17 replies to this topic

[colgy]

Trying to investigate boost pressure on my stage 2 (LEH turbo) tubby. I had overboosting to 12psi and holding 9 psi - too low. I tweaked the actuator and found it overboosting to 14 psi and holding 10 psi. Winding it in more saw 19 psi overboost and holding 10 psi. With this last position when accelerating through the mid-range I felt the car slow down and the boost pressure drop off - almost like easing up on the accelerator. My questions are: 1. Is this the boost solenoid detecting too much boost and subsequently reducing it? 2. Does an normal idling vacuum of 22 in hg indicate that there are no leaks in the boost/vacuum pipework? 3. The boost control solenoid - the rear one(mounted between engine and boot?) - what does that connect to (FPR/vacuum box)? Does the rear BCS control the boost when the wastegate is open and the BCS on the turbo control the re-circ valve? I'm thinking that turning down the overboost and changing the rear BCS might be the way to go...in the mean time, any comments/ideas very much appreciated!

[siztenboots]

try unclipping the plug on the amm , ( plug right by expansion water bottle ) then does it still have consistent boost on partial and full throttle steady inputs

[dannynewport]

Std is overboost to 11psi & hold at 8 according to CS & my car before remap. I think 19psi is just too much for the std VXR actuator so could maybe causing the boost to overboost & drop off. 22HG in idling seems fine & the boost solenoid IIRC connects to vac box,T piece leading to FPR & not sure on this one but possibly turbo. I replaced both boost solenoids last week as I though maybe that was my problem but there was nothing wrong with my old ones, just worked out there was not a problem just me getting used to the car quickly.

[Nev]

Changeing the winding nuts on the actuator without approriate fueling changes is dangerous, especially if you are increasing boost by so much. You are almost certainly running very lean AFR (which may explain why you are getting less power) and will lead to burnt out pistons with holes in them, possible melted exhaust valves and a very expensive bill...

Edited by Nev, 25 October 2009 - 09:59 AM.

[colgy]

Yeah, as soon as I seen the boost reach that, I limped home the half-mile and re-adjusted. Towards the end of the thread, a small adjustment makes a big difference The ecu should sort out small trims to fuelling though, if I set the pre-load to give 15 psi max of overboost? (believe this is what a stage 2 should be at) I'll try and unplug the AMM and see what happens...

[colgy]

Ok, with the actuator wound (and wound down more than normal IMO) to provide a maximum overboost of 15psi, car seems to be running ok, except it only holds 9.5-10 bar. Disconnecting the AMM, car runs exactly the same!!! No EML, no lumpiness or hesitation, no really noticeable difference! With the engine in closed loop at idle, it is trying to make the short term fuel trim lean by 10% (was expecting 10% richer on a 'safe' map?!) but you can't tell its disconnected from driving. Really strange as I've had it go last year, it was really obvious and whilst the car drove ok with it disconnected, it wasn't quite 100%, until I had the current one fitted. Explain that one?! Siztenboots, the car seems to hold exactly the same boost on full throttle, on part throttle I can't really get it to hold as the re-circ valve operates as the engine accelerates through the rev range (as it should do to control the boost on part throttle, I believe). Really can't believe the AMM could have gone (given that it was replaced last year and has none of the syptoms associated with failure) so I'm still leaning towards replacing the rear boost control solenoid - the rear as the front will have been replaced with the new LEH turbo and people seem to have had issues with the rear. Does anybody know what the 2 boost control solenoids do, do they perform the same function? Is this why there are 2 seperate (and different) boost commands that you can see on OP-COM? Whew, I know thats a lot, but I'd love to hear any ideas!

Edited by colgy, 25 October 2009 - 07:16 PM.

[colgy]

After a little more digging around AMM is working correctly (it appears), the fault code (P100) had been store but not flagged on the EML as it was recorded as 'intermittent'. Also, found out that the rear boost control solenoid controls the re-circ valve whilst the turbo-mounted solenoid controls the wastegate - not sure how this works as I thought the wastegate was purely mechanical?

[cheeky_chops]

Changeing the winding nuts on the actuator without approriate fueling changes is dangerous, especially if you are increasing boost by so much. You are almost certainly running very lean AFR (which may explain why you are getting less power) and will lead to burnt out pistons with holes in them, possible melted exhaust valves and a very expensive bill...

actuator controls boost/speed of turbine and has chuff all to do with AFR

[colgy]

Cheeky, I'm guessing from some of your other posts that you know a bit about this How does the solenoid on the turbo actually control the actuator?

[Kristopha]

Try asking Duncan VXR - He ws a big help with me

[Duncan VXR]

.

