Boost issue on stock twins, in stock RS

[ascari]

I hadn't realised I had a boost problem, till I nearly hijacked @Nickmms94's thread, so I've brought the discussion here.

I did some testing, this is what I found:

1. Accelerator pedal fully down in 1st or 2nd = no\little boost
2. Accelerator pedal fully down in 3rd from a rolling start = high boost (when the rpm catches up), but then jolts the car (like it's cutting out then in) around 4,500rpm, then smooth to red line with high boost
3. Accelerator pedal halfway down in 1st or 2nd = high boost, to red line

@jdmr_neil I've had the Intercooler out before, and have double checked the intercooler pipe joiners, from the turbo outlet to the throttle body, they are all connected without sounds of leaking.

 

[Jit]

Check the check valve going into the little pressure tank next to the alternator. See if it’s become a two way valve (should only be able to blow air one way)

 

[Spendyrx]

I would start with the basics! Check the actuator on the y pipe to make sure it moves. To test: engine off look at actuator rod. engine on and it should be in a different position! I think it gets sucked in at idle if I remember rightly.

From there id maybe loom at the actuator under the turbos to make sure the c clip hasn't fallen off!

Crv is also a good check and from there I can't really remember as I don't have paperwork in front of me

 

[Spendyrx]

Yes jit has a good shout with that too

 

[ascari]

I will try all your suggestions... thanks.

 

[Spendyrx]

I have a pretty cool check sheet you could look at! If I get time in a bit ill get some pics for you

 

[rob fd]

The 4.5k dip is actually normal on a stock car and requires a ecu and map to smooth it out.

What year is your car?

 

[ascari]

The 4.5k dip is actually normal on a stock car and requires a ecu and map to smooth it out.

What year is your car?

It's a 2000 V reg. I understand the dip at 4,500 rpm is the turbos handing over, but the violent'ish juddering is concerning.

 

[ascari]

I have a pretty cool check sheet you could look at! If I get time in a bit ill get some pics for you

Pics would be grand

 

[rob fd]

It's a 2000 V reg. I understand the dip at 4,500 rpm is the turbos handing over, but the violent'ish juddering is concerning.

Yeah it shouldn't be violent. Sounds like a air leak somewhere.

 

[Spendyrx]

There ya go mate. Some information

 

[jdmr_neil]

I don't know if the fd3s.net page is still going but that helped me massively learning and diagnosing the sequential system.

 

[jdmr_neil]

Also when you say high boost, how high are we talking?