaced plugs. Power loss is gone on 3 pulls I did. Air fuel is now at 15:1 at full boost at high revs though. Noticed a/f on the 3rd pull. Trying the fuel pump rewire tonight or tomorrow. Will report back. Sent from my iPhone using Tapatalk

08-09-2016, 10:58 AM	#6
steveff Zilvia Member Join Date: Mar 2012 Location: New Jersey Posts: 295 Trader Rating: (1) Feedback Score: 1 reviews	Update: Replaced plugs with BCPR7ES-11 gapped at .030 Hard wired fuel pump Still losing power and leaning out around 5k and up in the rev range. Sent from my iPhone using Tapatalk

08-11-2016, 11:16 AM	#7
steveff Zilvia Member Join Date: Mar 2012 Location: New Jersey Posts: 295 Trader Rating: (1) Feedback Score: 1 reviews	Dropped boost from 13 to 10psi and raised fuel pressure from 43psi to 45psi without vacuum line and still running 15:1 under boost. Lower boost should eliminate chance of injectors being the issue? Pre tune it ran about 13:1 at 13psi with race fuel/ 93 octane mix on track days. And ripped like a bat outta hell. Now it's running crazy lean at every point other than light cruising. With more fuel pressure and less boost. Timing remained the same @ +20deg. Sent from my iPhone using Tapatalk

08-16-2016, 10:14 AM	#8
steveff Zilvia Member Join Date: Mar 2012 Location: New Jersey Posts: 295 Trader Rating: (1) Feedback Score: 1 reviews	Waiting on 550cc injectors to arrive in the mail. Waiting to see if this fixes the issue. Already had Enthalpy send me a new tune for them. Now we wait... While I'm waiting I'm figuring out how to plumb a new catch can set up. Probably going to run a closed loop with a drain line doing to the sump. Any idea if I still need to vent the sump and run 2 lines to it? The can will be under vacuum from being connected to the intake tube. Plumbing will go as follows: -Both valve covers to catch can via 2x -10AN lines -Catch can (bottom) drain to sump via 1x -12AN line T-d into existing turbo oil drain line on the block -Catch can (top) routed to intake tube after maf via 1x -10AN line -Will still be running intake-side valve cover to factory PCV valve -Air oil separator (for added filtration) in-line with catch can line routed to intake tube Think this will create an environment preventing oil from traveling from the sump back into the catch can? I'm thinking the -12AN line is large enough to provide enough air to vent the sump while blow by oil travels through it. The turbo oil drain line isn't vented......unless it's vented through turbo vacuum? If that makes sense. So in theory creating vacuum in the catch can will provide the same effect? Or am I wayyyy off? Thoughts?