rb20 wont run at 14psi?

[dwhe009]

Im still having trouble getting my rb20det engine going well.

standard computer

3" exhaust

big front mount

The problem is it runs very well at 10psi, but when i used a bleed valve to make it run 14psi ( standard turbo) it goes hard then cuts (like ignition cut). I pull over and check the self diagnostics and it shows 34, knock sensor. So i wound the base timing right of bit by bit until this does not happen, but by this stage the car is so retarded that it makes far less power than at 10psi.

The strange thing is i cannot hear the knocking at all though this.

Whats wrong?

What can i do to get it running better?

I am getting a rb25 turbo soon so i want to fix this promblem.

[sweetr33]

my rb25 used to do the same, used to go good on about12-13psi but anymore like 14-15psi and it used to do excatly the same thing as urs, i found that if u progressively put ur foot down once past 4000rpm then it worked fine, but obviously u dont want to drive like that. Its some sort of boost cut, im sure if u ran 12psi then it would be fine and go good then. U can get a fuel cut defender which will rectify the problem but rather save the 200 bucks and put it towards ecu.

[Cubes]

Check the plugs are connected properly on the knock sensor.

Check the fuel you are running, NO Premium. Its either a 98RON fuel such as BP Ultimate, Mobil Synergy 8000 or Optimax.

In the past with my RB20t I've had issues with knocking and hesitations when using Mobil Synergy 8000 fuel & running high boost with lots of ignition timing.

So It appears for my RB20t BP 98 has more head room and allows me to lean on it a little harder before detonation sets in.

If its nothing else then its an overactive knock sensor. Hence Dodgy.

[blind_elk]

Why not reset the timing for standard boost, then play with the bleed until it runs well.

I don't think it is ever going to run well at 14psi, but it may run well at 12 psi. And running well at 12 psi is FAR SUPERIOR to running against a brick wall at 14psi.

[BHDave]

Thats pretty weird as i ran up to 16psi in my r32 gtst with no problems, no boost cuts or anything.

What you are describing does sound like a cut though.

The error code is not necessarily saying your car is experiencing detonation, rather that you have a dud knock sensor. Try un plugging the sensor and see if you get the same error code. Also remember to reset the ecu once the knock sensors are unplugged as it displays all the old codes if you don't.

I would recommend winding the boost back to 12-13psi as a maximum as the turbo is at the edge of it's efficiency around this point anyway, once you start adding more boost you will definately start to get detonation without some sort of ecu mods

[Cubes]

Damn my Skim reading.... I missed the cut part.

Mine does that at around 17-18psi.

The RB30DET now does it at 8-9psi.

Just to note when I had mine on the dyno, as it nears the cut the fuel afr's really lean out bad. Like 14:1.

14psi sounds very low. Have you tried another AFM?

[ryan.e]

Hey mate i had the same problem with my 32 it was solved by adding a new computer or you could just buy a fuel cut defender. HKS make one bout $230

[dwhe009]

cheers guys,

I think i will try and see if the knock sensor is crook. How else could you test them?

[Cubes]

Sorry buddy.

If its fuel cutting then its not a knock sensor.

I skim read a lot and missed where you said it cuts (a bad habit i've developed due to reading so much for Uni)

Get it on the dyno and check the AFR's before you bother with a fuel cut defender.

The fuel cut is sometimes not directly related to the AFM voltage as with the rb30 the afm voltage hits around 3.5v and will fuel cut at 2500-3000rpm at 8-9psi. Even earlier if you load it up from really low rev's.

A few secs before it fuel cuts it leans out really bad so my guess is either the ecu's stock map has ran out of scope (duty cycle load etc) and freaks out in turn cutting all fuel. Another factory to consider with my motor but not yours is the rising rate fuel pressure reg is now seeing much less boost but expected to supply more more fuel pressure (which obviously doesn't work)

The RB25 head makes more power on 6psi than the rb20det head did on 11psi. So the fuel pressure isn't great enough which possibly causes my lean out.

Or the O2 sensor takes little samples every so often and fuel cuts when the afr hits 14:1 under load as that is where it will always fuel cut.

Not sure its a strange one.

[dwhe009]

well i have a VL commodore uel pump and have a jaycar mixture display and a fuel pressure gauge inside the car. I no the jay car thing isnt that accurate but it shows around 12-13:1 as this cut happens and i cant see the fuel pressure tappering off so........ ?

The thing is that the code 34 only comes up just after this cut happens....?

[dwhe009]

I would assume that its not making enough power (airflow) for the airflow meter to cut. All you guys get up around the 180+ rwkw range before the standard airflow meter maxes out... ?

[Mr GTS4]

at what rpm does it do it??? i had one knock senor dissconnected and it hit a wall at about 5 grand. would still go to 7 but just very slowly.

if its the knock sensor it will just retard the timing heaps.

[dwhe009]

yeah it happens at around 4-5000 rpm, but it cuts hard

[caminperth]

I thought at that sort of boost you usually max out the voltage on the AFM and the stock ecu cuts fuel - basically a method of boost cut.

Mine did it at 0.9bar on cold nights.. denser air means more airflow means more voltage for afm means maxed out afm..

[dwhe009]

yeah, i might have to drive around with meter on airflow signal. but at the moment its far to wet outside. i have shit tyres so it just wheelspins like mad.

Am i correct in saying the max voltage is 5.1 V ?

Surely this cant be happening as it happens at only 5000rpm. I thought it then happen at 10psi at 7000rpm? same airflow approx?

[The Dan]

Boost cut is at 20.5 PSI.

Sounds like your AFM is on it's way out. Possibly a coil pack as these play up around the same RPM.

Knock sensors usually only pick up signals at around 3800 RPM through to 7900 RPM

[The Dan]

you will find that 90% of R32 skylines have error code 34 come up. I don't think this is your problem.

[dwhe009]

3LIT3 FORS3,

how can a r32 have a boost cut, it has no map sensor. Cant it only have a airflow cut?

If a coil pack was dodgy, then one cylinder would just miss, not cut. wouldn't it?

When you say 90% of all R32 sylines have error 34 come up, this is bull, that would mean 90 % of all r32s are running like crap. any error code makes the engine run with much less timing and richer fuel. Plus this error code has only been happening since i upped the boost over 11psi.

[wsln33]

Off the topic, Cruise tonite, check out Vic section, "urgent cruise"

[Cubes]

dwhe009,

When saying a boost cuts its an airflow cut. I.e on the stock turbo this may prove to be 20.5psi.

If Error 34 only occurs since you have upped the boost then it is detonating.

As 3Lit3 ForS3 said it could be a dodgy AFM. I have always suspected mine was dodgy.

In my circumstance it is not the AFM hitting its max voltage (~5.1v) as it will cut any where from 3.5v to 4v. If it were hitting its max voltage then the car would be making 220rwkw or so. Which it most definately does not.

Mine too used to cut earlier on a fresh cold morning. Approx 15-16psi.

It also cuts much earlier if the car is not fully warmed up and pushed hard (rb20t not the new motor )

I've just bought my self a bran spankin Z32 AFM for under $300 this with a PowerFC will fix the problem.

In think it could have something to do with the stock ECU's map table, essentially the airflow requirements for that particular load, rpm & TPS has ran off the map.

Causing a lean out then a fuel cut for safety. Possibly?!?

Or maybe your VL Fuel pump is also on its way out.