The boost .... it\'s back!

[hmltnangel]

Right where to start…… prob right from the start would be best....

 

To begin with my primary turbo was working ace, nice transition to second turbo too but at this point I would lose a few psi of boost

 

Boost pattern was 10.5…..7…..8

 

Couldn’t find anything obvious so decided to attempt the “vac hose adventure”.  All went well with it â€" took me a couple of afternoons but I got there. Didn’t take the solenoid rack out but of the 4 hoses you need it out for none of them were hard â€" I think they must have been changed at the rebuild about 18 months ago. Every other hose was changed though.

 

I also replaced the following as there was more damage down there than I knew about

1. Acv Assembly (I cracked it when I was screwing it in!)

2. Air bypass solenoid (the front nipple was snapped off and not connected)

3. Charge control solenoid (same as above)

4. Aluminium Pcv valve as it was busted

5. 2 of the check valves too

 

Got the car back together but it wouldn’t boost above 8 psi regardless so went looking for the cause ….. I did remember that the restrictor pills weren’t as snug in the new hoses as the old ones so I used the smaller diameter (4mm) of hose and squeezed them in. …. Put it back together and now on primary it’s hitting a slightly dangerous 13/14 psi….. Can’t really check if the second turbo is coming on as I’m very reluctant to boost it hard to wide open throttle with so much boost.

Questions this far.....

1. Could this be caused by using too small a diameter of hose?

2. could the restrictor pill have turned in the hose slightly?

Anyways went under for another look on Saturday there and noticed the gasket on the new acv was leaking so I replaced that too. Also I remembered that when I was doing the vac hose replacement there was an odd vac hose that vented to atmosphere â€" as I was replacing the hoses on a one for one basis I left it to atmosphere….. Now a week later in my search for problems I realised that this hose was the second hose in the “impossible to do without removing the solenoids” list and was supposed to be connected to the block….. I then proved that you can JUST replace this one without removing the solenoids and hooked it back up. Thinking this to be a likely cause of the problems I put it all back together again and took the car out for a test…… Now it’s doing the same 13/14 psi on the primary. Did keep the foot down longer (still haven’t opened the throttle fully as I don’t want to bust the engine) and kept it boosting around 10 psi (about ¾ of the throttle) and when the revs got a little higher the car seemed to “buck” hard to explain â€" it just seemed to falter for a bit (bit like fuel cut though not as sudden and no warning on the dash either) so I quickly let the throttle out and continued normally. Tried this again and same thing. I think it might be at the point the second turbo is trying to come online? (Sorry can’t tell the rpm’s as I had to keep an eye on the cars in front and I don’t want to take it anywhere at the moment if I can help it) I\'m certain the second turbo is spooling up as when I\'m reaching around 3k rpm -4k rpm when I\'m not boosting hard I can hear sometimes one of the dump valves dumping boost continously - this would suggest to me that the second turbo is getting pre spool to start it up but at the point where it\'s supposed to come fully online something isn\'t opening

More questions....

3. Could this possibly be a problem with the Turbo control actuator?

4. or even the charge control actuator?

5. to keep the boost pressure down should I get an MBC and fit it on? thus allowing me to be certain of the exact pressure going to the wastegate actuator?

6. I have fitted aftermarket airfilters on .... could these be causing any problems? ... I have removed the front number plate and put a cold air feed to assist the filters in getting cooler air(nightmare trying to do it)

7. Only other symptoms I\'ve noticed are..... my car seems to take a little while longer to heat up (possibly because my number plates gone and theres a lot more cold air getting in???) and I do get a little extra popping from the exhaust (nothing major though) also I have noticed that regardless of the position of the heater control in the car I always get air at my feet unless I put it to demist the window......

C\'mon folks I\'ve got this far with your help ...... just needing that final push!

In closing ......A BIG THANKS TO ALL WHO HAVE HELPED SO FAR!!!!

[Shark]

Don\'t think I can answer all yer questions bud, but I\'ll try though you listen to me at your own risk...
(this all presuming no PFC or aftermarket ECU in play.)

