Waste Gate Solenoid

[CarlC]

Guys,

Hopefully you can provide an answer to a question I've been puzzling over.

I had very little boost with the car for a while and one of things I did was swap what was believed to be the broken bit of the waste gate solenoid with a redunant part from one of the EBPV/TJ. Car got boost back but this change was done along with other changes so I cant confirm if this fixed my intermittent boost problems.

The problem is the foam cap/cover on one of the exists to the origonal boost solenoid was corroded and could not be put back on. So not fully understanding the purpose at the time I stuck a small screw in the open soleniod exit to seal it.

So the top single inlet on the solenoid has the pipe coming in from the turbo.

The bottom has a screw seal in the centre most outlet with, as per spec, the outter most outlet going to the wastegate capsule.

I get boost and over boost, but i wondered if putting this seal in the solenoid would have any effect ??

I would say however that I find it almost impossible to know how to get the car to over boost on demand. The car seems to deciede when it wants to really go quick.

Edited November 15, 2005 by CarlC

[Paul C]

Remember the EBPV is only derprived of its vaccum on starting (for about 2 mins).

The Throttle jack only gets its vaccum when starting (for about 2 mins).

Therefore i'd assume that although the actuator head on each component 'looks'

the same, the chances are they might have opposite 'normally open/closed'

positions and fitting the wrong one might mean it performs exactly the wrong way?

[CarlC]

Remember the EBPV is only derprived of its vaccum on starting (for about 2 mins).

The Throttle jack only gets its vaccum when starting (for about 2 mins).

Therefore i'd assume that although the actuator head on each component 'looks'

the same, the chances are they might have opposite 'normally open/closed'

positions and fitting the wrong one might mean it performs exactly the wrong way?

<{POST_SNAPBACK}>

Thanks Paul, interesting point. The bit I replaced was the lower "female" section of the solenoid which is the "dumb" bit without any wires "brains". Who'd have thought!

Im going to get in trouble here...

Hopefully the women among us will stick to the "General Chat Forum"!

Really big trouble....

[x6gas]

Guys,

Hopefully you can provide an answer to a question I've been puzzling over.

I had very little boost with the car for a while and one of things I did was swap what was believed to be the broken bit of the waste gate solenoid with a redunant part from one of the EBPV/TJ. Car got boost back but this change was done along with other changes so I cant confirm if this fixed my intermittent boost problems.

The problem is the foam cap/cover on one of the exists to the origonal boost solenoid was corroded and could not be put back on. So not fully understanding the purpose at the time I stuck a small screw in the open soleniod exit to seal it.

So the top single inlet on the solenoid has the pipe coming in from the turbo.

The bottom has a screw seal in the centre most outlet with, as per spec, the outter most outlet going to the wastegate capsule.

I get boost and over boost, but i wondered if putting this seal in the solenoid would have any effect ??

I would say however that I find it almost impossible to know how to get the car to over boost on demand. The car seems to deciede when it wants to really go quick.

<{POST_SNAPBACK}>

I'm not sure I follow the situation here, but just to clarify. The EBPV and Throttle Jack vacuum solenoids are actually exactly the same (Paul's point is wrong - yes Paul is wrong, it does happen it appears! - the two solenoid valves are controlled by the ECM via changeover relay)

The wastegate solenoid valve is a different part number so you shouldn't replace it with either the EBPV of TJ solenoid....

[x6gas]

Oh no, having re-read this it appears that I am wrong - well at least I misunderstood Paul's comment.

The solenoids are the same, but I think Paul was saying that the control was different - yep there now.

Off to write a hundred times "Paul is never wrong, Paul is never wrong...."

[Paul C]

Just in time. Had the range rover started, shotty loaded, bristol bound...

yeah, you got my point. If when there is no power to each unit then

despite the actuators (solenoids) being the same, the gubbins they are

opening/closing must be different, as one unit lets vaccum through when

no voltage, yet the other blocks vaccum with no voltage.

PLEASE, always chip in on tech if you think me or anyone is wrong

(or if i still am!!!). I'd never mind, as the alternative is someone getting bad

advice...

[CarlC]

Erm... Ok, I think i see where you guys are going but I suspect there is no need.

Let me ask the question in different way as I've probably confused the issue.

Basically the waste gate solenoid has one exit that is covered with foam. This was knackered so instead I stuck screw in it to seal it instead. Is this a problem or would it be better not to have the screw in ?

For some reason it 'feels' like there is less boost with this screw out but this could just be me.

Edited November 16, 2005 by CarlC

[fmxa]

Don't think you should put a screw in it, the foams there as a filter to prevent debris entering the solenoid (FWIW my foam is also missing).

[mchlrodrigues]

Erm... Ok, I think i see where you guys are going but I suspect there is no need.

Let me ask the question in different way as I've probably confused the issue.

Basically the waste gate solenoid has one exit that is covered with foam. This was knackered so instead I stuck screw in it to seal it instead. Is this a problem or would it be better not to have the screw in ?

For some reason it 'feels' like there is less boost with this screw out but this could just be me.

<{POST_SNAPBACK}>

Carl,

Remove the screw. The foam covered port is a relief port allowing pressure from the wastegate line to vent to the atmosphere when the ECU decides to cut off the boost signal (e.g. for overboost). The foam is a filter intended to prevent the entry of debris into the port.

By plugging it, you've done exactly what the foam was intended to avoid.

Michael

[Jonathan]

Just about to add that comment !

