21 replies to this topic

[Trevsked]

Since I have had my VXT I have been niggled by the way it jumps on boost very quickly and equally quick to drop off boost. This happens at part throttle setting so if I potter around it is fine and likewise the boost is controlled when flat out but given half or three quarter throttle the car jumps on boost accelerates like mad until the car is beginning to unload (acceleration is catching up with throttle position) it drops off power hugely. As this happens the wastegate chatters too. Motor has ahad lot of tuning done in the past with Regal and Courtnay and on TMS dyno it was about 275-280hp. Biggest problem is that on the track in longer corners it requires part throttle and here the car will be jumping on and off boost which doesn't inspire confidence as it upsets the handling. Wastegate actuator too tight? Trevor.

[spuk87]

What map is it running? Regal don't have the best reputation around if it's one of theirs...

[Ormes]

For boosting issues, I think the list goes something like this (in no particular order): -Check all vacuum pipes carefully for good connection, perishing and splits. -Remove re-circ valve and check condition (splits in the rubber) -Replace front and rear solenoids (one bolted to bracket on top of turbo, one on inlet mani) -Check operation of the wastegate actuator -Inlet pipe collapsing (not likely with these symptoms IMO) Turkey noises tend to be vacuum pipes/recirc/inlet mani solenoid) Hope this helps (and hope its accurate too )

Edited by Ormes, 23 August 2011 - 07:30 PM.

[Trevsked]

Spuk, I assume it is a Regal map as they did most of the work and have no receipts to suggest anybody else has had a go. Ormes, A good start thanks. Need to have a look at the manual to see where these various parts you mention are. Trevor.

[Ormes]

Spuk,

I assume it is a Regal map as they did most of the work and have no receipts to suggest anybody else has had a go.

Ormes,

A good start thanks. Need to have a look at the manual to see where these various parts you mention are.

Trevor.

Working right now but will post some information on how to find the various bits later.

[Trevsked]

That sounds ideal thanks. Trevor.

[Ormes]

Where to find stuff:



As you can see, the AMM is connected to the left of the Intake pipe, and beyond the AMM is a small pipe followed by the Air Box

Turbo is beneath the Silver heat shield.

One solenoid is bolted to a bracket located in the top of the turbo. The bracket is attached using 3 allen head screws, that also attach the re-circ valve into the right hand side of the turbo.

The 2nd solenoid is as marked in the photo, and looks near identical to the other soleniod - 3 vacuum pipes and an electrical connector attached.

Actuator is to the left side of the turbo, and can be seen clearly with the intake pipe removed.

Recirc valve, when fitted looks like this:


Recirc valve and mounting bracket for the solenoid look like this if removed.


Split recirc valve


Solenoid looks like this when bolted to the top of the bracket


Solenoid not attached


Solenoid part numbers
Rear - Inlet/Vacuum, located boot side of the engine bay - 55557829
Front - Boost, located bulkhead side of the engine bay above the Turbo - 55557806

Edited by Ormes, 24 August 2011 - 04:19 PM.

[Trevsked]

Many thanks, that will give me something to look for. So is the recirc valve you have fitted a different/better one and are the solenoid valves just better to replace anyway? Trevor.

[Ormes]

Many thanks, that will give me something to look for. So is the recirc valve you have fitted a different/better one and are the solenoid valves just better to replace anyway?

Trevor.

None of the pictures I used are of my car, however I have fitted the forge recirc valve as shown in one of the pictures. I have a standard car but fitting it made a positive difference.

The solenoids are about 20 quid each so could just go ahead and replace.

Changing the solenoid on the intake mani is an easy job. To do the DV or Turbo solenoid, you'll need to remove the intake pipe and accept you will end up with a bad back. The little finger munching clips attaching the vacuum hoses are a right PITA.

If I were you I would check all of the vacuum hoses running to both solenoids, the DV and actuator before spending money.

[spuk87]

useful pics Ormes, will come in handy for me at some point I'm sure.

[Ormes]

[Dashwood]

I replaced the turbo side solenoid in about 20mins in a field at le mans. It's held in by torx bolts and the small horrible clips were alot easier with a small set of needle nose pliers and patience. Do this before unbolting the solenoid. You only need to take one bolt out and loosen the other. Makes it alot easier to relocate.

[Trevsked]

I have to say I am guilty of throwing money at a problem so did no more than order the two solenoids and a Forge recirc valve. The valve I fitted tonight which was a 30 minute job and it seems the turbo side solenoid has been bypassed as I assume this is usually ecu controlled and controls boost pressure? My car is fitted with an AEM Tru Boost contoller with a dash mounted adjustable gauge. Didn't get to road test it earlier so will do that on the way to the MOT station in the morning. If that has no effect then will change the inlet manifold side solenoid. Not sure what that one does so still learning:-). Trevor.

[P11 COV]

What you describe sounds fairly typical for a 275 - 300 bhp car. Mine was like that and I had various things done at courtenay - 80 AMM, different top hat, fixed a intake temp sensor, rolling road adjustments to the map, after fitting a 3 inch Tullet exhaust. After all that it was slightly improved but I still struggle at certain revs to hold the power steady and on certain corners on track this can be annoying but as I said I think its the nature of the engine at this level of tune. Excessive chatter can point to a failed re-circ valve.

