Why is my S15 boosting high?

[Viper]

Hi guys,


I have recently got an S15 and it's boosting above stock. I had it on a dyno yesterday and it showed about 1.1bar (17psi).


There is no boost controller on the car so I'm trying to find out how the boost has been turned up. The guy at RDT said he didn't know the S15 engine perfectly and wasn't sure if the actuator hoses were right?


Can you have a look at this photo and see if everything is as it should be. If it all looks ok can you suggest ways the boost has been increased?

Here's the full engine bay in case you need to see it

I've also got a photo of what I think is the actuator. Someone on SXOC said the car might have an adjustable one. I know **** all though so I'm just providing as many photos and as much explanation as I can!


Thanks in advance for any help,


Tom

 

[Jay]

i think you got a mechanical boost controller in the engine bay on the right hand side of that last photo...

 

[Viper]

hi,

Which part do you mean? I will go and get a closer photo.

 

[pegliobaglio]

Hey mate.I had this mine runs about 1.1-1.2 bar as it has a nismo sports resetting map.I only say this as I see you car has nismo strut brace maybe it has had more done there. Maybe a long shot but have a look in the passenger footwell the kick panel by the door hides the ecu if it's been mapped will have a nismo sticker on, as I said maybe a long shot but would explain it if all else is stock( as mine was when it arrived )

 

[Viper]

Thanks! I'll have a look.

It does look like they have been at the ECU for something, although the tamper sticker is still on it. I'll have a look for a Nismo sticker!

It really wouldn't surprise me as you said, it has a lot of Nismo parts on it!

 

[Nickichi]

i think someones been playing about with the wastegate under the exhaust heat shield, looks like your missing the bolts that holds the heat shield in place in the pic

 

[Jammygit]

As said above, you may have a manual boost controller (can't quite see in the picture) or an adjustable actuator. If your actuator has a thread on it then it's an aftermarket one, if you post up a picture of it will be easy to tell

 

[Viper]

i think someones been playing about with the wastegate under the exhaust heat shield, looks like your missing the bolts that holds the heat shield in place in the pic

That wouldn't surprise me as the heatshield bolts were quite loose.

As said above, you may have a manual boost controller (can't quite see in the picture) or an adjustable actuator. If your actuator has a thread on it then it's an aftermarket one, if you post up a picture of it will be easy to tell

Someone on SXOC suggested that as well actually, although they said its a standard actuator. Here's the only photo I can get at the moment.

 

[Auss15]

Ok, looking at those photos I can't see a mechanical boost Contoller Tee fitted in the boost lines.

The 2 things that could cause your boost spike are if the boost solenoid hose restrictor has been removed or the actuator (it is the stock one) is sticking stopping the waste gate opening.

One other thing I would do is cable tie those plugs, one is for your O2 sensor, to the loom behind the ABS unit. It tidies it up and gets them away from the heat sheild.

 

[CMR]

When you say it is running at 1.1 bar, does it go to 0.7/0.8 ish then at higher revs creep up to 1.1 bar? Or spool straight up to 1.1 bar.

Looking at your engine bay there is nothing changed, that actuator is the stock one and all the standard hoses for the OEM boost controller are in tact.

 

[Viper]

Ok, looking at those photos I can't see a mechanical boost Contoller Tee fitted in the boost lines.

The 2 things that could cause your boost spike are if the boost solenoid hose restrictor has been removed or the actuator (it is the stock one) is sticking stopping the waste gate opening.

One other thing I would do is cable tie those plugs, one is for your O2 sensor, to the loom behind the ABS unit. It tidies it up and gets them away from the heat sheild.

Hi there, thanks for your reply.

Where would I find the solenoid hose restricted? I'll have a looking get some photos. To check for the actuator sticking, I assume I can take it off and just give it a good clean?

Ill have to get some cable ties too!

When you say it is running at 1.1 bar, does it go to 0.7/0.8 ish then at higher revs creep up to 1.1 bar? Or spool straight up to 1.1 bar.

Looking at your engine bay there is nothing changed, that actuator is the stock one and all the standard hoses for the OEM boost controller are in tact.

Hi. It's a consistent 1.1. It doesn't go to normal and then gradually go up.

Good to know all hoses and the actuator are as they should be. Although that's no closer to finding the reason now. Haha

 

[CMR]

The solenoid restrictor hasn't been removed, you can see the silver rings on the pipes that go to the T piece. They are the Restrictors inside.

The waste gate latch could be very stiff or stuck on something but it's unusual it holds a steady 1.1 bar though.. If the gate was jamming the boost could keep climbing. Take the actuator off and see how easy it is to move the wastegate arm, it should move freely.

Edit: it could also be the standard solenoid malfunctioning, to test this simply run a piece of 6mm
hose from the actuator to the intercooler pipe, this will take the oem controller and t piece etc out of the loop and mean you should be running just actuator pressure of 0.6/0.7 bar. Try that first, easy to do.

 

[spoonman]

the guy you took the car to should have tested you actuator..................... simple really,, get a hose one end on the actuator one end on the compressor (with a gauge) then pressurize it, you will only be able to go upto a certain pressure, and then the actuator will open, here from the nissan hand book itself.."

WASTEGATE VALVE ACTUATOR
NMEM0050S06
Apply compressed air to wastegate valve actuator and check it for
smooth movement.
I Do not applying compressed air to the actuator continuously.
I The air pressure should be in the range of 38.7 to 44.0 kPa
(290 to 330 mmHg, 11.42 to 12.99 inHg).