Edited by Duncan VXR, 27 October 2009 - 09:53 AM.

[Duncan VXR]

slow network connection caused multi post?

Edited by Duncan VXR, 27 October 2009 - 09:53 AM.

[Duncan VXR]

Will have a full read of this thread later but had a very quick read of 1 or 2 of the posts. The ECU controls the boost solinoids and the ECU uses the reading of the boost sensor on you C/C or I/C (depending on what you are using) you need to set the actuator static break point as per your map (cannot remember the pressure for stg 2, but just ask who mapped it) the ECU then controls the overboost feature etc using various peramiters of the engine. Part throttle will bleed off the boost as the revs rise due to how the ECU controls the engine for better mpg etc. All tests for boost readings really need to be in 3rd or 4th gear and start at 2.5k to 4k between 2.5-3k will be your overboost peak reading and 4k will be what the the engine is holding. At idle expect to see -25 reading. So worth checking all vac pipes, based on having the static pressure set on the actuator you will be able to see if you are running lower boost than normal which may help you track a boost leak. Increasing the actuator static break off point is not the way to go well not on the oe setup You could have a weak actuator, split / losse vac pipe / boost hose split / loose or a faulty solinoid. My experiance is the solinoids tend to function slower with age when they go faulty or they perm do not operate which is obvious. They do not fail as much as people make out. Hope this helps a bit and if required will have a full read / reply later DG

[cheeky_chops]

Cheeky, I'm guessing from some of your other posts that you know a bit about this
How does the solenoid on the turbo actually control the actuator?

lol - i spent alot of time figuring out what the rear solenoid does as the chatter does my head in! (basically 2 inputs, FPR/vacuum > output to recirc - the ecu swaps the solenoid FPR input to the vacuum when needed to "hit" or speed the recirc opening (when it detects throttle closing)

Alas, i havent had a real need to pull the actuator/solenoid/pipes apart I guess its similar to above, causing the wastegate to open faster. Here you can see the solenoid. 2 inputs, 1 output (cant remember where the 1 goes..) The "solenoids" cant sense or detect anything, they are simple switches to divert the air input one way or another

[colgy]

Thanks for the reply guys I set the overboost so that it achieves a maximum of 15 psi (believe this is what other TMS stage 2 cars are set to) in 3rd & 4th, althought the actuator had to be wound down about 50mm(!). Possibly the spring gone 'weak' as people say, although the turbo was replaced 10k miles ago so maybe the fornt BCS.... Just can't hold more than 9.5 psi after that though, I've got my fingers crossed that a new rear BCS might do something...... I have a vacuum of 24 in hg, all the pipework looks secure, boost side looks ok, but then how do you pressure test it? Think I'm starting to get my head around it - think the vacuum box there to help the re-circ valve open more quickly/postively? Been looking at OP-COM logs whilst accelerating; there are 2 sepearte boost pressure commands - do you think this might be to the 2 BCS? When the pulse ratio is 0% (when asking for no boost) to the 'boost pressure solenoid valve', one of these commands is atmospheric pressure but the other lags about a second behind. Or maybe its the actual intake pressure its reading?

[cheeky_chops]

Possibly the spring gone 'weak' as people say, although the turbo was replaced 10k miles ago so maybe the fornt BCS....

you could see the boost gauge wave when mine went weak and was only lower down where the penny was being pushed by the higher boost pressure

Just can't hold more than 9.5 psi after that though, I've got my fingers crossed that a new rear BCS might do something......
I have a vacuum of 24 in hg, all the pipework looks secure, boost side looks ok, but then how do you pressure test it?

24 is bang on. Not convinced the rear BCS is your problem

Think I'm starting to get my head around it - think the vacuum box there to help the re-circ valve open more quickly/postively?

spot on

[colgy]

Yeah I'm not convinced its the rear BCS either, but for £26 you can't go wrong... If this rear solenoid is controlling the boost on part throttle (and it is, you can hear it), is it also limiting boost at full throttle too? As both solenoids can't be doing the same job otherwise they would be fighting each other! Maybe the wastegate solenoid only operates if something goes wrong and it exceeds a set pressure?

[colgy]

Ok, I'm confused now (again!)



Does this look like boost demand/boost achieved?
The demand could be the blue line and the red line could represent the actual boost lagging about a second behind it. If that was the case, you can see that the engine is only demanding 9-10 psi, which is what I can see on a mechanical boost gauge. The last portion represents 4th gear and the demand(?) is bang on 10 psi.

Or maybe I'm completly wrong and its a graph for each boost control solenoid???