[Nev]

What you are describing is a general characteristic of the engine/turbo. However, do check your recirc valve. You also may benefit from fitting a Bailey DV30 recirc valve as this helps release boost better than the integral recirc valve in the OEM turbo. The root cause of the issue is the fact that the turbo is so tiny and willing to rev that it is very much like an on/off switch. Bear in mind that a stage 4 map also forces it to run 50% more boost than OEM so it is running out of its ideal compressor map (look this up if you don't understand it). All in all, it's an semi-unresolvable issue that requires a bigger turbo to eliminate. With time, you can learn to feather th throttle and pre-empt the on/off nature of the turbo, even on a roundabout. Where abouts in the country are you (update your profile) ?

Edited by Nev, 27 August 2011 - 08:09 AM.

[Trevsked]

P11 COV, Nev, Thanks for your input and advice. I did wonder if it was characteristic of the tune but as it on/off power was so aggressive I thought it didn't seem right. I got to road test it today on the way to the MOT and back and the turkey noises were more regular/often with the Forge recirc valve than the one I took out which wasn't OEM as I has assumed. I was sent a couple of spring rates to try in the new unit so will give them a go although it did drive a little better so not sure if this is ok. The solenoid on the turbo side had been disconnected but not sealed off and I did wonder if the ECU was opening this valve at times and causing a vacuum/boost leak so plugged the open connections and this improved things to the point I thought was ok. I then replaced the inlet manifold solenoid as I had bought it so may as well rule that one out too and frankly not much difference apart from now I have a cough at 2500 rpm accompanied sometimes by a pop. Over all now the drive has improved and doesn't come off and on as hard as it did. A couple of questions. Is the recirc meant to turkey away merrily as you shift and what effect will stronger springs in this have? Did the solenoid on the turbo used to control boost? What does the solenoid on the inlet manifold do? Trevor.

[Nev]

Trevor, the 'turkey' sound you hear is in fact the turbo stalling. This occurs when the boosted air the system flows backwards (due to the throttle being suddenly closed). This is a bad thing really as it stresses the thrust washer/bearing in the turbo which is already a weak part and will speed up how fast your turbo needs replacing. Severe + very sudden reversing of the CHRA can even cause the fan blades to shear with the stress, though I have never heard of this happening on the OEM turbo. I 80% resolved this issue by installing a DV30 into my 'stage 4' and I very rarely got the turbo to stall after that. Having said this though, every car is a bit different. I would however recommend the DV30 as it's quite a cheap solution and may save a bill for £600 for a new turbo. I am not sure a stronger spring will necessarily help in the recirc. Ring up Bruce at Bailey Motorsport, he is both helpful and knowledgeable and will offer free advice to you. The solonoid on the inlet manifold differentiates/measursures the air pressure entering the engine (which may be either vacuum or boost) and supplys a pressure signal down the vacuum pipe that leads round the alternator side of the engine to the turbo's integral recirc valve. On my car which is wholey different to yours, I too had to seal off the vacuum pipe leading from this component, as I now use the DV30 as a replacement of the OEM recirc valve. Thus my solonoid on my inlet manifold is in fact redundant (to my knowledge), but I left it in just in case it was required for some reason by the mappers. Trevor, where are you in the country? Anywhere near Bristol ?

Edited by Nev, 27 August 2011 - 06:46 PM.

[Trevsked]

Nev, Updated my profile as you suggested with my location which is Rickmansworth near Watford. Been for another drive and have to say that I am now pretty happy with the way the car is throttles on and off boost, now that I have changed these components and blocked off the solenoid mounted on the turbo. Two things have occurred that I don't understand and perhaps you may be able to shed some light on. 1/ Since changing to the Forge recirc valve there is an increase in the turkey noise which I understand is the stalling of the compressor and now you say that makes sense. Why since changing this has this increased? 2/ The turkey noise happens at low revs when shifting when the car is cold and much less so once it is warm. Why? Trevor.

[Ormes]

Nev,

Updated my profile as you suggested with my location which is Rickmansworth near Watford. Been for another drive and have to say that I am now pretty happy with the way the car is throttles on and off boost, now that I have changed these components and blocked off the solenoid mounted on the turbo. Two things have occurred that I don't understand and perhaps you may be able to shed some light on.
1/ Since changing to the Forge recirc valve there is an increase in the turkey noise which I understand is the stalling of the compressor and now you say that makes sense. Why since changing this has this increased?
2/ The turkey noise happens at low revs when shifting when the car is cold and much less so once it is warm. Why?

Trevor.

In answer to number one. I think 1 of 2 issues.

1) Forge recirc needs installing with the flat section and hole pointing roughly 10 o'clock.
2) I think you need the yellow spring with your state of tune. Green spring is for unmodified cars. See below (lifted from Courtenays):

Green Spring - For Standard Cars/Standard Boost

Yellow Spring - For mapped cars:
Astra G, Zafira A - Stage 1, 2, 3 and 4 using the OE or VXR turbo unit.
Astra H, Zafira B - Stage 1, 2, 3 and 4 using the OE or VXR turbo unit.
Astra VXR, Zafira VXR - Stage 1, 2, and 3 using VXR turbo unit.
Corsa 1.6 SRiT/VXR - Stage 1, 2, and 3
Meriva VXR - Stage 1, 2, and 3
VX220 Turbo - Stage 1, 2, 3 and 4 using the OE or VXR turbo unit.

Blue Spring - For Hybrid VXR Turbos running higher boost

[Trevsked]

Thanks. Pretty sure I installed with the flat portion at 10oclock. I will check from the paperwork which turbo I am running as I believe it is not standard. First thing tomorrow I will try the yellow spring and see how that goes, Trevor.