BOOST PROBLEM

[patty2k8]

hi people, recently my turbo started whining louder than usual so i got a reconditioned one and changed them, my problem is that after all my effort i dont think the boost is the same.

I know this because i used to put my foot down in every gear and i could feel it pull like a mother f$&*er through all the revs starting at about 2250 but now when i put my foot down it pulls like a mother f£$*er from about 2250 rpm untill about 4000rpm and then i can feel a very noticable drop in boost especially in 3rd and above, my question is that if i tinker with the wastegate (the flappy valve thingy on the turbo with a threaded rod controling it lol) will it get my hi rev boost back, when i first finished the car it had very little boost and i moved the nuts that hold the valve about 10mm closer to the actuator and it got my boost back but im worried if i alter it too much it will break, my octy is remapped and has stainless exhaust with sports cat and poly bushes etc so i would like to know what im doing before i break anything, should be running 220 bhp but feels like 220 between 2250 rpm and 4000 rpm but after that it feels more like standard 180 bhp, can someone please help I NEED MY BOOST BACK LOL , thanks.

p,s sorry if my technical terms etc are wrong lol

[chicken_eyebrow]

Don't mess about with the wastegate actuator setting. That will provide more boost but the ECU won't know what ignition timing and fuelling to use.

If the turbo wasn't set up when you got it so the nut on the actuator rod was in the right position then I can measure the distance on mine if you need it

You're best off letting the map control the boost. If you think the boost isn't right then I would be getting it fault code scanned and looking for boost and/or vac leaks.

Edited 1 September, 2010 by chicken_eyebrow

[Rob_OctaviavRS]

I've got exactly the same problem, pulls like a bitch early in the rev range, then the boost winds of quickly around 4k RPM.

I've also had the turbo replaced with a recon unit (before I bought the car it was changed) so I'm also wondering if the wastegate has been set properly.

Sounds like we've got the same issue here!!!!!

My car should be running well in excess of 220bhp (cams, exhaust, remap and jabba intake) but it made 168bhp and 192lb ft due to the lack of high RPM boost!!!!

[patty2k8]

Yea, it's a pain in the bum, I had mine on a dyno before turbo went and it was producing 215 bhp with 269 lb/ft torque and it showed that the boost was dipping because the turbo was on it's way out so it should be more with a healthy turbo so I'm a bit mystified about the lack in power, I think I'll have to get the guy with the dyno to have a tinker and hopefully sort the problem out, I have checked all vacuum hoses and replaced all the hose clips so I don't think there is a vacuum leak unless I missed one,thanks chicken_eyebrow and if I find the problem I'll let u know Rob_OctaviavRS.

thanks guys I'll update if I find out the cause in the mean time all input is appreciated, Thanks.

I have got my car booked in on the dyno for Thursday 9th sept ( next week ) so he's going to see if he can get my hi rev boost back so I'll let ya know how it goes.

Oh and chicken_eyebrow if u can get that measurement for me I would appreciate it so I can compare it with my own and see if there is a difference, thanks.

Edited 1 September, 2010 by patty2k8

[patty2k8]

By the way guys, I got rid of my old turbo because it was whining really loud and it turned out to be a snapped compressor blade and now I have got my new one ( reconditioned ) I can still hear a faint whine at full boost, I was just wondering if this was normal because I fitted it as instructed and a blade can't be damaged already because it's barely done 100 mile since I put it on, I have asked people and some say it's normal and some don't know so if anyone else has an octy vrs and also has a faint whine at near enough full boost I would be able to relax a bit lol, thanks

[chicken_eyebrow]

I've checked my turbo and the distance between the end of the wastegate actuator rod and the first nut (just before the metal bar connected to the wastegate) is 15mm or about 15 threads on the rod.

[patty2k8]

I've checked my turbo and the distance between the end of the wastegate actuator rod and the first nut (just before the metal bar connected to the wastegate) is 15mm or about 15 threads on the rod.

Thanks alot for that I'll check mine in the morning and see if it's anywhere near.

Oh and I was just wondering if someone put the lambar ( sorry if it's spelt wrong lol ) sensors back on the wrong way round, would this cause a loss in boost? Because my engine management light is on and when I got it checked there were a few fault codes but the guy said the main one was emissions.

And if they are NOT on wrong will it hurt to drive it for a few mile switched over to check.

Edited 1 September, 2010 by patty2k8

[patty2k8]

I've checked my turbo and the distance between the end of the wastegate actuator rod and the first nut (just before the metal bar connected to the wastegate) is 15mm or about 15 threads on the rod.

I just checked mine and it was 25mm so I moved it back to 15mm and it feels slower all throughout the rev range now, I'm hoping when the engine management light is sorted the car will sort itself out. Thanks.

[Bodge]

A 2 square inch (diaphragm area) actuator typically has a total available operating range of 10mm, and a working range of 3 to 5mm.

