Rb25Det Boost Control

[savage1987]

Hi guys, I have an R33 s1 engine that is misbehaving.

I have an engine manual here but it doesn't really help me because the diagrams are super confusing and overcomplicated.

Looking for pics of the factory boost control solenoid (as far as I can tell mine is missing - I understand it's meant to be near the boost controller but I just have an empty plug there.. it's all been gutted as far as I can see to fit this crappy little turbosmart 2 stage manual boost controller and I've no idea how the vacuum control piping was set up from factory.

I'm trying to go back to stock setup to start a proper diagnosis of why it's not producing the power it should. I replaced the atmo BOV today with a stock plumb back and that seemed to help a bit. Trying to eliminate boost controller from the equation now.

I have done plugs - NGKs with a 0.6 gap as recommended to me by antilag.com - and the coilpacks are new looking splitfires. I replaced and rewired the fuel pump too, it's a Walbro 255Lph now. A dodgy injector or a playing up boost controller are next on my list of suspicions. Maybe even a vac leak but I can't find one (fixed a few already though). The ECU is still stock as far as I can tell, and it uses over 16L/100km suburban driving in Townsville - even my 5.0L (even my 5.7L!) doesn't use that much.

Car was treated shit before we bought it and sat unused for a long time as far as I can tell, so we are sort of trying to clear things up and get it back to 100% again.

Any ideas/help appreciated

Sam

[KiwiRS4T]

You need to be a bit more specific than "misbehaving". Do you have a boost gauge? Is it meant to be a stock RB25DET? Its not hard to get down to 16L/100km if you boost it a lot. 0.6 plug gap is a bit extreme - usually 0.8 is enough to help compensate for dud coils and yet you say it has new Splitfires - I would gap the plugs at 1.0 in a stock engine.

This pic shows a Stagea RB25DET with the solenoid bypassed. The stock solenoid can be seen below the power steering fluid reservoir.

The stock hoses run from the boost source to the solenoid and from the solenoid to a T where one line goes to the bov return line and the other to the actuator. There is a restrictor in the standard set up - can't remember exeactly where.

If you haven't got a stock solenoid you can just plumb it as per the picture and regulate boost by varying the size of a restrictor in the bleed line off the T that goes to the bov return pipe (by filling and drilling that branch of the T or using different sized welding tips or I have even used a needle valve on that hose).

[DVS JEZ]

Does it blow excessive smoke when driving?

Have u tried disconnecting ir replacing the 02 sensor on the dump pipe?

[savage1987]

You need to be a bit more specific than "misbehaving". Do you have a boost gauge? Is it meant to be a stock RB25DET? Its not hard to get down to 16L/100km if you boost it a lot. 0.6 plug gap is a bit extreme - usually 0.8 is enough to help compensate for dud coils and yet you say it has new Splitfires - I would gap the plugs at 1.0 in a stock engine.

This pic shows a Stagea RB25DET with the solenoid bypassed. The stock solenoid can be seen below the power steering fluid reservoir.

The stock hoses run from the boost source to the solenoid and from the solenoid to a T where one line goes to the bov return line and the other to the actuator. There is a restrictor in the standard set up - can't remember exeactly where.

If you haven't got a stock solenoid you can just plumb it as per the picture and regulate boost by varying the size of a restrictor in the bleed line off the T that goes to the bov return pipe (by filling and drilling that branch of the T or using different sized welding tips or I have even used a needle valve on that hose).

The motor is fairly close to stock. Just has an exhaust, pod filter, crappy boost controller and the atmo BOV I removed yesterday.

Thanks for the photo, it confirms at least that my solenoid has been removed. Would that unplugged solenoid be causing problems with the ECU? The instructions I found for the boost controller state:

1) INTERNAL WASTEGATE SETUP

• Allow the engine to cool down before installing your boost controller

• Locate the pressure source port and the wastegate actuator port on the turbocharger assembly (refer drawing 1)

• Remove the factory boost control solenoid if fitted from the boost pressure supply port while leaving the solenoid connected to the

ECU

• Install the DSBC Tee piece in the wastegate pressure line with the wastegate arrow pointing towards the wastegate actuator

• If your wastegate actuator has additional ports, these will need to be blocked

• Secure all silicone hose ends with hose clamps

• Mount your boost controller bracket onto the vehicle, and then attach the boost controller onto the bracket with the supplied screws

• Make sure the boost dials are turned completely anti-clockwise before making adjustments.

Misbehaving = feels like it loses a cylinder intermittently(?) under boost. Sounds like an old carby breaking down spark (same fluttering noise) and the power does not come on smoothly, it hesitates and carries on. Only have the standard boost gauge and I don't really know where stock boost should sit on it to be honest, I have wound the turbosmart controller down so full boost is just under 350mmHg on that gauge, I figured that should be lower than stock if anything, and eliminate ECU R&R spasms from the picture..?

This engine does not get driven around on boost a lot, so 16 is, to me, absurd. It did 9L/100km on a 200km highway trip with a mountain drive in the middle, so that side of things is OK. Makes no sense to me, I think I need to find a tuner up here who knows Skylines inside out or find/buy some tuning software and have a crack on my own - I'm sure there's enough online support to get me through something like that.

Does it blow excessive smoke when driving?

Have u tried disconnecting ir replacing the 02 sensor on the dump pipe?

Not that I know of; and I have replaced the O2 sensor on the dump pipe, yes.

[KiwiRS4T]

If your boost gauge is accurate that's just under 7 psi which sounds pretty stock - up to 500 mmHg should be fine. I don't think disconnecting (or removing) the factory solenoid should do anything. Try opening up the plug gap to at least 0.8mm to get a fatter spark.

Also clean afm (or ideally swap out with known good one) and check plug/wiring.

If the car has been sitting around for a while could be the fuel system. Try changing the filter in the engine bay - cut it open to see if its full of cr*p. Maybe also pull out the fuel pump and clean the sock at the bottom [just noticed you put in a new pump so I guess that's covered] and look inside the tank for excessive sediment. If you can swap out the injectors that would be good or consider getting them cleaned.

Put your location up on your profile then people can suggest a good workshop or tuner!

[savage1987]

If your boost gauge is accurate that's just under 7 psi which sounds pretty stock - up to 500 mmHg should be fine. I don't think disconnecting (or removing) the factory solenoid should do anything. Try opening up the plug gap to at least 0.8mm to get a fatter spark.

Also clean afm (or ideally swap out with known good one) and check plug/wiring.

If the car has been sitting around for a while could be the fuel system. Try changing the filter in the engine bay - cut it open to see if its full of cr*p. Maybe also pull out the fuel pump and clean the sock at the bottom [just noticed you put in a new pump so I guess that's covered] and look inside the tank for excessive sediment. If you can swap out the injectors that would be good or consider getting them cleaned.

Put your location up on your profile then people can suggest a good workshop or tuner!

Should have mentioned that the AFM is a brand new genuine unit, I replaced it thinking that may have been part of the problem.

I also have done the fuel filter, didn't cut the old one open though. The inside of the tank looked fine when I did the pump. Injectors are a maybe - are there rebuild kits available anywhere for these? I don't mind doing the work to save some cash.

[savage1987]

well with the factory bypass valve or whatever they call the plumb back BOV the last tank of fuel was 13.9L/100km, a bit better than 16.

Hopefully a tune (eventually, not just yet unless there is cheap software and lots of support for home tuning a near-stocker) will see that drop a little more near the 10-11 mark.