I've stripped mine out during the restore and the exact thing happened to my boost control solenoid. Basically its a dump valve for your wastegate

Personally I see no real need for the foam, the port is a vent so any dirt ingress (again which is not likely given it's position....well on my car at least) gets blown out by the pressure from the turbo, plus it is pointing down...

I was going to make a extension for mine using some silicon vac pipe I bought on eBay, just loop it sideways...cant see that'll do much harm.

[CarlC]

Carl,

Remove the screw.

Edited November 16, 2005 by CarlC

[docf]

Cheers guys.

Would it then mean that the waste gate potentially would stay open longer because it wont vent back through the open exit of the solenoid with the screw in?

<{POST_SNAPBACK}>

Yes. The ecu will sense this and try to compensate by changing the pulse width to the solenoid. The end result will be erratic boost control. On the S4 I would like to note that the 3 solenoids are NOT the same. On the TJ/EBPV the top port is sealed off and the lines connect to the 2 bottom ports. If you drill out the plate on top of the solenoid you can exposed the top port and glue in a plastic nipple to replicate the boost solenoid. The stupid little foam block serves no purpose. The wastegate capsule is by no means delicate or sensitve... not something that can be damaged by a spec of dust.

[CarlC]

Yes.  The ecu will sense this and try to compensate by changing the pulse width to the solenoid.  The end result will be erratic boost control...

<{POST_SNAPBACK}>

Thank you Doctor. and everyone who contributed.

Just to confirm the point, I havent swapped the solenoid. I took the bottom part of one solenoid and switched it with the bottom of the boost solenoid. These parts are identical. The top sections with connection have been left exactly as origonal spec.

Im very interested to see your comment about irractic boost. My next thread was going to be just that.

At present My over boost appears to be totally random and rare. When I try to recrate the conditions that gave me overboost it doesnt happen.

I will remove the screw seal from the boost solenoid and do a full ecu reset asap!

Are there set parameters / conditions were the S4 would provide over boost ?

[fmxa]

Are there set parameters / conditions were the S4 would provide over boost ?

On the S4 Yes - quickly rev the engine to 5000 RPM while the vehicle is stationary (zero road speed) and you'll get 1.0BAR for ~15 seconds.

*Warning* - if you launch your pistons through the block trying this, don't say I didn't warn you!

[patpong]

Exact same thing happened to my S4... I got overboost from time to time. The car accelerate well then, about half way of its acceleration, the car sort of jerked. I didn't know that it was because of overboost. The waste gate solenoid was a problem. It's still in working condition but sort of sore, not responsive and not accurate. It's never been changed since new 1993...

[fmxa]

Exact same thing happened to my S4... I got overboost from time to time. The car accelerate well then, about half way of its acceleration, the car sort of jerked. I didn't know that it was because of overboost.  The waste gate solenoid was a problem. It's still in working condition but sort of sore, not responsive and not accurate. It's never been changed since new 1993...

<{POST_SNAPBACK}>

If you get too much boost under normal conditions (not doing the 5000 RPM trick), the ECU will shut the fuel off, and you get what feels like a cylinder dropping out/miss. I had a bad WG solenoid causing too much boost, would hit ~1.2 BAR and then fuel would be cut off. Diagnosed thanks to freescan and Dermot's help.

[Rick2005]

Chaps,

I followed your thread with great interest.

I

[fmxa]

Have you run the car while connected to FreeScan? FWIW I also traced a similar issue down to some micro-cracks in the hoses connecting to the wastegate solenoid. Replaced with better hose and new clamps, problem went away.

Chaps,

I followed your thread with great interest.

I

[CarlC]

... Fact is: sometimes it works  - most of the time it doesn

[fmxa]

So is it just a few of us who have "Random" over boost problems or is this more common amogst  S4/GT3 cars ????

Couple of points I've found on my testing...

I've run freescan but no errors reported.

I am much more likey to get overboost or generally far better acceleration by using the accelerator pedal with progressive pressure to WOT rather than flooring it.

<{POST_SNAPBACK}>

Yep, once in a blue moon I still get overboost and fuel shut off, although since I switched to revision 2 of the number 5 chip its very rare.

[CarlC]

Yep, once in a blue moon I still get overboost and fuel shut off,

Edited November 23, 2005 by CarlC

[mchlrodrigues]

I suppose the difference is the stock S4 chip is restricting boost in 1st and 2nd as I usually get the most noticable turbo kick in 3rd. When the pressure pipe was split I would have maximum boost (overboost) in all gears with no control other than me not thrashing the car.

Sadly with the pressure pipe off the cars performance was awesome. with it back on it was quick. Roll on the new chip I think.

<{POST_SNAPBACK}>

It sound's like you're a candidate for a stand alone boost controller.

[Rick2005]

Have you run the car while connected to FreeScan? FWIW I also traced a similar issue down to some micro-cracks in the hoses connecting to the wastegate solenoid. Replaced with better hose and new clamps, problem went away.

Paul,

how have you detected the cracks and where exactly?

Can you actually see them?

[fmxa]

Have you run the car while connected to FreeScan?  FWIW I also traced a similar issue down to some micro-cracks in the hoses connecting to the wastegate solenoid.  Replaced with better hose and new clamps,  problem went away.

Paul,

how have you detected the cracks and where exactly?

Can you actually see them?

<{POST_SNAPBACK}>

I took the two hoses off the WG solenoid (one connects to the capsule, and other to the manifold), squeezed them all over a little, and sure enough you could see very tiny cracks in the hose right on the bends (hose was also really oily inside). Replaced with new hose and clamps, problem went away.

Edited November 24, 2005 by fmxa

[Rick2005]

Will have another look at it.

Cheers.