By pulling down the rod/piston by 10mm, you have massively increased the pre-load on the valve. Probably to a point that the P2 pressure can no longer have a sufficient effect upon the spring to allow the P3 pressure to open the valve. This is a very dangerous thing to do for two reasons. The wastegate limits turbo speed and boost, by increasing the pre-load you will get more performance (on an old school passive system), but you will also destroy the turbo. Secondly you will damage the diaphragm within the actuator. The actuator assembly has been carefully selected based on the performance requirements, and the piston position is set accordingly. If you move the piston position by as much as you have, then the spring or diaphragm may have been damaged.

Now as Chicken has said, it's not even that simple on modern engines. It's not a passive system, it's dynamic. When you wound the rod down by 10mm, the car will have overboosted, the MAP sensor will have picked this up, and set about putting you into limp mode and forcing the boost down by other means. It will have tried to use the N75, but since you changed the actuator setting, that will have failed.

Basically your original issue was probably nothing to do with the wastegate setting, and you ran the risk of damaging something by adjusting it beyond its operating range. 20 years ago it was fine to give the setting a slight tweak, or swap in different actuators, but things have advanced a bit since then.....

If you want to be certain that the original 15mm was correct, you will need the setting pressure and lift from the turbo assembly drawing. Companies that recondition these turbo's should be able to help you with this information, or Borg Warner.

Do you even have a boost gauge?

[Rob_OctaviavRS]

I'll add a bit to this....

I've got a boost gauge fitted to mine, and hard acceleration gives a peak of 26psi which is massively over what it should on a stage 1 map, then a drop and hold around 12-14psi.

If I feather the boost in, I can get the car to hold 24psi up to the top of the useful rev range, again a massive overboost but the car goes like hell.

Obviously I'm not doing this all the time due to the fact I know its going to mash the brand new turbo!!!!!!

So I'll leave it now to the tech experts to shed some light and advice!

[chicken_eyebrow]

I'm wondering if your map is taking into account your cams. If the exhaust valves are opening for longer then possibly the turbo is spooling up a lot faster than usual and hitting a much higher peak psi than it should before the wastegate can open and knock it back.

Problem is there's not many (if any) members on here who have changed their cams. I'd say it would at least need a stage 2 map tailored to the cams to run with them safely.

Edited 3 September, 2010 by chicken_eyebrow

[Bodge]

I'll add a bit to this....

I've got a boost gauge fitted to mine, and hard acceleration gives a peak of 26psi which is massively over what it should on a stage 1 map, then a drop and hold around 12-14psi.

If I feather the boost in, I can get the car to hold 24psi up to the top of the useful rev range, again a massive overboost but the car goes like hell.

Obviously I'm not doing this all the time due to the fact I know its going to mash the brand new turbo!!!!!!

So I'll leave it now to the tech experts to shed some light and advice!

Have you tried a different map? Ask the tuner what the peak boost should be roughly. Also your non-standard cams will surely demand a fully custom map, or atleast a Stage 1 map that has been modified to take them into account.

[Bodge]

Haha beaten to it!

[VRS Mike]

if it were mine I'd be booking into R-tech for them to take a look. Could get very expensive if its not set-up right.

[Rob_OctaviavRS]

I'm currently saving up (and taking driving nice and steady) to get the car looked and and booked in for a mapping session if required.

Why would the cams cause boost issues, I would presume it would be something to do with the VVT kicking in and all the sensor readings going a*******!? Thats just my rough guess tho.....

[chicken_eyebrow]

The aftermarket cams are probably more aggressively profiled so they make the exhaust and inlet valves open for longer. On the exhaust side of things thats going to mean loads more exhaust gases driving the turbo so it spools up a lot faster than it should. The ECU should be able to rein it in by opening the wastegate earlier but I would've thought the map has to be custom written to tell it to do that.

[Rob_OctaviavRS]

The aftermarket cams are probably more aggressively profiled so they make the exhaust and inlet valves open for longer. On the exhaust side of things thats going to mean loads more exhaust gases driving the turbo so it spools up a lot faster than it should. The ECU should be able to rein it in by opening the wastegate earlier but I would've thought the map has to be custom written to tell it to do that.

Ok to throw another spin on it, should the map be fubarred, would removing the map possibly sort the problem, or would I still be looking at the same issues just with less boost?

Its had a new turbo at 87k (90k now) so I'm wondering if maybe the actuator is set wrong, obviously its all french to me lol, gonna have to get it diag'd at R-Tech I think asap.

[chicken_eyebrow]

I think thats for the best. The last thing you want is the new turbo going t*ts up as well. R-tech should be able to figure out what the problem is and I would've thought they could remove the map if it's causing issues and put a more suitable map (not necessarily standard) on it .

[David 8]

i thought cams were a no-no on these engines, I can't think why though lol:wonder: