BSV info required...Overboost problem.

[Marcus_uk]

Hi all,

I think my car is psychic, Im unfortunatly putting her up for sale and she has started miss behaving! I dont think she wants to go!... perhaps its a sign... anyway i digress:

Ive got overboost problems. I first thought it would be stuck wastegate. Whilst the wastegate was indeed stuck freeing it off hasnt cured the problem! Doing the wiggle again and checking for the 90 degrees of movement this time didnt change anything.... The wastgate moves really easily in one plane of side to side movement through the full 90 degrees... (I hope that makes sence) but feels like it has stiff spots if I hold the actuator capsule in a different possition and move it side to side and this dosent change no matter how much I wiggle it... i think this is just down to basic geometry... not a sticky spot ont the wastegate.

My question is: Is there anything else that could be causing my overboost... I have a stock diameter exhaust system with the Cat and squish section removed, but surely it cant be boost creep. Ive done an elanscan log and posted it in the ElanScan forum. Any pointers or input would be welcome... I'm not the sort of person that can sell a car that isnt 100% right (I know how I would feel if the situation was reveresed and I bought a car that wasnt 100%)

As always thanks for your input.

ElanScan file: viewtopic.php?f=34&t=17322

[rip]

Have you checked the timing?
When my base timing was correct, mine popped & spluttered badly, the exhaust was very sooty, boost gave me very little performance & I got overboost at just over 4000rpm.

I then experimented with the ignition timing & found that by advancing it another 16 degrees, all the above problems were cured & my car felt really quick again.

[Marcus_uk]

The car currently runs great ...no popping and spluttering just overboost in 3rd gear or higher if you keep it at wot for a few seconds.

Might be worth a try though, the timing is spot on 16 degrees... do you mean you are now running 32 degrees?

Have you checked the timing?
When my base timing was correct, mine popped & spluttered badly, the exhaust was very sooty, boost gave me very little performance & I got overboost at just over 4000rpm.

I then experimented with the ignition timing & found that by advancing it another 16 degrees, all the above problems were cured & my car felt really quick again.

[rip]

Might be worth a try though, the timing is spot on 16 degrees... do you mean you are now running 32 degrees?

Yes. My CAS is advanced almost all the way to the rear stop.
I still do not understand why mine is advanced this far, nor can I remember when it started to need to be set like this.
I checked with Elanscan & am getting no knock detected, so it sounds like I do not have to back it off at all.

Mine was spluttering a lot when set to 16. It also spluttered when starting the engine (which I rather liked the sound of), although it left a big sooty mark on my toolbox!

Your problem sounds totally different.

[HJ2]

I experienced overboost after porting the wastegate, and wiggeling did not help...
It turned out that the sparkplug gap was 1.1mm (factory set)
After adjusting to 0.8mm... Presto! Smooth running engine again

[Marcus_uk]

I experienced overboost after porting the wastegate, and wiggeling did not help...
It turned out that the sparkplug gap was 1.1mm (factory set)
After adjusting to 0.8mm... Presto! Smooth running engine again

I'm 99% sure that im running 0.8mm as I also first fitted the 1.1mm that are recommended in the service manual, I later switched to 0.8mm as recommend on here which solved an occasional missfire issue that I had...although that could have just been a cracked plug....

[rip]

I experienced overboost after porting the wastegate, and wiggeling did not help...
It turned out that the sparkplug gap was 1.1mm (factory set)
After adjusting to 0.8mm... Presto! Smooth running engine again

That doesn't agree with what we're led to believe: that the ECU simply triggers overboost protection at 0.94bar.
Do you get the feeling that something else can trigger this too?

[HJ2]

I just share my experience, You can read the full version here:
viewtopic.php?f=79&t=16507&start=20
(the last few posts, and the story continues a few pages further.)

Although my problem was not the same asthe classic overboosting after replacement of the exhaust, most people pointed at the wastegate (as with your problem)
Perhaps the advice of fellow LEC peeps in my tread will give you a bright idea!


now that i am thinking about your problem... did you check correct operation of the actuator itselve ? Perhaps the rubber dome has a crack.
Computer says 90% open, but only 70% reach the flapper.. overboost...

[Marcus_uk]

How can do I check the operation of the actuator? (if the actuator is faulty wouldnt I get 100% (or zero... cant remember which round it goes) wastegate duty cycle?

[HJ2]

unplug the rubber hose, stick on a spare piece of hose on the actuator and pressurize (carefully, it's just a rubber dome inside a can!) with an airgun.
That is... if i am right and it doesn't operate on vacuum (wich would be illogical to me )

Anyone?

[Marcus_uk]

Doh... dont have an air gun....time to pest my tame mechanic down the road

[Alan_C]

You can use a decent bicycle or foot operated car tyre pump, it won't keep the presure but you'll be able to see that the actuator can move the waste gate valve at least.

[Marcus_uk]

Ok its finally time for me to get the route of the problem. I have a few questions which I hope you can help me with regarding how boost is actually controlled.

1) Is the boost solenoid valve & actuator only required/employed to raise the boost pressure above ~0.5 bar (~1.5 bar total)?

2) Is the actuator supplied with varying amounts of "vacuum" (ie pressures less than 1 bar total) by the BSV which effectivly adds resistance to the wastegate being forced open?

[Jackonicko]

Check for play in the CAS spindle.

I changed out plugs, leads, coil packs and HES (as well as freeing off the wastegate) before changing the CAS cured my overboost.

[Marcus_uk]

Check for play in the CAS spindle.

I changed out plugs, leads, coil packs and HES (as well as freeing off the wastegate) before changing the CAS cured my overboost.

Thanks, but I have a brand spanking new CAS.

[mikeydude]

Ok its finally time for me to get the route of the problem. I have a few questions which I hope you can help me with regarding how boost is actually controlled.

1) Is the boost solenoid valve & actuator only required/employed to raise the boost pressure above ~0.5 bar (~1.5 bar total)?

2) Is the actuator supplied with varying amounts of "vacuum" (ie pressures less than 1 bar total) by the BSV which effectivly adds resistance to the wastegate being forced open?

Yo dude!..I don't really understand thew questions..but I will try to answer them!

OK...The BSV valve allows the ECU to increase the boost by bleading air away from the wastegate actuator, it allows the sudden jumps in boost that you get if you shove your foot down. It is the means by which the Everest chip increases boost

[tigerdog]

1) Is the boost solenoid valve & actuator only required/employed to raise the boost pressure above ~0.5 bar (~1.5 bar total)?

The wastegate is held closed by a spring/diaphragm in the wastegate capsule. The diagram is connected to the pressure side of the turbo. When the boost pressure is stronger than the spring, it pushes the wastegate open. In the Elan, the nominal spring pressure is .41 Bar (6 P.S.I.) The BSV is normally open when de-energized, so full pressure reaches the diaphragm.

2) Is the actuator supplied with varying amounts of "vacuum" (ie pressures less than 1 bar total) by the BSV which effectivly adds resistance to the wastegate being forced open?

As I understand it, just the opposite. The BSV is opened and closed by the ECU to limit the pressure on the diaphragm. It vents excess pressure to atmosphere when the BSV is activated and the wastegate stays closed.

So things that can cause overboost:

Wastegate stuck closed (wiggle eliminates this)
Insufficient wastegate flow (made worse with free-flow exhaust, made better by porting the wastegate)
Defective wastegate capsule (tested by disconnecting the short hose connected to the capsule and blowing > 6 PSI air into the the capsule. The actuator should move 2mm at 9-10PSI)
Leaky plumbing between turbo pressure output spigot and wastegate capsule input or the BSV. (anything - cracked hose, loose/leaking connections - that bleeds pressure out of this circuit will cause the wastegate to stay shut longer than it should)
BSV not function (tested by pulling the hose at the turbo spigot, blowing in. Air should not pass. Next, apply voltage to the BSV, blow in again; pressure should bleed out through valve.)

It's very important these hoses not leak and the ends seal tightly, especially when running higher than stock boost. I've replaced all of mine and secured the ends with pairs of small nylon ties pulled extra-snug.

If you download the manuals from LEC, there's a dandy paragraph and diagram on pages 47-48 of the "M100 Training Centre Notes - Engine" and a full diagnostic procedure on page 62 of the "M100 Service Manual v6". Sometimes there's no substitute for RTFM.

[Marcus_uk]

Thanks guys,

its now sorted and back to perfect running.

Mike we should go out for a drive sometime before my car sells and see how the two cars compare. Have you changed your heater core yet?

[tigerdog]

its now sorted and back to perfect running.

So what was the problem and how did you sort it? You can't leave us hanging.