1 - In theory, pressure/vacuum in the lines will respond to changes quicker with smaller diameter lines.  I don\'t however see how they would leave you with this problem.  Check the hoses on the charge relief valve and the charge control valve to make sure operating okay.  Also check the connections around your boost pressure sensor to make sure that is reading right.

2 - I\'d guess unlikely but could be very wrong.

3 - Do you get a spike or a dip when the secondary stops venting at 4,500 rpm?  How big?

4 - seem a possibility to me, venting all and suddenly snaping shut to introduce all that pressure to the system would create a bit of a kick until the wastegate opens to regulate.  perhaps your wastegate or the related controls are a bit sticky??

5 - not sure what this would do for you.  If it doesn;t work for the standard ECU would this make it work?

6 - I\'m a bit more confident on these last 2.  I think this unlikely but the cold weather and this will mean much more, and denser air is being sucked into your engine - on a stock ECU at WOT this could be a different problem but I seriously doubt it.

7 - The timne of year and temperature means this will happen.  for example - it take s about 7-10 minutes from (overnight) cold for my thermostat to open when the starting temps for water and intake are in the low single figures.  

BTW
The only ventilation setting that isn\'t the window or feet is the mid level air.  That includes the lap vent.  The pipe for the lap vent isn;t the most secure in the world so may have popped off - hence your ventilation to the feet problem.


Is any of that rambling useful?

[hmltnangel]

Hi Gregor

right

1. I\'ll check th hoses as soon as the car comes back....it\'s in getting the install done in the boot!

2. If the pills had turned then the wastegate and pre control actuators wouldn\'t be opening so therefore really high boost ..... which leads on to point 5

3and 4 When I say "buck" it\'s like the car loses power at this point .....problem is as I can\'t floor it due to the high boost - therfore I don\'t know if the second turbo is actually coming online. what it seems like is - primary boost is coming in - great - getting prespool on the second turbo( can hear the pressure being vented from the first dump valve) but at the point where the first turbo spools down and the second should come online .... it feels like the 1st spools down and nothing happens with the second - just a sudden loss of power ( as I said it feels like what happens when you get fuel cut though not quite as suden)

5. cont ......If I put an mbc in the wastgate line then I can set it at 10 psi then I know the wastgate will open at 10 psi - if it doesn;t then it\'s faulty! This would in theory stop the overboosting on the primary turbo and in theory allow me to try wot to see if the second is coming online??!!

6 and 7 ... these were just theories didn\'t think too much of them.

cheers

[Shark]

I wouldn;t worry too mmuch about the \'buck\' then.

Sounds like this could be the normal power dip when the second turbo joins the party.  really depends how quick it recovers if you apply loud pedal but I can understand your hesitance.

I know that to maintain the same pressure of boost above 4500 RPM I need slightly more throttle with my setup.  -  Although I\'m off boost till map tweaking this weekend so can\'t do a test run at the mo to see if I can recreate your bucking on my car.

MBC sounds like a sensible idea then.  Be interested to hear how you get on bud.

This may do nothing but it usually makes me more comfortable.... before going for WOT or road testing under boost, just stay off boost and slowly (in1st or 2nd gear) allow the speed to build within the vacuum range right up to the top of the rev range.  That way you can be fairly sure that your engine has has a bit of a cleanout.  Usually if you have a problem you\'ll drive cautiously and could have a little build up there.

[hmltnangel]

It\'s just that the power loss is really severe - almost as if the second turbo isn\'t being allowed to come online - ie the boost is still going to the first turbo or the charge control actuator isn\'t opening.

Imagine this ....

3/4 throttle - revving up 2k ....3k... round about here you can hear the prespool being vented 4k..... 5k ....suddenly car bucks forward (imagine what happens when you get fuel cut - the sudden throwing you forward/loss of power) then foot off the gas as I don\'t want a busted engine.....this is what happens every time.

Think the revs are ok - if you don\'t floor itr then the second turbo shouldn\'t come online till a little later - say around 5000-5300revs.